Genotypic Response of Canola (Brassica Napus L.) Accessions to Moisture Stress

Abstract

Pakistan is an agrarian economy heavily dependent on crop production, yet it faces a substantial edible oil import burden due to low domestic oilseed yields. To address this, drought-tolerant canola (Brassica napus L.) varieties are essential for sustainable production. This study evaluated the genotypic response of 15 canola accessions to moisture stress under controlled conditions. Two experiments were conducted: (1) a germination assay using polyethylene glycol (PEG-6000) to simulate osmotic stress at four levels (0, -0.2, -0.4, and -0.6 MPa), and (2) a pot trial comparing well-watered and drought-stressed conditions. Germination percentage declined significantly with increasing stress, ranging from 62.33–100% (control) to 0–53.3% (-0.6 MPa). The range of germination stress tolerance index percentage was 18.40 - 78.56% across the treatments. The ranges of germination stress tolerance index percentages were 55.3-100%, 31-100% and 0-53.3% in T₂ (-0.2 MPa), T3 (-0.4 MPa) and T4 (-0.6 MPa) respectively. Accessions Dunkeld and Zn-R-7 exhibited high drought tolerance, maintaining better germination and seedling vigor, whereas Zn-M-9 and Zn-N-6 were highly sensitive. Under drought, root length increased (3.87–9.92 cm vs. 1.67–7 cm in controls), likely as an adaptive response, while shoot length (1.58–5.32 cm vs. 1.92–8.13 cm) and seedling dry weight (0.03–0.44 g vs. 0.05–0.51 g) decreased. High heritability (>90%) and strong genotypic correlations indicated that these traits were predominantly genetically controlled. Path analysis revealed that shoot length had the most significant direct positive effect on seedling dry weight, emphasizing its importance in drought resilience. The findings demonstrate substantial genetic variability among canola accessions, providing a basis for breeding programs aimed at enhancing drought tolerance. Selecting genotypes with superior stress adaptability, such as Dunkeld and Zn-R-7, could improve canola productivity in water-limited environments, reducing reliance on edible oil imports.