Investigation of host plant resistance mechanisms in chilli against black thrips, Thrips parvispinus (Karny)

Thrips parvispinus (Karny) (Thysanoptera: Thripidae) is a recently invasive and highly polyphagous pest species causing significant damage to chilli ( Capsicum spp .) and other economically important crops in India and worldwide. Despite its quarantine significance, limited studies exist on the biochemical factors influencing its infestation dynamics on different chilli hybrids. This study was conducted during Summer 2024 at the College of Agriculture, V. C. Farm, Mandya, Karnataka, India, to assess the biochemical traits of chilli leaves that affect T. parvispinus infestation under field conditions. Biochemical profiling at 60 days after transplanting (DAT) revealed that infestation levels were positively correlated with soluble sugars, reducing sugars, and crude protein content, indicating that nutrient-rich tissues favor thrips population growth. Conversely, defensive phytochemicals such as total phenols, free amino acids, and tannins showed strong negative correlations with thrips infestation, suggesting their role in host resistance by deterring feeding and reproduction. These findings provide valuable insights into the biochemical basis of host susceptibility and resistance, informing the development of chilli hybrids with enhanced defensive traits and integrated pest management strategies to mitigate the impact of T. parvispinus on chilli production.