Drought-resistant grass to spur milk production

By Baraka Rateng’

Struggling East African dairy farmers could benefit from new varieties of high-quality, drought-resistant forage grass known as Brachiaria that boosts milk production by 40 per cent, a report says.

The forage grass could enable farmers to increase their incomes, according to experts at the Colombia-headquartered International Center for Tropical Agriculture (CIAT) – a CGIAR Research Center.

Steven Prager, a co-author of the report —  which was published last month — and a senior scientist in integrated modelling at the CIAT, says the report  was based on many years of forage research in Latin America and the Caribbean, and recent field trials in Kenya and Rwanda from 2011 to 2016.

According to Prager, the study demonstrates the high potential for improved forages in East Africa and high payoff for investment in improved forages.

“The results are based on multiple scenarios of an economic surplus model with inputs derived from a combination of databases, feedback from subject matter experts and a literature review,” he explains, adding that the economic analysis was carried out at CIAT headquarters with the support of tropical forage experts in East Africa.

Drought resistant grass
“The objective of this study was to understand the potential payoff for investment in action to improve dissemination and use of improved forages,” Prager tells SciDev.Net.

“The objective of this study was to understand the potential payoff for investment in action to improve dissemination and use of improved forages.”

Steven Prager, International Center for Tropical Agriculture (CIAT)

One of the big unknowns in the development and implementation of agricultural technology, according to Prager, is how many potential users are required to make it worthwhile to invest in the development and designation of different technologies.

Solomon Mwendia, a co-author of the report and forage agronomist at CIAT, Kenya, says the Brachiaria grass is climate-friendly and has high crude protein and less fiber, which leads to better use and digestion by cattle, in turn leading to less methane gas produced for each unit of livestock product such as milk or meat. Methane is one of the gases associated with global warming.

“This grass is relatively drought-tolerant compared to the Napier or elephant grass commonly used in East Africa. In addition, the grass can easily be conserved as hay for utilisation during forages scarcity or for sale,” Mwendia adds.

Smallholder dairy farming is important in East Africa for household nutrition and income. In Kenya, for instance, Mwendia says that milk production increased by 150 per cent between 2004 and 2012, from 197.3 million litres to 497.9 million litres.


East Africa cattle density 


The grass is native to Africa, according to Mwendia. It can grow in areas with up to 3,000 millimetres of rainfall and also withstand dry seasons of three to six months during which the leaf may remain green while other tropical species die. These conditions exist in other regions outside eastern Africa such as in Democratic Republic of Congo, Malawi, Zambia and Zimbabwe.

Sita Ghimire, a senior scientist at the Biosciences eastern and central Africa (BecA) Hub, who leads a research programme that focuses on Brachiaria, says 40 per cent increase in milk production is achievable in East Africa after feeding livestock with Brachiaria.


Livestock production in East Africa 


“Forage has been always a major challenge in livestock production in East Africa. It is mainly because of declining pastureland, frequent and prolonged drought and not many farmers conserve forage for dry season,” Ghimire says.

The major challenges for adoption of Brachiaria technology in East Africa are limited availability of seeds or  vegetative materials, lack of standardised agronomic practices for different production environments and lack of varieties that are well adapted to East African environment, Ghimire explains, citing other challenges such as pest and diseases, and low funding forage research and development.

This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.

References

Carlos González and others Improved forages and milk production in East Africa. A case study in the series: Economic foresight for understanding the role of investments in agriculture for the global food system (October 2016, Internacional de Agricultura Tropical [CIAT])

 

This article was originally published on SciDev.Net. Read the original article.

Plantwise – promoting and supporting plant health for the Sustainable Development Goals

Andrea Powell

Andrea Powell, CABI

Promoting and supporting plant health will be an important part of how we achieve the United Nations’ Sustainable Development Goals (SDGs). Andrea Powell, Chief Information Officer of the Centre for Agriculture and Biosciences International (CABI) looks at how the CABI-led Plantwise programme is helping to make a difference.

By Andrea Powell

 

On 26th and 27th July 2016, CABI held its 19th Review Conference. This important milestone in the CABI calendar saw our 48 member countries come together to agree a new medium-term strategy. As always, plant health was a key focus to our discussions, cutting across many of CABI’s objectives. For CABI, with 100 years of experience working in plant health, it has become one of our most important issues, upon which our flagship food security program, Plantwise, has been built.

Plant health can, quite simply, change the lives and livelihoods of millions of people living in rural communities, like smallholder farmers. Human and animal health make headlines, while plant health often falls under the radar, yet, it is crucial to tackling serious global challenges like food security. Promoting and supporting plant health will be an important way to achieve the Sustainable Development Goals (SDGs).

