Fenotipagem de caracteres associados à resistência à brusone no trigo (Triticum aestivum L.) brasileiro

Abstract

Wheat blast, caused by the fungus Pyricularia oryzae pathotype triticum, has been considered one of the main threats to wheat production worldwide, due to its potential to cause severe damages to the crop. Genetic resistance is the most efficient method for plant disease control, in addition to its economic and environmental advantages. However, obtaining genetic resistance is still a considerable challenge for breeders and plant pathologists, due to the wide genetic variability of P. oryzae and the complexity of the inheritance of the trait. Crop breeding has available several techniques for the development of resistant cultivars and, along with the current advances in genomic science, has received even more attention. Among these, the ones based on molecular biology, such as genetic mapping, using molecular markers, has shown a high potential to achieve this aim. More specifically, the association mapping or linkage disequilibrium mapping, also known as genome-wide association studies (GWAS), is considered an important approach and represents a powerful alternative in the search of new blast resistance genes, as the method comprise the whole crop genome, allowing for the identification of trait-marker associations. A crucial step of any association mapping study is the phenotyping. In view of the above, the present study aimed to present and discuss the main aspects related to wheat blast resistance as well as to phenotype a panel of 195 Brazilian wheat accessions, assaying the main agronomic traits and blast severity, and their association. The experiment was carried out in 2019 and 2020, in greenhouse, belonging to Plant Genomics and Breeding Center, located at Capão do Leão Campus, Universidade Federal de Pelotas, Capão do Leão –RS. The panel of accessions was assayed for the following traits: blast severity at leaves at 10 (SF10), 15 (SF15), 20 (SF20), 25 (SF25) and 30 (SF30) days; blast severity at spikes at 15 (SE15), 20 (SE20) and 25 (SE25) days; plant height (Est); number of fertile tillers (NAF); spike length (CE); spike weight (PE); number of spikelets per spike (NE); number of grains per spike (NGE) and grain mass per spike (MG). Univariate, frequency distribution and Pearson correlation analyses were applied. The analyses allowed one to identify different phenotypic classes in which the population was grouped regarding the traits assayed. There is genetic variability in the studied population for the assayed traits. This variability endorses the use of the panel in the association mapping study. There are different levels of association between the traits, however, the correlation between agronomic traits and blast resistance is only null to weak, which limits its use in indirect or multitrait selection methods. The results obtained through this study will contribute both for the development of improved wheat cultivars but also as a mapping population for QTLs and genes of blast resistance.