This book is about the research work on "Relationships of yield and yield related characteristics with maturity duration in near isogenic rice lines", related to the genetic improvement of plants. Development of rice (Oryza sativa) varieties with short maturity duration is important in rice improvement programs. The objective of this study was to ascertain the genetic variability of yield and yield related characteristics and their relationships with maturity duration using near isogenic lines in comparison to cultivated varieties in rice. The ideal study to highlight the influence of maturity duration on grain yield would be to compare grain yield of near isogenic lines with different maturity durations in the same genetic background. Attention must be paid to increase above ground biomass and root clump length as much as possible in short duration varieties. However, there is a possibility of developing 90 day varieties without sacrificing much grain yield if efforts are made.