Plant growth-promoting rhizobacteria (PGPR) provide critical ecological value in sustainable agriculture by enhancing plant growth and stress tolerance through improved nutrient acquisition and increased environmental adaptability. As a versatile genus of PGPR, Streptomyces shows great potential for promoting plant growth. However, the molecular mechanisms by which Streptomyces regulates plant root development remain largely unclear. In this study, we explored the molecular basis associated with wheat root developmental responses to Streptomyces pactum Act12 using pot experiments combined with multi-omics approaches. The pot experiment demonstrated that Act12 treatment significantly increased wheat biomass and enhanced total root length (44.6%), root surface area (73.3%), root diameter (34.0%), and root tip number (66.6%). Integrated transcriptomic and metabolomic analyses suggested that Act12 treatment was associated with altered auxin signaling and coordinated changes in carbohydrate metabolism, the TCA cycle, and sterol biosynthesis. These multi-omics signatures provide hypotheses for how Act12 may contribute to root developmental regulation in wheat.

Background Drought critically compromises agricultural productivity and threatens sustainable wheat production. Streptomyces pactum Act12 confers benefits to plant growth under drought stress, but its possible effects on root-associated microbiomes remain understudied. Here, shotgun metagenome sequencing and culture-dependent approaches were integrated to investigate the responses of rhizosphere and rhizoplane microbiomes in dryland winter wheat to exogenous S. pactum Act12 and their potential linkage to plant drought resistance. Results Seed biopriming with S. pactum Act12 increased plant aboveground dry weight at flowering (by 63.2%) and maturation (by 41.9%) stages, leading to improved grain yield (by 8.7%). Microbial inoculation reduced malondialdehyde contents in wheat leaves and roots at the flowering stage alongside compartment-specific alterations in soil microbiomes. Metagenomic analysis revealed inoculation-induced enrichment of distinct taxa in rhizosphere soils (flowering: Fibrobacterota, Altererythrobacter; maturation: Mucoromycota, Rhodospirillum) and rhizoplane soils (flowering: Pseudomonadota, Serratia; maturation: Candidatus_Pacebacteria, Variovorax). Functional profiling showed up-regulation of key pathways related to oxidative phosphorylation in inoculated rhizosphere soils at the flowering stage. In rhizoplane soils, ABC transporters and pyrimidine metabolism were up-regulated across stages upon inoculation. Two key strains isolated from rhizoplane soils, designated Glycomyces lechevalierae A4 and Microbacterium algeriense B3, demonstrated the ability to enhance drought resistance in wheat seedlings. Conclusions Inoculation of S. pactum Act12 heightens drought resistance in dryland winter wheat through compartment-specific phylogenetic restructuring and functional reprogramming of root-associated microbiomes.

Dihydrofolate reductase-thymidylate synthase (DHFR-TS) is a bifunctional enzyme that catalyzes the conversion of dihydrofolate (DHF) into tetrahydrofolate (THF) by the DHFR domain and dUMP to dTMP as well as 5,10-methylene-THF to DHF by the TS domain. To date, the contributions of DHFR-TS to chlorophyll biosynthesis and plant growth are not well defined. In this study, we isolated a grain-filling-stage premature senescence (fps1) mutant in rice (Oryza sativa), whose causal gene encodes OsDHFR-TS1. In the fps1 mutant, a point mutation in OsDHFR-TS1 resulted in the loss of approximately two-thirds of the TS domain. Interestingly, the DHFR activity was remarkably reduced both in the fps1 mutant and in the OsDHFR-ts1 recombinant protein. Furthermore, DHFR and TS domains within OsDHFR-TS1 mutually enhanced each other's enzymatic activities through their interaction. In fps1 leaves at the mid-to-late stage of grain filling, Mg-protoporphyrin IX accumulated significantly, accompanied by sharp decreases in tetrahydrofolate and chlorophyll levels, which suggests that the methyl groups supplied by tetrahydrofolate become insufficient to maintain normal chlorophyll synthesis. Accordingly, photosensitizing protoporphyrin IX accumulated excessively, promoting the overproduction of reactive oxygen species. These two aspects collectively contributed to the premature senescence phenotype of fps1. This study provides insights into understanding the interrelationship between tetrahydrofolate synthesis, chlorophyll synthesis, and leaf senescence. Additionally, we demonstrated that OsDHFR-TS2, homologous to OsDHFR-TS1, likely plays only a minimal role in tetrahydrofolate synthesis in rice.

