[Objective] The study aims to examine the rhizosphere soil enzyme activity and bacterial community response to foliar application of 1,1-dimethyl-piperidinium chloride (DPC) and sodium nitroprusside (SNP) at the cotton seedling stage, and to screen rhizoshpere events potentially involved in cotton seedling growth. [Method] An upland cotton line A201 was grown in nursery trays under a controlled environment. The treatment with DPC of 50 mg·L-1 and SNP of 500 μmol·L-1, respectively, was foliar-applied at the one-leaf-one-heart stage, and the treatment with deionized water application was selected as the control. The rhizosphere soil was sampled to quantify the activities of sucrase, urease, catalase, and alkaline phosphate at the three-leaf-one-heart stage. The rhizosphere bacteria composition examined by 16S rRNA sequence analysis. [Result] The root growth, stem diameter, and dry mass of whole cotton plant were significantly increased by the DPC and SNP treatments. The activities of urease and sucrase were significantly improved by the DPC treatment. SNP application significantly enhanced sucrase activity but significantly decreased urease activity, while DPC treatment and SNP treatment had no significant effect on the activities of catalase and alkaline phosphatase. DPC application increased the relative abundance of Patescibacteria and Simpson's diversity index of soil bacterial community, but reduced the relative abundances of Chloroflexi and Acidobacteriota and Shannon Wiener’s diversity index of soil bacterial community. The results of redundancy analysis on family and genus level showed that the abundances of Saccharimonadaceae and TM7a were higher in the DPC treatment; the abundance of Cellvibrionaceae was greater in the SNP treatment; the abundance of Rhizobiaceae was greater in the DPC and SNP treatments. The control exhibited greater Nitrospiraceae and Nitrospira abundances compared with the DPC and SNP treatments. Urease activity was positively correlated with Saccharimonadaceae and TM7a relative abundances. [Conclusion] DPC and SNP could promote the growth of cotton roots and aerial parts, and influence the soil enzyme activity and bacterial community composition in the rhizosphere.
[Objective] This study aims to explore the effects of exogenous methyl jasmonate (MeJA) on cotton tolerance to the heat stress. [Method] The self-bred line ZS08 was used as the test material. Distilled water (CK) and MeJA with different concentrations (200 μmol·L-1, 400 μmol·L-1 and 600 μmol·L-1) were used on plants at the flowering and boll-setting stage. And after the artificial heat stress of 38.0 ℃/30.0 ℃ (day/night) for three days or under natural heat stress of 35.2-37.5 ℃/26.4-27.2 ℃ (day/night) for ten days, the pollen viability, photosynthetic characteristics, antioxidant enzyme activity, malondialdehyde (MDA) content, yield and fiber quality of each treatment were measured. [Result] The pollen viability was reduced under the artificial heat stress. The MeJA treatment of three concentrations all had alleviated the inhibition of heat stress on pollen viability compared with the water control. The net photosynthetic rate (Pn), transpiration rate (Tr) and stomatal conductance (Gs) of the fourth leaf from top of the main stem in the 400 μmol·L-1 and 600 μmol·L-1 MeJA treated plants were increased in various degree than those of the control under 2-3 days heat stress by 1.6%-3.7%, 7.2%-15.7%, and 44.4%-53.4%, respectively. The activity of superoxide dismutase (SOD) and peroxidase (POD) of the second leaf from top on the main stem in 400 μmol·L-1 and 600 μmol·L-1 MeJA treatment were increased by 3.1%-7.2% and 5.7%-20.0% than those of the control under 2-3 days heat stress. While the content of MDA was reduced by 10.9%-17.9%. Under the natural heat stress, plants which were treated by different concentrations of MeJA had improved boll-setting rate and boll weight in varying degree, and had significantly improved lint yield by 9.0%-18.3% compared with the control. [Conclusion] When encountering heat stress during the flowering and boll-setting stage, the application of MeJA can increase Pn and the activities of SOD and POD, reduce the degree of leaf damage, and improve pollen viability, thereby enhance the heat tolerance of cotton, and reduce the impact of heat stress on boll-setting rate, boll weight, and yield loss.
