https://ag.arizona.edu/research/cottylab/apdfs/Cotty%20and%20Jaime%20Climate.pdf

Influences of climate on aflatoxin producing fungi and aflatoxin contamination.

Climate change is altering the productivity of natural resources with far-reaching implications for those who depend on them. Resource-dependent industries and communities need the capacity to adapt to a range of climate risks if they are to remain viable. In some instances, the scale and nature of the likely impacts means that transformations of function or structure will be required. Transformations represent a switch to a distinct new system where a different suite of factors become important in the design and implementation of response strategies. There is a critical gap in knowledge on understanding transformational capacity and its influences. On the basis of current knowledge on adaptive capacity we propose four foundations for measuring transformational capacity: (1) how risks and uncertainty are managed, (2) the extent of skills in planning, learning and reorganizing, (3) the level of financial and psychological flexibility to undertake change and (4) the willingness to undertake change. We test the influence of place attachment and occupational identity on transformational capacity using the Australian peanut industry, which is presently assessing significant structural change in response to predicted climatic changes. Survey data from 88% of peanut farmers in Queensland show a strong negative correlation between transformational capacity and both place attachment and occupational attachment, suggesting that whilst these factors may be important positive influences on the capacity to adapt to incremental change, they act as barriers to transformational change.

https://iopscience.iop.org/article/10.1088/1748-9326/7/3/034022/pdf

Transformational capacity and the influence of place and identity

Human activities affect both the size and structure of fungal populations. Construction, war, recreation, and agriculture disrupt large expanses of vegetation and soil; disruption causes redistribution of fungal propagules and makes nutrients available to fungi. Many fungi, including the aspergilli, exploit these human engineered resources. This results in the association of large fungal populations with various human activities, especially agriculture. When crops are grown or animals raised, fungi are also grown. From a human perspective, most fungi associated with cultivation increase inadvertently. Human activity, however, partly dictates which and how many fungi occur and the fungi, both directly and through fungal products, influence human activities, domestic animals, and even humans themselves.

Agriculture, Aflatoxins and Aspergillus

Excessive use of agrochemicals in conventional crop management has caused serious environmental and health problems, including loss of biodiversity and human disorders. A number of chemical biocides show complex chronic effects, such as changes in endocrine functions and immune systems. Application of different chemical biocides to the soil and plants has increased substantially over the last five decades. Total consumption of chemical fertilizers worldwide increased 10-fold from 1950 to 2000. This is also true for chemical biocides, with our annual current use of 3 billion liters and a value of 30 billion dollars. There is ample evidence that indicates that plants grown in rich soil associated with N-P-K availability are prone to pests and diseases. Managing and exploiting soil environmental conditions as part of an integrated control strategy can make a significant contribution to agricultural sustainability and environmental quality. Application of organic matters and practices that increase the total microbial activity in the soil might enhance the general suppression of pathogens by increasing competition for nutrients. The choice of crops in a rotation with plants less susceptible to specific pathogens causes a decline in population due to natural mortality and the antagonistic activities of coexistent root zone microorganisms. Plants growing in disease-suppressive soil resist diseases much better than in soils with low biological diversity. Understanding the effect of soil’s environmental factors on plant disease incidence and the best crop management strategies to prevent, avoid, escape, and control diseases were the aims of this literature review. This article, which comprises the main topics on soil fertility associated with N-P-K and other macro- and micronutrients, and also soil pH, structure and texture, organic matter, and microbial reserves, describes the use of various crop management practices that reduce the incidence of plant diseases.

Soil management for sustainable crop disease control: a review

Mycotoxins are poisonous chemical compounds produced by certain fungi. There are five mycotoxins or groups of mycotoxins that occur quite often in food: deoxynivalenol/Nivalenol, zearalenone, ochratoxin, fumonisins and aflatoxins. The fungi that produce mycotoxins in food fall broadly into two groups: those that invade before harvest, commonly called field fungi, and those that occur only after harvest, called storage fungi. There are three types of toxicogenic field fungi: plant pathogens such as  Fusarium graminearum (deoxynivalenol, nivalenol); fungi that grow on senescent or stressed plants, such as Fusarium moniliforme (fumonisin) and sometimes Aspergillus flavus (aflatoxin); and fungi that initially colonize the plant before harvest and predispose the commodity to mycotoxin contamination after harvest, such as Penicillium verrucosum (ochratoxin) and A. flavus (aflatoxin). The favourable conditions for mycotoxins production are instigated with poor hygienic conditions at the time of transport...

Occurrence, importance and control of mycotoxins: A review

Three genotypes of peanut (Arachis hypogaea L.), with ICG numbers 221, 1104, and 1326, were grown in three replicate plots and drought stressed during the last 58 days before harvest by withholding irrigation water. Within each plot there were eight levels of stress ranging from 1.1 to 25.9 cm of water. Kernels harvested from the plots were hydrated to 20% moisture and challenged with Aspergillus flavus. Fungal colonization, aflatoxin content, and phytoalexin accumulation were measured. Fungal colonization of non-drought-stressed kernels virtually ceased by 3 days after inoculation, when the phytoalexin concentration exceeded 50 micrograms/g (fresh weight) of kernels, but the aflatoxin concentration continued to rise exponentially for an additional day. When fungal colonization, aflatoxin production, and phytoalexin accumulation were measured 3 days after drought-stressed material was challenged, the following relationships were apparent. Fungal colonization was inversely related to water supply (r varied from -0.848 to -0.904, according to genotype), as was aflatoxin production (r varied from -0.876 to -0.912, according to genotype); the phytoalexin concentration was correlated with water supply when this exceeded 11 cm (r varied from 0.696 to 0.917, according to genotype). The results are discussed in terms of the critical role played by drought stress in predisposing peanuts to infection by A. flavus and the role of the impaired phytoalexin response in mediating this increased susceptibility.

H R Wotton

Papers

Increased susceptibility and reduced phytoalexin accumulation in drought-stressed peanut kernels challenged with Aspergillus flavus.