Abstract
ABSTRACT: The first report of wheat blast in the world was in Brazil, in 1986. Since then, a great effort has been made towards the development of wheat cultivars resistant to this disease, which is caused by the fungus Pyricularia oryzae Triticum (PoT). The objective of this research was to (i) evaluate the resistance of wheat genotypes to blast and (ii) verify the correlation between disease severity on wheat spikes and sporulation rate of PoT on spike rachises. Plants of 40 cultivars grown in pots, at the flowering stage (stage 65 on the Zadoks scale), were inoculated with a suspension of conidia of a PoT isolate representative of the main variant of the fungus reported in Brazil. Severity of blast on the spikes at 5 and 7 days after inoculation (dai) and the rate of sporulation of the fungus on the rachis (conidia per g of rachis) were evaluated. Eighty percent of the cultivars that were classified in the group with the lowest sporulation rate were also classified in the group with the highest resistance at 7 dai. However, the correlation coefficients of the analysis established between the cultivar severity at 5 and 7 dai averages and the PoT sporulation rate averages were not significant (r=0.2464 and r=0.2047, respectively). Results obtained represent the updated characterization to blast of wheat cultivars in Brazil and constitute an important exploratory framework for the evaluation of the reaction of wheat genotypes based on the sporulation rate of PoT on their tissues.
Highlights
Blast, as it is known in many different crops, is caused by the fungus Pyricularia oryzae Cavara 1892 (synonym to Magnaporthe oryzae (Catt.) B.C. Couch 2002) (Couch & Kohn, 2002; ZHANG et al, 2016)
Wheat blast is caused by a subpopulation within P. oryzae, the P. oryzae Triticum pathotype (PoT)
The most susceptible group at 7 dai was formed by the cultivars BRS Guamirim, IPR Potiporã, BRS 264, IAC 385 - Mojave, CD 108, IPR 144, BRS Reponte and IPR Panaty, with severity ranging from 12.2 to 32.7%
Summary
As it is known in many different crops, is caused by the fungus Pyricularia oryzae Cavara 1892 (synonym to Magnaporthe oryzae (Catt.) B.C. Couch 2002) (Couch & Kohn, 2002; ZHANG et al, 2016). As it is known in many different crops, is caused by the fungus Pyricularia oryzae Cavara 1892 (synonym to Magnaporthe oryzae (Catt.) B.C. Wheat blast is caused by a subpopulation within P. oryzae, the P. oryzae Triticum pathotype (PoT). Wheat blast is one of the main diseases that restricts Brazil’s interests in achieving self-sufficiency in wheat production (GOULART et al, 2007) causing damage of up to 100% in Brazilian wheat fields (MACIEL et al, 2020). Leonardo Araujo to wheat production with potential of affecting more than three million hectares of wheat fields in the continent (KOHLI et al, 2011). In February of 2016, wheat blast was first identified outside the South American continent, in Asia, with reports of serious epidemics of the disease in wheat fields of Bangladesh (CALLAWAY, 2016). Its occurrence was reported in Zambia, Africa (TEMBO et al, 2020)
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