In three field experiments, plants subjected to post‐flowering water stress and inoculated with Macrophomina phaseolina had greater development of charcoal rot symptoms than did inoculated plants not subjected to water stress. Two sorghum genotypes (B35‐6 and SC265‐14E) were found to be consistently more resistant to M. phaseolina, an assessment that was facilitated by the use of appropriate soil moisture conditions at the time of greatest plant susceptibility to charcoal rot. In addition, an isolate of M. phaseolina originally isolated from a sorghum genotype with resistance to charcoal rot caused greater symptom development than did two other isolates originally obtained from sorghum genotypes susceptible to charcoal rot.

ABSTRACT. Anthracnose caused by Colletotrichum graminicola remains the most important foliar disease of sorghum in West and Central Africa. This paper describes the advances made in sorghum anthracnose research that has led to a better understanding of pathogenic and genotypic diversity, epidemiology and important disease management strategies. We further highlight how understanding pathogen diversity interplays with the major sustainable anthracnose management strategies such as the use of host plant resistance and crop residue management within the region.

<p>Several studies on farmers’ perceptions on climate variability tend to provide bulked information at either regional or national level. Assessing the disparities of skills and the strategies of adaptations among farmers across locations could be the first step towards solutions in adaption to the climate variability and change. The objective of this paper was to assess and compare local farmers’ perceptions on meteorological events, adaptations and access to agricultural extension services in two agro-ecological zones, Diffa and Aguie, in Niger Republic. The results revealed that climate challenges are well distributed in both areas but, there are significant discrepancies in the perceived climate variabilities compared to meteorological observations. Respondents noted an increase in temperature which is in agreement with climatic data evidence. It was found that majority of respondents adopt crop diversification in the sense of mixed cropping as their major adaptation strategy to climate variability. However, the extent to which farmers perceived crop diversification as a climate change adaptation strategy is not a response to the subjectively perceived changes in weather patterns, but rather a traditional strategy to reduce risk and to adapt to the long-standing inter-annual and intra-annual rainfall variability in the area. The lack of sufficient educational knowledge, external support and access to information are the constraints that hindered farmers to adapt effectively and, this leads to low agricultural productivity. It is recommended to empower farmers with information, technological skills, access to heat resistant crop varieties that enable them to adapt to increasing maximum temperatures.</p>

Aims:  To determine the effect of water activity (aw = 0·880–0·960) and temperature (15–35°C) on the percentage of viable conidia and mycelial growth of three biocontrol agents effective against water hyacinth in Mali: Alternaria sp. isolate Mlb684, Fusarium sacchari isolate Mln799 and Cadophora malorum isolate Mln715. Methods and Results:  The fungi were grown in vitro on plates containing potato dextrose agar medium at different aw values (glycerol being added to adjust the aw). The percentage of viable conidia and radial growth rate decreased with decreasing water activity. Statistical analysis showed a significant effect of aw, temperature and the aw × temperature interaction on mycelial growth (P < 0·0001). Water activity emerged as the factor exerting the greatest influence. Differences were observed between the fungi tested, the C. malorum appearing more tolerant to low aw and the F. sacchari more tolerant to high temperature (35°C). Growth models predicting the combined effect of aw and temperature were developed and response surfaces generated, showing fairly good agreement with the experimental values. Conclusions:  Our results confirm the previous finding that aw has a greater influence than temperature on fungal growth. Under most conditions, variation of environmental factors has a detrimental influence on the percentage of viable conidia and mycelial growth rate of fungal isolates. Significance and Impact of the Study:  The developed models may contribute to predicting the best environmental conditions for use of these fungi as effective biocontrol agents against water hyacinth.

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