Abstract:
Rice blast (Magnaporthe oryzae) is one of the most devastating rice diseases which
can lead a complete failure of the crop under severe infection. Development of
durable blast resistant variety is the best option to control the disease. A better option
for such attempt is the use of native blast resistant germplasm. Therefore, experiment
was conducted to explore the phenotypic reaction of native rice germplasm for
selection of resistant source. Further, identification of major blast resistance gene(s)
exist in these germplasm were detected using molecular markers and analyze the
population structure on the basis of blast resistance genes. Forty-four native
germplasm, collected from Bangladesh Rice Research Institute (BRRI) Genebank,
were tested for phenotypic reaction in uniform blast nursery (UBN) of BRRI against
blast disease during T. Aman 2018 and Boro 2018-19 season. Molecular screening
was performed at the molecular laboratory of Plant Pathology Division, BRRI.
Among the tested genotypes, Acc. 3080 having Pita-2 gene was resistant (disease
score 1). While nine accessions viz. Acc. 3058, Acc. 3060, Acc. 3068, Acc. 3071,
Acc. 3073, Acc. 3975, Acc. 3076, Acc. 3083 and Acc.3085 were found moderately
resistant (disease score 2-3). Accessions 3058 and 3075 having 6 genes (Pit, Pib,
Pi9, Pi40, Pita-2 and Pita/Pita-2) with disease score 2. Germplasm possessing blast
resistance genes varied from 0 to 6 and gene frequency of resistance genes ranged
from 2.27% to 59.09% among the tested germplasm. PIC values of eight markers
varied from 0.04 to 0.37 at an average 0.29. Out of eight markers one marker Pita3
was found to be significantly associated (p=0.003, R
2
=0.19) with blast disease.
Population structure analysis based on genotypic and phenotypic against blast
disease divided the germplasm into two distinct subgroups. Acc. 3076 having Pit,
Pi40 and Pita/Pita-2 genes with disease score 2 was detected in a separate group
from other moderately resistant germplasm in cluster analysis. Therefore, Acc 3058,
Acc 3075, Acc. 3076 and Acc. 3080 could be used for the development of durable
blast resistant variety.
