The recent development and current status of research on the cotton weed in China were summarized, including the weed occurrence, distribution rule, population dynamics, weed damage and control techniques. Although the research on basic theory and chemical management technologies of cotton weed in China has got a faster development, problems of frequent herbicide injury, dominant weed population changes, lag in control techniques and deficiencies of transgenic resistant herbicide cotton still exit. Therefore, the study on basic theory should be strengthened. On the basis of chemical control, we should speed up the creation of novel chemical herbicide, strengthen the monitoring and management of herbicide resistant weeds, and carry out further research on biological weed control and herbicide resistant cotton.

Cotton fiber development usually consists of four overlapping stages: fiber initiation, cell elongation, secondary cell wall formation, and maturation. Fiber length and strength are both key traits of its quality, and mainly depends on two biological processes: fiber elongation, secondary cell wall formation, respectively. Transcription factors and plant hormone play very important roles in the stage of fiber differentiation and initiation. The R2R3 MYB transcription factor GaMYB2 and WRKY transcription factors GhTTG1, GhTTG3，have been demonstrated playing significant roles in control cell fate determination. The genes encoding predicted proteins involved in auxin, brassinosteriod (BR), gibberellin acid (GA), abscisis acid (ABA) and ethylene signaling pathway are upregulated in the period of fiber cell initiation. During fiber cell elongation period，many genes that represent three majors functional groups, including：cell wall structure and biogenesis, cytoskeleton, lipid and carbohydrate metabolism, show higher expression level. Plant hormones also play some regulatory roles in cotton fiber elongation. BR and ethylene can promote the fiber cell elongation in vitro culture. The initiation and rapid elongation of fiber requires the expression of sucrose synthase (SuSy), suppression of this gene represses fiber and seed development. Cellulose synthesis is a predominant event in fiber cells during in the secondary cell wall synthesis stage，cellulose synthase genes and SuSy are key regulatory and play significant role in this period. Based on the research of cotton fiber development at molecular level, improvement of fiber quality through genetic engineering has made some progress. For instance, overproducing spinach sucrose phosphate synthase to enhance fiber quality; transforming the acsA and acsB genes from Acetobacter xylinum, which are involved in cellulose synthesis, into cotton to improve the cotton fiber strength, etc. Color is also a main trait of cotton fiber and some progress has been made in produce color fiber through genetic engineering.

There are three phases of DNA fingerprint technology based on molecular marker：the first is RFLP based on Southern blot，the second are several markers based on PCR and the third is SNP（single nucleotide polymorphism）.Research and application of variety identification technology was discussed，four main molecular marker technologies applied in cotton variety identification were introduced in detail as follow:RFLP,RAPD,AFLP and SSR.Technology principle,research and application status,advantage and disadvantage about each molecular marker applied in cotton variety identification were expatiated.As compared，the viewpoint was put forward:SSR marker was the most appropriate molecular marker in cotton variety identification,and the necessity of construction of Chinese cotton DNA fingerprint database based on SSR marker technology was analyzed.

The dynamics of the activities of protective enzymes and MDA content in two kinds of genetically modified (GM) cotton varieties and their non-GM parents after being piercing-sucked by Lygus lucorum were studied. The results showed that: before and after the vaccination of Lygus lucorum, there were no significant difference on the activities of protective enzymes and MDA content between two kinds of GM cotton varieties and their non-GM parents, so it has no effect on physiological indices when exogenous genes were introduced into cotton. Throughout the period of Lygus lucorum's attacking, there was very significant difference in the activities of protective enzymes and MDA content to the same cotton variety; the three indicators, SOD, MDA and PAL activities or content, showed significant or very significant differences in the interaction effect between variety and bug accepting time, and the rest of the interaction was not significant.