Plant health and the SDGs

Take, for example, SDG 1, which calls for ‘no poverty’. The UN states that one in five people in developing regions still lives on less than $1.25 a day. We know that many of these people are smallholder farmers. By breaking down the barriers to accessing plant health knowledge, millions of people in rural communities can learn how to grow produce to sell to profitable domestic, regional and international markets.

Plantwise ReportSDG 2 focuses on achieving ‘zero hunger’. Almost one billion people go hungry and are left malnourished every day – and many are children. Subsistence farmers, who grow food for their families to eat, can be left with nothing when their crops fail. Access to plant health knowledge can help prevent devastating crop losses and put food on the table.

Interestingly, SDG 17 considers ‘partnerships for the goals’ and is critical to the way in which we can harness and share plant health knowledge more widely to help address issues like hunger and poverty. By themselves, individual organizations cannot easily resolve the complicated and interconnected challenges the world faces today. This is why partnership is at the heart of CABI’s flagship plant health programme: Plantwise.

What is Plantwise?

Plantwise Report 2015

Since its launch in 2011, the goal of Plantwise has been to deliver plant health knowledge to smallholder farmers, ensuring they lose less of what they grow. This, in turn, provides food for their families and improves living conditions in rural communities. Plantwise provides support to governments, helping to make national plant health systems more effective for the farmers who depend on them. Already, Plantwise has reached nearly five million farmers. With additional funding, and by developing new partnerships, we aim to bring relevant plant health information to 30 million farmers by 2020, safeguarding food security for generations to come.

Plantwise ‘plant clinics’ are an important part of the fight against crop losses. Established in much the same way as clinics for human health, farmers visit the clinics with samples of their sick crops. Plant doctors diagnose the problem, making science-based recommendations on ways to manage it. The clinics are owned and operated by over 200 national partner organizations in over 30 countries. At the end of 2015, nearly five thousand plant doctors had been trained.

Plantwise

A Plantwise plant clinic in action. Credit: Plantwise

Harnessing technology for plant health

The Plantwise Knowledge Bank reinforces the plant clinics. Available in over 80 languages, it is an online and offline gateway to plant health information, providing the plant doctors with actionable information. It also collects data about the farmers, their crops and plant health problems. This enables in-country partner organizations to monitor the quality of plant doctor recommendations; to identify new plant health problems – often emerging due to trade or climate change issues; and develop new best-practice guidelines for managing crop losses.

Plantwise

The first ever e-plant clinic, held in Embu Market, Kenya. Credit: Plantwise

The Plantwise flow of information improves knowledge and helps the users involved: farmers can receive crop management advice, and researchers and governments can access data from the field. With a new strategy for 2017–19 agreed, CABI will continue to focus on building strong plant health systems. We are certain that plant health is of central importance to achieving the SDGs and, together in partnership, we look forward to growing the Plantwise program and making a concrete difference to the lives of smallholder farmers.

“A few years ago, I would make ZMW 5000 per year. Last year I got 15 000. I have never missed any plant clinic session. I’ve been very committed, very faithful, because I have seen the benefits.”––Kenny Mwansa, Farmer, Rufunsa District, Zambia.

Take a look at Plantwise in action in Zambia (YouTube):

Plantwise in Zambia

Meet Linda, a Zambian plant doctor

Meet Kenny, a Zambian farmer

 

Learn more about Plantwise at www.plantwise.org.

Lessons from the oldest and most arid desert on Earth

Atacama Desert

Image credit: Center for Genome Regulation

The Atacama Desert is a strip of land near 1000 km in length located in northern Chile. With an average yearly rainfall of just 15 mm (close to 0 in some locations) and high radiation levels, it is the driest desert in the world. Geological estimates suggest that the Atacama has remained hyperarid for at least eight million years. Standing in its midst, one may easily feel as though visiting a valley on Mars.

Despite these harsh environmental conditions, it is possible to find life in the Atacama. At the increased altitudes along the western slopes of the Andes precipitation is slightly increased, allowing plant life.

Convergent evolution

The driest and oldest desert in the world acts as a natural laboratory where for 150 million years plants adapted to and colonized this environment. These adaptations are likely present in multiple desert plant lineages, thus providing an evolutionary framework where these traits can be associated with a signature of convergent evolution.

Surviving a nitrogen-limited landscape

Plant in the Atacama Desert

Image credit: Center for Genome Regulation

The interplay of environmental conditions in the transect of the Atacama, ranging from 2500 to 4500 meters above sea level, results in three broad microclimates; Pre Puna, Puna, and High Steppe. These microclimates have different humidities, temperatures, levels of organic matter and even different pH levels, but share one common feature: low nitrogen levels.

To engineer crops with higher nitrogen use efficiency, it is very useful to first learn how plants adapt to growth in low nitrogen environments. Here the Atacama Desert enters into the game. Plants growing in the desert can survive 100-fold less nitrogen below optimum concentrations. Using phylogenetics it is possible to uncover novel genes and mechanisms related to adaptation to these extreme conditions, which have not been discovered through traditional genetic approaches.

