Rice is very sensitive to salinity stress during the reproductive stage and salinity
stress causes reduced grain yields. The salinity concentration, critical point and phenotypic
parameter of the reproductive stage were identified for screening a large fast neutron mutant
population (M4). The results showed a 150 mM NaCl treated in irrigated water at the early
booting stage (R2) had the greatest effect on flag leaf and panicle damage, and it also reduced
seed setting, especially in susceptible genotype. However, seed setting was a suitable parameter
for screening salinity tolerance in the large mutant population. Then, the 9,000 JHN mutant
lines were screened for salinity tolerance under 150 mM NaCl at early R2 - R9. The result
showed 5,397 mutant lines failed to produce seed setting and found 20 lines produced seed
setting above 60% in the preliminary screening. In repeated screening, the 20 lines (M5) were
confirmed a potential to produce seed set under salinity stress and found M1145 produced the
highest seed set. Finally, the validated screening, M1145 showed a stable tolerance under salt
stress and produced the highest seed setting at 48%, which was not significantly different from
the standard salinity tolerant (Pokkali, FL496 and FL530). In conclusion, seed setting during
salinity stress at reproductive stage was representative of salinity tolerance and can be used as a
screening parameter for salinity tolerance on a large scale. In addition, the fast neutron mutant
population showed variations in salinity tolerance levels, and M1145 was identified as a salinity
tolerant and is a potential genetic stock for use in a salinity tolerance breeding program.
Keywords
rice (Oryza sativa L), salinity stress, salinity tolerance, seed setting, screening, large mutant population
INTERNATIONAL JOURNAL OF AGRICULTURAL TECHNOLOGY
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