Effects of nitrogen application rates and mepiquat chloride （DPC） sparing doses on content of chlorophyll and SPAD value in leaf of earliermiddle spring cotton variety Yuza 35 and shortseason one Yinshan 1 were studied.The results showed that content of chlorophyll and SPAD value in leaf of two cotton varieties increased with enhancing nitrogen application rates or DPC sparing doses.There were significantly positive correlations between SPAD value and content of chlorophyll in leaf in most growth stages.But content of chlorophyll in leaf decreased more quickly than SPAD value in later growth stage,i.e.,the content of chlorophyll in leaf in boll opening stage decreased significantly than that in full bolling stage, and the SPAD value in boll opening stage decrease slightly than that in full bolling stage.Therefore,SPAD value is still efficient to conduct leaf color threshold when DPC is applied to cotton,but attention should be paid to the different tendency of content of chlorophyll and SPAD value in later growth stage of cotton.

Based on the cotton pot experiment involving four varieties (three were upland cotton and one was sea island cotton) and two N treatments and field experiment with different N treatments,the spatial differences of N and Chlorophyll contents (SPAD value) in the four upper fully expanded leaves and their relationships with whole leaf and plant N concentration were investigated. The results showed that leaf N contents and SPAD values at different leaf positions differed obviously,leaf N contents and SPAD values increased and differences among different position leaves decreased at high N rates. The sensitivity of the fourth leaf from the top to N was the highest,and next was that of the second leaf from the top was the lowest,while that of the first and the third leaves varied within the varieties. The SPAD value of the fourth leaf from the top was most correlated with whole leaf and plant N concentration among the top four leaves through the bud stage,initialflowering stage. The CV of SPAD value of the fourth leaf from the top was the smallest under optimal N level. It was suggested that the fourth leaf from the top was the most ideal indicator when using SPAD value or leaf color difference to diagnose N status in cotton.

In this review，we mainly summarized the recent research advances on cotton Verticillium wilt in the following aspects：mechanism of Verticillium pathogenicity，mechanism of host resistance，cotton resistance breeding against Verticillium wilt．We analyzed the different factors lagging the resistance breeding，such as limited resistant resources and lack of efficient breeding methods，and proposed measures for accelerating the Verticillium wilt resistance breeding progress．

The difference for resistant effects to bollworm, the dynamic of resistance and the content of Bt toxin protein in different organs during developmental stages of different varieties of Bt transgenic cotton were explored in laboratory. The results showed that there were significant differences for resistance to cotton bollworm during every growing stage of all varieties; DP 99B has the highest resistance to cotton bollworm, while Hanza 154 has the lowest, and their average corrected mortality to cotton bollworm were 89.23% and 75.91%, respectively. The resistance to cotton bollworm of cotton plants in each growing stage was presented in the following order, budding stage > flowering stage > flowering-boll stage >boll stage. The results of ELISA showed that Bt toxin protein could be detected in all organs of transgenic cotton, but its content varied significantly among organs along the developmental stages. There were significant differences of Bt toxin protein content among the functional leaves in different stages, the order of the content was: seven-leave stage > three-leave stage > budding stage > boll stage > flowering-boll stage.

Soil samples (0~20 cm) from 318 saline cotton fields randomly selected in the Yellow River Delta were used to study the [JP2]characteristics of salinity,contents of organic matter and major nutrients.The results showed that,of the total 318 saline fields tested,the lightly salty (LS) fields (salt content <2.5g·kg^-1),moderately salty (MS) fields (2.5~4.49 g·kg^-1) and severely salty（SS）fields (>4.50 g·kg^-1) accounted for 44.3%,40.6% and 15.1%,respectively. The levels of N,P,K in MS fields were moderate,but K level in LS fields was low. The contents of organic matter,N and P were deficient,but K content was abundant in SS fields where cotton had been planted shorter than 5 years.In contrast,the contents of organic matter,N and P were moderate,but K content was relatively low in SS fields where cotton had been planted longer than 5 years.Regression analysis showed a significant linear correlation between soil salt content (y) and soil solution conductivity (x) at 25°С (y=3.4058x+ 0.1427,n=27,R²=0.9964^**). Normal emergence and stand establishment rates were obtained when soil salinity was lower than 2 g·kg^-1. Rates of emergence and stand establishment were reduced to 60%~78% and 45%~55%, respectively,when salinity was 2~3g·kg^-1.The emergence and stand establishment rates were only about 40% and < 30%,respectively,in saline fields with salinity higher than 4 g·kg^-1.Reasonable agronomic measures for stand establishment and chemical fertilization should be taken according to the characteristics of salinity and fertility,to improve cotton productivity in saline fields.