Currently, nitrogen fertilizers are widely employed to increase crop yield. In 2008 100 million tons of this fertilizer were used and it is projected that for 2018 the demand for nitrogen will rise to 119 million tons. Regretfully, the production and over-usage of this type of fertilizer has an enormous impact in the environment and human health. Around 60% of the nitrogen introduced to the soil for agricultural purposes is leached and lost. Moreover, nitrogen runoffs to the water cause eutrophication in both freshwater and marine ecosystems, leading to algae and phytoplankton blooms, low levels of dissolved oxygen, and finally the migration or death of the present fauna, forming dead zones such as the one in the Gulf of Mexico.
 

Plants in the Atacama Desert

Image credit: Center for Genome Regulation

Nitrogen fertilizers are not the only major concern in modern agricultural procedures. The co-localization of drought and low nitrogen levels is especially detrimental for plant growth and development. We need to support not only the nutritional requirement of an expanding global population but also new energetic strategies based on production of biomass for biofuels on marginal nutrient poor soils. In order to increase crop yields while reducing the environmental impact of nitrogen fertilizers, it is necessary to develop new agricultural strategies and cutting edge technologies.

Learning from the desert

What if we could profit from the extraordinary plants that have had thousands of years to learn how to cope with nitrogen scarcity, drought and extreme radiation? Specifically, can we unravel the genes and mechanisms that allow them to survive in such a barren place?

Atacama Desert

Image credit: Center for Genome Regulation

Over the past three years our group has identified 62 different plant species that inhabit the Atacama Desert, and established a correlation between their habitat attributes and biological characteristics. Using tools such as whole transcriptome shotgun sequencing or RNA-Seq complemented with different bioinformatics approaches, we have identified over 896,000 proteins that are expressed in these conditions.

In this way we aim to learn which processes are highly utilized in these “extreme survivors” compared to similar species that are present in the deserts of California, where the climatic conditions are similar but there is no nitrogen scarcity. That is how we expect to find new mechanisms (or, more precisely, very old mechanisms) that enable plants to survive and grow efficiently in extreme environments.


 
Susana Cabello

Dr Susana Cabello

Written by Dr Susana Cabello, Center for Genome Regulation, Millennium Nucleus for Plant Systems and Synthetic Biology, Chile. Susana would like to acknowledge Maite Salazar & Rodrigo Gutierrez for their suggestions and edits.

Increasing Food Production in a Changing World

The fifth report of the International Panel on Climate Change (IPCC) published last year announced that climate change is already negatively affecting our food supply and this problem is only going to be amplified in coming decades.

Our climate is projected to warm by 5ºC by 2050, with increased incidence of extreme weather events. Coinciding with this is a rapidly rising global population, predicted to reach 9.6 billion by 2050. Feeding all these extra mouths is challenge enough. Doing this under changing weather and climate conditions becomes even more difficult.

Food shortages resulting from population growth or unusual weather events can lead to rising food prices and political instability. A global rice shortage in 2008 saw prices rise by over 50%, resulting in riots in Asia and Africa. We might expect events such as this to become more common in the future as the food supply becomes more and more affected by climate change.

Not surprisingly food security is currently a buzz word in the research community, and many resources are being poured into trying to ensure a stable food supply for future generations.

Some climate skeptics argue that increases in carbon dioxide could boost plant growth, resulting in higher yielding plants under climate change. However, the reality is that any positive effect the increased CO2 could have on plant growth is likely to be outweighed by higher temperatures and extreme weather events.

Since the IPCC report there have been a number of studies focussed on the staple food crop wheat, and how yields could be affected in the future.

Wheat

Wheat was first domesticated 10,000 years ago and is now grown more widely than any other crop. Photo by jayneandd used under CC BY 2.0.

Wheat yields are sensitive to temperature, and are predicted to fall by around 6% for every 1ºC rise in temperature. If we do not cut down current emissions, the earth could warm by 5ºC by 2050, equating to a 30% reduction in wheat yields due to temperature increases alone.

This 30% reduction in yield is only the tip of the iceberg. Yields could be further reduced by increased instances of disease epidemics. For example, Fusarium Ear Blight is a wheat disease that causes spikelet bleaching and enhanced senescence. A severe epidemic can wipe out 60% of a wheat crop. In order to take effect, the disease requires wet weather at flowering, something which we can expect to happen more often in the future according to climate models.

Extreme weather events, such as flooding, are predicted to increase over the coming decades, and will cause unavoidable crop losses. This will exacerbate problems with declining yields, further increasing the difficulty of feeding a growing population.

What can we do?

Primarily, we should be trying to limit the extent of climate change, and to do so we need to act now. Reducing emissions and moving to sustainable energy sources should be at the top of the agenda.  However, most climate scientists agree that even if we act now to reduce our emissions, there will be at least 2ºC of warming, which is already impacting on food production.

