J Mycol Plant Pathol, 2015 190 Rice ( L.) is an important cereal crop which is grown over an area of 43.90 mha with a production, and productivity of 106.29 MT and 2416 kg/ha, respectively. In Haryana, it occupied 1.228 mha area with a production, and productivity of 39.98 MT and 3256 kg/ha, respectively during 2013-14. Out of various biotic constraints, sheath blight of rice caused by Kuhn is one of the major fungal diseases of rice in India causing up to 58% loss in yield (Chahal et al 2003). In Haryana sheath blight, considered to be a minor disease upto 2005, but it has attained the status of a major disease on all types of rice varieties including scented and non-scented inbreds, and hybrids. The disease appeared in severe form during 2010 and caused considerable losses in grain yield (Singh et al 2012). Although, lot of literature is available on various aspects of the disease, yet the information on rice genotypes showing slow blighting against sheath blight, and the extent of grain yield losses caused in commonly grown rice varieties in Haryana is lacking. None of commercially grown scented and non-scented inbreds Oryza sativa Rhizoctonia solani kharif and hybrids of rice are resistant to this disease. Keeping in view, the lack of available information on extent of losses caused by sheath blight in popular scented and non-scented rice varieties and non-availability of resistant cultivars in the state, it was planned to estimate the yield loss caused by the disease, and to identify rice genotypes showing slow blighting against sheath blight. Thirty days old seedlings of a scented (Basmati CSR 30) and a non- scented (HKR 127) rice variety were transplanted in triplicate set in 1.5 x 1.0 m plots at a spacing of 20 x 15 cm in a randomized block design. The plants were inoculated artificially at 45, 60 and 75 days after transplanting representing maximum tillering, stem elongation and booting stages, respectively along with uninoculated plots as check. The disease severity was recorded at dough stage on 20 randomly selected plants from each plot following Anonymous (2002) formula. The grain yield loss due to sheath blight was calculated by comparing the grain yield and yield parameters such as number of Material and Methods a. Estimation of grain yield losses. Assessment of Losses and Identification of Slow Blighting Genotypes Against Sheath Blight of Rice Nitesh Bhukal, Ram Singh and Naresh Mehta Department of Plant Pathology, CCS Haryana Agricultural University, Hisar India -125004, ; E-mail:- nareshmehta282@gmail.com Abstract Key words: Citation Rice ( L.) is an important cereal crop which is grown over a large area especially in Asian countries. Amongst the various diseases occurring on rice, sheath blight caused by Kuhn is one of the major fungal diseases in India. The present investigations have revealed that the losses in grain yield at more or less same disease severity differed with cultivars. There was no significant reduction in grain yield of plots inoculated at 60 (stem elongation) and 75 days after transplanting (booting) when vertical disease spread ranged between 38.43 to 49.78 per cent in Basmati CSR 30, while there was 11.11and 4.04 per cent reduction in grain yield with a vertical disease spread of 51.54 and 37.05 per cent in non-scented variety HKR 127. Out of fifty scented and non-scented rice genotypes evaluated, five genotypes viz. N-22 (Acc. 6264), N-22 (Acc. 4819), HKR 05-476, Tetep and N-22 (Acc. 19379) exhibited slow blighting against sheath blight as the disease progress was significantly reduced. The apparent infection rate and area under disease progress curve was considerably lower in these genotypes. Moreover, in most of these genotypes, the incubation period was delayed and there was no sclerotia formation till maturity of the plants. Comparison of scented and non-scented rice genotypes with respect to sheath blight development showed that the vertical disease spread was more in non-scented high yielding rice genotypes/cultivars with high tillering ability than the tall scented cultivars with fewer tillers. It might be attributed to production of closed canopy and a favourable microclimate for disease development much earlier in short statured cultivars than the tall ones. The apparent infection rate (r) and AUDPC were also found to be considerably higher in non-scented genotypes vis-à-vis scented genotypes. Based on these observations, it could be inferred that slow blighting trait against sheath blight is more common among scented rice genotypes then non-scented ones. Rice, sheath blight , slow blighting, yield loss : Bhukal Nitesh, Singh Ram and Mehta Naresh. 2015. Assessment of losses and identification of slow blighting genotypes against sheath blight of rice. . 45 (3): 000-000 Oryza sativa Rhizoctonia solani , Rhizoctonia solani J Mycol Pl Pathol Research Article