[Objective] Cotton boll blight, which caused by Phytophthora boehmeriae, is one of the most important diseases of cotton boll rot. The aim of this study was to optimize the artificial inoculation method of cotton boll blight and to apply for further studies. [Method] The population of P. boehmeriae in adult bolls sampled from different parts of cotton plant was compared under the suitable culture conditions. The disease occurrences of surface sterilization and non-sterilization, as well as injury and non-injury cotton bolls inoculated with P. boehmeriae were compared. The artificial inoculation method of cotton boll blight was established through pathogenesis tests and used to screen 12 kind of chemicals against the disease, to identify the resistances of 16 cotton varieties and to test the pathogenicity of 10 strains of P. boehmeriae. [Result] The disease incidence of the boll from the 1-3rd fruit branches was more serious than that from the 4-6th fruit branches, the 7-9th fruit branches and the 10-12th fruit branches. P. boehmeriae and other microorganisms on cotton boll surface could be eliminated by soaking cotton bolls in 75% (volume fraction) alcohol for 2 min. Cotton bolls from the 4-9th fruit branches of cotton were soaked in 75% alcohol for 2 min, and then wounded with sewing needles on the middle and upper part of the cotton bolls. The wounded parts of cotton bolls were inoculated with the mycelium disks of P. boehmeriae. Cotton boll blight occurred completely in 3-7 d under moisture culture at 25 ℃. Among the 12 kind of chemical fungicides, 25% (mass fraction) Metalaxyl propamocarb hydrochloride wettable powder (WP), 70% Propineb WP and 52.5% Famoxadone cymoxanil wettable granule (WG) showed significant control effects against cotton boll blight with the artificial inoculation. For 16 cotton varieties, there were differences in resistance to the disease. Among the 10 strains of P. boehmeriae, JP18-4 showed the highest pathogenicity, while JP15-2 showed the lowest. [Conclusion] Artificial inoculation method of cotton boll blight was established and optimized in this study. The method can be used for screening control agents against cotton boll blight and the identification of resistant cotton varieties and pathogenicity difference of P. boehmeriae.
[Objective] There is a shortage of fresh water and abundant shallow saline water in Hebei Low Plain. This research aims to make scientifical and reasonable use of saline water resources. [Method] The field experiment with five treatments (CK, freshwater irrigation; T1, blended irrigation by mixing fresh water and saline water into 3 g·L-1 saline water; T2, rotated irrigation of 5 g·L-1 saline water with fresh water; T3, direct irrigation with 5 g·L-1 saline water; T4, irrigation before sowing no irrigation in bud stage) was conducted to study cotton growth, chlorophyll fluorescence parameters, communication and transportation of soil salinity based on short-term saline water irrigation experiment at the 3rd and 4th year. [Result] The results showed that the T1 and T2 treatments had no significant differences in seedling emergence, plant height, dry matter weight, leaf area index, chlorophyll fluorescence parameters, yield, and pre-frost cotton rate compared with CK. While, there was an increasing tendency in soil salt content, the plant growth was not impacted, either. In comparison with CK, growth indicators and chlorophyll fluorescence parameters of the treatment T3 decreased significantly, but salt content in 0-100 cm depth of soil layers increased evidently. To sum up, the treatments T1 and T2 did not show obvious negative impacts on cotton growth. [Conclusion] From the perspective of soil quality and efficient use of saline water, the blended irrigation pattern (mixing fresh water and saline water into 3 g·L-1 saline water) and the rotated irrigation pattern (fresh water and 5 g·L-1 saline water) of saline water utilization can save freshwater, but do not decrease cotton yield. The study provided an important technical reference for use of saline water irrigation of cotton.