We therefore need to make our food sources more resilient to climate change. In terms of wheat this means breeding varieties that are tolerant to higher temperatures and diseases. Additionally, we will need to adapt our farming methods, to be more intensive yet sustainable, and perhaps alter our diets.

Stress Resilience Forum, 23–25 October, Iguassu Falls, Brazil

In October the Global Plant Council, in collaboration with the Society of Experimental Biology, will bring together experts from around the world to discuss current research efforts in plant stress resilience. Abstract submission and registration for the Stress Resilience Forum is now open, and we welcome researchers at all levels to take part.

The meeting takes place immediately before the International Plant Molecular Biology Conference (25–30 October), also at Iguassu Falls, and which also includes several scientific sessions on plant stresses.

The Nature of Crop Domestication

Why do we eat some plants but not others? What makes a good crop, and how have we transformed these species to suit our own needs?

Around 12,000 years ago, humans began to transition from nomadic hunter-gatherer societies to a more settled agricultural life. We began to selectively breed cereals and other crops to improve desirable traits, such as their yields, taste and seed retention. Today we eat less than 1% of all flowering plant species, relying on a handful of staples for almost all of our calories.

Why do we eat so few plant species?

Professor John Warren, Aberystwyth University

Professor John Warren, Aberystwyth University

We spoke with Professor John Warren at Aberystwyth University in the UK, who delves into the history of crop domestication in his new book, ‘The Nature of Crops: How We Came to Eat the Plants We Do,’ published on 24th April 2015. He blogs about how we came to eat certain plants over at Pick of the Crop, and said that his book developed from there. “The stories of crop domestication are just so interesting, weird, biologically strange, fun – they just demand to be told,” he enthused.

So why do we eat so few of the edible plants in the world? Based on his research into gene flow and plant breeding systems, Professor Warren presents novel theories in his book: “Previously people have argued that it’s because most plant are poisonous, but I don’t think that holds water. We actively seek out toxic plants as crops; plants with large food stores tend to be well defended with toxins. Instead I argue that it’s plant sexual habits that limit crop domestication. Plants with the usual pollination mechanisms don’t make ideal crops as they will fail to set seed when grown on an agricultural scale. Thus we domesticate things that are wind pollinated or pollinated by common generalist insects.”

Science-led crop breeding

Why do we eat poisonous plants?

How did our ancestors come to realise that rhubarb leaves are poisonous but the stems make a tasty crumble? Professor Warren says, “Its discovery was an accident and a fairly recent one – but read the book for the full story.” Image credit: Cory Doctorow used under CC BY-SA 2.0.

Professor Warren works at the Institute of Biological, Environmental and Rural Sciences (IBERS) at Aberystwyth University, which houses much of the research into agriculture and the environment that ties into the theme of his book. “Previously it’s been argued that there haven’t really been any new crops in the last 5,000 years. Here in Aberystwyth, we know that ryegrass, clover, elephant grass and others are still in the process of being domesticated, so you don’t need to be an archaeologist to study the process,” he explained. In addition to breeding new varieties of cereals and forage crops for food and feed, the Public Good Plant Breeding group at IBERS are also in the process of breeding Miscanthus, a fast-growing grass species that could be used for sustainable bioenergy in the future.

Resources like the Diversity Seek (DivSeek) initiative, established by the Global Plant Council in association with the Global Crop Diversity Trust, the CGIAR Consortium and the Secretariat of the International Treaty on Plant Genetic Resources for Food and Agriculture, could be used to enable science-driven crop breeding and domestication. DivSeek aims to unlock the genetic diversity that is currently stored in genebanks around the world by using cutting edge sequencing, phenotyping and ‘big data’ technologies. The genetic variation that is identified can then be used as the basis for breeding programs and could assist in the domestication of novel crops.

The future of agriculture

Drought damage

Drought damage in California, 2014. Image credit: US Department of Agriculture used under CC BY 2.0.

The crops we eat today were domesticated in highly fertile conditions; this means they are nutritious but tend to demand a high input of fertilizers and water. Professor Warren argues that we can use modern science to develop more sustainable ways to feed the global population: “It’s important that we start to think outside the box and try and domesticate a whole range of new crops that are more sustainable and less demanding of agricultural inputs.” An important source of future crop species could be stress-tolerant plants living in difficult environments: “I think the crops of the future could still be waiting to be domesticated from plants growing in harsh conditions,” explained Professor Warren.

Professor Warren also discussed how we could use underutilized crops in new ways to make agriculture more sustainable in the future: “I think and hope that we will eat more species, and that we will grow many more of these as perennials in poly-culture systems. That makes ecological sense in terms of niche exploitation and yield sustainability. It also makes more genetic sense in terms of resistance to pests and diseases.” The only downside, he said, is that these systems are so different to what we have now that we will need innovative research to develop them.