Water scarcity and low soil fertility represent significant limitations to productivity within the dryland farming systems of the Loess Plateau. Consequently, optimizing summer fallow management to improve soil water retention and fertility is critical for enhancing soil quality in this region. To assess the maximum efficiency of rainfall capture during the summer fallow period, elucidate its interactions with soil microbial communities, and clarify the mechanisms underlying yield enhancement, a two-year field experiment was conducted. This study evaluated several treatments applied during the summer fallow: organic fertilizer alone (OF); organic fertilizer combined with deep tillage (OD); organic fertilizer with deep tillage and furrow-ridging (ODR); organic fertilizer with deep tillage, furrow-ridging, and plastic film mulching (ODRP); and organic fertilizer with deep tillage, furrow-ridging, and biodegradable film mulching (ODRB). Compared to conventional farmer practice (FP), the optimized rainfall management (ODRP) implemented in early summer fallow increased winter wheat grain yield by an average of 26.3 %, with spike number identified as the primary yield determinant. Between 2022 and 2024, the average efficiency of summer fallow rainfall storage under the OF, OD, ODRP, and ODRB treatments exceeded that of the FP treatment by 4.5 %, 36.3 %, 48.1 %, and 27.0 %, respectively. Notably, the ODR treatment reduced rainfall storage efficiency by 25.1 % relative to OD. The application of organic fertilizer during early summer fallow enhanced soil organic carbon content in the 0-40 cm soil profile by 8.8-24.8 % in the 0-20 cm layer and by 17.8-46.7 % in the 20-40 cm layer. Improved water and nutrient availability during the summer fallow period led to a decrease in the relative abundance of oligotrophic bacteria (Acidobacteria) and an increase in copiotrophic bacteria (Firmicutes). Correlation analyses demonstrated significant positive associations among soil moisture, Firmicutes abundance, and winter wheat yield. Partial least squares path modelling, coupled with Monte Carlo uncertainty analysis, identified soil moisture as the principal factor influencing yield formation via its effect on spike number, accounting for 63 % of the yield variability. Additionally, soil moisture and microbial metabolic activity contributed to organic carbon sequestration. In summary, maximizing rainfall-harvesting efficiency during the summer fallow period in conjunction with organic fertilizer application, constitutes a crucial strategy for promoting sustainable and high-quality agricultural development in the dryland wheat systems of the Loess Plateau.

IntroductionThe unmanned aerial vehicle -based light detection and ranging (UAV-LiDAR) can quickly acquire the three-dimensional information of large areas of vegetation, and has been widely used in tree species classification.MethodsUAV-LiDAR point clouds of Populus alba, Populus simonii, Pinus sylvestris, and Pinus tabuliformis from 12 sample plots, 2,622 tree in total, were obtained in North China, training and testing sets were constructed through data pre-processing, individual tree segmentation, feature extraction, Non-uniform Grid and Farther Point Sampling (NGFPS), and then four tree species were classified efficiently by two machine learning algorithms and two deep learning algorithms.ResultsResults showed that PointMLP achieved the best accuracy for identification of the tree species (overall accuracy = 96.94%), followed by RF (overall accuracy = 95.62%), SVM (overall accuracy = 94.89%) and PointNet++(overall accuracy = 85.65%). In addition, the most suitable number of point cloud sampling of single tree is between 1,024 and 2048 when using the NGFPS method in the two deep learning models. Furthermore, feature value of elev_percentile_99th has an important influence on tree species classification and tree species with similar crown structures may lead to a higher misidentification rate.DiscussionThe study underscores the efficiency of PointMLP as a robust and streamlined solution, which offers a novel technological support for tree species classification in forestry resource management.

