False smut of rice is an emerging disease and caused severe damage to hybrids and inbred rice cultivars grown in Asian countries. The objective of the study was to quantify of false smut resistance and identification of donors in some of the advanced breeding lines and rice varieties developed at Punjab Agricultural University, Ludhiana, India. A total of 31 genotypes were evaluated for three years in two planting date per year under field conditions. The lines were categorized into short, medium and long durations based on days to flowering. False smut was quantified using different disease variables such as per cent infected panicle, number of false smut ball per plant and disease score. Disease variables were significantly and positively correlated to each other. The infected panicle ranged 0.0–75.4% was observed among the genotypes. Three advanced lines namely RGS-2 (short), RGM-3 (medium) and RGL-3 (long) showed the lowest ranged 0.0–4.9% of infected panicle as compared to susceptible checks (47.7–75.4%). The genotypes were divided into five groups according to a component of resistance. The third group had the lowest average values (3.3%) of infected panicle as compared to the fifth group with the highest values (36.2%) of the infected panicle. The overall trend of disease variables was higher in short duration genotypes as compared to medium and long durations. Weather factors such as rain fall, rainy days and high relative humidity during the flowering period were favourable for disease development. The genotypes with lower disease variables could be utilized in diseases resistance breeding programme.

Sheath blight caused by soil borne necrotrophic fungus Rhizoctonia solani [teleomorph-Thanatephorus cucumeris (Frank) Donk.] is a major disease of rice. The disease is increasing over the year in India and cause up to 69% yield loss under favourable conditions. A total of 67 accessions of Oryza nivara were screened to identify resistance against sheath blight during 2015. Out of these, 16 accessions were found moderately resistant (MR) which were further evaluated during the year 2016 and 2017. After three years of screening, 12 of them were found to have a consistent moderate resistant reaction whereas four of the O. nivara accessions namely, IRGC81941, IRGC102463C, CR100097 and CR100110A have shown moderately susceptible to susceptible reaction against sheath blight. A correlation study revealed that different disease variables measured were significantly (P < 0.05) correlated. All the genotypes and genotype × environment interaction had a significant (P < 0.001) effect on all the disease variables. Cluster analysis showed that all the accessions were clustered into four groups which showed resistant, MR, moderately susceptible and susceptible reactions. Among all the O. nivara accessions IRGC81941A showed the maximum potential against sheath blight due to a least relative lesion height of 22.80%. None of the accession had complete resistance to the disease. The identified promising accessions such as IRGC81835, IRGC81941A, CR100008 and CR100111B can be utilized in a sheath blight resistance breeding program.