About Professor John Warren

Akee fruit

The akee is the national fruit of Jamaica. Image credit: Loren Sztajler, used under CC BY-ND 2.0.

John is a plant ecologist at Aberystwyth University, UK, with research interests in the origin and maintenance of diversity and enhancement of conservation value, particularly within agricultural ecosystems. He is the Director of Teaching and Learning and a Professor of Botany in the Institute of Biological, Environmental and Rural Sciences. John says the strangest plant he’s ever eaten is the akee, a plant beloved of Jamaicans that looks and tastes a bit like scrambled eggs but which is delicious with saltfish.


Over to you

What do you think will be the most important crops of tomorrow, and which underutilized plants will become dietary staples in an effort to feed the world more sustainably?

Can you crowdfund the sequencing of a plant genome?

Dr Peng Jiang, University of Georgia, USA

Dr Peng Jiang, University of Georgia, USA

Peng Jiang and Hui Guo at the University of Georgia think you can! They are currently raising money via a crowdfunding approach to sequence the first cactus genome – but the question is: why would they want to? Peng explains all in this guest blog post.

A Prickly Proposal: Why Sequence the Cactus?
In these times of growing food insecurity due to climate change and population pressures, the prickly pear cactus (Opuntia ficus) has growing commercial and agricultural importance across much of the world – you will find it growing in Mexico and Brazil, Chile, large parts of India and South Africa, and in Spain and Morocco.

The goal of our proposal is to sequence the genome and transcriptome of the prickly pear cactus, a recognized food and forage crop in these challenging semiarid regions of the world.

With more than 130 genera and 1,500 species of Cactaceae, we will create a draft genomic and transcriptome database that would aid the understanding of this understudied plant family, and provide the research community with valuable resources for molecular breeding and genetic manipulation purposes. Here are some of the reasons why we think a first cactus genome would be so important:

The Prickly Pear Cactus

The Prickly Pear Cactus

1. Ecological Improvement
The beauty of the drought-tolerance cactus is that it can grow on desert-like wastelands. Nowadays, more than 35% of the earth’s surface is arid or semiarid, making it inadequate for most agricultural uses. Without efforts to curb global warming, “Thermageddon” may hit in 30–40 years time, causing desertification of the US, such that it may become like the Sahara. Opuntia helps create a vegetative cover, which improves soil regeneration and rainfall infiltration into the soil. This cactus genome research may help us to adapt our food crops to a much hotter, drier climate.

2. Food Crops, Feed and Medicine
The fruits of prickly pear cactus are edible and sold in stores under the name “tuna”. Prickly pear nectar is made with the juice and pulp of the fruits. The pads of prickly pears (“Nopalito”) are also eaten as a vegetable. Both the fruits and pads of prickly pears can help keep blood sugar levels stable because they contain rich, soluble fibers. The fruit contains vitamin C and was used as an early cure for scurvy.

Furthermore, there has been much medical interest in the prickly pear plant. Studies [1, 2, 3] have shown that the pectin contained in prickly pear pulp lowers cholesterol levels. Another study [4] found that the fibrous pectin in the fruit may lower a diabetic’s need for insulin. The plant also contains the antioxidant flavonoids quercetin, (+)-dihydroquercetin (taxifolin), quercetin 3-methyl ether (isorhamnetin) and kaempferol, which have a protective function against the DNA damage that leads to cancer.

3. Biofuels in Semiarid Regions
Planting low water use, Crassulacean acid metabolism (CAM; a water saving mode of photosynthesis) biofuel feedstocks on arid and semiarid lands could offer immediate and sustained biogas advantages. Opuntiapads have 8–12% dry matter, which is ideal for anaerobic digestion. With an arid climate, this prevents the need for extra irrigation or water to facilitate the anaerobic digestion process. Requiring only 300 mm of precipitation per year, Opuntiacan produce a large amount of dry matter feedstock and still retain enough moisture to facilitate biogas production. It’s possible to get as much as 2.5 kWh of methane from 1 kg of dry Opuntia.

4. Phylogenetic Importance
Trained botanists and amateurs alike have held cacti in high regard for centuries. The copious production of spines, lack of leaves, bizarre architecture and impressive ability to persist in the harshest environments on Earth are all traits that have entitled this lineage to be named a true wonder of the plant world.

The cacti are one of the most celebrated radiations of succulent plants. There has been much speculation about their age, but progress in dating cactus origins has been hindered by the lack of fossil data for cacti or their close relatives. Through whole genome sequencing, we help will reveal the genomic evolution of Opuntia by comparing this genome with that of other sequenced plant species.

Cacti are typical CAM plants. We will analyse the evolution of CAM genes in the cactus to help reveal the secret of drought tolerance. Furthermore, plant architecture genes and MADS-box gene family members will be analysed to reveal the specific architecture and structure of cactus.

