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Asian Journal of Agriculture and Development (AJAD) - Call for papers!

Genetic analysis of bruchid resistance in cowpea (Vigna unguiculata (L.) Walp)

(Myanmar), Master of Science in Agricultural Research and Development (Kasetsart University)

Thesis Abstract:

Bruchids or seed weevils of the genus Callosobruchus, especially Callosobruchus chinensis (L.) (azuki bean weevil) and Callosobruchus maculatus (F.) (cowpea weevil), are the most destructive pests that cause significant losses to cowpea (Vigna unguiculata (L.) Walp.) seeds during storage. Development of cultivar(s) resistance to bruchids is a major goal in cowpea breeding program. Cowpea accession "TVu 2027'' has been identified as moderately resistant to C. maculatus. Genetic studies of the seed resistance in this accession using strains of C. maculatus from Africa and America have demonstrated that the resistance is controlled by one or two recessive genes. However, there are no reports on genetic of the resistance to C. chinensis and to strain(s) of C. maculatus from Asia. Moreover, identification of molecular markers associated with bruchid resistance to the strains of C. chinensis and C. maculatus in Asia are not yet been done. Therefore, the objectives of this study were to (i) investigate genetics of the resistance to C. chinensis and C. maculatus in cowpea accession “TVu 2027” and (ii) identify molecular markers associated with C. chinensis and C. maculatus resistance in cowpea accession “TVu 2027”. PK2015VTN001 (P1; susceptible cowpea) and TVu 2027 (P2; resistant cowpea) were used to develop six basic generations (populations), viz. P1, P2, F1 (P1 x P2), F2 (P1 x P2), BC1P1 (P1 x F1) and BC1P2 (P2 x F1). The populations were grown under a field condition and seeds harvested from these populations were evaluated for percentage of damaged seeds (PDS) and area under the disease progress stairs (AUDPS; indicating infestation severity) by C. chinensis and C. maculatus. The results showed that TVu 2027 was moderately resistant to both bruchid species with PDS of about 50%. Broad-sense heritability for PDS and AUDPS was moderate, being 70% and 73% for C. chinensis, respectively, and 64% and 61% for C. maculatus, respectively. The number of effective factors (genes) controlling PDS and AUDPS calculated for C. chinensis was 1.53 and 1.86, respectively, and for C. maculatus was 0.76 and 0.97, respectively. However, generation mean analysis revealed that genes with additive and additive x dominance gene interaction were involved in both PDS and AUDPS caused by C. chinensis and C. maculatus. Bulk segregant analysis revealed that SSR marker cp01354 was associated with C. maculatus resistance in TVu 2027.