Screening for resistance to cowpea aphids (Aphis craccivora Koch.) In mutation derived and cultivated cowpea (Vigna unguiculata L. Walp.) Genotypes.

Siyunda AC¹*, N Mwila², M Mwala², KL Munyinda², K Kamfwa² and D Nshimbi¹

Published: April 30, 2022

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Abstract  

Research studies aimed at screening cowpea genotypes against Aphis craccivora K. commonly known as black aphids, under the no-choice infestation condition, were conducted in the greenhouse at Natural Resource Development College (NRDC), Lusaka, Zambia in 2021. The main objective was to discern the cowpea genotype that is resistant to Aphis craccivora K that would aid the reduction of yield losses encountered in cowpea production. The materials consisted of 21 cowpea genotypes advanced from the open field screening method. These 21 that were selected from an initial set of 110 genotypes exhibited the resistance trait during the open field screening method and thus were advanced to validate their resistance levels. The cowpea genotypes evaluated included 1 landrace variety, 2 mutation derived cultivated varieties, 15 advanced mutation derived varieties, and 3 pure line genotypes from IITA. The experimental design used was a Completely Randomized Design (CRD) with 3 replications. The variables collected were aphid score, aphid population build-up, plant vigour scores, and plant survival rate. Significant differences were seen among the genotypes for all the parameters considered in the investigation. The most resistant genotypes (BB10-4-2-3-2 and BBBT1-11) across all parameters investigated recorded an average aphid score of 1.0 and 1.68, respectively compared to LT11-3-3-12 which recorded the highest score of 7.0. The aphid population build-up of BB10-4-3-2 and BBBT1-11 was the lowest at 0.9 and 1.0 respectively compared to the highest recorded by LT11-5-1-1-4 at 3.54. The highest plant vigour of 3.0 was recorded by BB10-4-3-2, BBBT1-11 and LT11-5-1-1-4 and the lowest was recorded by Sanzi (1.2). Both BB10-4-3-2 and BBBT1-11 recorded a survival percentage of 100% at 21DAI compared to the lowest recorded by TVu 2027 (20%). Genotypes BB10-4-2-3-2 and BBBT1-11 could further be assessed for the possible presence of biochemical and traits, that could explain the basis of the observed differences among the genotypes in their reaction to Aphis craccivora K. Besides, BB10-4-2-3-2 and BBBT1-11 can also be incorporated in the breeding program with the target of breeding cowpea varieties that are resistant to aphid infestation. Furthermore, BB10-4-2-3-2 and BBBT1-11 may be released to address the yield losses experienced in cowpea production as a result of A. craccivora K.