Crowdfunding the Cactus Genome Project
Cactus has several fascinating aspects that are worth exploring, not just for its biology, but also its relevance to humanity and the global environment. We plan to generate a draft genome for Opuntia, and have launched a crowdfunding campaign to help fund this project – we have already raised $2300 USD (46% of what we need), but we only have 15 days to raise the rest. If you would like to help fund this project, please visit our Experiment page at: https://experiment.com/projects/sequencing-the-cactus-genome-to-discover-the-secret-of-drought-resistance.

If we are successful in raising enough money to initiate the Cactus Genome Project, not only will this be the first plant genome to be sequenced in the Cactaceae family, we will be releasing the results to the plant science community through GeneGarden, an ornamental plant genome database. Our citizen science approach is also allowing us to reach out directly to members of the public, creating exciting opportunities for outreach and engagement with plant science.

If you have any further questions, please contact project leader Dr Peng Jiang at [email protected].

This blog post is slightly adapted from a post originally appearing on GigaScience Journal’s GigaBlog. Reproduced and adapted with permission, under a CC-BY license.

References

  1. Wolfram RM, Kritz H, Efthimiou Y, et al. Effect of prickly pear (Opuntia robusta) on glucose- and lipid-metabolism in non-diabetics with hyperlipidemia – a pilot study. Wien Klin Wochenscr. 2002;114(19–20):840–6.
  2. Trejo-Gonzalez A, Gabriel-Ortiz G, Puebla-Perez AM, et al. A purified extract from prickly pear cactus (Opuntia fulignosa) controls experimentally induced diabetes in rats. J Ethnopharmacol. 1996;55(1):27–33.
  3. Fernandez ML, Lin EC, Trejo A, et al. Prickly pear (Opuntia sp.) pectin alters hepatic cholesterol metabolism without affecting cholesterol absorption in guinea pigs fed a hypercholesterolemic diet. J Nutr. 1994;124(6):817–24.
  4. Frati-Munari AC, Gordillo BE, Altamirano P, et al. Hypoglycemic effect of Opuntia streptacantha Lemaire in NIDDM. Diabetes Care. 1988:11(1):63–66.

Cellulosic Ethanol from Sugarcane in Brazil

sugarcane fieldBrazil is a major producer of ethanol from sugarcane, and this leading global position is the fruit of scientific and technological advances resulting from a development program that was initiated in the 1970s. Driven by the oil crises of 1972-1973, Brazil transformed several sugar mills into ethanol producing units that became capable of co-production of ethanol and raw sugar (5). This was technically possible due to the high levels of sucrose in sugarcane and to the development of yeast strains capable of fermenting this sugar efficiently. At the same time, the first automobiles running exclusively on ethanol were introduced, which on the one hand helped Brazil face major world energy crises, and on the other implanted the basis for development of future technologies. Over the following 40 years, Brazilian sugar mills undertook a technological transformation that significantly increased the efficiency of sucrose and alcohol production. This method, now called first generation (1G), has reached a level of 90% conversion of sucrose into ethanol (5). At the same time, advances in sugarcane agricultural technology improved the sugarcane crop to a high level of productivity (averaging 80 tones per hectare). Using intensive breeding programs, a number of sugarcane varieties have been developed that are increasingly better adapted to the diverse climate and soils encountered in Brazil. The result is that Brazil is now the second largest producer of ethanol and the first placed producer of sugarcane in the world.

The necessity to produce second-generation ethanol

Until 2006, Brazil was the only country to produce and use ethanol on a large scale as a fuel alternative for cars. Since then, increased public awareness and governmental focus around the world on issues related to climate change and the excessive use of fossil fuels has led to increased interest in the use of renewable energy. It was at this moment that Brazil, with its highly efficient sugarcane bioethanol sector, became a leader worldwide in the production and use of renewable energy. Nevertheless, production of 1G bioethanol was already at the limit of efficiency both from industrial and agronomical viewpoints.

It was in this context that the Brazilian scientific community and the Federal and State of São Paulo governments took the initiative in the search for ways to increase production of sugarcane ethanol beyond current limits. An idea that was already being revived in several places in the world was the possibility to produce ethanol from sugar polymers, including cellulose, present in cell walls of plants. This search for ‘cellulosic ethanol’ is generally referred to as second-generation (2G) ethanol. Although establishment of 1G technology was highly successful, the potential for ethanol production from 2G is much higher because energy accumulated in sugarcane in the form of sucrose represents only 1/3 of the total. The other two-thirds are distributed equally between the bagasse (stems) and the leaves.

