Brazil develops beans resistant to quarantine bacterial disease

Embrapa obtained the first Brazilian variety of carioca beans resistant to halo bacterial blight (Pseudomonas syringae pv. phaseolicola). It is a disease not yet registered in the country, but widely spread throughout the world and present in neighboring countries such as Argentina, Chile, Peru, Colombia and Venezuela. The variety was developed through preventive genetic improvement, which studies high-risk diseases and pests for the main agricultural species before they reach the national territory. This research was supported by the Federal University of Goiás (UFG), the State of Goiás Research Support Foundation (Fapeg) and the National Council for Scientific and Technological Development (CNPq).

The study began with the identification, within the collection of the Active Germplasm Bank (BAG) of Embrapa Arroz e Feijão, of two bean lines: BelNeb-RR1 and ZAA-43, known for each having a gene for resistance to bacterial blight. haloed. Both were crossed with the BRS Estilo variety, which is an Embrapa bean cultivar with commercial quality grain from Rio. 

Preventive improvement can bring disease control forward by ten years

As halo bacterial blight is a quarantine disease, not present in Brazil, it was not possible to test the success of the incorporation of resistance genes to BRS Estilo in the presence of the pathogen, in the field or in a greenhouse. In this case, the solution was to use knowledge from preventive genetic improvement to verify whether the desired genetic inheritance had actually been introduced into the variety. For this, the technique of molecular markers was used, which function as “chips” that help analyze DNA and identify the insertion of genes in the plant.  

“The research was carried out using selection assisted by molecular markers applied to the bean genome. In this case, SSR markers were used (Simple Sequence Repeat), who confirmed the presence of the two resistance genes after the advancement of generations, via backcrossing, with the BRS Estilo cultivar. These genes have dominant action and confer resistance to eight of the nine known races of bacteria”, says Embrapa researcher Paula Torga, one of the coordinators of this work.   

The next step of the research is to validate the resistance incorporated into BRS Estilo, exposing the variety to direct contact with the disease, which will be done outside Brazil so as not to put national crops at risk. The tests will be conducted in partnership with international research institutions that will carry out the final test in a controlled greenhouse environment and also in the field.

Researcher Helton Pereira, who is part of Embrapa's Bean Genetic Improvement Program, comments that one of the main methods of controlling halo bacterial blight is the use of resistant cultivars. According to him, if good results are confirmed outside the country with BRS Estilo, the research will have brought forward improvements in combating the disease by ten years.

Molecular tools add value to genetic collections

“Disease-resistant bean cultivars represent one of the most relevant contributions of agricultural research to society. The use of these cultivars is an investment that can be considered low-cost for the farmer, but has a high impact, because it eliminates crop losses and the need to apply pesticides. Furthermore, beans are a product of great economic and social value, linked to the basic diet and food security of the population”, points out Pereira.  

All of this work was anchored in the use of a broad base of genetic resources and knowledge of molecular biology. Torga highlights this contribution. “Marker technology provides more genetic information about BAG’s collection of resources, helping breeders choose genotypes to be crossed, which increases the probability of success in breeding programs,” he explains.

Disease can cause losses of more than 50%

Bacterial halo blight on common bean (Pseudomonas syringae pv. phaseolicola) is present in Africa, Asia, Europe, Oceania and America. In Brazil, it is considered a high-risk quarantine organism for bean production, capable of causing great losses and losses. The disease can reduce crop yield by more than 50%. The main source of spread is contaminated seed. Therefore, it is recommended to plant healthy seeds, associated with crop rotation and the cultivation of resistant varieties.