Induced mutation and silicon derived resistance to aphids in common bean and cowpea genotypes

Abstract

Common bean and cowpea are major legume crops grown in Zambia. They are a cheaper source of dietary protein and livestock fodder. Aphids negatively impact the productivity of common bean and cowpea, jeopardizing food security and livelihoods. Mutagenesis offers a relatively quick method of creating genetic variation in plants, providing an opportunity to develop aphid resistant crop varieties. In addition, induction of plant defense by use of compounds such as silicon could further enhance plant resistance to aphids and effectiveness of natural enemies. This study aims to identify and characterise aphid resistance mechanisms in mutation and conventionally bred bean and cowpea genotypes while also assessing the potential of silicon to improve aphid resistance and biological control.

Description

Common bean (Phaseolus vulgaris) and cowpea (Vigna unguiculata) are important staple crops for millions of people in Africa, serving as low-cost sources of vegetable protein, dietary fibre, starch, vitamins and micronutrients. Yields from these crops are lowered by insect pests, including aphids. The black bean aphid (Aphis fabae) and cowpea aphid (Aphis craccivora) affect crop productivity by consuming photosynthates and vectoring viral diseases, notably, Bean Common Mosaic Virus (BCMV) and Cowpea Mosaic Virus (CMV). Management of aphids has for a long time relied on synthetic pesticides but with variable success due to their relatively high costs and development of pesticide resistance in target organisms. Synthetic pesticides may also be harmful to human health and the environment. Therefore, there is an urgent need for cost-effective and sustainable alternatives to manage aphid pests. Mutagenesis offers a relatively quick method of creating genetic variation in plants, providing an opportunity to develop aphid resistant crops. In addition, induction of plant defense by use of compounds such as silicon could further enhance plant resistance to pests and effectiveness of natural enemies. This study aims to identify and characterise the sources of resistance to aphids in mutation and conventionally bred common bean and cowpea genotypes while also assessing the potential of silicon to improve host-plant resistance and biological control against aphids. In particular, the study will test two main hypotheses: (1) induced mutation generates genetic variation for resistance to aphid pests and (2) silicon application alters plant chemistry, reducing aphid feeding while increasing attraction/retention of natural enemies. This study will thus contribute to the diversification of current management options, and development of an effective IPM system against aphids in legume crops.