Resistant beans through modern plant breeding
ETH researchers are heavily involved in a method that can quickly and efficiently produce disease-resistant beans for different regions of the world. In doing so, they help to improve food security of self-sufficiency in tropical countries.
For many small farmers and self-employed people in Africa and Latin America, beans are one of the most important staple foods. Meat can not often afford these layers of the population. Beans are rich in protein and minerals – and they fill you up. As a result, these legumes come to the plate every day at every meal.
Plant diseases, however, reduce the harvest in many places with sensitivity. In particular, a fungus responsible for the terrible leaf spot disease causes crop losses of up to 80%, particularly in Africa, where smallholders often do not have access to plant protection products and do not know how use them.
In collaboration with Bodo Raatz and his team at the International Center for Tropical Agriculture (CIAT), the ETH researchers from Bruno Studer's group, professor of molecular plant breeding, now have the natural genetic resistance of beans at the angular spot of the examined leaf. Thanks to their discoveries, resistant bean varieties can be grown faster and more efficiently.
The genetic profile of beans potentially adapted to the selection of new resistant varieties is at the heart of the new method. This profile indicates in advance whether the offspring resulting from crossing two varieties is resistant to various local strains of the pathogenic fungus (called pathotypes).
Genetic profile of 316 varieties created
First of all, Michelle Nay, who led this project as part of her doctoral dissertation with Bruno Studer, assembled a diverse collection of bean seeds from the CIAT seed collection. The Nay collection included 316 different varieties with characteristics relevant to the mushroom for their continuous reproduction.
Nay then planted the beans from their collection in Uganda and Colombia, both in the field and in the greenhouse. In this way, she wanted to know if and how the different varieties reacted to the respective strains of the harmful fungus in the respective countries and which genes were at the origin of the resistance.
In addition, the researcher created a high resolution genomic profile of each of the 316 bean lines based on genetic variation and identified markers found only in resistant beans. The markers were used to predict which cross products would resist which strains of fungi in a country and which would not.
Progress in conventional breeding
"Our process is dramatically accelerating reproduction," says Studer. It was a big step forward, because he was more or less happy to cross different varieties and to test the resistance of each plant. Thanks to the genomic profiles, it is now possible to evaluate the resistance of the offspring. "This is extremely useful for selecting beans and good news for people who are in desperate need of beans."
Studer also considers that the production of disease-resistant beans helps to reduce the use of pesticides. Today, in Latin America, many pesticides are used in the cultivation of beans, but very few in East Africa, because farmers often do not have access to them. "With resistant beans, we kill two birds with one stone: farmers in Latin America need fewer pesticides, African farmers can harvest more, even without pesticides."
Simple and cheap technology
The seeds from this project are distributed by CIAT to various partner organizations, which deliver the varieties obtained to farmers. The analytical technique for determining genetic markers is also relatively simple and inexpensive, so that it can be used by the agricultural science programs of the respective countries. Testing a genetic marker costs less than 20 cents, says Nay. Laboratories in poor countries can also afford it. Moreover, everything that has emerged in this work is openly accessible. "That's exactly where we get people who really need access to such resources," Nay says.
Nay and Studer worked closely with CIAT on this project. She runs a major breeding program in Colombia and has the largest seed collection in the world of several thousand beans. In the CIAT Variety Garden in Colombia, new varieties are produced using a conventional cross, tested seeds and, through the partner organization "Pan African Alliance for research on beans ", also made available to African breeders for additional breeding activities.
In a follow-up project, Studer and his group will further develop the selection method in collaboration with CIAT and with the support of the World Food Systems Center of ETH Zurich. While researchers focused on the molecular markers of a disease, the new project takes a more holistic approach, trying to predict as many characteristics of the plant as possible based on the genetic material profiles.
Teacher. Dr. Bruno Studer, Molecular Plant Breeding, ETH Zurich, +41 44 632 01 57
Nay MM, CM Mukankusi, Studer B, Raatz B: Php-2 haplotypes determine the specificity of pathotypes of angular leaf spot resistance in common beans. Frontiers in Plant Science, 2019. DOI: 10.3389 / fpls.2019.01126
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