The sink strength of developing ovaries in wheat determines the grain weight potential.  The period from booting to the grain setting stage is critical for ovary growth and development and potential sink capacity determination.  However, the underlying regulatory mechanism during this period by which the wheat plant balances and coordinates the floret number and ovary/grain weight under water stress has not been clarified.  Therefore, we designed two irrigation treatments of W0 (no seasonal irrigation) and W1 (additional 75 mm of irrigation at the jointing stage) and analyzed the responses of the ovary/grain weight to water stress at the phenotypic, metabolomic, and transcriptomic levels.  The results showed that the W0 irrigation treatment reduced the soil water content, plant height, and green area of the flag leaf, thus reducing grain number, especially for the inferior grains.  However, it improved the grain weight of the superior and inferior grains as well as average grain weight at maturity, while the average ovary/grain weight and volume during –3 to 10 days after anthesis (DAA) also increased.  Transcriptomic analysis indicated that the genes involved in both sucrose metabolism and phytohormone signal transduction were prominently accelerated by the W0 treatment, accompanied by greater enzymatic activities of soluble acid invertase (SAI) and sucrose synthase (Sus) and elevated abscisic acid (ABA) and indole-3-acetic acid (IAA) levels.  Thus, the sucrose content decreased, while the glucose and fructose contents increased.  In addition, several TaTPP genes (especially TaTPP-6) were down-regulated and the IAA biosynthesis genes TaTAR1 and TaTAR2 were up-regulated under the W0 treatment before anthesis, which further increased the IAA level.  Collectively, water stress reduced the growth of vegetative organs and eliminated most of the inferior grains, but increased the ABA and IAA levels of the surviving ovaries/grains, promoting the enzymatic activity of Sus and degrading sucrose into glucose and fructose.  As a result, the strong sucrose utilization ability, the enhanced enzymatic activity of SAI and the ABA- and IAA-mediated signaling jointly increased the weight and volume of the surviving ovaries/grains, and ultimately achieved the trade-off between ovary/grain weight and number in wheat under water stress.

Cotton breeding for the development of early-maturing varieties is an effective way to improve multiple cropping indexes and alleviate the conflict between grains and cotton in the cultivated fields in China.  In the present study, we aimed to identify upland cotton quantitative trait loci (QTLs) and candidate genes related to early-maturity traits, including whole growth period (WGP), flowering timing (FT), node of the first fruiting branch (NFFB), height of the node of the first fruiting branch (HNFFB), and plant height (PH).  An early-maturing variety, CCRI50, and a late-maturing variety, Guoxinmian 11, were crossed to obtain biparental populations.  These populations were used to map QTLs for the early-maturity traits for two years (2020 and 2021).  With BSA-seq analysis based on the data of population 2020, the candidate regions related to early maturity were found to be located on chromosome D03.  We then developed 22 polymorphic insertions or deletions (InDel) markers to further narrow down the candidate regions, resulting in the detection of five and four QTLs in the 2020 and 2021 populations, respectively.  According to the results of QTL mapping, two candidate regions (InDel_G286-InDel_G144 and InDel_G24-InDel_G43) were detected.  In these regions, three genes (GH_D03G0451, GH_D03G0649, and GH_D03G1180) have non-synonymous mutations in their exons and one gene (GH_D03G0450) has SNP variations in the upstream sequence between CCRI50 and Guoxinmian 11.  These four genes also showed dominant expression in the floral organs.  The expression levels of GH_D03G0451, GH_D03G0649 and GH_D03G1180 were significantly higher in CCRI50 than in Guoxinmian 11 during the bud differentiation stages, while GH_D03G0450 showed the opposite trend.  Further functional verification of GH_D03G0451 indicated that the GH_D03G0451-silenced plants showed a delay in the flowering time.  The results suggest that these are the candidate genes for cotton early maturity, and they may be used for breeding early-maturity cotton varieties.