Relationship of bruchid (Callosobruchus maculatus) resistance genes in three cowpea cultivars

The relationship between the bruchid resistance genes present in seeds of TVu 2027, TVu 11952 (KNW), and TVu 11953 (KNS) was investigated. The phenotypic expression of seed resistance in all three varieties was characterized by a reduced percentage adult emergence, a prolonged development time, and a reduced rate of development as compared to the susceptible California Blackeye #5. The developmental response of Callosobruchus maculatus to each of these three varieties, as judged by the above criteria, was nearly identical. No susceptible F1 or F2 progeny were recovered in crosses between TVu 2027, KNS, and KNW, and the level of bruchid resistance in these progeny did not exceed the level of resistance in the parents, indicating that these three varieties possess the same genes for resistance to C. maculatus. Additional studies of maternal and cytoplasmic effects, general and specific combining ability effects, and Jinks and Hayman's Vr, Wr analysis, provided corroborative evidence that TVu 2027, KNS, and KNW possess the same genes for C. maculatus resistance. Pod resistance to C. maculatus was assessed in each of the seed resistant varieties and in three agronomically advanced derivatives of TVu 2027, KNS, KNW and TVu 2027 exhibited a minimal level of pod resistance, however some of the derivatives of TVu 2027 possessed a moderate level of seed resistance combined with significant pod resistance. This combination resulted in a much higher level of overall resistance to C. maculatus which should be more durable over time.