Artificial selection of the Green Revolution gene Semidwarf1 is implicated in upland rice breeding

Semidwarf breeding has boosted crop production andis a well-known outcome from the first Green Revolution. The Green Revolution gene Semidwarf 1 (SD1),which modulates gibberellic acid (GA) biosynthesis, plays a principal role indetermining rice plant height. Mutationsin SD1 reduce rice plant height and promote lodging resistance andfertilizer tolerance to increase grain production. The plant height mediated by SD1 alsofavors grain yield under certain conditions. However, it is not yet known whether thefunction of SD1 in upland rice promotes adaptation and grainproduction. In this study, the plantheight and grain yield of irrigated and upland rice were comparatively analyzedunder paddy and dryland conditions. Inresponse to dryland environments, rice requires a reduction in plant height tocope with water deficits. Upland riceaccessions had greater plant heights than their irrigated counterparts underboth paddy and dryland conditions, and appropriately reducing plant heightcould improve adaptability to dryland environments and maintain high grainyield formation. Moreover, upland ricecultivars with thicker stem diameters had stronger lodging resistance, whichaddresses the lodging problem. Knockoutof SD1 in the upland rice cultivar IRAT104 reduced the plant height andgrain yield, demonstrating that the adjustment of plant height mediated by SD1 could increase grain production in dryland fields. In addition, an SD1 genetic diversityanalysis verified that haplotype variation causes phenotypic variation in plantheight. During the breeding history ofrice, SD1 allelic mutations were selected from landraces to improve thegrain yield of irrigated rice cultivars, and this selection was accompanied bya reduction in plant height. Thus, fiveknown mutant alleles were analyzed to verify that functional SD1 isrequired for upland rice production. Allthese results suggest that SD1 might have undergone artificial positiveselection in upland rice, which provides further insights concerning greaterplant height in upland rice breeding.