Effect of reduced plant height on drought tolerance in rice

Abstract

Drought stress due to water deficit is a major problem of rice cultivation as a most drought-sensitive crop plant. A rice mutant line (MT58) was developed after mutagenesis of cv. Neda by ethyl methane sulfonate (EMS) and selected for dwarfism (18 cm shorter than Neda). The extent of its molecular changes relative to parental cultivar was assessed by SSR and ISSR markers, and the response of the line along with parental cultivar and another mutant line (MTA) to mild and severe water deficit, was evaluated in a field experiment. A molecular assessment using 41 SSR markers showed that dwarf line MT58 had significant molecular difference with two other lines. ISSR assay also proved the considerable mutational effect of EMS on two mutant lines compared with the original wild line. Field experiments revealed that limited irrigation caused mild-to-severe decrease in all the studied traits, including chlorophyll contents. In mild water-stress mutant line, MT58 showed a low (3 %) yield loss as compared with cultivar Neda with a high (14 %) yield loss. Interestingly, in severe water-stress mutant line, MT58 showed a low (19 %) yield loss as compared with mutant line MTA and cv. Neda with high (33 and 31 %, respectively) yield loss. In severe stress, mutant MT58 had the highest values of panicle length, total kernels per panicle, fertile kernels, and chlorophyll contents, while cv. Neda had the highest values of plant height, tiller number, and plant yield, and reduction in chlorophyll content at drought stress condition was correlated with yield loss (0.64 and 0.697 for chl.a and chl.b, respectively). The results of this research obviously confirm that mutant line MT58 despite of its stunt figure shows a low yield loss due to drought stress and hence is a promising line for cultivation under drought condition.

Keywords: Drought; Dwarf; Morpho-physiological; Mutation; Rice; Yield loss.

Fig. 1

Dendrograms of the studied genotypes using the UPGMA method based on SSR (top) or ISSR (bottom) markers

Fig. 2

Response of studied genotypes to water deficit. Left plant height, right plant yield, S ₀ normal irrigation, S ₁ 1 day irrigation followed by 1 day no irrigation, S ₂ 1 day irrigation followed by 2 days no irrigation. Columns with common letters have not significant differences at 5 % level of probability

Fig. 3

Yield loss due to water deficit of studied genotypes at two water deficit levels relative to normal irrigation condition. S ₁ 1 day irrigation followed by 1 day no irrigation, S ₂ 1 day irrigation followed by 2 days no irrigation

Fig. 4

Reaction of the studied genotypes to water deficit in chlorophyll contents at T2 stage of panicle emergence