Contributions to crop improvement and sustainable agriculture in tropical and subtropical Australia
Lawn, Robert John (2004) Contributions to crop improvement and sustainable agriculture in tropical and subtropical Australia. Professional Doctorate (Research) thesis, The University of Queensland.
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Abstract
During the past 36 years, the Author has contributed to the science and practice of agriculture in tropical and subtropical Australia, in the areas of crop improvement and sustainable agricultural production. These contributions were made during three phases of activity (i) through postgraduate studies at the University of Queensland (M Agr Sc, 1968-1971) and at the University of Minnesota (Ph D, 1971-1973); (ii) as a research scientist with the Commonwealth Scientific and Industrial Research Organization (1973-1994); and (iii) through leadership of the Cooperative Research Centre for Sustainable Sugar Production (CRC Sugar) and its education program, and concurrently as professor of tropical crop science at James Cook University (1994-2003).
Contributions during the period 1968-1994 focussed heavily on developing a scientific understanding of the physiological basis of genotype X environment (g X e) interaction effects on the phenology, growth and yield of tropical grain legume crops. The main target crops were soybean (Glycine max L. Merr.), mungbean (Vigna radiata (L.) Wilczek) and black gram (V. mungo L. Hepper), and to a lesser extent cowpea (V. unguiculata (L.) Walp.), pigeon pea (Cajanus cajan (L.) Millspaugh) and minor pulses in the Vigna group (rice bean, adzuki bean). Particular emphasis was placed on elucidating the physiological basis of adaptation of these legumes in tropical and subtropical environments, and the implications for crop improvement.
The physiological processes of main interest were phenological development, crop growth, yield and its components, seed quality and symbiotic nitrogen fixation. Environmental factors of main interest were day length, temperature, and water supply (both in excess and deficit), with some lesser focus on biotic factors such as insects and crop diseases. It was established that differential genotypic responses to photo-thermal regime contributed to variation in phenological response, with major implications for crop growth and yield potential and adaptation to the environment with respect to latitude and sowing date. These in turn interacted with agronomy and influenced optimal management.
In the process, genotypic relations between rate of development and photoperiod and temperature in the field were described and quantified, as were the relations between crop duration, harvest index, biomass accumulation and seed yield. Interaction effects between varietal duration and sowing density were explained and the implications for optimal sowing density established for both irrigated and rain fed crops. Advances were made in understanding the effects of host plant physiology on nitrogen fixation. Relations between harvest index and nitrogen harvest index in different legumes and their implications for crop improvement were described. Differences in drought stress response strategy among tropical grain legumes were discovered and described. The ability of soybean to acclimate to saturated soil was described and the novel saturated soil culture system developed. Advances were made in understanding the physiology of weathering in mungbean and black gram, and genotypic differences in resistance were identified.
Studies were extended beyond the cultivated germplasm to explore the natural genotypic variation for traits of agronomic and/or adaptive significance in related wild Vigna and Glycine species found in Australian and nearby islands. In the process, a unique collection of more than 400 native legume accessions was assembled and described, and seed committed to long-term storage in a national germplasm collection. Cross-fertility between cultivated and wild Vigna species was explored and the inheritance of key traits documented.
The research findings on the tropical grain legumes were synthesised into a more coherent generalised understanding of their physiology, and the potential application of physiological knowledge in crop improvement was explored using the tropical grain legumes as a model. The then-novel idea was advanced that the most effective use of physiology in crop improvement was in developing a biological understanding of g X e to augment the statistical models used by breeders. It was also argued that crop improvement should concurrently involve breeding better adapted crop varieties, and developing agronomic practices that best enabled the genetic potential of crop varieties to be exploited. Among the areas where these concepts were applied was the novel concept of using the long-juvenile gene to ‘convert’ high-yielding, lodging resistant, temperate soybean germplasm to tropical adaptation.
During the period 1994-2003, scientific contributions focussed on improving the sustainability of sugar production systems in northern Australia, with emphasis on three broad program areas: enhancing crop productivity, sustaining soil and water resources, and protecting the wider environment. Contributions included a leadership role in the development in collaboration with others of novel approaches for fostering team-based, multi-disciplinary research and postgraduate research training on complex sustainability issues. At a personal research level, the focus was on the application in the context of student training projects of physiological concepts to improve sugarcane productivity in the wet tropics. Advances were made in identifying the effects of harvest timing and other management practices on cane yield and CCS, in quantifying the effects of lodging on productivity and in elucidating environmental stimuli of suckering.
The improved scientific understanding of soybean and mungbean provided the basis for undertaking, in collaboration with others, improvement programs on these legumes for northern Australia, and in Thailand and Vietnam. Recommendations for agronomic management of these crops were promulgated in collaboration with industry, and three cultivars (1 tropical soybean, 1 mungbean and 1 black gram) were released for commercial production. These outputs contributed to the establishment and subsequent development of soybean and mungbean cropping in northern Australia. In the case of sugar cane, the strategic research on low productivity in the wet tropics focussed attention on lodging and suckering as key constraints in the wet tropics, while the research on sustainable sugar production more generally has helped map the path for a sustainable future for the sugar industry.
In the research on both grain legumes and sugar cane, innovation was demonstrated in the contributions that were made, and in the processes whereby they were accomplished. The research on new grain legume crops for Australian agriculture was by definition novel, as was the early focus on using physiological understanding of these species to develop biological explanations for g X e. The use of contestable industry research funds to support postgraduate research training pre-dated the formal introduction of postgraduate research training scholarships by the rural industry research and development committees, while the extensive supervision of postgraduate students was then unprecedented for a CSIRO scientist.
Also demonstrated was leadership in fostering team-based, multi-disciplinary collaborations, often in the context of joint projects supported by national and international agencies, and in developing countries where the tropical crops of interest were widely grown. The research was also usually undertaken in close collaboration with relevant industry interests, which facilitated uptake of the outputs. At the time, these collaborations, which included students, colleagues and industry end-users, initially with funding support from industry and later from the Australian Centre for International Agricultural Research (ACIAR) and then the Cooperative Research Centre (CRC) Program, were at the forefront of the development of team-based R&D models in Australia.
The synergies from these collaborations with colleagues, students and industry stakeholders enhanced the contributions that were able to be made. They also enabled initial discoveries to be explored and elaborated in ways that otherwise would not have been possible.
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