BACKGROUND:Drought stress is one of the major abiotic stresses that limit wheat growth and yield. Streptomyces, a class of plant growth-promoting rhizobacteria (PGPR) with multifarious metabolic potential and remarkable stress resistance properties in soil, have significant potential in enhancing the drought tolerance of crops. However, the molecular mechanisms by which Streptomyces improve the drought tolerance function of the wheat root are poorly understood. RESULTS:In this study, we investigated the role and molecular mechanisms of Streptomyces pactum Act12 in regulating the drought tolerance of wheat root by combining pot experiments and multi-omics techniques. The pot experiment results demonstrated that under drought stress, Act12 treatment significantly promoted the development of the wheat root system, including the total root length, surface area, number of root tips, and diameter. Furthermore, Act12 treatment increased the activity of antioxidant enzymes (SOD activity increased by 23.7%), the content of osmotic regulators proline (265.8%) and soluble protein (116.8%), and significantly decreased the content of malondialdehyde (39.0%). The integrated analysis of the transcriptome and metabolome demonstrated that Act12 might promote root development through the synergistic regulation of phytohormone signaling. Concurrently, it might optimize energy supply and enhance the stability of cell membranes via the regulation of metabolic pathways, including glycolysis, the tricarboxylic acid (TCA) cycle, and glycerophospholipid metabolism. CONCLUSION:Consequently, Act12 enhanced the drought adaptability of the wheat root system from multiple perspectives. This study reveals the central role of Act12 in the regulation of drought resistance in plants and provides a theoretical basis for the development of drought-resistant biologics based on Streptomyces.

The positive effects of nano-carbon on plant growth and soil C sequestration within the rhizosphere have been widely recognized. Nevertheless, information is seriously deficient in understanding the underlying mechanisms based on microbial communities and carbon cycle functional genes. Here, metagenomic sequencing was employed to explore different responses of poplar seedling growth and organic carbon fractions to nano-carbon fertilizers at concentrations of 0 ml/kg (CK), 5 ml/kg (NC-5), 10 ml/kg (NC-10) and 20 ml/kg (NC-20). We observed that, after 120 days of nano-carbon fertilizers treatments, the growth indexes (height and biomass) of poplar were significantly increased by 37.83-173.13 %, and C fractions in the rhizosphere soil were significantly increased by 1.64-8.16 % with the NC-5 treatment having a greater impact on organic carbon components than the NC-10 and NC-20 treatments. Compared to CK, the additions of nano-carbon fertilizers significantly increased the content of total nitrogen (TN), nitrate nitrogen (NN), and available potassium (AK) in the rhizosphere soil and decreased the pH, and improved stochastic processes in microbial communities, which elevates the abundance of microbes involved in carbon fixation (e.g., Proteobacteria, Actinobacteria) and carbon-cycling genes. In addition, network complexity and stability of microbes were significantly enhanced by nano-carbon treatments. Structural equation model indicated that microbial community assembly processes directly alter rhizosphere SOC accumulation. Carbon functional genes influenced by microbial structure have positive effects on biomass of poplar and SOC contents. Our observations provide key evidence for evaluating how nano-carbon fertilizers may influence functional changes in C cycle that are mediated by microbial synergy.

Brassinosteroids (BRs) are a crucial class of plant hormones and regulate many important agronomic traits in crops. In Arabidopsis (Arabidopsis thaliana), BIR3 interacts with the BR receptor BRI1 and coreceptor BAK1 to negatively regulate BR signalling. In contrast, OsBIR3 interacts with OsBRI1 and OsBAK1 to positively regulate BR signalling in rice (Oryza sativa). However, our understanding of OsBIR3 remains incomplete. In this study, we isolated a reduced upper branch (rub1) mutant of rice, exhibiting a significant reduction in grain number. The causal gene for the mutant phenotype was LOC_Os04g41030 (OsBIR3). OsBIR3 interacts with both OsBRI1 and the remorin protein OsREM4.1, but interactions of the mutated Osbir3 with both OsBRI1 and OsREM4.1 were decreased. Furthermore, BL interferes with the interaction of OsBIR3 with OsBRI1, but promotes the interaction of OsBIR3 with OsREM4.1. Overexpression of OsREM4.1 and OsBRI1 individually in the rub1 mutant caused an exacerbation of the mutant phenotype. Additionally, OsBIR3 interacts with Brd2, involving BR biosynthesis in the early stage, and the interaction of the mutated brd2 with wild-type OsBIR3 was increased. Besides, BL promotes the interaction between OsBIR3 and Brd2. Collectively, the data indicate that OsBIR3 plays a key role in maintaining the homeostasis of OsBRI1, OsREM4.1, and Brd2 at their respective protein levels. This work provides insight into the roles of OsBIR3 in BR signalling and biosynthesis pathways of rice.

