Thielaviopsis basicola is a ubiquitous soil borne fungal plant pathogen with a wide host ran e. It is the causal agent of black root rot on many agriculturally important crops such as cotton, tobacco and legumes. Twenty-five T. basicola isolates collected from three cotton growing regions, and peat and lettuce soils from a range of locations were examined for genetic variation using the RAPD-PCR technique with 10 arbitrary primers. DNA polymorphisms were detected among isolates from the cotton-growing regions of Goondiwindi, Qld, and Narrabri and Warren, NSW. A phenogram was constructed using the unweighted pair-group method with arithmetic averages (UPGMA) for cluster analysis. Isolates from two cotton-growing regions each clustered into a distinct group based on RAPD-PCR profiles suggesting independent evolution of T. basicola between these regions. Isolates from the third cotton-growing region did not cluster and were distributed between the other two regions, suggesting migration and gene flow between these regions. Lettuce isolates clustered with peat isolates providing more evidence that peat is a source of T basicola found in lettuce soils. The results indicated that RAPD-PCR is a useful tool in detecting genetic variability in populations of T. basicola.

Managing sustainable cotton production is becoming more difficult with the ever increasing demand on limited resources. In addition cotton growers are facing increased pressures to manage resources more cost effectively and to be more accountable for the impact that their decisions make on the surrounding environment. Computer based decision support systems and simulation models are being developed to provide cotton growers with the best information and tools available from research to assist with their management decisions. A primary aim of the decision support and modelling teams in the cotton industry is to utilise sound and up to date technology, and integrate this technology across different electronic platforms and mechanisms, and finally delivering it to the industry for adoption. We in the cotton industry are in an enviable position with an agricultural industry rich with successes and failures in computerised decision support. Therefore we can call on a number of approaches to assist acceptance, development and evaluation of its products and activities. One principle approach is to use multifaceted skills and knowledge, coordinated effectively with expertise and input of others when available. The first part of this paper will discuss the operation and means by which the decision support team, which now includes a number of people working on the crop simulation models to deliver decision support tools. The second part of the paper will address the significance of decision support and models to the cotton industry. Finally, the paper will present future activities being undertaken, involving both the decision support team and those associated with modelling

Biotechnology is currently reshaping agriculture throughout the world with over 16 million hectares planted annually to genetically modified (GM) soybeans, corn and cotton, mainly in the US, but increasingly in Australia, Asia and South America. Some controversy remains towards GM food products and there is still a reluctance to embrace GM crops in Europe, but GM cotton is partially buffered from these concerns, as only its highly processed oil is used for human consumption, and it is now being widely grown in many cotton producing counties.

The ongoing development and adoption of decision support tools within the Australian cotton industry has led to the need for refinement of several crop data collection techniques. Present and future applications of the crop growth simulation model OZCOT (Hearn, 1994), whole farm water use efficiency calculator (Tennalcoon and Milroy, 2000), and the crop water management tool HydroLOGIC will be greatly enhanced by updates of crop status and development entered throughout the season. One of those needed is crop leaf area, which will help to improve estimates of evapotranspiration of moisture from the soil and crop. Leaf area of the crop is often referred to as the leaf area index (LAI), which represents the leaf area of the crop above a known area of ground surface. This paper presents the results of initial studies comparing a range of simple methodologies that could be used by cotton managers to obtain estimates of Lal throughout the cotton season

The disease black root rot (BRR) is caused by the soil born fungal pathogen Thielaviopsis basicola. This fungus has a broad host range, infecting 137 species, with a worldwide distribution (Honeess, 1994). The combination of a wide host range with the ability to produce persistent resting spores contributes to a high disease impact. BRR symptoms are readily identifiable in the field, with stunting of seedlings and characteristic black lesions on younger roots. While not killing the seedlings, except in extreme cases or in association with other seedling diseases, the stunting can carry through to maturity with significant yield reductions. in Australia BER is a relatively new disease, having only been found in cotton fields in 1989 (Allen, 1990), yet it has rapidly become a widespread major problem particularly when season temperatures are below average. Investigations are underway as a Cotton CRC project to assess the genetic diversity of the pathogen T.basicola. All understanding of the diversity is important for disease control measures to be instigated effectively; this includes plant breeding (even though resistance in cotton is yet to be found). The focus of this work is to examine the variation in Australia of strains of T.basicola, and from this information determine the pathogen's likely origins and effects on field outbreaks. To achieve this, molecular analysis of diversity will be combined with pathogenicity testing.