Cell wall recalcitrance

At first sight, the idea of producing ethanol from biomass seems straightforward: it would be enough to convert cellulose to free sugars that could be fermented by yeast. Although many advances have been made in this area, this problem is far from being solved, and developing 2G processes that are economically viable has proven to be a major challenge. The plant cell wall is composed mainly of carbohydrates in the form of polysaccharides that associate to form a supramolecular structure where polymers aggregate through non-covalent linkages. Some polysaccharides are branched with phenolic compounds (ferulic an p-coumaric acids). Ferulic acid can dimerize interlocking polysaccharide chains or these can still undergo polymerization with other phenylpropanoids, including p-hydrocinammic, sinapyl and coniferyl alcohols, forming lignin. Together, the supramolecular structure of cell-wall polymers constitute the main obstacle to enzymatic hydrolysis. Furthermore, known hydrolytic enzymes have molecular sizes that prevent their penetration into the polymer matrix. Therefore, when a mixture of enzymes is added to the surface of the cell wall, the catalytic attack is mainly on the surface of the composite. To perform more complete hydrolysis, enzymatic complexes would have to act in a synergetic fashion on the entire cell wall composite. At present this is not feasible as researchers cannot adequately control the process because very little is known about the synergism between the enzymes involved. One of the principal limitations to understand such mechanisms is that until recently our knowledge of the structure and architecture of the sugarcane cell wall was very limited.

Sugarcane buckAt the biological level, cell wall recalcitrance in plants is thought to be due to the wall’ ability to protect against herbivores and the penetration of pathogens. At the molecular level, the cell wall of sugarcane presents three domains of polysaccharides that interact through non-covalent linkages: the pectic domain, the hemicellulosic domain and the cellulosic domain. The cellulosic domain is embedded within the hemicellulosic domain and both are embedded in the pectin domain. Thus, the basic unit of the cell wall of sugarcane consists of a core with macrofibrils (agglomerated of microfibrils) of cellulose strongly linked to structurally complex hemicelluloses that display a glycomic code, the complex branching pattern of these compounds (2). In addition, this core of polysaccharides is surrounded by an agglomerate of polymers that interact with themselves. Phenolic compounds are also thought to interlock the three polysaccharide domains so that the covalent linkages are protected, effectively sealing the whole unit and creating a structure that is extremely resistant to mechanical, chemical and biochemical degradation.

Several publications produced by the research labs of the National Institute of Science and Technology of Bioethanol (INCT-Bioetanol – www.inctdobioetanol.com.br) have demonstrated that it is possible to disassemble the cell wall using chemical reagents (4). The procedure consists of initially attacking the phenolic compounds and eliminating them from the wall. This makes subsequent separation of the wall polysaccharides possible via treatment with a series of alkali solutions of increasing concentration (6).

A procedure called pretreatment (chemical and physical treatments with hot water, ammonia, acids and/alkali), eliminates the porosity barrier so that all polymers become accessible to attack by hydrolases. However, the branching nature of hemicelluloses still acts as a barrier and prevents further enzyme attack of the polymer chains. This highlights the necessity of using specific enzymatic complexes in order to produce free sugars that can be utilized for fermentation (1-7). As branched hemicelluloses alter the way polysaccharides are recognized by enzymes, their branching pattern (glycomic code) can alter the interaction between enzyme and substrate, affecting enzyme kinetics and cell wall degradation efficiency. The available data shows that the cell wall of sugarcane displays at least 18 glycosidic linkages, and suggests that approximately the same number of enzymes will be necessary to degrade the cell wall completely (5,6). Nevertheless, this chemical process is extremely complicated, laborious and expensive, and this is therefore not a viable strategy for industry.

The collection of enzymes characterized during the first phase of the INCT-Bioetanol contains practically all the catalytic capabilities needed for complete sugarcane cell wall hydrolysis. For this reason, the Institute has reached a point of prioritizing experiments focused on combining enzymes, forming consortia capable of dealing with each of the limiting factors related to recalcitrance. The possible combinations of enzymes have been proposed (1,6) and during the next phase of the project, these strategies will be put into practice by an integrated group of researchers in a series of experiments that will test this hypothesis.

At the same time, it will be necessary to understand the variability in the structure of the sugarcane cell wall in order to find Brazilian sugarcane varieties possessing structures and architectures that are more amenable to hydrolysis. Although the variation in cell wall composition is relatively limited among sugarcane tissues, one may expect to find considerable variation among the great number of extant varieties. This has been recently observed for Miscanthus and maize, two grass species that are genetically related to sugarcane and with very similar cell walls. Several research groups have concentrated efforts on understanding the role of lignin in recalcitrance and have concluded that this interference is somewhat limited. The reduction in lignin content leads in general to an increase in saccharification in a non-linear fashion depending on the pre-treatment, morphological distribution and the level of lignin aggregation (9), suggesting that other cell wall domains make equally important contributions to the recalcitrance of biomass. Research groups of the INCT-Bioetanol have already obtained transformed sugarcane in which the gene encoding one of the enzymes of lignin biosynthesis (COMT) has been silenced. These transgenic plants have cell walls that are modified, and saccharification tests are currently in progress. During the second phase of the INCT we intend to verify whether such genetic variability also exists in sugarcane and to use this information to obtain varieties in which differences among cell wall composition lead to lower recalcitrance to hydrolysis.