The increasing frequency of droughts driven by global warming poses a significant threat to wheat (Triticum aestivum L.) growth and yield. This study investigated stably inherited cuticular-wax mutants of wheat leaf sheaths, generated by ethyl-methanesulfonate (EMS) mutagenesis and isolated through phenotype-based screening. We systematically analyzed physiological responses, leaf sheath wax architecture, and lipid metabolism in a multi-wax mutant (mw; characterized by abundant leaf sheath wax crystals), a low-wax mutant (lw), and the wild type (WT) under both well-watered and drought conditions. Scanning electron microscopy (SEM) revealed a distinctive honeycomb-like network on the mw sheath epidermis, whereas the lw primarily displayed scattered block-like crystals. Under drought stress, lw leaves lost water significantly faster than mw (P < 0.01). Additionally, the mw leaf sheath exhibited significantly higher peroxidase (POD) and superoxide dismutase (SOD) activities, lower malondialdehyde (MDA) levels, and greater proline accumulation than lw (all P < 0.05). Untargeted lipidomics using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS) identified ten major lipid components, with fatty acids representing the largest proportion (25.7%). Aliphatic aldehydes and hydrocarbons were markedly enriched in mw and were positively correlated with drought tolerance indices. Overall, our results suggest that leaf-sheath wax enhances wheat adaptation to drought through the formation of a physical barrier together with modulation of lipid pathways, thereby promoting water retention and antioxidant defense. These findings provide novel metabolic insights into the drought-response mechanisms of leaf-sheath wax and lay a theoretical foundation for breeding drought-resilient wheat cultivars.

Land use change driven by vegetation succession significantly enhances soil carbon storage, yet the microbial mechanisms underlying this process remain poorly understood. This study aims to elucidate the mechanistic linkages between bacterial community dynamics and organic matter carbon stabilization across four vegetation succession stages on the Loess Plateau: abandoned farmland (AF), grassland stage (GS), shrub-land stage (SS), and forest stage (FS). We analyzed soil organic matter carbon (SOM_C) fractions, physicochemical properties, and bacterial communities (16S rRNA sequencing), employing structural equation modeling to quantify causal pathways. The results showed that the content of soil total organic matter carbon (TOM_C), labile organic matter carbon (LOM_C), dissolved organic matter carbon (DOM_C), and microbial biomass carbon (MBC) increased progressively with succession, peaking in the FS, with 23.87 g/kg, 4.13 g/kg, 0.33 mg/kg, and 0.14 mg/kg, respectively. Furthermore, vegetation succession also led to heterogeneity in the bacterial community structure. The number of soil bacterial operational taxonomic units (OTUs) for the four succession stages was 9966, 13,463, 14,122, and 10,413, with the shrub-land stage showcasing the highest OTUs. Nine bacterial taxa were strongly correlated with SOM_C stabilization. Affected by soil bacteria, soil physicochemical properties and litter biomass directly influence SOM_C, with the physicochemical pathway (path coefficient: 0.792, p < 0.001) having a greater impact on organic matter carbon than the litter pathway (path coefficient: 0.221, p < 0.001). This study establishes that vegetation succession enhances SOM_C content not only through increased litter inputs but also by reshaping bacterial communities toward taxa that stabilize carbon via physicochemical interactions.

