Physiological investigation of crown rot disease development in wheat (Triticum aestivum)

Physiological investigation of crown rot disease development in wheat (Triticum aestivum)

Crown rot (CR), caused by Fusarium pseudograminearum (Fp), is a serious soil-borne disease of wheat and barley both internationally and in Australia, where it causes $79 and $18 million, respectively, in lost yield per annum to the Australian wheat industry. CR has been exacerbated in recent years by reduced tillage practices and its control is principally based on management practices such as crop rotation which over time decreases field inoculum. Soil factors, including moisture, temperature, nutrients and stubble borne inoculum form complex relationships which play major roles in determining the severity of disease. Although commercial wheat cultivars with a low level of CR resistance are available to growers in some environments, the most promising sources of resistance identified to date are quantitative in character and currently in non-agronomic backgrounds. Further, understanding of fundamental mechanisms of crop development of resistance to CR is essential to breed new cultivars having strong resistance. The aim of this project is to investigate mechanisms involved in CR disease development in wheat (Triticum aestivum) caused by Fp. We hypothesise that colonisation of xylem vessels reduces water flow through the plant. Simultaneously to this, we also hypothesise that disruption of water flow and subsequent phloem colonisation will alter the dynamics of sugar transport in the plant, carbon and nitrogen content in stem, leaf and grain. The physiological mechanism of development of CR disease, caused by Fp is not fully understood. Three seedling, three glasshouse and three field experiments were conducted to examine the CR impact on shoot length, biomass, carbon and nitrogen content, stem water pressure, and leaf gas exchange including rate of photosynthesis, stomatal conductance, internal CO2 concentration and transpiration rate of the plant canopy. This research explored the host reaction of different bread wheat genotypes which varied in susceptibility to CR at seedling, flowering and maturity growth stages across nine experiments. In this investigation, Fp had a negative impact on the fundamental physiological parameters measured across all genotypes. Significant reduction in gas exchange parameters were observed in all field experiments; however, only internal CO2 increased in seedling experiments. Inoculated genotypes displayed a reduction in the wheat biomass and required higher stem water pressure. The findings further our understanding of the relationship between experimental conditions, plant genotypes, and inoculation status. They reveal the intricate physiological responses of wheat to Fp inoculation at different growth stages and within various plant tissues. Collectively, our discoveries clarify ii the effects of Fp infection on wheat during crucial stages of growth, potentially reshaping our comprehension of disease resistance. This information provides a foundation for developing new cultivars that have improved resistance to crown rot, which offers substantial benefits in terms of agricultural productivity. Employing advanced breeding techniques based on comprehensive physiological knowledge can greatly enhance the ability of crops to withstand CR, thus ensuring food security in countries heavily reliant on wheat.

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