In Africa, cold temperatures occur in the highlands of East and Southern Africa and in some areas of the Sahel region of West Africa leading to substantial rice yield losses. Cold tolerance (CT) at booting stage on basis of spikelet fertility after cold water irrigation was evaluated using F 2 population derived from a cross between temperate japonica, Hananomai, and tropical japonica, WAB56-104. Two Quantitative trait loci (QTLs) for CT were detected on chromosome 8 and 10 with enhanced effects on the trait coming from Hananomai and WAB56-104 allele, respectively. The QTLs explained 30% and 33% of phenotypic variation in spikelet fertility, respectively. CT was negatively correlated with panicle number (r = −0.35, p < 0.01) and positively correlated with panicle weight (r = 0.61, p < 0.001). Selected BC 1 F 4 and BC 1 F 5 genotypes having homozygous alleles for both CT QTLs exhibited higher spikelet fertility under cold stress. The identified QTLs will be useful in the development of cold-tolerant varieties for production in high altitude areas through marker-assisted selection.

To elucidate the resistance mechanisms of the rice ( Oryza sativa L.) cultivar ‘Milyang 44’ against rice stink bugs, we compared the number of stylet sheaths, husk perforations, and feeding marks on the surface of the grains caused by Leptocorisa chinensis and Cletus punctiger on Milyang 44 and the control cultivar, i.e., ‘Aichinokaori SBL’. We also examined the cross-sectional structure of the rice husks. We found that the number of stylet sheaths per panicle was higher in Milyang 44 than in Aichinokaori SBL for both rice stink bug species, except in one test involving C. punctiger . However, Milyang 44 had significantly less damage per number of stylet sheaths than Aichinokaori SBL, resulting in a lower percentage rates of pecky rice grains in Milyang 44. Interestingly, there was no difference in the percentage rates of pecky rice between the two cultivars after removing one third of the husks. Histological analysis showed that the sclerenchymatous cell wall containing lignin of husk was thicker in Milyang 44 than in Aichinokaori SBL, suggesting that the husk of Milyang 44 plays an important role in its resistance to these two rice stink bug species.

Seven near isogenic lines (NILs) for six partial blast-resistance genes— Pi35, pi21, Pi37(t)( Pi37-KRIL17), Pb1, and Pi34 (two: Pi34-Chubu32 and Pi34-Chugoku40, originating from different Japonica Group rice lines, ‘Chubu 32’ and ‘Chugoku 40’, respectively)—and one quantitative trait locus (QTL), PiPHL9, derived from Japonica Group line ‘Hokkai PL9’, were developed in rice ( Oryza sativa L.). These NILs have the genetic background of an Indica Group susceptible line ‘US-2’, which does not harbor complete resistance genes and can clarify the effects of partial resistance genes and the QTL. These NILs and US-2 were used to determine the effects of the partial resistance genes and the QTL based on the results of an inoculation test for leaf blast using international standard differential blast isolates in the young seedling stage and a natural infection test in the mature stage after heading at a blast field. The NILs produced mainly moderate reactions in the inoculation test and rarely exhibited “resistant” and “susceptible” reactions. Each of the partial resistance genes and the QTL had different effects in panicle blast. Two genes, Pi35 and Pb1, were the most effective with respect to resistance, followed by Pi37-KRIL17. Pi34-Chugoku40 was the weakest. The effects of pi21, Pi34-Chubu32, and PiPHL9 varied among cultivation seasons and could be easily affected by environmental conditions. This is the first report clarifying the effects of partial resistance genes without the major complete genes, which will be helpful for advanced genetic and pathological studies and as a source of genes for rice breeding. [Formula: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .