Abstract
The flower bud thrips, Megalurothrips sjostedti Trybom (Thysanoptera: Thripidae), is an economically important pest of cowpea in sub‐Saharan Africa. Varietal resistance is the most preferred, environmentally friendly, cost‐effective and sustainable option for controlling this pest. The objective of this study was to identify sources of resistance to M. sjostedti among mini core accessions from the largest world cowpea germplasm collection maintained at the International Institute of Tropical Agriculture (IITA). The study was conducted during the 2015 and 2016 cropping seasons where 365 accessions were screened under field conditions. Each accession was rated visually for thrips damage score, flower abortion rate, number of pods per plant and number of thrips per flower. The resistance levels observed in genotypes TVu8631, TVu16368, TVu8671 and TVu7325 were similar to that of the resistant check “Sanzisabinli” (called Sanzi) during both seasons. In addition, 56 mini core genotypes showed moderate resistance to thrips damage. High heritability values were associated with thrips damage scores at 65 days after planting (0.60), percentage of effective peduncles (0.59), flower bud abortion rate (0.59), number of pods per plant (0.51) and number of peduncles with pods (0.5). The accessions identified with good levels of resistance to flower bud thrips will be used in cowpea breeding programs to develop improved resistant varieties.
Highlights
| MATERIALS AND METHODSThe study was conducted at Fashola, Latitude 7.9°N and Longitude 3.7833°E located between Oyo and Iseyin towns at about 60 km from Ibadan (Oyo State, Nigeria)
High levels of heritability were associated with parameters such as damage scores at 65 days after planting (DAP), pod number per plant, pedun‐ cles with pods, flower bud abortion rate and percentage of effective
With the identification of several promising lines characterized by good levels of resistance to flower bud thrips, development of improved cowpea with resistance to this pest appears feasible in the foreseeable future
Summary
The study was conducted at Fashola, Latitude 7.9°N and Longitude 3.7833°E located between Oyo and Iseyin towns at about 60 km from Ibadan (Oyo State, Nigeria). Test lines with low damage scores showed significantly higher num‐ ber of pods per plant (ranging from 5.1 to 10.5) except genotypes TVu8877, and TVu16521 with relatively low pod number per plant (3.7 and 4.2, respectively) despite their low damage scores. Apart from the four lines that showed good levels of resistance to thrips, fifty‐seven accessions made up of 56 from the mini core col‐ lection and one wild relative were regarded as moderately resist‐ ant They had moderate damage scores of between 4.8 and 6.4 and relatively high number of pods (three to five pods/plants) except the wild relative, TVNu699 that had an average of 1.6 pods per plant. High levels of heritability were associated with parameters such as damage scores at 65 DAP, pod number per plant, pedun‐ cles with pods, flower bud abortion rate and percentage of effective.
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