 

Marcos S. Buckeridge

[email protected]

Laboratory of Plant Physiological Ecology, Depatment of Botany, Institute of Biosciences, University of São Paulo (www.lafieco.com.br)

Director of the National Institute of Science and Technology of Bioethanol (www.inctdobioetanol.com.br)

 

REFEFENCES

  1. Buckeridge, M.S., Dos Santos,W.D., Tiné, M.A.S., De Souza, A.P. (2015) Compendium of Bioenergy Crops: Sugarcane edited by Eric Lam. CRC Press, Taylor and Francis (in press)
  2. Buckeridge, M.S. & De Souza, A.P. (2014) Breaking the “glycomic code” of cell wall polysaccharides may improve second generation bioenergy production from biomass. Bioenergy Research DOI 10.1007/s12155-014-9460-6
  3. Buckeridge, M.S.; Souza, A.P.; Arundale, R.A.; Anderson-Teixeira, K.J.; DeLucia, E. (2012) Ethanol from sugarcane in Brazil: a “midway” strategy for increasing ethanol production while maximizing environmental benefits. GCB Bioenergy, 4:119-126.
  4. Buckeridge, M. S. (Org.) ; Goldman, G. H. (Org.) . Routes to cellulosic ethanol. 1. ed. Nova Iorque: Springer, 2011. v. 1. 263p.
  5. De Souza, A. P. ; Grandis, A. ; Leite, D. C. C. ; Buckeridge, M.S. (2014) Sugarcane as a Bioenergy Source: History, Performance, and Perspectives for Second-Generation Bioethanol. Bioenerg Res, 7:24-35.
  6. De Souza, A. P., Leite, D. C. C., Pattathil, S. ; Hahn, M. G. ; Buckeridge, M. S. (2013) Composition and Structure of Sugarcane Cell Wall Polysaccharides: Implications for Second-Generation Bioethanol Production. Bioenergy Research, 6: 564-579.
  7. Mccann, M. ; Buckeridge, M. S. ; Carpita, N.C. . Plants and Bioenergy. 1. ed. New York: Springer, 2013. v. 1. 300p.
  8. Magrin, G.O., J.A. Marengo, J.-P. Boulanger, M.S. Buckeridge, E. Castellanos, G. Poveda, F.R. Scarano, and S. Vicuña, 2014: Central and South America. In: Climate Change 2014: Impacts, Adaptation, and Vulnerability. Part B: Regional Aspects. Contribution of Working Group II to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Barros, V.R., C.B. Field, D.J. Dokken, M.D. Mastrandrea, K.J. Mach, T.E. Bilir, M. Chatterjee,K.L. Ebi, Y.O. Estrada, R.C. Genova, B. Girma, E.S. Kissel, A.N. Levy, S. MacCracken, P.R. Mastrandrea, and L.L. White (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. XXX-YYY
  9. Rezende, C.A.; Lima, M.; Maziero, P.; Azevedo, E.; Garcia, W.; Polikarpov, I. (2011) Chemical and morphological characterization of sugarcane bagasse submitted to a delignification process for enhanced enzymatic digestibility. Biotechnology for Biofuels. 4: 54

Why nutrition-smart agriculture matters

Orange Sweet PotatoThe focus of agricultural policy should be to increase productivity, provide employment and reduce poverty.

How often have you read or heard statements like this?

I am an economist, and I understand this thinking. It has its place. But I will argue that the reason global food systems are failing is because they have neglected the most fundamental purpose of agricultural systems — to nourish people.

Today, more than 2 billion people are suffering from hidden hunger — most will get enough calories, which has been the metric for food systems thus far, but not enough vitamins and minerals. We know too well the global costs of this hidden hunger. We see it in women as they risk death during childbirth. We see it in a stunted child with a diminished IQ. And we see it in men and women too weakened by illness and poor immunity to be able to work at an optimal level.

We need to re-envision agriculture as the primary source of sound nutrition through the food people harvest and eat. This is a radical concept in the true sense of the word — returning to the root or fundamental purpose of agriculture.

To read the rest of this blog post that was originally posted on Devex as part of the Feeding Development campaign, please click here.

This blog was written by Howdy Bouis who holds a joint appointment at the International Food Policy Research Institute in Washington, D.C. and the International Centre for Tropical Agriculture in Cali, Colombia.

“Children in Uganda share a plate of orange sweet potato” Photo used in this blog is by: A. Ball / HarvestPlus / CC BY-NC