**6. Potential climate change effects on ear rots and related mycotoxin contamination**

Mycotoxins contamination in pre and post-harvest maize is most important and the attention focused this important disease in terms of their presence and toxicity, including variety of toxins viz., aflatoxins, ochratoxins, fumonisins, trichothecenes, and zearalenone, are secondary metabolites produced by various fungi. *Aspergillus flavus* and produces aflatoxin, *Fusarium verticillioides* produces fumonisin, and produces deoxynivelanol and zearalenone [41, 42]. Among these toxins, aflatoxin is the most important in terms of health risk and high toxicity produced by *A. flavus* and by *A. parasiticus,* which are most prevalent in tropical and subtropical regions where high temperature and drought conditions prevailed. Aflatoxins are highly carcinogenic, produced by *A. flavus* and *A. parasiticus* [43].

Aflatoxins are a group of 20 related fungal metabolites, the major ones are aflatoxin B1 B2 G1 and G2. Among them AFB1 is the most potent naturally occurring liver carcinogen [44]. Ingestion of aflatoxins in contaminated food or feed results in aflatoxicosis, while long-term exposure of moderate to low concentration of causes chronic toxicity and immune system disorders [45, 46]. Aflatoxin contributes to significant economic losses in maize which prevents commodities from meeting internation al standards governing agricultural trade and food safety. High temperatures and low rainfall favors the production of *A. flavus* conidia and their dispersal.

### *The Impact of Climate Change on Changing Pattern of Maize Diseases in Indian Subcontinent... DOI: http://dx.doi.org/10.5772/intechopen.101053*

Several studies reported that the high soil temperature and drought stress are positively correlated with aflatoxin contamination and increased incidence of aflatoxigenic strains or species [47–49]. The high temperature coupled with dry weather conditions favors growth, conidia formation and dispersal of fungi *A. flavus.* These factors are contributing to high concentrations of aflatoxins. Therefore these environmental factors has an important role in development of aflatoxin in maize [50–55]. High temperatures and low rainfall also favor production of conidia of *A. flavus* and their dispersal. The most important environmental influences on fumonisin risk are insect damage to grain and moisture stress in maize plants [56, 57].

The Indian subcontinent having land of diversity with diversified climatic condition. If hot humid weather prevailed at the time of critical stage of maize crop like North east, some part of western hills with limited sunshine hours at the maturity of the maize crop are predisposed condition to mycotoxin contamination. Sometimes due to unpredictable weather condition the *rabi* and *kharif* maize crop faces the same situation and ultimately spoiled due to mycotoxin contamination. Extreme dry condition at the time of flowering is also one of the predisposing factors to AFB1 contamination. In Indian subcontinent there is extreme diversity in soils and climatic condition and maize is grown in a wide range of environments, extending from extreme semi-arid to sub-humid and humid regions. Mold inoculums that occur naturally throughout the environment in all over the world. Although maize is grown mainly in wet, hot climates, it has been said to thrive in cold, hot, dry or wet conditions.

Hence, in future there are more chances of mycotoxin contamination due to rise in temperature and unpredictable rainfall in Indian subcontinent. Maize crop from tropical and/or sub-tropical areas are affected more frequently and severely by aflatoxin contamination, but temperate areas could be of increasing importance due to climate change. In the near future, there is reason to believe that increased climate variability associated with climate change trends may result in higher pre-harvest levels of mycotoxins in Indian subcontinent, posing both economic and health risks for maize crop and food security. The occurrence of aflatoxin in maize is strongly influenced by weather during and after the growing season. Cool, wet growing seasons may delay grain maturity in maize, and result in mold contamination in the field such cobs/grains are prone to develop aflatoxin contamination. Climate change is likely to lead to an increase in hot and dry spells; this implies an expectation of increased risk of aflatoxin contamination. Insect damage of grain and moisture stress in maize favor fumonisin contamination of maize [56, 57]. The optimal conditions for fumonisin production are a temperature close to 30°C and high water activity [34, 58]. It is therefore important to determine impacts of climate change to future food security, in terms of mycotoxin-related economic and health risks. If current climate patterns continue in this century, aflatoxin and fumonisin concentrations in maize will likely increase, more aggressive isolates of *F. graminearum* occur. The overall effect may likely be increased economic and health risks, particularly due to increased aflatoxin concentrations in maize.
