[Objective] This study aimed to analyze and clarify the biological function of Gossypium hirsutum GhVAS1, and to elucidate its regulatory mechanism underlying boll abscission. [Methods] Using the Arabidopsis thaliana VAS1 gene as a query sequence, two GhVAS1 homologs (GhVAS1-A05 and GhVAS1-D05) were identified and cloned from the upland cotton cultivar TM-1. Subsequently, phylogenetic analysis, conserved motif prediction and protein structure characterization of the cloned GhVAS1 genes were performed. The spatiotemporal expression patterns of GhVAS1 were analyzed by integrating RNA-sequencing (RNA-seq) data with quantitative real-time polymerase chain reaction (qRT-PCR) analysis. The subcellular localization of GhVAS1 was determined using a transient expression system in Nicotiana benthamiana. To assess the role of GhVAS1 in boll abscission, cotton leaf crumple virus (CLCrV)-mediated virus-induced gene silencing (VIGS) was employed in cotton plants. Endogenous levels of auxin (indole-3-acetic acid, IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) in abscission layer tissues were quantified, and the transcriptional profiles of abscission-related genes were analyzed. In parallel, heterologous overexpression of GhVAS1 in A. thaliana was conducted to validate its conserved regulatory role in organ abscission across plant species. [Results] Phylogenetic analysis revealed that the two GhVAS1 share a close evolutionary relationship with AtVAS1 and encode highly conserved proteins in G. hirsutum. GhVAS1 transcripts exhibited preferential accumulation in the abscission layer and were significantly and consistently upregulated in response to abscission-inducing signals. Subcellular localization assays demonstrated that both GhVAS1 proteins are localized to the nucleus and plasma membrane. VIGS-mediated silencing of GhVAS1 resulted in a significant reduction in cotton boll abscission, which was accompanied by a marked increase in endogenous IAA content and a concurrent decrease in ACC levels in abscission layer tissues. Consistently, the transcriptional levels of key ethylene biosynthetic genes (GhACS and GhACO) and cell wall hydrolysis-related genes (GhPG and GhCEL) were significantly downregulated in GhVAS1-silenced plants. In parallel, heterologous overexpression of GhVAS1 in A. thaliana accelerated floral organ abscission compared with wild-type plants. [Conclusion] GhVAS1 positively regulates boll abscission in cotton by coordinating the IAA-ethylene metabolic balance in abscission layer tissues and upregulating the expression of cell wall degradation-related genes, thereby promoting abscission layer cell separation and subsequent organ shedding.
[Objective] This study aimed to investigate the function of the GhMLO6 gene in cotton Verticillium wilt resistance and identify a candidate gene for disease resistance breeding in cotton. [Methods] Quantitative real-time polymerase chain reaction (qRT-PCR) was used to analyze the expression pattern of GhMLO6. The virus-induced gene silencing (VIGS) technique was employed to transiently silence GhMLO6 in cotton to study its function in Verticillium wilt resistance. Agrobacterium-mediated transient expression technology was applied to Nicotiana benthamiana to explore the subcellular localization of GhMLO6. [Results] The qRT-PCR results revealed that GhMLO6 presented the highest expression level in cotton roots, followed by stems and leaves. Compared with the control, infection with Verticillium dahliae significantly increased the expression level of GhMLO6 in roots. Compared with the control plants in which empty vectors were used, GhMLO6-silenced plants displayed a significant decrease in disease index and relative fungal DNA content. After stem recovery and cultivation, the accumulation of hyphae was reduced, and the resistance of cotton to Verticillium wilt was significantly increased. Transient expression analysis indicated that GhMLO6 localizes on the cell membrane. [Conclusion] GhMLO6 is localized to the cell membrane and performs a negative regulatory function in cotton Verticillium wilt resistance. Therefore materials with Verticillium wilt resistance could be obtained via gene editing technology.