Cotton stalks were inoculated with some rhizospheric soil and decomposed under the temperature of 35 ℃. After decomposing 60 hours,the decomposing products were extracted by mixture of acetone and ethyl acetate in 5 days. The extract was concentrated and then subjected to bio-assay and chemical constituents analysis by GC-MS technique. The results indicated that cotton stalk decomposing products showed allelopathy on seed germination and seedling growth. It was observed that under concentration of 0.5g·L^-1,1.0 g·L^-1,1.5g·L^-1 extract,the seed germination was constrained under higher concentration but promoted under lower concentration. The cotton stalk decomposing products showed significant inhibition on seedling growth（P < 0.01）even under the concentration of 0.5g·L^-1. And weakened root vigor,reduced chlorophyll contents and declined fresh weight and plant height were found when the extract added into hydroponic culture. A lethal effect on tested cotton seedling was observed when the concentration of extract in nutrition solution reached to 1.5g·L^-1. Activities of SOD and POD were induced at lower concentration but inhibited by higher concentrations of the extract. Higher contents of MDA were also found in higher concentration extract treatments. Total of 24 main constituents were detected in cotton stalk decomposing products by GC-MS analysis,the predominant constituents including 4-hydroxy-4-methyl-2-pentanone (27.31%),dibutyl phthalate (7.87%),hexadecanoic acid (6.69%),butanedioic acid,methyl-,bis (1-methylpropyl) ester (6.40%),9,12-octadecadienoic acid (Z,Z)-(5.43%),etc. Several of them have been identified as allelochemicals which were frequently reported.

Nitrogen application rates of 0, 75, 150, 225, 300 and 375 kg ·hm^-2 on dry matter accumulation and distribution as well as the N, P, K uptake and utilization of hybrid cotton were studied under high yield conditions. The results showed that the nitrogen utilization and dry matter content were significantly positive correlated with N, P, K accumulation. The nitrogen can improve the dry matter and N, P, K accumulation. But the effect that applying nitrogen was no longer significant when the nitrogen application rate increased to 300 kg·hm^-2. The analysis of nitrogen content on dry matter accumulation of different organs indicated that nitrogen content was positive correlated with leaves and negative correlated with stems in the middle stage of cotton growth periods and positive correlated with stems in the latter growth stage. The nitrogen content was positively correlated with cotton bud and flower in the middle growth stage while negative in the latter growth stage. When the nitrogen application rate increased to 300 kg·hm^-2, nitrogen decreased the proportion of N, P, K and dry matter distributed to reproductive organs and increased the proportion of leaves and stems. The vegetative growth of the hybrid cotton was excessively vigorous. In this experiment, applying the nitrogen of 300 kg·hm^-2 had the highest seed cotton yield which was 1.66％ higher than the nitrogen of 225 kg·hm^-2, but there was no significant difference. When nitrogen rate increased to 375 kg·hm^-2, the seed cotton yield decreased by 2.23％ and 3.92％ compared with N 300 kg·hm-2 and 225 kg·hm^-2, respectively. The nitrogen utilization decreased distinctly while the phosphorus and potassium utilization increased with the more nitrogen fertilizer added.

The effects of transgenic Bt and Bt+CpTI cottons on soil enzyme activity in different stages were study under the greenhouse experiment condition. The results showed that from the seeding stage to the flower and boll stage, the activities of soil urease，polyphenoloxidase, acid phosphatase and alkaline phosphatase increased at first and then decreased. However, the activities of protease and the neutral phosphatase decreased at first and then increased.As for the same variety between the two neighboring stages of duration, the differences of the soil urease, protease, acid phosphatase and neutral phosphatase activities have reached the great remarkable level(P<0.01).Compared with nontransgenic cotton，the planting of transgenic cotton GK12 had a decrease of soil urease activity(23.06%) and a decrease of soil acid phosphatase activity(10.89%). The Bt+CpTI cotton sGK321 also decreased the enzyme activity. The transgenic Bt+CpTI cotton sGK321 caused a fewer disturbances on soil biological activities: compared with its parent nontransgenic cotton, it had an extremely significant effects on the activities of soil urease, protease, acid phosphatase and neutral phosphatase.