[Objective] The mechanism of sucrose metabolism of potassium regulating the cotton fiber strength under salt stress was investigated to provide theoretical basis for proper potassium application in saline-alkali land. [Methods] A field experiment was conducted to investigate the effects of potassium on the fiber strength, the accumulation of cellulose, the sucrose and callose content and related enzyme activities during the cotton fiber thickening of two cotton cultivars with contrasting salt sensitivity (CCRI 79, salt tolerant cultivar, and Simian 3, salt sensitive cultivar). Three potassium supply treatments (0, 150, 300 kg·hm-2) under three soil salinity levels (Low salinity 1.68~1.78 dS·m-1, Medium salinity 6.21~6.42 dS·m-1, High salinity 10.59~11.08 dS·m-1) were applied. [Results] (1) Salt stress significantly reduced the strength of cotton fiber. The effect of medium and high salt on fiber strength was alleviated by potassium, but there was no significant difference between 150 and 300 K2O kg·hm-2. The effect of potassium on the fiber strength of CCRI 79 was better than that of Simian 3. (2) Salt stress reduced the accumulation of cellulose during the thickening stage, fiber sucrose content was reduced while the content of callose was increased. The maximum accumulation rate of cellulose, the activity of sucrose phosphate synthase and β-1,3-glucanase at 28 days post anthesis were increased by potassium application, which increased the content of sucrose and callose. With the aggravation of salt stress, the alleviating effect of potassium gradually weakened. The maximum accumulation rate of cellulose and the increase of β-1,3-glucanase activity in CCRI 79 were higher than those in Simian 3. [Conclusion] The potassium application under saline-alkali land can alleviative the effect on cotton fiber strength caused by salt.
[Objective] The purpose of this study is to map quantitative trait loci (QTL) related to fiber quality traits in upland cotton. [Method] Using CCRI 679 with high-quality fiber and Nongken 5 as parents, we constructed a F2 population with 200 individual plants and the corresponding F2:3 population, and five fiber quality traits of the two populations were tested. We used 6 688 pairs of SSR (Simple sequence repeat) to screen between the two parents, and 149 polymorphic primers were obtained. The linkage map of F2 genotype data and QTL mapping of F2 and F2:3 populations were carried out using the QTL IciMapping software. [Result] A genetic linkage map including 119 markers, 28 linkage groups and a total length of 1 173.5 cM (centiMorgan) was constructed. Nine and eleven QTLs related to fiber quality traits were detected in F2 and F2:3 population, respectively. These QTLs were distributed in 11 linkage groups. Among them, qFL-D11-1 and qBT-D11-1 of F2 population and qFL-D11-1 and qMIC-D11-1 of F2:3 population were all located between DPL0062 and HAU0423. It was speculated that these loci may be important QTLs controlling fiber quality traits. [Conclusion] Using multiple generations to map QTL is helpful to obtain stable QTL loci, and the genes controlling fiber quality traits may exist in clusters, and these QTLs will lay a foundation for mining fiber quality related genes and molecular marker-assisted breeding.
[Objective] In this study, we analyzed the effect of exogenous hormone abscisic acid (ABA) on cotton callus dedifferentiation and embryogenic callus differentiation during somatic embryogenesis, and aim to optimize the somatic embryogenesis system and to reveal molecular mechanism of ABA regulating somatic embryogenesis. [Method] The hypocotyl of CCRI 24 cotton was used as the explants for callus induction. Callus and embryonic callus were induced by adding different concentrations (0, 0.02, 0.04, 0.06, 0.08 μmol·L-1) of ABA to MSB medium (MS medium plus vitamin B5) to study the effect of ABA on the initial cellular dedifferentiation, callus induction and embryonal callus induction of cotton hypocotyl. [Result] The initial cellular dedifferentiation was promoted by of 0.02-0.08 μmol·L -1 ABA. During the callus induction phase, ABA (0.02-0.08 μmol·L -1) significantly increased callus dedifferentiation rate (CDR) and callus proliferation rate (CPR). In the embryogenic callus induction phase, 0.02 μmol·L -1 ABA significantly increased embryogenic callus differentiation rate (ECDR), but 0.04-0.08 μmol·L -1 ABA treatment significantly inhibited ECDR. ABA treatment (0.02-0.08 μmol·L -1) significantly increased embryogenic callus proliferation rate (ECPR) and non-embryogenic callus proliferation rate (N-ECPR), and affected the texture of embryogenic callus and non-embryonic callus. ABA treatment (0.02-0.08 μmol·L -1) significantly activated the transcription of LBD16 and LBD29 at the beginning of callus induction. 0.02 μmol·L -1 ABA treatment significantly up-regulated the expression levels of BBM, LEC1 and AGL15 at the early and middle stages of callus proliferation, and up-regulated FUS3, LEA, ABI3 expression at the late stage of callus proliferation. [Conclusion] ABA regulated somatic embryogenesis is closely related to the spatiotemporal expression of marker genes, and the increased expression levels of these marker gene is the molecular basis of ABA-mediated differentiation of callus and embryogenic callus.