Tillering contributes greatly to grain yield in rice (Oryza sativa). At present, many genes involved in rice tillering regulation have been cloned and characterized. However, the identification of more novel genes is still necessary to fully understand the molecular mechanisms regulating rice tillering. In this study, we isolated a low-tillering and dwarf 1 (ltd1) mutant in indica rice. Map-based cloning and MutMap analysis showed that the candidate gene LTD1 (LOC_Os01g19760) encodes a putative FAM91A1 protein with an unknown function in plants. LTD1-complementation and -RNAi confirmed that LTD1 is responsible for the mutant phenotype of ltd1. The LTD1 protein is localized to the plasma membrane, endoplasmic reticulum, and multi-vesicular bodies. Furthermore, protein interaction and colocalization assays showed that LTD1 interacts with both the TFB2 subunit of the core subcomplex and the CycH1;1 subunit of the cyclin-dependent kinase-activating kinase (CAK) subcomplex of the TFIIH complex, and TFB2 also interacts with CycH1;1. qRT-PCR demonstrated that the expression levels of most genes related to the cell cycle are changed significantly in the ltd1 tiller buds, and flow cytometry assays revealed that there are more polyploid nuclei in the ltd1 leaves and roots, suggesting that LTD1 could be involved in cell cycle regulation. Taken together, our findings indicated that LTD1 plays a key role in rice tillering regulation by involvement in the cell cycle through cooperation with CycH1;1 and TFB2 subunits of TFIIH. This work also sheds light on the biological function of FAM91A1 in regulating important agronomic traits of rice.

Plant height is a crucial agronomic trait in wheat, regulated by multiple genes, and significantly influences plant architecture and wheat yield. In this study, a novel dwarf mutant, designated as m097, was developed and characterized through the treatment of seeds from the common wheat cultivar Jinmai47 with ethyl methanesulfonate (EMS). Microscopic analysis revealed that the dwarf phenotype was attributed to a reduction in the longitudinal cell size of the stem. Similar to the wild type, m097 exhibited sensitivity to exogenous gibberellic acid (GA). Genetic analysis indicated that the reduced plant height in m097 was regulated by a semi-dominant dwarfing gene, Rht_m097. Through bulk segregant analysis (BSA) utilizing the wheat 660K SNP array, Rht_m097 was mapped and confined to a region of approximately 2.58 Mb on chromosome arm 4BS, encompassing 16 high-confidence annotated genes. In addition, transcriptome sequencing (RNA-seq) was conducted on the first internode below the panicle of JM47 and m097 at the jointing stage, leading to the identification of two potential candidate genes exhibiting differential expression. Furthermore, the analysis of gene ontology and metabolic pathways from RNA-seq data indicated that the down-regulated differentially expressed genes (DEGs) in m097 were biologically classified as regulating actin cortical patch organization and assembly. Concurrently, it was observed that the up-regulated DEGs were significantly enriched in various phytohormone metabolic pathways, including those involved in indole-3-acetic acid (IAA) biosynthesis, jasmonic acid biosynthesis, and gibberellin signaling. Overall, this study provides a novel genetic resource for the breeding of dwarf wheat and establishes a foundation for subsequent gene cloning.

Scientific and rational straw return can release certain nutrient resources and improve soil structure, thus affecting soil microbiological environments. Here, the effects of replacing some fertilizers with different amounts of straw return on soil carbon and nitrogen changes and on microbial metabolism were conducted from 2018 to 2023 in the winter wheat Triticum aestivum cultivation area of the Loess Plateau drylands in Jinnan. Four treatments were used: S0 (0% returned), S1/2 (50% returned), S1 (100% returned), and S2 (200% returned), based on the range of straw yields for winter wheat production in the region (straw was returned to the soil at a depth of 0–20 cm in all treatments). The results showed that straw return increased the total organic carbon and nitrogen content and their fractions in the tillage soil of wheat fields, and the enhancement increased with the rise in straw return. The soil total organic carbon/nitrogen, dissolved organic carbon/nitrogen, microbial biomass carbon/nitrogen and light fraction organic carbon/nitrogen of S2 for five consecutive years were elevated by 39.82/15.14, 37.93/33.08, 129.30/62.59 and 155.86/166.69%, respectively, compared with S0. The straw returned to the field greatly increased the content of active carbon and nitrogen fractions. Additionally, straw return elevated microbial community abundance and significantly increased soil carbon metabolism. Based on the results of redundancy and correlation analyses, Proteobacteria (p = 0.002), Acidobacteriota (p = 0.004), Mortierellomycota (p < 0.05), and amino acid‐based carbon sources (p < 0.01) were closely associated with changes in soil carbon and nitrogen fractions. Under the conditions of this experiment, S2 (10 682.4 kg ha −1 ) significantly enhanced the soil nutrient supply capacity and microbial metabolism of dryland wheat fields. Hence, scientific straw return is an effective way of comprehensively solving the problem of dryland soil fertility enhancement and utilizing agricultural by‐products.