The research on 42 earliness cultivars planted in Xinjiang was conducted, using SSR molecular markers. Among 2300 pairs of primers, 52 pairs with steady polymorphism were selected. Three to 24 polymorphic loci were detected by each pair of primers. There were 506 polymorphic fragments detected in total. The average number of polymorphic fragments detected were 9.7 per pair of primers. The band size ranged from 100 to 2000 bp. The 52 SSR fingerprint maps were combined and analyzed comprehensively, it turned out to be that all the cotton cultivars could be identified by two primer pairs. The results indicated that the SSR markers can help to construct fingerprint map with high efficiency and accuracy rapidly, and it is feasible and effective to identify cotton cultivars with SSR molecular markers. This study will lay a solid foundation for rapid authentication and quality control of cotton seeds with large sample size.

Activities of SOD, POD, CAT protective enzymes and MDA content in main-stem leaf and anther at different developmental stages and their responses to high temperature stress at peak flowering stage were analyzed comparatively using three cotton lines exhibiting tolerance, moderate sensitivity and sensitivity to high temperature in the present paper. The protective enzyme activities in main-stem leaves were nearly same among the three cotton lines at seedling and peak squaring stages, but significantly higher in tolerant line than susceptible ones at peak flowering and boll-setting stages. The MDA content was markedly lower in tolerant line than susceptible ones from peak squaring stage. Activities of protective enzymes in cotton anther increased with developmental processing, and remarkably higher SOD and POD activities in anther at the pollen maturing stage were measured in tolerant line. During the whole developmental period of anther, CAT activity was greater, while the MDA content was lower distinctly in tolerant line than susceptible ones. The protective enzyme activities were inhibited, and the MDA content increased excessively in main-stem leaves and anther of the three cotton lines under high temperature stress at the peak flowering stage. However, changes of decreasing in activities of protective enzymes and increasing in the MDA content in leaves and anther were less obviously in tolerant line than susceptible ones.

Salinity and waterloging are two important abiotic stresses to agricultural production. Since the period of plant growth and development of cotton and the rainy season overlap, a combination of waterloging and salinity may occur in saline cotton field, but the effect of the combined stress on cotton is still not well documented. In attempt to investigate the single and the combined effects of waterlogging and salinity on cotton (Gossypium hirsutum L.), two cotton varieties (SCRC17 and SCRC28) were cultured and treated with either fresh water (CK), salinity, waterlogging or a combination of both stresses at the 3 true-leaf stage in a greenhouse. The photosynthetic rate (Pn), chlorophyll fluorescence parameters, chlorophyll contents in seedling leaves and plant dry weight were examined at 14 d after stress. The results showed that salinity, waterlogging or the combination significantly reduced Pn and dry weight for both cultivars，but the effect of waterlogging was significantly greater than that of salinity, and that of the combination of both stresses was greater than either stress alone. A significantly combined inhibitory effect on plants growth and leaf photosynthesis was observed in the combination treatment. The decreased Pn under salinity stress was greatly attributed to the decline of leaf chlorophyll contents, while the decreased Pn under waterlogging and a combination of both stresses might be attributed to the reduced stability of chloroplast and PSⅡ. It is suggested that improvement in irrigation and drainage in saline cotton field is a practical way to enhance cotton yield and fiber quality.

