Artificial selection of the Green Revolution gene Semidwarf 1 is implicated in upland rice breeding

Semidwarf breeding has boosted crop production and is 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 in determining rice plant height. Mutations in SD1 reduce rice plant height and promote lodging resistance and fertilizer tolerance to increase grain production. The plant height mediated by SD1 also favors grain yield under certain conditions. However, it is not yet known whether the function of SD1 in upland rice promotes adaptation and grain production. In this study, the plant height and grain yield of irrigated and upland rice were comparatively analyzed under paddy and dryland conditions. In response to dryland environments, rice requires a reduction in plant height to cope with water deficits. Upland rice accessions had greater plant heights than their irrigated counterparts under both paddy and dryland conditions, and appropriately reducing plant height could improve adaptability to dryland environments and maintain high grain yield formation. Moreover, upland rice cultivars with thicker stem diameters had stronger lodging resistance, which addresses the lodging problem. Knockout of SD1 in the upland rice cultivar IRAT104 reduced the plant height and grain yield, demonstrating that the adjustment of plant height mediated by SD1 could increase grain production in dryland fields. In addition, an SD1 genetic diversity analysis verified that haplotype variation causes phenotypic variation in plant height. During the breeding history of rice, SD1 allelic mutations were selected from landraces to improve the grain yield of irrigated rice cultivars, and this selection was accompanied by a reduction in plant height. Thus, five known mutant alleles were analyzed to verify that functional SD1 is required for upland rice production. All these results suggest that SD1 might have undergone artificial positive selection in upland rice, which provides further insights concerning greater plant height in upland rice breeding.

Genetic characterization and linkage disequilibrium mapping of resistance to gray leaf spot in maize(Zea mays L.)

Gray leaf spot(GLS),caused by Cercospora zeae-maydis,is an important foliar disease of maize(Zea mays L.)worldwide,resistance to which is controlled by multiple quantitative trait loci(QTL).To gain insights into the genetic architecture underlying the resistance to this disease,an association mapping population consisting of 161 inbred lines was evaluated for resistance to GLS in a plant pathology nursery at Shenyang in 2010 and 2011.Subsequently,a genome-wide association study,using 41,101 single-nucleotide polymorphisms(SNPs),identified 51 SNPs significantly(P<0.001)associated with GLS resistance,which could be converted into 31 QTL.In addition,three candidate genes related to plant defense were identified,including nucleotidebinding-site/leucine-rich repeat,receptor-like kinase genes similar to those involved in basal defense.Two genic SNPs,PZE-103142893 and PZE-109119001,associated with GLS resistance in chromosome bins 3.07 and 9.07,can be used for marker-assisted selection(MAS)of GLS resistance.These results provide an important resource for developing molecular markers closely linked with the target trait,enhancing breeding efficiency.

Integrated metabolome and transcriptome analysis revealed carotenoid metabolism difference in pepper(Capsicum annuum L.)yellowing mutants under different light quality

Light is an important environmental factor for plant growth and development,different light qualities have different regulatory effects on plants.To investigate the effect of light quality on plants,we determined the physiological characteristics,transcriptome and metabolome analysis of pepper yellowing mutants yl1 treated with blue,red,green,and purple light.Results showed that the leaf of yl1 was obviously yellowing,and the contents of chlorophyll,carotenoid and net photosynthetic rate in yl1 were significantly decreased under purple light.A total of 31,853 genes were quantified under blue,red,green and purple light.The genes related to carotenoid metabolism pathway such as PSY,LUT5 and VDE were significantly increased,while the expression levels of chlorophyll synthesis related genes POR and CAO were significantly decreased under purple light.At the same time,21 carotenoid pathway metabolites were detected under the four light different lights,and 10 metabolites were more abundant in pepper leaves.α-carotene,β-carotene,lutein,neoxanthin,α-cryptoxanthin andβ-cryptoxanthin were significantly accumulated under blue,red and green light.However,zeaxanthin and antheraxanthin were accumulated in large quantities under purple light.After silencing the CaVDE gene under purple light,leaf etiolation degree was significantly weakened,chlorophyll,carotenoids and net photosynthetic rate were significantly increased,and the accumulation of zeaxanthin and antheraxanthin was significantly decreased.These results provide a reference for analyzing the changes of carotenoid components induced by VDE in purple light and provide new insights into the mechanism of leaf color change in plants.