A Comparative Study on Root Traits of Spring and Winter Canola (Brassica napus L.) under Controlled and Water Stressed Conditions

Abstract

Root system in canola (Brassica napus L.) varies largely in different growth habit types. A study was conducted with five winter and five spring types of canola germplasm. The objective was to identify the gradual change of root traits at different growth habits stages under controlled and water stressed conditions. Two experiments, controlled and water stressed, were conducted in a greenhouse. Data on different root traits were collected at 30, 40, 50 and 60 days after planting. In controlled experiment, no significant difference was observed for root traits between winter and spring types at 30 days after planting. However, significant variations were appeared for taproot length (F = 10.17***) and root dry weight (F = 16.96***) between winter and spring types at 40 days after planting. All other root parameters such as basal taproot diameter (F = 22.14***), bottom taproot diameter (F = 4.59*), primary root branches (F = 78.70***) and root vigor (F = 47.18***) were significantly higher in the winter types compared to those of the spring types at 60 days after planting. Growth pattern curves indicated that all the root traits of spring types increased in a steady fashion, where the root traits of winter types increased rapidly after 40 days of planting. In water stressed experiment, the water stress was applied from 20 to 60 days after planting, and data was taken at 60 days after planting. All the root parameters except taproot length were significantly (P < 0.001) lower in the stressed spring and winter plants compared to the control plants. The root growth reduction in stressed winter type germplasms was higher. Basal taproot diameter, bottom taproot diameter, primary root branches, root vigor, and root dry weight were decreased by 43%, 63%, 19%, 31% and 53%, respectively in stressed winter type plants. In contrast, the root growth reduction of the spring type germplasms were relatively lower. This study indicated that winter type canola generates vigorous root system in comparison to spring types under normal growing conditions, but ceases its root growth rate more than the spring types under water stressed conditions.