Combining Ability Studies in Rice ( Oryza sativa L.) Under Salinized Soil Conditions
An experiment involving 8 x 8 diallel crossing was conducted with rice to investigate the nature of gene action in governing the various traits studied and to explore the combining ability behavior of various genotypes used in the studies. Twelve agro-physiological characters were included in the study in F1 generation. High additive effects were recorded for plant height, panicle length, productive tillers/plant and primary branches/panicle. The non-additive effects were more pronounced for panicle fertility, days to maturity, shoot dry weight, paddy yield; Na, Ca and K contents of the shoot and K/Na ratio of the shoot. Out of the height parental lines/varieties studied Jhona-349 and Bas-385, respectively, proved to be the best general and specific combiners in the experiment under salinized soil conditions
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ABSTRACT: Pakistan is well known for its basmati rice with long grain and aroma, as well as for non-basmati indica varieties; however average yield is lower as compared with other countries. Besides, cultural practices, the main reason for low productivity in Pakistan is that, local varieties are susceptible to different biotic and abiotic factors like insect pests, diseases, drought, and salinity. Different approaches have been undertaken in Pakistan to tackle these problems through traditional breeding of selection and crossing, mutation breeding, somaclonal variation as well as plant transformation studies in recent past. For variety development, the most successful examples arose from traditional breeding that produced famous basmati varieties like Basmati 370, Basmati 385 and Super basmati, and non-basmati varieties such as IRRI-6, DR-82, DR-83, DR-92, Swat-I and Swat-II, which earn a significant share of foreign exchange every year. Six varieties have also been developed through mutation breeding, and one through exploitation of somaclonal variation but their contribution to the national economy is not significant. On the other hand, no variety has been registered as commercial by plant transformation groups. This review discusses the problems and prospects of rice breeding with special emphasis on basmati rice in Pakistan particularly in Pakistani Punjab (a major producing area), as well as focuses on future research programs.
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ABSTRACT: Salinity is a major abiotic stress that limits rice production across rice areas as high-yielding modern rice varieties are generally sensitive to salt stress. The study was conducted to deduce heritability and combining ability estimates of rice for various morphological and physiological traits using a 7 × 7 full-diallel-cross analysis at seedling and reproductive stages. The salinity stress treatment was 12 dS m−1 at the seedling stage and 8 dS m−1 at the reproductive stage. Diallel analysis revealed high for salinity tolerance scores and shoot height, moderate for shoot dry weight and root dry weight and low for Na+ and K+ concentrations and K+/Na+ ratio. The low-to-moderate narrow-sense heritability for number of panicles, number of fertile spikelets, grain weight, spikelet fertility and K+/Na+ ratio suggests a large breeding population and delayed selection for tolerance until later generations. Significant maternal effects indicate that selection of the female parent is very important for desired trait development. The results of this study confirmed that salinity tolerance at the seedling and reproductive stages is regulated by a different set of genes that could be pyramided using different donors to enhance the level of tolerance.