Multiple nitrate transporter (NRT) genes exist in the genome of bread wheat, and it is of great importance to identify the elite NRT genes for N-efficient wheat cultivar breeding. A candidate gene association study (CGAS) of six N use efficiency (NUE) related traits (grain N concentration (GNC), straw N concentration (SNC), grain yield (GY), grain N accumulation (GNA), shoot total N accumulation (STN) and N harvest index (NHI)) was performed based on SNPs in 46 NRT2 genes using a panel composed of 286 wheat cultivars. CGAS identified TaNRT2.1-6B as an elite NRT gene that is significantly associated with four (NHI, SNC, GNA and GY) of the six NUE-related traits simultaneously. TaNRT2.1-6B is located on the plasma membrane and acts as a dual-affinity NRT. The overexpression of TaNRT2.1-6B increased the N influx and root growth of wheat, whereas gene silence lines resulted in the opposite effects. The overexpression of TaNRT2.1-6B also improved GY and N accumulation of wheat under either limited or sufficient N conditions. The data provide the TaNRT2.1-6B gene and the two associated SNP markers as promising powerful tools for breeding wheat cultivars with high N uptake ability and NUE.

Drought is the main limiting factor of maize productivity, therefore improving drought tolerance in maize has potential practical importance. Cloning and functional verification of drought–tolerant genes is of great importance to understand molecular mechanisms under drought stress. Here, we employed a bioinformatic pipeline to identify 42 ZmHDZ drought responsive genes using previously reported maize transcriptomic datasets. The coding sequences, exon–intron structure and domain organization of all the 42 genes were identified. Phylogenetic analysis revealed evolutionary conservation of members of the ZmHDZ genes in maize. Several regulatory elements associated with drought tolerance were identified in the promoter regions of ZmHDZ genes, indicating the implication of these genes in plant response to drought stress. 42 ZmHDZ genes were distributed unevenly on 10 chromosomes, and 24 pairs of gene duplications were the segmental duplication. The expression of several ZmHDZ genes was upregulated under drought stress, and ZmHDZ9 overexpressing transgenic plants exhibited higher SOD and POD activities and higher accumulation of soluble proteins under drought stress which resulted in enhanced developed phenotype and improved resistance. The present study provides evidence for the evolutionary conservation of HD-ZIP transcription factors homologs in maize. The results further provide a comprehensive insight into the roles of ZmHDZ genes in regulating drought stress tolerance in maize.

Consuming rice with low starch digestibility is beneficial for reducing the risk of diabetes. Several factors have been shown to influence starch digestibility, but the combined effects of these factors on starch digestibility have not been studied. We assessed multidimensional relationships between the glucose production rate (GPR) of cooked rice with 16 indexes, including physicochemical, pasting and textural properties in 30 rice varieties. The stepwise multiple regression analysis showed that amylose content (AC), gel consistency (GC) and pasting temperature (PT) were closely related to GPR. This relationship could be described by the equation: GPR = −0.080 AC + 0.008 GC + 0.034 PT + 0.720, with a determination coefficient of 0.84. The variation partitioning analysis further indicated that AC, GC and PT independently explained 36%, 5% and 4% of the GPR variation, respectively. The interaction of AC and GC explained 46% of the variation in GPR. This study identifies the key indexes (AC, GC and PT) affecting starch digestibility and quantifies contributions of these indexes to the variation in GPR. The finding of our study provides useful information for breeding and selecting rice varieties with low GPR.