The genetic diversity of 48 cotton accessions were analyzed by using ISSR markers.11 primers were screened out of 60 primers. Total of 92 bands were detected, 77 of them were polymorphic. The percentage of polymorphic bands was 83.70%. UPGMA Cluster analysis based on ISSR data showed that the genetic similarity (GS)coefficient of 48 accessions ranged from 0.27 to 0.93. 48 germplasm resources could be categorized into four major groups, wild cotton of Zhanjiang and Lianjiang, Guangdong province, showed great genetic difference from other materials, fell into one group, belong to primitive group. G.barbadense cotton were obvious genetic diffrent from G.hirsutum, also fell into one group, and high similarity among the rest cultivars from different provinces formed other groups. The study indicated that ISSR molecular marker is an efficient tool with high polymorphism and stability for analysis the genetic diversity and relationship of cotton germplasm resources.

The cotton yield factors, the hereditary effect of cotton fiber quality and the genetic correlation were studied using the incomplete diallel analysis (8×8), and the genetic correlation was divided into addictive correlation and dominant correlation. The results showed among cotton yield factors, the inheritance of lint yield and boll numbers per plant were mainly controlled by addictive effect and dominant effect, and the addictive effect and dominant effect of inheritance for boll weight and lint were equally important as well. The effect of environment variance on lint was the least, so it was better to take breeding selection in the population of F₂~F₃ generations. As for the characters of cotton fiber quality, the inheritance of fibre length, specific tenacity and micronaire value were mainly controlled by addictive effect. The effect of environment variance on them above-mentioned were all bigger. The correlation between cotton yield factors and fiber quality characters generally showed that genotypical correlation was bigger than phenotypical correlation. The nature of phenotypical correlation, genotypical correlation and addictive correlation for each character was similar, however, it was different for dominant correlation. It was concluded that genotypical correlation, especially addictive correlation, could assist cotton breeding, while dominant correlation was very important to utilize the hybrid vigor.

The effect of water stress on germination of cotton seeds was studied, while different treatments were simulated as different concentrations of polyethylene glycol (PEG). The result showed that as water  potential decreased, germination percentage, speed of germination, germination index, vigor index, sprout length, roots length, R/S (ratio of root to shoot), fresh and dry weight of plant decreased in different extent. The decreasing extent of percentage germination and R/S were not distinct in lower stress. However, all of the indexes were restrained intensely while concentrations of PEG exceed 15%.

Effects of nitrogen and potassium fertilizer on photosynthetic characteristics and yield & quality of shortseason cotton were studied under field experiments. Two urea (N) levels 225 kg·hm^-2  and 300 kg·hm^-2 and three KCl (K) levels 0 kg·hm^-2,120 kg·hm^-2 and 195 kg·hm^-2 were used in the experiments. The results indicated that photosynthetic capability in leaves of cotton and yield were higher applied more N than less N under the same K levels, and N utilize efficiency increased when applying more K. Meanwhile, photosynthetic capability in leaves of cotton , yield and quality was higher applied K than no K under the same N levels, and seed cotton yield were significantly different when applying different K levels. The highest yield was gained when applying urea 300 kg·hm^-2  and KCl 195 kg·hm^-2  under this experiments condition. So, supplying suitable K to keep balance of N and K is extremely important to improve N utilize efficiency, yield and quality of cotton under enough N.

In order to explore the genetic basis for photosynthesis and its related physiological trait of cotton, a mapping population of 273 F_2：3 inbred lines derived from a four-way cross of Simian 3/Sumian 12//Zhong 4133/8891 was employed to map quantitative trait loci (QTL) of leaf chlorophyll content and photosynthetic rates in cotton by interval mapping method with MAPQTL5.0. The results showed that a total of three QTLs were detected for leaf chlorophyll content on chromosome D6,D8 and A10, respectively, which explained 4.3%，4.5% and 5.2% of the phenotypic variance, and a total of three QTLs were detected for photosynthetic rates on chromosome D5,D6 and A11，respectively, which explained 3.8%, 7.4% and 8.4% of the phenotypic variance. Additive effects were mainly genetics effects for all QTLs of two traits. These QTLs concerned with leaf chlorophyll content and photosynthetic rates in cotton were first reported, and these results should be very useful for marker-assisted selection in cotton high photosynthetic rates breeding program.