Abstract
The experiment was aimed at assessing the response of 30 rice genotypes to different levels of salinity using NaCl concentration as salt stress at early seedling stage under hydroponic conditions. The experiment was replicated three times in a Completely Randomized Design for two years. The 30 rice genotypes evaluated for root length, fresh root weight, dry root weight, shoot length, fresh shoot weight, dry shoot weight, seedling biomass and shoot/root length ratio. The four salinity treatments/levels (0, 4, 6 and 12 dS/m) significantly affected the response of the 30 rice genotypes for all the traits evaluated. The interaction between salinity treatments and the genotypes was significant for all traits except fresh root weight, shoot length and dry shoot weight. The genotypic response revealed reduction in performance as the salinity level increases for all the traits, 10 genotypes were tolerant at all salinity levels. The most affected seedling trait due to salinity stress was seedling biomass at 6 dS/m (54.84%) and was expressed by genotype IR29 (susceptible check), followed by ROK 24 at 12 dS/m (54.43%). Eight rice genotypes; CK73, ITA212 (FARO 35), ITA222 (FARO 36), OG0315, OG250315, OW0315, TOG 5681 and Pokkali (Tolerant Check) were classified highly tolerant by both Stress Tolerance Index (SST) and Stress Susceptible Index (SSI), while FARO 61 (NERICA L – 34) and IR72 were moderately tolerant. These rice genotypes have good potentials for further salt tolerance breeding. Keywords: salt stress, genotypes, seedling traits, tolerance index, susceptible index
Highlights
Salt-affected soils are distributed throughout the world and every continent is faced with this problem (Brandy and Weil, 2002; Dubey and Singh, 1999)
The salinity levels as treatment was highly significantly different as obtained in all traits measured. This result showed that the rice genotypes reacted differently to the level of salinity stress imposed
Similar report was documented by Azaizeh et al (1992), Rodriguez et al (2002) and Momayezi et al (2009) that root length reduction was due to the effect of high concentration of salt. 16, 14 and 19 rice genotypes had higher fresh root weight than their genotypic average at 4 dS/m, 6 dS/m and 12 dS/m respectively
Summary
Salt-affected soils are distributed throughout the world and every continent is faced with this problem (Brandy and Weil, 2002; Dubey and Singh, 1999). Salinity is the second most widespread soil problem in rice growing countries after drought and is considered as a serious constraint to increasing rice production worldwide (Gregorio, 1997). Several rice-growing countries, both in the tropics and the temperate regions, are facing high soil salinity as a major problem which is more severe in the arid, semiarid, and coastal rice-producing areas of the tropics (Lee et al, 2003). The use of hydroponic evaluation of rice has been identified to be free of soil-related difficulties. This method can reliably assess the response of genotypes to salt stress and, identify salt-tolerant genotypes (Ashraf et al, 1999; Bhowmik et al, 2009).
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