Effects of water deficit stress on physiological and biochemical traits of sugar beet genotypes (Beta vulgaris L.)

In order to evaluate the physiological and biochemical aspects of water deficit stress on six sugar beet genotypes, a factorial experiment based on completely randomized design with eight replications was carried out under greenhouse condition at Sugar Beet Seed Institute, Karaj, Iran, in 2015. Irrigation included two levels (normal irrigation and water deficit stress). Irrigation was equally applied to the both levels from sowing up to plant establishment after which irrigation in the water stress condition was done on the basis of stress symptoms appearance. Results showed that water deficit stress significantly decreased relative water content, root dry weight and water use efficiency and increased specific leaf weight, electrolyte leakage, leaf chlorophyll content, proline and betaine content. Chlorophyll and proline contents, root dry weight and root dry weight and water use efficiency were significantly influenced by genotype. The genotype by water treatment interaction was significant only for proline content and root dry weight. Electrolyte leakage, as a measure of cell membrane stability, was increased from 5242.58 µs.m-1 in normal condition to 941.21 µs.m-1 in water stress condition. The leaf chlorophyll content was increased in water stress condition. The highest and lowest chlorophyll content was observed in genotypes 1 (drought tolerant check) and 5 (PB13-S2-52.HSF-977), respectively. The highest proline content in water stress condition was observed in genotype 6 (PB13-S2-52.HSF-987), whereas the lowest value was observed in genotypes 3 (PB13-S2-37.153.80.HSF–1007) and 1. It seems that root dry weight, water use efficiency, and chlorophyll and betaine contents could be considered to initially screen the sugar beet genotypes for tolerance to water deficit stress.