The genetic evaluation of bruchid resistance in seed of cowpea

Abstract

Seed resistance of cowpea (Vigna unguiculata L. Walp.) to bruchids at the F3 plant generation was assessed by various methods. The most discriminating variable for measurement of seed resistance was mean emergence day, followed by percentage of adult emergence up to an optimum time, then in descending order, percentage of undamaged seed, mean number of holes per seed and percentage loss in seed weight. The simplest reliable variable to use for assessment of resistance to bruchids was the percentage of undamaged seed with zero emergence holes. However, greater control and manipulation of egg laying on seeds would be required to obtain uniform infestation. Three (or less) eggs per seed is suggested as acceptable. Care, particularly on the uniformity of eggs laid, is necessary when using percentage seed weight loss as an index of resistance. The other variables are laborious to estimate. In general, seed weight, number of eggs per seed, seed testa texture and number of seeds per sample did not appear to influence estimates of resistance, with the exception of seed weight loss. The natural rate of increase of bruchids, which is a critical variable for measurement of resistance, was very difficult to estimate with consistency.

Breeding Food Legumes for Resistance to Storage Insect Pests: Potential and Limitations

“…Consequently, it is appropriate to screen and evaluate a broad array of wild species in search of these genes. In the future, special attention should be paid to producing plants resistant to storage insect pests which can simultaneously hinder the development of resistance by the insects under question as occurs with the α-amylase inhibitor [32]. One possible way to achieve this is by stacking two or more resistance genes with different modes of action into a single genotype [55].…”

“…Optimum environmental conditions, particularly temperature and relative humidity, can also be simulated. For instance, optimization of the test environment particularly of temperature level under regulated conditions enabled identification of resistant cowpea genotypes with better precision [31,32]. Recent collections of accessions of crops or their wild relatives may provide solutions to the problem of limited genetic resources for resistance breeding to storage insects in legume crops [30].…”

“…Nevertheless, a few cases of complete resistance were also reported in cultivated or germplasm collections of haricot bean [26][27][28], field pea [29,30], cowpea [31][32][33], black gram [34] and chickpea [13,35]. A number of reports indicate that varieties with improved yield are more susceptible than landraces [6,36].…”

“…This will minimize excessive reliance on phenotypic traits for screening with bioassay tests using controlled pest infestation on seeds [32], and thus increase breeding efficiency and precision. While conventional breeding will continue to have a valuable role in providing storage insect pest resistant cultivars of many legume crops, it appears that in some systems there will continue to be barriers to achieving resistance using this approach.…”

Estabilidade da resistência de genótipos de caupi a Callosobruchus maculatus (Fabr.) em gerações sucessivas

“…09-1 2F 88,1 ± 3,01 aA 81,7 ± 6,81 aA 86,0 ± 7,57 aA 84,4 ± 3,26 bA 85,6 ± 2,86 aA 83,0 ± 3,41 aA 84,8 ± 1,82 a TE90 -180 -3E 85,4 ± 7,24 aA 78,1 ± 5,80 bA 82,0 ± 7,59 aA 82,9 ± 8,98 aA 83,1 ± 6,22 aA 79,7 ± 7,23 aA 81,9 ± 2,09 a BR17 -Gurguéi a 79,6 ± 3,59 bA 78,2 ± 8,07 bA 80,4 ± 6,67 aA 80,8 ± 6,10 aA 82,8 ± 3,00 aA 76,0 ± 8,78 aA 79,6 ± 1,87 a TE87-9 8-8 G 87,4 ± 2,56 aA 77,4 ± 2,51 bA 80,4 ± 5,20 aA 78,9 ± 4,18 aA 80,4 ± 6,23 aA 70,9 ± 12,71 bB 79,2 ± 4,27 a CNC 0434 95,1 ± 4,61 aA 72,3 ± 6,01 bB 79,4 ± 3,28 aA 72,7 ± 3,43 bB 75,0 ± 3,01 bB 65,3 ± 3,53 bB 76,6 ± 8,11 b Na avaliação da resistência de grãos de caupi a C. maculatus, a viabilidade e a duração da fase imatura são considerados os parâmetros m ais importantes (Redden & McGuire, 1983). No entanto, neste trabalho, o índice de resistência que também utiliza no seu cálculo estes dois parâmetros, mostrouse mais apropriado.…”