Improving crop tolerance to drought is essential for maintaining yield stability under the continued threat of climate change and a key factor for achieving sustainability in agriculture by saving water resource usage. Molecular breeding focusing on monogenic transgenic intervention has so far achieved limited success in the development of drought tolerance in crops. This project focuses on a gene family that is the basis of quantitative trait loci (QTL) affecting drought tolerance in Brassicaceae.

Drought tolerance, like many other important agronomic traits, is one of complex traits controlled by quantitative trait loci (QTLs). A gene family, Kanghan (KH), underpinning drought tolerance was discovered though QTL analysis of Arabidopsis ecotypes, and homologs of the KH gene family were identified from Brassica napus. Canola lines harboring KH mutations have the potential of reducing yield loss under drought conditions. This project was conducted to assess the field performance of the BnKH line under drought stress. Growth chamber assessment demonstrated that RNAi suppression of the KH gene family in Canola leads to drastically improved drought tolerance. A two-year confined field trials in the Okanagan Valley of British Columbia was conducted to assess water-limited yield potential under field conditions. This project also conducted CRISPR gene editing of the KH genes in canola to generate stable knockout lines with improved drought tolerance.

The field trial site experienced not only drought but also above normal heat conditions during the last 2 trial seasons. The heat stress was much more severe than what would be typically expected from prairie Canola growing regions. There was noticeable unevenness of soil quality at different sections of the trial site. Given the technical challenges of the field trial site, we reasoned that comparing lines raised close to each other in the same “deficit irrigation” subsections would help interpret the data. The yield of different lines raised close to each other in the same “deficit irrigation” subsections displayed a trend that some of RNAi lines performed better than the control under drought. Also, during the 2023 growing season, the RNAi lines with better yield displayed consistent yield advantage line across a majority of trial subsections.

Most field trial experiments of this type require more than two years of experiments. RNAi technology as a gene suppression molecular tool has its inherent shortcomings of higher variation and instability. It is suggested that future research to generate knockout lines using CRISPR editing in all members of the BnKH gene family would be a worthy effort for trait stability and regulatory approval.