Combining physiology and molecular biology to improve drought performance of canola (Brassica napus)

Drought and suboptimal rainfall constrain production of canola by restricting cropping regions and annual production in Australia. Canola cultivars with improved drought performance may increase the cropping area and production. This research was therefore launched to discover and implement possible ways of improving drought performance and the yield of canola in dry environments. Transpiration efficiency (TE = ratio of biomass production per unit of water transpired) is a key trait for improving drought resistance where crop production depends mainly on seasonal rainfall and stored soil-moisture. However, due to the difficulties associated with measuring TE at the field level, present research investigated the suitability of other physiological/morphological traits including carbon isotope discrimination (Δ= difference of carbon isotope ratio between air and plant biomass), leaf chlorophyll content (SPAD) and specific leaf weight (SLW) to justify their use as surrogates of TE in canola. Significant genotypic variation was revealed for all these traits in 111 canola materials including hybrids and inbreds with different cytoplasms in four separate field experiments conducted in 2005, 2006 and 2007. The Δ of Triazine tolerant canola (ranged 21.8-23.2‰) was significantly higher than napus (ranged 18.7-22.4‰), INRA-Ogura (ranged 19.7-22.6‰) and Polima (ranged 20.7-21.7‰). All traits, except HGT, exhibited low genotype and environment ( ) interactions and high repeatability (0.66 to 0.82). Significant genetic (rg) and phenotypic (rp) correlations were observed between Δ and SPAD (rg= -0.43 to -0.62; rp= -0.35 to -0.47 at