[Objective] The effects of different organic fertilizer replacement rates on cotton biomass, nutrient accumulation, yield, N:P ratio soil fertility in the Yellow River Basin were studied, and the suitable replacement rates of organic fertilizer to replace part of chemical fertilizer were explored, in order to provide reference for the rational application of organic and inorganic fertilizers in the cotton field in the Yellow River Basin. [Method]The experiment began in 2016, six fertilization treatments were set up in the experimental base of Institute of Cotton Research, Chinese Academy of Agricultural Sciences. T1: no fertilization, T2: 100% chemical fertilizer, T3: 20% organic fertilizer + 80% chemical fertilizer, T4: 40% organic fertilizer + 60% chemical fertilizer, T5: 50% organic fertilizer + 50% chemical fertilizer, T6: 100% organic fertilizer. After 3 years of fertilization, field sampling was conducted in 2018 to analyze the effects of different fertilization treatments on cotton biomass, nutrient accumulation, yield, N:P ratio and soil fertility. [Result] (1) Organic fertilizer treatment instead of 50% chemical fertilizer treatment had the greatest effect on the biomass of cotton plant, the nutrient accumulation of cotton plant and cotton yields. (2) Compared with the 100% chemical fertilizer, the application of organic fertilizers increased the content of soil organic matter, total nitrogen, available phosphorus, and alkali-hydrolyzable nitrogen, and application of 100% organic fertilizer significantly increased the content of soil available phosphorus. (3) There was a significant positive correlation between the accumulation of total nitrogen and total phosphorus of cotton plant and the biomass of cotton plant, and a significant negative correlation between the N:P ratio in root and stem and seed cotton yield. [Conclusion] Partial substitution of chemical fertilizer with organic manure could reduce chemical fertilizer use, and continuous application of organic fertilizer to replace some chemical fertilizers has a tendency to increase soil fertility. Substitution of chemical fertilizer by 50% organic fertilizer was most effective to improve cotton biomass and nutrient accumulation and increase seed cotton yield.
[Objective] Phenylalanine ammonia-lyase is a key enzyme in the metabolism of phenylpropanoids and plays an important role in plant growth regulation and stress tolerance. The evolution and function study of cotton phenylalanine ammonia-lyase gene family at the whole genome level will provide data support for related researches. [Method] HMMER and BLASTP were used to search phenylalanine ammonia-lyase genes from cotton genomes, and MEGA was used for evolutionary analysis, MCScanX was used for collinear analysis; in addition, NCBI SRA data were used for expression analysis. [Result] In this study, 12, 13, 7, and 8 phenylalanine ammonia-lyase genes were obtained from Gossypium hirsutum, G. barbadense, G. arboreum, G. raimondii, respectively. According to the evolutionary analysis and collinearity results, we speculated that the diploid ancestors of the four cotton species should have six phenylalanine ammonia-lyase genes initially. The results of the cis-element analysis indicated that the phenylalanine ammonia-lyase gene family contains cis-elements related to light, hormone, stress, and development. The protein sequence of phenylalanine ammonia-lyase has a conserved motif. Twelve phenylalanine ammonia-lyases in G. hirsutum have different expression patterns under cold, hot, salt, and PEG stress. [Conclusion] The results of this study are helpful to understand the evolution and function of the phenylalanine ammonia-lyase gene family in cotton, and provide a theoretical basis and reference for the follow-up study of their specific functions in cotton. In this study, the numbers, physicochemical properties, evolution, and expression characteristics of phenylalanine ammonia-lyase of cotton were determined, which will provide resources for further study of phenylalanine ammonia-lyase.
