Three decades of disease survey data have shown Verticillium wilt was one of the first major diseases of cotton recorded in the 1984–85 season. Survey reports the mean incidence was 4.1% in the 1984–85 season and rose to 16.6% in the 1989–90 season. Prior to 1984 all commercial varieties of cotton available in Australia were susceptible to bacterial blight and the disease was common. The adoption of the resistant varieties contributed to a dramatic decline in the incidence of bacterial blight and the removal of bacterial blight as a significant pathogen to Australian cotton crops by 1992. Survey results showed the incidence of black root rot increased on farms with a long history of growing cotton during the 1990s. Fusarium wilt of cotton was first reported in New South Wales (NSW) in 1994. The disease is now widespread, being confirmed on 86 NSW farms in six of the eight cotton production areas in NSW. These four significant plant disease ‘problems’ have challenged the cotton industry in NSW. Data provided by the surveys have indicated the relative importance of each of the diseases present and the impact of cultural practices and the adoption of new varieties on disease distribution, incidence and severity. The results have therefore been used to support and justify requests for research funding and have contributed to the development of Integrated Disease Management strategies. The NSW Department of Primary Industries continues to monitor the distribution of disease and the incidence and severity present in commercial cotton crops in all production areas of NSW. The aim of this paper is to highlight four significant cotton diseases in Australia and show relationships between cultural practices and declining and increasing incidence of disease.

In recent year, extention of Cotton planting as double crope is important due to planting of compentitative crops such as Wheat and Canola. Late planting of Cotton (Gossypium hirsutum L.) is resulted in flowering delay and so boll development at lower temperature. For this reason, an experiment was conducted as 8 research project to identify suitable earliness cultivars for planting after Wheat and Canola harvesting. In this Research, with respect to genotypes comparison, Agronomical management of Cotton double crop was studied based on Irrigation planting layout, diseases, pests, and tillage. In this research, 20 earliness cotton genotypes were studied. In HashemAbad cotton research station, Gokorova, Tabladila and NO:200 in view of yield and B557, Bolgar 539, 4-S-4, Mehr and NO:200 with respect to earliness were in first class, respectively. In Karkandeh station, cotton genotypes had no significant difference in view of earliness but Bolgar 539 and NO:200 were in first class for seed cotton production. In Mogan station, Tabladila and NO:200 for yield and Opal, Bolgar539 and Gokorova for earliness were in first class, respectively. In the best suitable planting pattern and plant density Projects, the best planting pattern and variety was Mutajeneze early variety and 60Χ10 cm plant spacing (166000 plant per hectar). In hashemabad and Karkandeh Cotton Research Station ، the best plant pattern was 43259 'S genotype and 60Χ20 cm plant spacing (83000 plant hectar). In tillage projects, Siokra had good response to strip plowing + no tillage + two discs, but Syndose8o in plowing + disc and Mutagens earliness in chisel plowing +disc were better than other treatments. In projects of Crop residual management, the highest total yield was obtained by interaction effect of tillage + disk, remove crop residue and 20 kg/ha nitrogen fertilizer over recommended doses. In yield function project, maximum Cotton seed yield of Sahel, 43259 and 43347 were obtained with water consumptions of 1739,1832 and 1593 m3/ha, respectively. In order to determination of ferequency and irrigation water depth, the best treatment could be irrigation after 105 mm evaporation of pan with 80 % water requirement and 43347 cultivar. The results showed that various row spacing has affected yield and index of verticillum wilt. The best plant pattern and earliness variety was mutajeneze and 60Χ10 cm plant spacing (166000 plants per hectare). There was significant difference among pest's population. Number of Aphis gossypii (Glove.), Asymmetrasca decdens (Dlabo.), Bemisia tabaci (G.) and Thrips tabaci (L.) populations on B-557 and 43259 were less than Sahel. Number of cotton bollworm Helicoverpa armigera(Hub.) was no significant difference among varieties. Therefore, with respect to lesser pollution to cotton diseases the varieties of 43259 and B-557 are recommended to be grown as double crops (cotton after rapeseed) in Golestan provience.

