Identification of Resistant Cultivars for Sheath Blight and use of AMMI Models to Understand Genotype and Environment Interactions.

One hundred and one rice genotypes were evaluated for response to sheath blight disease under greenhouse and lowland irrigated field conditions in Guyana. The level of resistance varied from highly resistant to resistant in 14 genotypes over five experimental trials. These genotypes were also observed with low area under the disease progress curve values and slow blighting reactions against artificial inoculation of the pathogen. Genotypes GR1568-31-9-1-1-2-1 and cultivar Rustic had susceptible reactions in all experiments. Additive main effect and multiplicative interaction analysis was used to study the genotype and environment interactions. The analysis revealed that 52.98% of the total sum of square was attributed to genotype effect, 7.50% was attributable to environment effect, and 39.52% was attributable to genotype by environment interaction (G × E) effects. The G × E was almost as large as the genotype effect, thus indicating significant differences of genotypes across the testing environments. This revealed that resistance was slightly influenced by the G × E. The genotypes that showed stable resistance in all environments in this study could be used for breeding the sheath blight resistance in rice.