The importance of research and development to the Australian cotton industry is unquestionable. History details the achievements such as plant breeding that have contributed to significant improvements in cotton yield and quality. Worldwide recognition exists for much of the research including the management of chemical resistance in heliothis. Thirst for the latest research results and technology drives the industry extension efforts at an increasing pace. One can only contrast the success of the Australian cotton industry with the failures of those countries that do not have strong R&D programs. As growers we have become accustomed to researchers providing the basis for solutions to whatever challenges we have experienced. But there is no room for complacency. The question now is how can we maintain the efficacy of our R&D efforts to meet the challenges created by the increasing complexity of crop management, community and environmental scrutiny.

Plants can utilise an array of biochemical mechanisms to protect themselves against viral, bacterial, fungal and nematode pathogens. Systemic induced resistance can be achieved by using an activator, either an organism or a chemical, at the early stage of a crop. The activator 'switches on' the host plant's defence mechanisms. There are few reports of induced resistance against soil born and vascular pathogens. A significant reduction in the severity verticillium wilt in cotton disease was observed under field conditions after the use of isonicotinic acid (Colson-Hanks and Devera11, 2000). Application of the Novartis product Bion 50WG (a. I. bellzothiadiazole 50%) to grapevines resulted in a reduced the incidence of root knot nematodes. The rate of maturity of nematodes and egg production appearing to reduced (Owen et al 1999). Colonisation of roots by mycorrhizal fungi (VAM) may also induce systemic resistance in plants and protect them from pathogens (Dassi et al 1998). Rotation with non-host crops (eg. cereals) does not prevent the build-up of spores of T basicola in the soil with each cotton crop (see paper by Nehl et al this proceedings). Rotation with susceptible hosts, such as certain legumes, may add to the build-up of spores in cotton fields. Hence, the increasing interest in rotation with legumes presents a challenge to management of black root rot in cotton farming systems. In this paper we examine the potential for induced resistance to decrease the severity of black root rot in both cotton and legumes.

Irrigation in the Australian cotton industry has traditionally been dominated by the use of furrow irrigation practiced almost exclusively on the heavy clay soils associated with riverine flood plains. However, increasing pressures on water availability, expansion onto more marginal soils, the potential yield benefits of improved control of soil-water in the root zone, and the potential for reduced labour, fertiliser and pesticide costs have raised grower interest in alternative irrigation application techniques. In order to make informed investment decisions regarding irrigation application systems, it is necessary to understand the characteristics and performance of both the existing and alternative systems available. This paper draws on the results of recent studies looking at the in-field irrigation performance of furrow irrigation, large mobile irrigation machines (LMIM's) and subsurface drip irrigation (SDl) within the cotton industry. However, in discussing alternative irrigation options, it is important to realise that no single application system and management practice will be appropriate for all growers in all environments. As with most things in life, one size does not fit all! Hence, it is important to understand the nature of the alternatives and the factors which influence the performance, operation and management of each option

Black root rot is an intractable soil borne disease that threatens the sustainability of Australian cotton fanning. In this paper we describe the factors contributing to the spread of black root rot, the effects of black root rot on the maturity and yield of cotton, and prospects for its management and control. Black root rot was first observed in Australian cotton in 1989 (Allen, 1990). Annual disease surveys have shown an exponential increase in the number of fields with black root rot in NSW (Figure I) and the disease now occurs in all cotton glowing regions of NSW except Menindee. Black root rot is also widespread in south west Queensland and the Darling Downs (J. Kochman, personal communication). All understanding of the life cycle of the pathogen, Thielaviopsis basicola (Figure 2), is a key factor in explaining the increasing spread and severity of black root rot. T basicola is a soil borne fungus that produces two types of spores; thick walled chlamydospores and thin-walled endospores (Figure 2). Both spore types can cause disease. The spores of T basicola are primarily soil borne but may also occur internally with stem rot (Figure 2). Consequently, most spread of T basicola is by movement of soil, carried either in moving water or on vehicles and machinery.

Limited genetic variation in cotton has presented a significant challenge for the isolation of DNA markers linked with valuable traits such as resistance to Verticillium wilt and Fusarium wilt. Nevertheless, effective new techniques are now yielding DNA markers that can be used by cotton breeders to select for disease-resistant varieties in the absence of the pathogens.