Folate plays essential role in sustaining cell activity, promoting cell growth, and participating in cell division and proliferation. The demand for colored wheat is increasing day by day due to its high content of anthocyanin, iron, zinc, selenium, and other beneficial elements. To investigate the folate content and its derivatives in colored grains wheat, in this study employed a total of 113 wheat varieties (lines) with varying grain colors. The content of four folate derivatives, tetrahydrofolate (THF), 5-methyltetrahydrofolate (5-CH3-THF), 5-formyltetrahydrofolate (5-CHO-THF), and 5,10-methylenetetrahydrofolate (5,10-CH+THF), in grains cultivated under three different growing conditions were quantified using high performance liquid chromatography (HPLC). The results revealed that the four folate derivatives were distributed among wheat varieties exhibiting varying grain colors, with a coefficient of variation (CV) ranging from 15.34% to 20.10%. Among them, Lin 4179 emerged as a high-folate variety with a total content of 76.00 μg · 100 g-1. The contents of 5-CH3-THF and 5-CHO-THF in the four folate derivatives accounted for approximately 70% of the total folate content and exhibited a significant correlation with total folate content. The mean total folate level in purple and blue grains was 61.84 and 60.95 μg · 100 g-1, respectively, which was significantly higher than that in white (41.93 μg · 100 g−1) and red grains (42.40 μg · 100 g−1). The genotypic effect is the main factor affecting total folate content, while environmental factors had less impact. Genome-wide association studies (GWAS) identified four major loci associated with folate content on the chromosomes 1B, 4D and 7A, of which QFac.4D and QFac.7A.1 were stated as novel. The results of this study provide valuable insight into the development and breeding of folate biofortified wheat varieties.

Wheat (Triticum aestivum L.) is a crucial cereal crop, contributing around 20% of global caloric intake. However, challenges such as diminishing arable land, water shortages, and climate change threaten wheat production, making yield enhancement crucial for global food security. The heading date (HD) is a critical factor influencing wheat’s growth cycle, harvest timing, climate adaptability, and yield. Understanding the genetic determinants of HD is essential for developing high-yield and stable wheat varieties. This study used a doubled haploid (DH) population from a cross between Jinmai 47 and Jinmai 84. QTL analysis of HD was performed under three phosphorus (P) treatments (low, medium, and normal) across six environments, using Wheat15K high-density SNP technology. The study identified 39 QTLs for HD, distributed across ten chromosomes, accounting for 2.39% to 29.52% of the phenotypic variance. Notably, five stable and major QTLs (Qhd.saw-3A.7, Qhd.saw-3A.8, Qhd.saw-3A.9, Qhd.saw-4A.4, and Qhd.saw-4D.3) were consistently detected across varying P conditions. The additive effects of these major QTLs showed that favorable alleles significantly delayed HD. There was a clear trend of increasing HD delay as the number of favorable alleles increased. Among them, Qhd.saw-3A.8, Qhd.saw-3A.9, and Qhd.saw-4D.3 were identified as novel QTLs with no prior reports of HD QTLs/genes in their respective intervals. Candidate gene analysis highlighted seven highly expressed genes related to Ca2+ transport, hormone signaling, glycosylation, and zinc finger proteins, likely involved in HD regulation. This research elucidates the genetic basis of wheat HD under P stress, providing critical insights for breeding high-yield, stable wheat varieties suited to low-P environments.

