The impact of varying glucosinolate and phenolic levels in different genotypes of cauliflower on the larval population of Pieris brassicae

A field experiment was carried out to assess the susceptibility of 14 different cauliflower genotypes against infestation by cabbage butterfly. Throughout the growing season of the crop, observations on larval infestation were made by assessing the presence of larvae on randomly selected and tagged plants. The total concentrations of glucosinolates and phenols in the leaves of different varieties were determined. Glucosinolate concentration was estimated by processing samples in triplicates and measuring content by spectrophotometry method utilising a Na 2 PdCl 4 assay, with sinigrin standards for calibration. The estimation of total phenols from field collected samples on the other hand, was carried out using an 80% ethanol extraction method. Following the grinding of samples and ethanol extraction, samples were processed using Folin-Ciocalteau reagent and sodium carbonate. This was followed by spectrophotometric measurement at 650 nm, performed to estimate the phenol content via a pyrogallol standard curve. Statistical analysis demonstrated a significant negative correlation ( r = -0.985) between cabbage butterfly infestation and total glucosinolate content. Conversely, a significant positive correlation ( r = 0.901) was observed between total phenols and cabbage butterfly infestation. It was found that the Pusa Snowball-1 genotype had the lowest mean larval population at 21.66 and the lowest total glucosinolate content (9.35 µmoles/g). In contrast, the Olympus genotype, which had the highest total phenol concentration of 931.42 mg/100 g, exhibited the highest mean larvae per plant at 30.86. This study underscores the crucial role of host-plant resistance in pest management, highlighting that variations in glucosinolate and phenol content among different cauliflower genotypes significantly influence susceptibility to cabbage butterfly infestation.