Conference on advances with soybean rust genome brings perspectives for disease management

Results achieved and advances related to the three genomes of the fungus that causes Asian soybean rust (Phakopsora pachyrhizi), obtained between 2019 and 2021, by the international research consortium ASR Genome Consortium, in which Embrapa participates, among other scientific approaches conducted at Embrapa Soja , in Londrina (PR) and its partners, were shared this May 17th, at the conference “The genome of P. pachyrhizi: opening new perspectives for the control of FAS in the era of modern agriculture”, taught by researcher Francismar Correa Marcelino- Guimarães, during the IX Brazilian Soy and Mercosoja Congress 2022, held from May 16th to 19th, in Foz do Iguaçu, PR. “The availability of the fungus reference genome has been essential for us to advance in our knowledge of the biology and factors involved in the adaptability of this fungus, with the aim of accelerating the development of new strategies for controlling Asian rust, the most severe crop disease. of soybeans”, explains researcher Francismar C. Marcelino-Guimarães, from Embrapa Soja. 

Using the reference genome, the researcher explains that comparative genomics studies, involving the comparison of the entire set of genes of the fungus with other different species, have been conducted, revealing genes involved in essential biological processes conserved between these species, as well as particularities adaptive based on the contraction or expansion of gene families. “In the case of Asian soybean rust, we observed an important expansion of genes involved in amino acid metabolism and energy production, as a possible reflection of its biotrophic nature, with total dependence on the host. Such genes are important targets for the development of control strategies, such as gene silencing, as they can compromise the species' vital processes”, highlights Francismar. “Studies conducted at Embrapa, with the silencing of fungus genes, have demonstrated the potential of this strategy in reducing the severity of the disease”, she reveals.

Partnership with UFV

Teams from Embrapa Soja, in partnership with the Federal University of Viçosa (UFV), are seeking to decipher the fungus' attack mechanisms, identifying which soybean targets are being manipulated by the pathogen. “We identified that the fungus acts on a soybean protein involved in the defense response, and its presence inhibits the activity of this protein, highly expressed in rust-resistant soybeans”, he explains. Francismar also says that the analysis of natural variations in soybean DNA showed a polymorphism that separates the sources of resistance genes in susceptible soybean cultivars to the fungus. “This reveals a potential molecular marker that can assist in the development of soybean cultivars by combining such genes with resistance genes (Rpp genes), already used in Embrapa soybean cultivars with Shield Technology”, he highlights.

Partner with Bayer

Another line of research between Embrapa, in partnership with Bayer, has been exploring the variability existing in the natural populations of the fungus, which has been widely occurring in the country and on the American continent since 2002/2003. “Such studies have revealed a lack of population structure, with isolates from different continents such as Africa, Asia and the Americas grouping into the same groups based on variations present in the DNA. A possible differentiation between the isolates was observed on a temporal scale, considering samples obtained between 1972 and 2017”, he says. “The identification of variations in DNA, in a temporal context, has revealed regions of the genome with different rates of differentiation. Such analyzes allowed the identification of new mutations within one of the main target genes of fungicides, which may be associated with the efficiency of these molecules.”  

about the disease

Asian soybean rust has been the main disease of soybeans since its identification in the 2000s. The disease can lead to losses of up to 80% if left uncontrolled, while management costs for farmers exceed US$2 billion per harvest in Brazil alone. The fungus is capable of adapting to control strategies, whether by losing sensitivity to fungicides or breaking the genetic resistance present in soybean cultivars, so the number of practical solutions for controlling the disease is still limited. 

About the Consortium

Between 2019 and 2020, the international research consortium ASR Genome Consortium made publicly available the sequencing and assembly of the reference genome of three isolates of P. pachyrhizi, whose data are publicly available to the scientific community at the link https:// mycocosm.jgi.doe.gov/Phapa1. The international consortium is made up of 12 public and private institutions, listed below: the Brazilian Agricultural Research Corporation (Embrapa), the German Universities of Hohenheim and RWTH Aachen, the National Institute for Agricultural Research (INRA-France) and the University of Lorraine (France), in addition to the Joint Genome Institute (JGI, USA), the 2Blades Foundation, Bayer, Keygene, the Sainsbury Laboratory (United Kingdom), Syngenta and the Federal University of Viçosa (Brazil).