Tolerance to sality and its Inheritance in lowland rice in Uganda

Abstract

In Uganda, soil salinity contributes to one of the most serious ecological and environmental problems in most of irrigation schemes. Developing a tolerant rice genotype to salt is one of the solutions to the problem of salinity. The objectives of the study were to quantify the level of tolerance to salinity and to determine the mode of inheritance of tolerance to salinity in available rice germplasm. Twenty-four rice genotypes from International Rice Research Institute (IRRI), AfricaRice Center and national Rice Breeding Programs were evaluated at three levels of salinity (0 dS/m≈0 mM NaCl, 6 dS/m ≈ 60 mM NaCl and 12 dS/m ≈120 mM NaCl) to identify parental materials for the studies. The evaluation was done at the germination and seedling stage in the Tissue culture laboratory and screen-house respectively. Two indices were used to identify the tolerant rice varieties: (1) modified Standard Evaluation Score (SES) and (2) tolerance to salinity index (TSI). The results showed that germination percentage, shoot weight, shoot, root lengths, root weight were significant (P<0.001) affected by salinity. Shoot length, root length, root dry weight, and plant dry weight were significantly (P< 0.001) decreased with an increase in salinity levels. Among the rice varieties AR 73, ARU 1189, ARU 1190, COM 2018-56-11, COM 2018- 56-31, K85, KAF-172-18, KAF-172-19, KAF-172-151, NM-18-58-1, NM-18-58-21, NM-18-58- 33, NM-18-58-34, NM-18-58-35, NM-18-58-58, PR 101, PR 26 and WITA 9 were not significantly stressed and were therefore considered tolerant. Correlation analysis studies among the morphological traits at germination and seedling growth stages revealed that root fresh and dry weight, shoot fresh and dry weight, and root length were good indicative characteristics of a better performing genotype at the germination and seedling stage and these traits in combination could make good criteria for selection of tolerant materials to salt under saline conditions. The study of inheritance and its mode for tolerance to salinity was conducted in a screen-house where two susceptible lines (Basmati 370 and Komboka) were crossed with four high tolerant lines (NM-18-58-34, NM-18-58-58, COM 2018-56-31 and Wita 9) using Griffing‟s Method 2 to generate F1 and F2 populations. Screening of F2 progenies revealed significant variation for tolerance to salinity among genotypes. Effects of general combining ability (GCA) and specific combining ability (SCA) were significant (P<0.001), indicating additive and non-additive effects, respectively, were important in determining tolerance to salinity.