Association analysis of F2 generation in rice (Oryza sativa L.) under salinity condition

Abstract

Rice occupies a pivotal place in the Indian agriculture and has been grown under diverse ecological conditionsand gets exposed to different environmental stresses like drought, salinity and submergence.  Development ofrice varieties for salinity affected areas is emphasized on the improvement of rice yield potential in a specificenvironment. Information related to the relationship between yield and its components in the breeding programmparticularly for salinity is very limited. Hence, the present investigation was carried out to study the correlationand path analysis in F2 generation derived from two crosses namely ADT 43 x FL478 (Cross 1) and ImprovedWhite Ponni x FL478 (Cross 2) were evaluated at a farmer’s field at Vedapatti village, Tuticorin district of TamilNadu which is a saline track. Another rice variety FL478 (IR 66946-3R-178-1-1, derived from crossing betweenPokkali and IR 29), has been promoted as an improved donor for breeding programs, as it has a high level ofseedling stage salinity tolerance and is photoperiod insensitive, shorter and ûowers earlier than the originalPokkali. FL478 also maintains a lower Na+/K+ ratio than both the parent lines (Gregorio et al. 2002). Based on itsability to tiller well and maintain high potassium content under salinity stress, FL478 appears to be a good candidatefor salinity stress tolerance in rice, particularly at the vegetative stage of growth. In Vedapatti village of Tuticorindistrict, due to over-pumping of groundwater in the past several years, normal irrigation water has become salinewater. Moreover, this village is considered as a hot spot area for the saline condition. Hence, the six generationsdeveloped through hybridization techniques were evaluated for salinity tolerance at Vedapatti village. The soiland water samples were collected from the field to analyze the EC and pH. The soil salinity and water quality inthe experimental plot were 4.82 ECdSm-1 and 8.09 (pH) for soil and 4.78 ECdSm-1 and 8.19 (pH)  for waterrespectively. From the present findings, it is clear that the characters viz., number of tillers per plant, number ofproductive tillers per plant, number of filled grains per panicle, total number of grains per panicle and spikelefertility have to be given prime importance during selection since they expressed significant and positive correlationwith single plant yield and also a positive inter-correlation among themselves. Therefore, selection for anyone  ofthe above characters would bring in the simultaneous improvement of other traits and also finally resort to improvethe grain yield under salinity condition. Path analysis also revealed that selection for the number of productivetillers per plant and the number of filled grains per panicle are to be given prior importance during selection sincethey had a positive correlation and high direct and indirect effect on grain yield under salinity condition in rice.