Improvement of resistance against rice bacterial blight (BB) disease is an important breeding strategy in breeding programs across the world, especially in Africa and southern Asia where BB is more prevalent. This report describes a high-resolution map and characterization of xa42 at XA42 locus, a rice BB resistance gene in XM14, a mutant line originating from IR24. The candidate gene region was narrowed down from 582 kb, which had been obtained in our previous study, to 57 kb. XM14 shows brown spots in its leaves like lesion mimic mutants. This line also shows a shorter stature than the original cultivar IR24. In XA42 gene segregating populations, homozygotes of xa42 allele were consistently resistant to the six Japanese Xanthomonas oryzae pv. oryzae races used for this study. They also showed brown spots and markedly short stature compared with the other genotypes, suggesting that xa42 gene exhibits pleiotropic effects.

Drought is the main constraint for crop growth worldwide. Selenium reportedly plays an important role in improving plant tolerance to drought stress. In this study, two experiments were conducted to investigate the effects of foliar selenium application on the drought tolerance of sesame. Five selenium concentrations (0, 5, 10, 20, and 40 mg/L) were used in the first experiment. Water deficit was triggered 25 days after sowing. The application of 5 or 10 mg/L of selenium maintained the number of leaves and increased the number of capsules. However, higher concentrations induced necrosis. The second experiment aimed to study the effect of selenium concentrations (5 and 10 mg/L) and the number of applications (one to three times). Drought stress was triggered 50 days after sowing, and selenium was sprayed 50, 55, and 60 days after sowing. The results indicated that a one-time foliar selenium application of 5 mg/L was able to maintain the number of leaves and to increase proline accumulation, plant biomass, and grain weight per plant. This finding confirms that selenium can be applied to enhance sesame’s tolerance to drought stress.