Drought Response and Recovery in Wild, Feral, and Domesticated Brassica rapa: Implications for Crop Climate Resilience

Drought poses a serious threat to agricultural production and food security. Wild relatives of crops, including pre-domesticated and feral varieties, contain genetic diversity that can serve as a breeding resource for increasing desirable crop traits such as drought resilience, but little is known about the relative ability of wild varieties to cope with climate change in most species. In this study, we investigated the drought response of wild, feral, and domesticated varieties of Brassica rapa, an important crop and model species. Twenty-five accessions were subjected to experimental drought and recovery, and variation in traits such as biomass retention, photosynthetic rate, and water use efficiency were quantified. We found several wild accessions of B. rapa had high biomass retention under drought and full recovery of maximum assimilation rate after rewatering, challenging the assumption that feralization produces stress-resilient phenotypes and suggesting that populations of wild crop progenitors are especially promising reservoirs of drought-response diversity. Our results also showed taproot biomass was positively associated with water use efficiency. Our findings provide candidate traits and genotypes for agricultural breeding aimed at increasing drought resilience in domesticated B. rapa cultivars and give insights into evolution under domestication and feralization in the context of climate change.