Genetic analysis of resistance to flower bud thrips (Megalurothrips sjostedti) in cowpea (Vigna unguiculata [L.] Walp.)

Abstract

Cowpea is an important legume in subSaharan Africa where its protein rich grains are consumed. Insect pests constitute a major constraint to cowpea production. Flower bud thrips (FTh) is the first major pest of cowpea at the reproductive stage and if not controlled with insecticides is capable of reducing grain yield significantly. Information on the inheritance of resistance to FTh is required to facilitate breeding of resistant cultivars. The genetics of resistance was studied in crosses of four cowpea lines. Maternal effect was implicated while frequency distributions of the F 2 and backcross generations suggest quantitative inheritance. Additive, dominance and epistatic gene effects made large contributions and since improved inbred lines are the desired product, selection should not be too severe in the early generations to allow for desirable gene recombination. This study suggested that some of the genes involved in the control of resistance to FTh are different in TVu1509 and Sanzi. Broad sense heritability ranged from 56% to 73%. Choice of maternal parent in a cross will be critical to the success of resistance breeding.

Stability and extent of resistance of cowpea lines to flower bud thrips in Uganda

“…Similar findings were reported by Omo-Ikerodah et al (2009) in Nigeria under field conditions, while evaluating the resistance of Sanzi, and TVu 1509 to flower thrips. In contrast, Alabi et al (2003) in Nigeria and Abudulai et al (2006) in Ghana, reported that the resistance in some cowpea cultivars under natural infestation was due to flower thrips infestation escape due to early flowering.…”

“…is the most well-known Papilionaceae species with an African origin (Omo-Ikerodah et al, 2009). The crop is an important staple food legume and inexpensive source of protein for many resource poor African households.…”

“…Several insect pests attack cowpea in the field and studies have indicated flower bud thrips (Megalurothrips sjostedti Trybom) to be the most damaging in Africa (Karungi et al, 2000;Ngakou et al, 2008;Muchero et al, 2009). The yield reduction due to flower buds thrips ranges from 20 to 80%, but under severe infestation, complete yield loss may occur (Omo-Ikerodah et al, 2009).…”

Grain Legumes

“…The critical yield losses caused by these insect groups make them a priority focus in cowpea breeding. In the case of flower thrips, Omo-Ikerodah et al (2008) identified DNA markers associated with QTLs that have effects on resistance to flower bud thrips in a biparental mapping population derived from a cross that had Sanzi, the land race from Ghana, as one of the parents. Many other improved breeding lines with resistance to diseases, drought, Striga, and pests were derived from crosses that involved above listed (Table 7.1) and other germplasm lines.…”

Identification of candidate genes controlling black seed coat and pod tip color in cowpea (Vigna unguiculataL. Walp)

“…One biparental population consists of 94 RILs developed at the University of California, Riverside, derived from a cross between "California Blackeye 27" (CB27), which has a medium-sized black eye seed coat and purple pod tips, and "IT82E-18," which has a solid brown coat and green pod tips (Muchero et al 2009). The other biparental RIL population was provided by the International Institute for Tropical Agriculture and consists of 121 RILs derived from a cross between "Sanzi," a landrace with a speckled black and purple seed coat and purple pod tips, and "Vita 7," which has a solid tan coat and green pod tips (Omo-Ikerodah et al 2009). The seeds of each of these four parents are shown in Figure 1A.…”