Effects of Defoliation Timing and Intensity on Yield Components and Grain Quality of Quinoa (Chenopodium quinoa...

Understanding plant tolerance to defoliation is crucial for sustainable pest management and reducing pesticide use in food production. This study explores quinoa's (Chenopodium quinoa Willd.) responses to foliar damage, which have been largely unexamined. Over two seasons, quinoa plants were subjected to mechanical defoliation at different pre-reproductive stages and intensities (0-60%) in the first season, and both mechanical and insect-induced (Trichoplusia ni (Hübner), Lepidoptera: Noctuidae) defoliation in the second. The results showed that quinoa plants consistently tolerated defoliation without reductions in grain number, weight, above-ground biomass, or harvest index. These compensatory responses were independent of the defoliation method, timing, or intensity. In the first season, overcompensatory effects were observed, leading to increased plant biomass at 60% early defoliation and 40% late defoliation. Additionally, early defoliation at 20% and 60%, as well as late defoliation at 60%, led to an increase in grain number without affecting grain weight. Defoliation did not significantly alter the phenolic content, sapogenins, or antioxidant capacity of the grains, preserving their phytochemical quality. These findings enhance the understanding of quinoa's resilience to herbivory, suggesting that it can withstand defoliation stress without compromising yield or quality.