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Helping build sustainably productive farming systems through the work of the Asian Cassava Breeders, and Forage Legumes, Networks

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by Madelline Romero

Researchers from eight Asian countries – Bangladesh, Cambodia, China, India, Laos, Myanmar, Philippines, Vietnam – gathered on December 12-13, 2017 in Haikou City, China, to form the Asian Forage Legumes Network.

This is in response to the increasing pressure for farming systems in Asia to produce more without causing further harm to the environment.

“As soils deteriorate and become unable to provide the nitrogen that crops need, crops tend to look for other ways to obtain nitrogen,” explains Didier Lesueur, soil scientist at the International Center for Tropical Agriculture (CIAT). “This is why nitrogen-fixation from the atmosphere is very important in agriculture. And the most important nitrogen-fixing agents in agricultural systems are the symbiotic – mutually beneficial – associations between crop, forage legumes, and rhizobia – the nitrogen-fixing bacteria that camp inside the root nodules of legumes.”

In addition to fixing atmospheric nitrogen (N), intercropped legumes contribute to enhancing soil carbon content through the leaves and root systems that remain in the field after harvest. When used as green manure, multipurpose legumes help in mitigation of soil erosion by providing a better soil cover. Beyond facilitating soil health, when used as forages, legumes provide high-quality livestock feed, thereby helping increase livestock production. These are some of the benefits of the integration of multipurpose legumes in farming systems. For scientists at CIAT, this is one way to sustainably diversify tropical crop-livestock systems in Asia.

“We would like for farmers to take advantage of the many benefits derived from nitrogen fixed in crop-livestock systems,” notes Sabine Douxchamps, integrated farming systems researcher at CIAT. “And we need to be able to answer a number of questions, like what are the economic benefits to a farmer, how much savings in fertilizer will it effect, and others, to encourage farmers to adopt certain farming practices.”

Building a Forage Legumes Network in Asia

The network looked into the current level of knowledge on biological nitrogen fixation (BNF) by forage legumes in Asian farming systems. In the end, the group of researchers identified several broad research subjects deemed critical to understanding and promoting biological nitrogen fixation within the region.

As members of the Asian Forage Legumes Network, the researchers have committed to collaborate on research studies, as well as on a number of initiatives, including the identification and conservation of forage legume species that are tolerant to stresses such as those caused by salinity, drought, waterlogging, and acidity. Others are the establishment of a forage legumes rhizobia bank, testing of some commercial rhizobia inoculants, and development of quality control guidelines to ensure high-quality inoculants.

“In tropical areas like the parts of China that suffer from acidity, nutrient loss, and degradation, soil research is very important,” said Prof. Changjun Bai, Director of the Tropical Pasture Research Center at the Chinese Academy of Tropical Agricultural Sciences (CATAS), the meeting host. “For the benefit of smallholders, it is important to pursue collaborative research projects.”

To this end, CIAT is brokering regional cooperation in agricultural science and technology by helping establish research platforms among Asian countries, jointly facilitated by CIAT and China.

Asian Cassava Breeders Network

An economically significant crop for many countries in Asia, cassava is one such research subject that has attracted collaboration among researchers in the region. A week before the meeting in Haikou City, researchers from CIAT, China, and a host of other research institutions and programs, met at the Kasetsart University in Thailand for the third annual meeting of the Asian Cassava Breeders Network (ACB-Net).

ACB-Net is a regional community of practice that brings together cassava breeders and other interested stakeholders for a systematic collaboration on cassava genetic enhancement and crop improvement. Established in 2015, the network includes classical breeding programs and molecular breeding laboratories, as well as public and civil society organizations interested in evaluating cassava varieties. Currently, some 28 organizations from the research, public, and private sectors, in 10 Asian countries, form membership of the network.

At the meeting, researchers shared updates on each their institution’s work on cassava breeding . They also discussed actions to address the issue of cassava mosaic disease (CMD), a disease caused by a virus and transmitted by whiteflies, and which causes cassava plants to produce few or no tubers at all. In Africa, yield losses induced by cassava mosaic virus (CMV) in different countries had ranged from 20 to 95 percent, at one point.

The disease’s presence was discovered in Cambodia in 2015. Since then researchers from CIAT and CATAS have been actively collaborating on regional surveillance together with partners in Cambodia and Vietnam. Results of the 2016 regional surveillance will be published in a peer reviewed publication, while a new round of regional sampling in 2018 will be coordinated by CIAT and CATAS.

“The fast pace of CMD spread is a huge concern for cassava production in mainland Southeast Asia,” said Stef de Haan, researcher at CIAT and member of the ACB-Net steering committee. “CIAT has already introduced sources of resistance to Thailand and Vietnam. ACB-Net will collaborate to further introduce additional breeding populations with resistance, from CCTRI in India and IITA in Africa. Incorporating resistance genes into breeding programs and testing the materials under intentional field-level exposure will require active collaboration between regional breeding programs. The network will allow for this international collaboration to take shape.”

Beyond CMD-resistance breeding, other activities that the network has in place for 2018 include capacity building events for young breeders; introduction and regional distribution of germplasm, including of elite progenitors; publication of standard procedures; and development of projects to address regional priorities.