Either canola (Brassica napus L.) or cotton (Gossypium hirsutum L.) production in China ranks the first in the world in planting area and/or output. Three quarters of Chinese canola are grown in Yangtze River Valley and half of cotton planting area is cropped with canola sequentially. Cotton stubble are normally removed from the field or burned in situ before canola sowing to facilitate field management, and potentially to reduce the incidence of diseases. However, the way of cotton stubble disposal is labor costing, resources wasting and/or air pollution contributing. Hence, two-growing-season field experiments were conducted to evaluate the effect of cotton stubble mulch with stalk remaining straight and lying down at elongation stage on canola grain yield, canopy temperature and soil nutrients status. The first experimental treatments were established following a split-plot design of a randomized complete block with cotton stubble mulching (0 and 3250kgha−1) as the main plot and canola planting density (22.5, 30.0, and 37.5plantsm−2) as the sub-plot. The results revealed that canola yield under cotton stubble mulching (CSM, 3250kgha−1) was 9.9% higher than that under no cotton stubble mulching (NCM, 0kgha−1) averaged across two growing seasons, possibly because canola canopy mean daily temperature (MDT) of CSM was 0.5°C higher than NCM during the winter. Planting density significantly affected canola yield as well, where moderate planting density (30.0plantsm−2) resulted the highest canola yield (2425kgha−1). The second experiment was designed to compare soil nutrient content between CSM and NCM, which revealed that soil nutrition, especially alkaline N and available K, was improved by cotton stubble mulching. The results suggest that cotton stubble mulching would be a multi-win alternative choice for cotton stubble disposal and 30.0plantsm−2 should be the optimal density for canola production in the region.

Verticillium wilt of cotton is a major limiting factor in cotton production. To investigate the combined control effects of endophytic bacteria in different growth stages of cotton on Verticillium wilt, antagonistic bacteria Paenibacillus xylanilyticus YUPP-1, Paenibacillus polymyxa YUPP-8 and Bacillus subtilis YUPP-2 were isolated from cotton in the seedling, squaring and boll-setting stages, respectively. Assessment of colonization showed that strains YUPP-1, YUPP-8 and YUPP-2 had the highest populations in the seedling, squaring and boll-setting period, respectively. Indoor pot experiment indicated that cotton plants in the combined biocontrol bacteria treatment group were not infected before squaring stage, while infection rates of cotton treated with a single strain in the seedling period were 6.7% (strain YUPP-8), 6.7% (strain YUPP-1) and 13.3% (strain YUPP-2). However, infection rate of the control plants reached 80%. Field experiment conducted during 2010–2011 showed that the combined application of three strains had better effect than individual application. Verticillium wilt morbidity rate and disease index of cotton at the boll-setting period with combined application of three strains in 2010 were 9.4% and 6.5, respectively, while those in the control group were 47.5% and 32.8. The results in 2011 were similar to 2010, with higher disease severity in both treated and control plants. These results illustrated that combined application of endophytic bacteria can achieve good control effects against Verticillium wilt of cotton. This study provides a new strategy for the control of soil-borne diseases.

The purpose of this study was to examine the variations in the microbial community structure of soil actinomycetes in fields with continuous cropping of cotton in Xinjiang Autonomous Region, China. Soil samples were collected from four depths in fields with 7-year continuous cotton cropping. The community structure of soil actinomycetes was examined using the 16S rRNA-based polymerase chain reaction-density gradient gel electrophoresis (PCR-DGGE) techniques. The microbial diversity indices of the soil samples from different depths generally decreased along with the period of continuous cotton cropping. When the period of continuous cropping of cotton reached 5 years, the diversity indices rose again and gradually stabilized at a level slightly lower than that of soils with original ecology (i.e., 0-year cotton cropping). Cluster analysis showed that at the 1-20-cm depth, the actinomycete community structure of the soil subjected to 1-year cotton cropping was similar to that of soil subjected to 0-year cotton cropping, whereas that of soils after 3-year continuous cotton cropping showed high similarity. At the 21-40-cm depth, the actinomycete community structure showed various changes but generally recovered to its original pattern after repeated fluctuations. Principal component analysis showed that at the 1-30-cm depth, the actinomycete community structure varied similarly regardless of the period of continuous cotton cropping. In contrast, there were no clear actinomycete community structure variation trends at the 31-40-cm soil depth. Homology comparison of sequences recovered from the DGGE bands showed that the obtained sequences shared similarities >88 %. Alignment with the known homologous sequences indicated a lack of microorganisms related to soil-borne cotton diseases. Continuous cotton cropping exerted significant influences on the community structure of soil actinomycetes in Xinjiang Autonomous Region, which were largely determined by the soil depth and the period of continuous cotton cropping. The microbial diversity of soil actinomycete communities gradually recovered after 5-year continuous cropping. Thereafter, a new actinomycete community structure that was beneficial for continuous cropping of cotton was formed and stabilized each year.

