CULTIVAR-LEVEL VARIATION IN POLLINATOR ATTRACTION AND EFFECTIVENESS IN CHILE PEPPERS

Abstract

Insect pollinators play a critical role in sustainable agriculture, enhancing crop yield andproductivity. Their contributions, however, are commonly overlooked when growers select plant varieties to cultivate. Crop traits such as fruit production, disease resistance, and marketability are prioritized over attractiveness to pollinators, largely because cultivar-level differences in insect pollination and their relationship to yield are poorly documented. The goal of this research is to provide novel insights into the importance of cultivar selection in the context of pollination, encouraging a holistic and eco-friendly approach to farming that increases yield and profitability. The specific objectives of this study are to 1) quantify differences in pollinator attraction among fifteen chile pepper (Capsicum annuum L.) cultivars, 2) measure floral structures across cultivars to identify important plant traits that may correlate with pollinator attractiveness, and 3) determine whether variation in pollinator visitation affects yield. For this research, I conducted both field pollinator surveys and greenhouse pollination experiments to examine relationships between cultivar-level differences in pollinator visitation rates, floral morphology, and yield. Mean visits per flower per 15-minute observation period varied more than eight-fold across chile pepper cultivars, ranging from 0.049 visits per flower in Desperado to 0.397 visits per flower in Capperino. The number of flowers per plant was positively associated with floral visitation rate across the cultivars; 42% of the variation in visits per flower was explained by the number of flowers per plant. To evaluate how floral morphology differed across cultivars, and how those traits might affect floral visitation, I measured corolla diameter, anther size, anther count, and style length from a subset of flowers from each cultivar. While all four morphological traits varied significantly across cultivars, none were correlated with floral visitation rate. For example, mean corolla diameter ranged from 13.65 mm to 21.86 mm across the cultivars but had no significant relationship with floral visitation rate. To estimate the effect of insect pollination on yield, I conducted flight cage experiments using six cultivars, in which half the plants from each cultivar were exposed to commercially reared bumblebees (Bombus impatiens), and the remaining half were not. Average pepper mass was higher in bumblebee-pollinated plants for Charger (54%), Sweet Cherry (26%), and Capperino (12%). Average pepper mass was unaffected by bumblebee pollination for Big Jim, Mesilla, and Mosco. These findings suggest variation in the effect of insect-facilitated pollination on fruit mass across cultivars. In conclusion, pollinator attraction varies significantly among chile pepper cultivars—this variation is strongly influenced by the number of flowers per plant. The effect of insect pollination on yield, however, also varied across varieties. Growers can use these findings to improve their integrated pest and pollinator management (IPPM) strategies when managing their farms, as the yield in some cultivars appears to depend on pollinator visitation. Additionally, breeders can apply this research by selecting for increased flower count in future C. annuum cultivars.