Numerous studies have reported the dynamics of microbes when biochar was applied, whereas the information on the alterations of bacterial community after application of rapeseed straw-derived biochar is limited. A pot experiment with two rapeseed straw-derived biochar application treatments (with biochar application at the rate of 200 g/pot, C1, and without biochar application, 0 g/pot, C0) was conducted. No significant differences were observed in the number of operational taxonomic units, observed species, Shannon index, Simpson index, Chao1, ACE, and phylogenetic diversity whole tree between the C1 and C0 treatments. Taxonomic analysis at the phylum level showed that the abundances of Bacteroidetes and Parcubacteria were higher in the C1 treatment compared to the C0 treatment, while Acidobacteria, Chloroflexi, Rokubacteria, Berkelbacteria, and Latescibacteria were observed with higher abundance in the C0 treatment compared to the C1 treatment. Taxonomic analysis at the genus level showed that the abundances of Gracilibacter, Lentimicrobium, unidentified Rikenellaceae, Hydrogenophaga, and Bacillus were higher in the C1 treatment compared to the C0 treatment, while Candidatus Solibacter, Candidatus Koribacter, and Lutispora abundances were found to be higher in the C0 treatment compared to the C1 treatment. Obvious clusters were observed between the C1 and C0 treatments in both principal component analysis and nonmetric multidimensional scaling. These results indicate that soil bacterial community was altered after rapeseed straw-derived biochar was applied.

Soil salinity is a major environmental stress that adversely affects the growth, development, productivity, and quality of crop species, in particular, in arid and semi-arid regions. Identification of chromosomal regions associated with agronomic traits under salinity stress is crucial for improving salinity tolerance in wheat. Genome-wide association study (GWAS) was employed to evaluate 289 elite lines of the Wheat Association Mapping Initiative (WAMI) population under low (LS) and high (HS) salinity conditions using 15,737 SNP markers for seven agronomical traits. The genotypes responded differently to the different environments for all traits, highlighting genetic diversity within the WAMI population in response to salt stress, where the heritability ranged from moderate (37%) to high (88%). GWAS identified 118 and 120 significant marker-trait associations (MTAs) under LS and HS conditions, respectively. Significant association of some markers with more than one phenotypic trait was observed, indicating possible pleiotropic or indirect effects. A high degree of significant linkage disequilibrium (> 52%) was observed among SNPs on different chromosomes, indicating epistatic interaction. The salt stress index (STI) exhibited a positive significant correlation to grain yield per plant (GYP) under both LS and HS conditions (R² = 0.851–0.856). Linear regression analysis between STI and GYP under HS conditions indicated that STI is the best tolerance index for predicting high-yielding genotypes. The results present the WAMI population as a valuable source for improving yield potential for salt tolerance in wheat. Furthermore, our findings emphasize that GWAS is a powerful tool in promoting wheat breeding through accurate identification of molecular markers significantly associated with agronomic traits, which is essential for marker-assisted breeding.

Leafy sweet potato is rich in caffeoylquinic acids (CQAs), including monoCQAs and diCQAs, which play important roles in plant resistance to environmental stresses. However, knowledge about the genes responsible for the accumulation of CQAs is limited. Studies have reported the involvement of glutathione S-transferase (GST) genes in the metabolism of various plant secondary compounds; yet, the mechanism of CQA-related GST proteins is not well understood. In this study, two sweet potato GST genes, i.e., itb01g35330 (IbGSTTCHQD) and itb09g30700 (IbGSTT), were selected from our transcriptome database and investigated for their correlation with the accumulation of CQAs, as they exhibited secondary metabolism functions based on gene ontology classification. The two genes were cloned from the leafy sweet potato varieties EC16 and FS7-6. Sequence alignment of the coding regions of these genes from the two varieties revealed slight mutations in the amino acid sequences. Besides, the expression of the two genes was higher in the EC16 compared to the FS7-6 variety, which corresponds to the accumulated amounts of CQAs in both varieties. The amplified IbGST sequences from the EC16 variety were further transformed into Agrobacterium tumefaciens and subsequently introduced into Nicotiana benthamiana and Nicotiana tabacum for transient expression and transgenic transformation, respectively. Gene expression profiling in both transformation approaches revealed significant increases in IbGST transcripts in transformed leaves, resulting in an enhanced accumulation of monoCQAs compared to the wild-types. However, no significant change was observed in the level of diCQAs. In addition, the IbGSTs responded positively to salinity and oxidative stresses. Our findings suggested that IbGSTTCHQD and IbGSTT genes might be involved in the accumulation of monoCQAs in leafy sweet potato.