[Objective] This study aims to analyze the effect of the Haloxylon ammodendron (C. A. Mey.) Bunge HaNAC12 gene on the fatty acid content and drought resistance of cotton, and to provide theoretical and technical guidance for cotton stress-resistant breeding. [Methods] The HaNAC12 gene was introduced into cotton through the cotton shoot apical meristem genetic transformation system. After molecular detection of T0 and T1 generation plants, the phenotypic and physiological indexes differences between transgenic and non-transgenic cotton were compared through drought stress experiments. [Results] After 30 days of natural drought stress (T30 treatment), the plant height of transgenic cotton was significantly increased by 11% compared with the non-transgenic control, and the degree of leaf wilting was less than that of the control. Physiological index analysis of cotton leaves under T30 treatment showed that the content of malondialdehyde in transgenic cotton was significantly 34% lower than that in the control, with less damage to the plasma membrane; the contents of soluble sugar, proline and chlorophyll were significantly 66%, 89% and 50% higher than those in the control, respectively, with stronger osmotic adjustment ability; the activities of superoxide, peroxidase and catalase dismutase were significantly 94%, 25% and 58% higher than those in the control, respectively, with stronger ability to scavenge reactive oxygen species. Under the T30 treatament, the expression levels of genes related to fatty acid metabolism, such as fatty acid synthase and desaturase, in transgenic cotton were significantly higher than those in the control after drought stress, and the content of free fatty acids in transgenic cotton was significantly 50% higher than that in non-transgenic cotton. There were no significant differences in leaf phenotypes and physiological and biochemical indexes between transgenic and non-transgenic cotton in the normal watering group. [Conclusion] The HaNAC12 may enhance the drought stress tolerance of cotton seedlings by promoting the synthesis and accumulation of fatty acids, providing new gene resources and material support for the genetic improvement of cotton drought resistance.
[Objective] This study aims to establish a rapid quantitative detection method for Rhizoctonia solani, the causal agent of cotton seedling damping-off in soil, and to investigate the correlation between pathogen abundance and disease occurrence, providing a scientific basis for effective disease control. [Methods] A quantitative detection method for R. solani AG-4 HGⅢ in soil was developed using internal reference strain correction and quantitative real-time polymerase chain reaction (qPCR). Pot experiments and field trials were conducted to study the relationship between R. solani abundance in soil and the incidence of cotton seedling damping-off. [Results] A qPCR-based quantitative detection method incorporating internal reference stain correction was successfully established, with high specificity and a sensitivity of 10 copies·μL-1. The critical threshold of R. solani in soil for severe disease occurrence and seedling mortality risk was determined to be 106 copies·g-1. [Conclusion] A rapid quantitative detection method for R. solani in cotton field soil was successfully developed, enabling accurate quantification of the pathogen and the early disease risk warning.
[Objective] This study aims to investigate the effects of different tillage practices combined with straw returning on cotton growth, yield, and rhizosphere soil bacterial communities in a potato-cotton rotation system, so as to provide a scientific basis for optimizing farmland management and improving soil microecological health in this system. [Methods] The cotton cultivar Xiang X1107 was used as material. Four treatments were designed: no-tillage (NT), no-tillage with straw returning (NTS), rotary tillage (T), and rotary tillage with straw returning (TS). Growth-related traits and biomass of cotton plant at key growth stages, as well as yield and its components were measured. High-throughput sequencing of the 16S rRNA gene was used to analyze the diversity and composition of rhizosphere soil bacterial communities at the boll-opening stage of cotton, and functional prediction was performed using the Functional Annotation of Prokaryotic Taxa (FAPROTAX). [Results] Straw returning and tillage practice had no significant effect on cotton emergence rate. Compared with no-tillage treatments (NT and NTS), rotary tillage treatments (T and TS) significantly increased plant height, stem diameter, and biomass at the seedling stage, and significantly increased boll weight. Whereas no significant differences in seed cotton yield and boll number were detected among all treatments. Straw returning treatments (NTS and TS) significantly elevated the Shannon Wiener's diversity index, Chao1 index, and evenness index of rhizosphere bacterial communities, with NTS showing the highest values for all indices except the Shannon Wiener's diversity index. Principal coordinates analysis (PCoA) revealed that tillage practice was the primary factor driving the differentiation of bacterial community structure. Proteobacteria was the dominant phylum across all treatments. Straw returning (NTS and TS) significantly decreased the relative abundance of Proteobacteria, while significantly increased the relative abundances of Acidobacteriota and Actinobacteriota. At the genus level, no-tillage treatments (NTS and TS) enriched nitrogen-fixing-related genera including Burkholderia_Caballeronia_Paraburkholderia, Klebsiella, Bradyrhizobium, and Allorhizobium_Neorhizobium_Pararhizobium_Rhizobium complex, and FAPROTAX prediction confirmed a significant enhancement of nitrogen fixation function. Treatment enriched Pantoea and Pseudomonas, and increased the abundances of chemoheterotrophy and human pathogen all related functional groups, whereas TS treatment effectively reduced the risk of pathogenic bacteria. [Conclusion] NTS is conducive to maintaining soil microbial diversity, enhancing nitrogen fixation function, and reducing pathogenic bacteria risk, and is thus the recommended tillage mode in the potato-cotton rotation system. TS can serve as an alternative to promote early-stage growth and regulate microbial functions. Appropriate combination modes can be selected according to local soil conditions, ecological and economic objectives in agricultural production.