[Objective] Based on the integrated technology of water and fertilizer, the effects of different phosphorus (P) application methods were studied, so as to provide a basis for the rational application of P fertilizer in cotton field with drip-irrigation under plastic-film. [Method] The experiment was carried out in Xinjiang cotton field in 2021. Xinluzao 63 was used as the object, and four treatments were set up, CK: no P application; MAP-B: basal application of monoammonium phosphate (MAP), total amount of P2O5 was 100 kg·hm-2 (same as below); MAP-D: basal application of 50% MAP + drip application of 25% MAP at bud stage and 25% at early flowering and boll development stage; MAP-DS: MAP-D + drip application of polyglutamic acid of 50% at bud stage and 50% at early flowering and boll development stage. Soil P content, inorganic P content in different forms, soil P adsorption-desorption characteristics, P use efficiency, and seed cotton yield of different treatments were compared and analyzed. [Result] P application could increase the available P content and total P content in 0-40 cm soil layer at the seedling stage and flowering and boll development stage, and the content of available soil P under MAP-D and MAP-DS treatment was significantly higher than that of other treatments at flowering and boll development stage. Compared with basal application of P (MAP-B), drip application significantly increased the content proportion of dicalcium phosphate (Ca2-P), octa-calcium phosphate (Ca8-P) and aluminum bounded phosphate (Al-P), and reduced the proportion of apatite(Ca10-P) at the flowering and boll development stage. The isothermal adsorption and desorption curves of P in 0-40 cm soil layers under different treatments at the seedling stage and flowering and boll development stage showed similar trend, that is, with the increase of P concentration in equilibrium solution, the soil P adsorption increased rapidly at first and then slowly, and with the increase of P concentration in standard solution, the P desorption rate decreased rapidly at first and then tended to be stable. Compared with CK, the seed cotton yield of P application treatments increased. The P use efficiency and seed cotton yield under drip application of P were higher than that of basal application of P (MAP-B). MAP-DS treatment showed the highest P use efficiency and the highest seed cotton yield(6 829.75 kg·hm-2). [Conclusion] Drip application of P fertilizer combined with polyglutamic acid under the integration of water and fertilizer in Xinjiang cotton planting region is more conducive to the absorption and utilization of soil P for Xinluzao 63, and further improves the P use efficiency and seed cotton yield.
[Objective] The effects of nitrogen fertilizer synergist N-life (main active ingredient: nitrapyrin) on cotton were studied, so as to provide theoretical support for the application of N-life in cotton production. [Method] The field experiment and pot experiment were carried out at Sanya, Hainan province in 2021 and 2022 with Zheda 12 as the experimental material. A field experiment was designed with two factors split-plot. The main plot was N-life application level (1.5 and 0 kg per 667 m2), and the secondary plot was pure nitrogen application level (normal nitrogen rate: 19.0 kg per 667 m2, and reduced nitrogen rate: 17.1, 15.2, and 13.3 kg per 667 m2). The effects of different treatments on physiological and biochemical indexes at the seedling stage, flowering and boll stage, and boll opening stage, agronomic traits, yield and fiber quality of cotton were analyzed. And the effect of N-life on nitrogen use efficiency of cotton was studied by pot experiment. [Result] Compared with the control of no N-life, the application of N-life could significantly improve the activities of superoxide dismutase, peroxidase, catalase, and nitrate reductase of cotton leaves, and reduce the malondialdehyde content significantly at the flowering and boll stages and boll opening stages, and increase the net photosynthetic rate in nitrogen reduction treatments. In the two-year pot experiments, N-life application significantly increased the nitrogen content and nitrogen use efficiency of cotton plants, and significantly reduced the nitrogen loss under the same nitrogen application level, also had an increasing effect on the total boll number of cotton plant, seed cotton yield and lint yield. In 2021 and 2022, the seed cotton yield increased by 12.80%-30.63% and 0.08%-5.96%, respectively, and the lint yield increased by 11.33%-34.25% and 0.31%-6.57%, respectively. In addition, the fiber upper half mean length and breaking strength were increased, and micronaire were improved, but N-life had no significant effect on the breaking elongation. [Conclusion] The application of N-life (1.5 kg per 667 m2) could improve the growth, development, and photosynthesis of cotton, enhance the nitrogen use efficiency of plants, and maintain high yield even at the condition of reducing nitrogen by 20% (pure nitrogen dosage of 15.2 kg per 667 m2).
Cotton is an important cash crop and main raw materials for textile industry, which plays a critical role in economic development of China. Since the founding of the People’s Republic of China, traditional breeding technology has made a great contribution to improve cotton production. With the advancement of sequencing technology, multi-omics research, and gene editing techniques, precise and efficient molecular design breeding has become an inevitable direction for cotton breeding. This review summarizes the present status of cotton production, the history of breeding development, and the achievements of molecular design breeding in genomic research, fiber development, disease resistance and mining of the molecular module of important traits, and proposes directions and path for the future cotton breeding.
Cotton has obvious heterosis, which is manifested in traits including yield, fiber quality, and resistance to diseases and insects. Hybrid seed production is a very important step in the utilization of cotton heterosis. Recently, as the cost of manual pollination in seed production increases year by year, the simplified, efficient, and low-cost seed production techniques have become an inevitable trend for future hybrid cotton development. The field practice shows that the use of cytoplasmic male sterile lines not only simplify the procedure of seed production but also save labor costs, so it has become a research hotspot in the utilization of crop heterosis. However, the sterile cytoplasm does have certain impacts on cotton morphogenesis, anther development, yield formation, fiber development, and have negative effects on cotton growth and development, thereby limiting the further promotion and utilization of “three-line (male sterile line, maintainer line, and restoring line)” hybrid cotton. In this paper, the effects of male sterile cytoplasm on the main traits of cotton and the molecular basis for its negative effects were systematically reviewed. And the potential ways to overcome the negative effects of male sterile cytoplasm in cotton were preliminarily discussed, which would provide new ideas for breeding and improvement of cotton cytoplasmic male sterile restorer lines and excellent “three-line” hybrids in the future.