Identification and quantification of slow blasting resistance in basmati/aromatic rice germplasm against neck blast (Pyricularia oryzae Cavara)

Abstract

A total of 44 basmati/aromatic germplasm lines were evaluated and quantified for slow blasting type of resistance to neck blast disease (Pyricularia oryzae) under both artificial and natural epiphytotic conditions. Among the test genotypes evaluated, significant differences were obtained with respect to Area Under Disease Progress Curve (AUDPC), lesion length (mm), susceptibility index (Sx) value and apparent rate of infection (r). Sx values differed significantly among test genotypes ranging from 2.83 to 12.83. Four genotypes i.e. Tetep, INGR 15001, INGR 15002 and Pusa Basmati 1637 were found to be moderately resistant to neck blast with Sx value less than 3, AUDPC value between 70-140, lesion length between 2-5mm and apparent infection rate (r) ranging between 0.31 to 0.34 indicating slow blasting tendencies as compared to Susceptible check (Pusa Basmati 1401) exhibiting AUDPC value of 349.8, lesion length (16.22mm) and apparent infection rate (r) of 0.44. Improved Pusa Basmati also showed slow blasting with r value of 0.41 but exhibited susceptible reaction to the disease with AUDPC value of 249.6 and LL (11.52 mm) respectively. However, three genotypes were found to be moderately susceptible, 18 were susceptible and 19 as highly susceptible to the disease with susceptibility index lying in the range of 3.1-6, 6.1-8 and greater than 8 respectively. Only one entry RYT 3672 showed moderately susceptible reaction to the disease having Sx value of 5.98, AUDPC value of 169.8 and lesion length of 8.34mm. Correlation analysis greatly illustrates the screening experiment as AUDPC was positively correlated with lesion length (mm) and disease incidence (%) while it was negatively correlated with incubation period (IP 50). None of the test entry showed complete resistance to the disease. The newly identified sources exhibiting slow blasting resistance despite moderate disease level with lowest apparent rate of infection can be used as donors for strengthening neck blast breeding programme in basmati rice.