RESUMO
Introduction: Cytoplasmic male sterility (CMS) is an important tool for hybrid heterosis utilization. However, the underlying mechanisms still need to be discovered. An adequate supply of nutrients is necessary for anther development; pollen abortion would occur if the metabolism of carbohydrates were hampered. Methods: In order to better understand the relationship between carbohydrate metabolism disorder and pollen abortion in S-CMS wheat, the submicroscopic structure of wheat anthers was observed using light microscopy and transmission electron microscopy; chloroplast proteome changes were explored by comparative proteomic analysis; sugar measuring and enzyme assays were performed; and the expression patterns of carbohydrate metabolism-related genes were studied using quantitative real-time PCR (qRT-PCR) method. Results: These results indicated that the anther and microspore in S-CMS wheat underwent serious structural damage, including premature tapetum degeneration, nutritional shortage, pollen wall defects, and pollen grain malformations. Furthermore, the number of chloroplasts in the anthers of S-CMS lines decreased significantly, causing abnormal carbohydrate metabolism, and disintegration of osmiophilic granules and thylakoids. Meanwhile, some proteins participating in the Calvin cycle and carbohydrate metabolism were abnormally expressed in the chloroplasts of the S-CMS lines, which might lead to chloroplast dysfunction. Additionally, several key enzymes and genes related to carbohydrate metabolism were significantly inhibited in S-CMS. Discussion: Based on these results, we proposed a carbohydrate metabolism pathway for anther abortion in S-type cytoplasmic male sterility, which would encourage further exploration of the pollen abortion mechanisms for CMS wheat.
RESUMO
KEY MESSAGE: Four stable QTL for adult-plant resistance (APR) to powdery mildew were identified on chromosome arms 1DL, 2BS, 2DL, and 6BL in the widely grown Chinese wheat cultivar Bainong 64. These QTL had no effect on response to stripe rust or leaf rust. Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is a devastating fungal disease. Seedlings of Chinese wheat Bainong 64 are susceptible to Bgt, but adult plants have maintained resistance since it was released in 1996. A population of 171 recombinant inbred lines (RILs) developed from cross Jingshuang 16/Bainong 64 (JS16/BN64) was used to dissect genetic components of powdery mildew resistance. A genetic map comprising 5383 polymorphic markers was constructed using the 15 K SNP chip and kompetitive allele-specific PCR (KASP) markers. Composite interval mapping identified four stable QTL with favorable alleles all from BN64 on chromosome arms 1DL, 2BS, 2DL, and 6BL in at least four environments. They accounted for 8.3%, 13.8%, 14.4%, and 9.0% of the total phenotypic variation explained (PVE) in maximum, respectively. QPmjbr.caas-1DL, situated about 22 Mb from centromere, is probably a new QTL. QPmjbr.caas-2DL located near the end of arm 2DL and explained the largest PVE. Using genetic maps populated with KASP markers, QPmjbr.caas-2BS and QPmjbr.caas-6BL were fine mapped to a 1.8 cM genetic intervals spanning 13.6 Mb (76.0-89.6 Mb) and 1.7 cM and 4.9 Mb (659.9-664.8 Mb), respectively. The four QTL independent of stripe rust and leaf rust resistance were validated for powdery mildew resistance in another RIL population related to BN64 and a cultivar panel using representative KASP markers. Since BN64 has been a leading cultivar and an important breeding parent in China, the QTL and markers reported in this study will be useful for marker-assisted selection of APR.