Virus‐induced gene silencing (VIGS) offers a powerful approach for functional analysis of individual genes by knocking down their expression. We have adopted this approach to dissect gene functions in cotton resistant to Verticillium wilt, one of the most devastating diseases worldwide. We showed here that highly efficient VIGS was obtained in a cotton breeding line (CA4002) with partial resistance to Verticillium wilt, and GhMKK2 and GhVe1 are required for its resistance to Verticillium wilt. Arabidopsis AtBAK1/SERK3, a central regulator in plant disease resistance, belongs to a subfamily of somatic embryogenesis receptor kinases (SERKs) with five members, AtSERK1 to AtSERK5. Two BAK1 orthologs and one SERK1 ortholog were identified in the cotton genome. Importantly, GhBAK1 is required for CA4002 resistance to Verticillium wilt. Surprisingly, silencing of GhBAK1 is sufficient to trigger cell death accompanied with production of reactive oxygen species in cotton. This result is distinct from Arabidopsis in which AtBAK1 and AtSERK4 play redundant functions in cell death control. Apparently, cotton has only evolved SERK1 and BAK1 whereas AtSERK4/5 are newly evolved genes in Arabidopsis. Our studies indicate the functional importance of BAK1 in Verticillium wilt resistance and suggest the dynamic evolution of SERK family members in different plant species.

Gossypium herbaceum var. africanum is the only wild cotton species within the cultivated diploid G. herbaceum. As the A sub-genome donor of tetraploid cotton, it is characterized by its resistance to insects, diseases, and other adversities. We have constructed the first bacterial artificial chromosome library (BAC) for G. herbaceum var. africanum. With high quality and broad coverage, this library includes 75000 clones, with an average insert size of about 115 kb and fewer than 4% empty clones. Our library is approximately five-fold the size of the A-genome (1667 Mb) and it provides 99.3% probability for isolating genes of interest or their sequences. Using nine SSR markers that are located on five different chromosomes and linked with resistance to Verticillium wilt, seven of nine could amplify the 40 superpools and got 1–14 hits. Because of its moderate wide coverage and relative large insert size, this library will be an important genomic resource for classifying and analyzing the evolution of cotton species, as well as for isolating disease-resistance genes and control elements.

Grey (Areolate) mildew (Ramularia areola) and Alternaria blight (Alternaria macrospora) are two important fungal foliar diseases affecting cotton in India. Both the diseases are polycyclic in nature. The primary inoculum for grey mildew is through conidia or ascospores from infected debris and/or perennial cottons and the secondary spread is through primarily infected leaves. Whereas for Alternaria blight the spread is initially from seed-borne inoculum (in Gossypium herbaceum and Gossypium arboreum cottons) and/or crop debris and the secondary spread is from sporulating lesions on older leaves. Both R. areola and A. macrospora require a temperature regime of 20–30 °C with prolonged high humidity (>80%) and frequent rains for infection and disease development. However, it has been observed that cool weather coupled with prolonged dewy periods in the absence of rains has also been found conducive for the development of both the diseases. So, suitable epidemiological tools and models are required to predict the disease development, spread and to design suitable management practices.