[Objective] The severe shortage of freshwater has severely restricted cotton production in the arid and semi-arid areas of Xinjiang, and water deficit during the key growth stages exerts an even more adverse effect on yield. Saline water supplemental irrigation can alleviate freshwater shortages, but its optimal salinity threshold remains unclear. This study investigated the effects of supplemental irrigation with saline water of different salinity levels on the photosynthetic characteristics and yield formation of cotton, aiming to determine the suitable salinity threshold for cotton supplemental irrigation in arid areas. [Methods] A two-year field experiment was conducted during the cotton growing seasons in 2023 and 2024. The conventional fresh water without supplemental irrigation was used as the control (CK, irrigation quota of 3 600 m3·hm-2), and five saline water supplemental irrigation treatments were established: 3.5 g·L-1 (S3.5), 5.0 g·L-1 (S5), 6.5 g·L-1 (S6.5), 8.0 g·L-1 (S8), 9.5 g·L-1 (S9.5). The saline supplemental irrigation regime consisted of one application at the bud stage (375 m3·hm-2) and two applications at the boll-setting stage (375 m3·hm-2 + 450 m3·hm-2). The total irrigation amount was 4 800 m3·hm-2 (including 1 200 m3·hm-2 of saline water and 3 600 m3·hm-2 of freshwater). Gas exchange parameters, chlorophyll fluorescence parameters in functional leaves after saline water irrigations, and yield components of cotton were measured. [Results] During the early boll-setting stage, the two-year average net photosynthetic rate (Pn) of treatments with salinity levels of S3.5, S5, and S6.5 increased by 6.89%-18.00% compared with CK, and the S3.5 treatment was significantly higher than CK. The transpiration rates (Tr) of the S3.5 and S5 treatments were significantly increased by 18.96% and 9.10%, respectively, compared with CK, and the stomatal conductances (Gs) were increased by 12.95% and 3.90%, respectively. After three saline water supplementary irrigations, the initial fluorescence (F0) of the S9.5 treatment was significantly increased by 5.99% (in 2023) and 6.54% (in 2024) relative to CK, while the maximum photochemical efficiency (Fv/Fm) of the S3.5 treatment was significantly higher than that of the S9.5 treatment. The boll-leaf ratio of cotton was the lowest in the S3.5 treatment, with two-year values of 24.58 and 24.87, followed by the S5 treatment with values of 25.02 and 25.05. The two-year average seed cotton yield of treatments with salinity levels of 3.5-6.5 g·L-1 significantly increased by 2.73%-12.67% compared with CK (5 721.00 kg·hm-2). [Conclusion] Supplemental irrigation with saline water with a salinity level of 3.5-6.5 g·L-1 can optimize the photosynthetic performance of cotton and achieve stable or increased yields. However, excessively high salinity level (>6.5 g·L-1) is prone to cause photoinhibition, leading to a significant reduction in cotton yield. This study provides an important theoretical basis for determining the salinity threshold for saline water irrigation in arid areas.