Chlorophyll content of the flag leaf is an important trait for drought resistance in wheat under drought stress. Understanding the regulatory mechanism of flag leaf chlorophyll content could accelerate breeding for drought resistance. In this study, we constructed a recombinant inbred line (RIL) population from a cross of drought-sensitive variety DH118 and drought-resistant variety Jinmai 919, and analyzed the chlorophyll contents of flag leaves in six experimental locations/years using the Wheat90K single-nucleotide polymorphism array. A total of 29 quantitative trait loci (QTLs) controlling flag leaf chlorophyll were detected with contributions to phenotypic variation ranging from 4.67 to 23.25%. Twelve QTLs were detected under irrigated conditions and 18 were detected under dryland (drought) conditions. Most of the QTLs detected under the different water regimes were different. Four major QTLs (Qchl.saw-3B.2, Qchl.saw-5A.2, Qchl.saw-5A.3, and Qchl.saw-5B.2) were detected in the RIL population. Qchl.saw-3B.2, possibly more suitable for marker-assisted selection of genotypes adapted to irrigated conditions, was validated by a tightly linked kompetitive allele specific PCR (KASP) marker in a doubled haploid population derived from a different cross. Qchl.saw-5A.3, a novel stably expressed QTL, was detected in the dryland environments and explained up to 23.25% of the phenotypic variation, and has potential for marker-assisted breeding of genotypes adapted to dryland conditions. The stable and major QTLs identified here add valuable information for understanding the genetic mechanism underlying chlorophyll content and provide a basis for molecular marker-assisted breeding.

In wheat, the leaf chlorophyll content in flag leaves is closely related to the degree of phosphorus stress. Identifying major genes/loci associated with chlorophyll content in flag leaves under different phosphorus conditions is critical for breeding wheat varieties resistant to low phosphorus (P). Under normal, medium, and low phosphorus conditions, the chlorophyll content of flag leaves was investigated by a double haploid (DH) population derived from a cross between two popular wheat varieties Jinmai 47 and Jinmai 84, at different grain filling stages. Chlorophyll content of the DH population and parents decreased gradually during the S1 to the S3 stages and rapidly at the S4 stage. At the S4 stage, the chlorophyll content of the DH population under low phosphorus conditions was significantly lower than under normal phosphate conditions. Using a wheat 15K single-nucleotide polymorphism (SNP) panel, a total of 157 QTLs were found to be associated with chlorophyll content in flag leaf and were identified under three phosphorus conditions. The phenotypic variation explained (PVE) ranged from 3.07 to 31.66%. Under three different phosphorus conditions, 36, 30, and 48 QTLs for chlorophyll content were identified, respectively. Six major QTLs Qchl.saw-2B.1, Qchl.saw-3B.1, Qchl.saw-4D.1, Qchl.saw-4D.2, Qchl.saw-5A.9 and Qchl.saw-6A.4 could be detected under multiple phosphorus conditions in which Qchl.saw-4D.1, Qchl.saw-4D.2, and Qchl.saw-6A.4 were revealed to be novel major QTLs. Moreover, the closely linked SNP markers of Qchl.saw-4D.1 and Qchl.saw-4D.2 were validated as KASP markers in a DH population sharing the common parent Jinmai 84, showed extreme significance (P <0.01) in more than three environments under different phosphorus conditions, which has the potential to be utilized in molecular marker-assisted breeding for low phosphorus tolerance in wheat.

Water availability is a crucial environmental factor on grain number in wheat, which is one of the important yield-related traits. In this study, a diverse panel of 282 wheat accessions were phenotyped for grain number per spike (GNS), spikelet number (SN), basal sterile spikelet number (BSSN), and apical sterile spikelet number (ASSN) under different water regimes across two growing seasons. Correlation analysis showed that GNS is significantly correlated with both SN and BSSN under two water regimes. A total of 9,793 single nucleotide polymorphism (SNP) markers from the 15 K wheat array were employed for genome-wide association study (GWAS). A total of 77 significant marker-trait associations (MTAs) for investigated traits as well as 8 MTAs for drought tolerance coefficient (DTC) were identified using the mixed linear model. Favored alleles for breeding were inferred according to their estimated effects on GNS, based on the mean difference of varieties. Frequency changes in favored alleles associated with GNS in modern varieties indicate there is still considerable genetic potential for their use as markers for genome selection of GNS in wheat breeding.