[Objective] This study aims to determine the effect of meteorological conditions on cottonseed vigor. [Method] Two cotton varieties, Liaomian 31 and Liaomian 25 were selected. Flowers were hanged on the day of flowering, and the population of seeds with different plant resident time was obtained. The 100-seed weight, 7 d germination rate, and main nutrient content of the seeds were measured. Malondialdehyde (MDA) concentration, peroxidase (POD) activity, catalase (CAT) activity, and superoxide dismutase (SOD) activity during germination were also measured. [Result] The 100-seed weight was related to seed residence time in plant but not to with flowering time. The crude fat content in Liaomian 31 seeds was significantly higher than that in Liaomian 25 seeds. The contents of soluble sugars and starch were not significantly different between the two cultivars, and the contents of soluble sugars were related to seed residence time in the plant. During germination, the MDA concentration increased first and then decreased, and was lower in Liaomian 25 than that in Liaomian 31 without significant difference. The POD activity increased first and then decreased obviously. The CAT activity decreased first obviously and then increased limitedly. The SOD activity decreased continuously and obviously. The activities of POD, CAT, and SOD in Liaomian 25 were higher than those in Liaomian 31 without significant difference. The correlation analysis between meteorological factors and seed physiological and biochemical indices indicated that 4 meteorological factors, namely, precipitation, the accumulated temperature of ≥12 ℃, diurnal range, and sunshine hours, exhibited significant or extreme significant correlation with 100-seed weight, soluble sugar content, MDA concentration, and CAT activity during seed germination. Twenty-five simulation models were obtained by stepwise regression method with the four meteorological factors as independent variables and the four seed characteristic indices as dependent variables. Among these models, 13 quadratic polynomial models were further analyzed by edge analysis to determine the marginal effects of meteorological factors. [Conclusion] Overall, four meteorological factors, precipitation, the accumulated temperature of ≥12 ℃, diurnal range and sunshine hours during seed resident in plants affected the four seed characteristic indices, 100-seed weight, soluble sugar content, MDA concentration, CAT activity, and consequently influenced seed vigor. Among them, the influence of diurnal range and sunshine hours on seed characteristic index is greater. The optimal plant resident time of cotton seeds in the Liaohe River Basin was 65-70 d. These bolls are mainly formed in the middle of July.
[Objective] The purpose of this study is to explore the feasibility of chemical topping with fortified mepiquat chloride (DPC+, a type of aqueous formulation containing 25% 1,1-dimethyl piperidinium chloride) on direct-seeded cotton after wheat/rape in the Yangtze River valley. [Method] Field experiments were conducted in Dafeng, Jiangsu province, Susong, Anhui province and Wuhan, Hubei province during growing seasons of 2015-2017. The randomized block design with three replicates was adopted. There were two chemical topping time (same time with local manual topping, and five days after local manual topping) and three DPC+ dosages (750,1 125,1 500 mL·hm-2), with manual topping as the control. [Result] Compared with manual topping, chemical topping with DPC+ increased plant height and the number of fruiting branches at most by 21.6 cm and 4.8 per plant, respectively; shortened the length of middle and upper fruiting branches (especially the upper ones), but did not influence the number of fruiting sites except few sites. Chemical topping with DPC+ showed similar yield with manual topping under most environmental conditions. However, the treatments with low DPC+ dosages reduced yield to some extent during growing seasons with high precipitation (more than 1 000 mm). The time of chemical topping had slight effects on cotton yield. [Conclusion] For direct-seeded cotton after wheat/rape harvest in the Yangtze River valley, manual topping could be substituted by chemical topping with DPC+. Future work will focus on optimizing the time and dosage of DPC+ application, and using agricultural practices for steady growth and development of cotton plants.
