Secondary metabolites in selected cowpea [Vigna unguiculata (L.) Walp.] lines mediated resistance to flower thrips (Megalurothrips sjostedti Trybom)

Abstract

Flower thrips (Megalurothrips sjostedti Trybom) are a major pest of cowpea worldwide. Although some cowpea varieties exhibit resistance to these pests, the underlying mechanisms of this resistance remain unclear. This study aimed to explore the biochemical factors contributing to resistance against thrips and to measure the levels of specific compounds in resistant cowpea varieties. Six cowpea cultivars were tested using a randomized complete block design across three field trials. At 44 days after planting, foliage and flowers from each cowpea variety were collected for laboratory analysis. Samples from ten randomly chosen plants from each variety were combined to measure total protein, soluble amino acids, phenols, flavonoids, and total antioxidants. Data analysis revealed significant differences among the cowpea lines. Most metabolites, except flavonoids, showed considerable variation among the tested varieties. Notably, the resistant lines TVu1509, Sanzi, and TVNu1249 exhibited the highest levels of total protein. Principal component analysis indicated that the first three components explained about 83.59% of the total variation, with contributions of 36%, 28%, and 19%, respectively. In conclusion, resistance in certain cowpea lines to flower thrips is associated with higher levels of total protein, soluble amino acids, and total antioxidants.