The Study of response of some sugar beet (Beta vulgaris L.) cultivars to water deficit irrigation and rhizomania disease under field conditions

Water deficit and Rhizomania disease are two major obstacles in reducing yields in the sugar beet fields of Iran. Each year, various commercial varieties which have different kinds of resistance to disease, especially Rhizomania, are distributed to the sugar beet growers. Due to complexity of drought tolerance, development of drought tolerant varieties takes time and the progress is very slowly, so the introduction and use of high yielding varieties among these current varieties under less water conditions can be effective in reducing water consumption. In order to reach this goal, the reaction of 30 commercial varieties to low irrigation and Rhizomania reaction, was investigated in 2016 and 2017 in non-infected (Karaj) and infected (Mashhad and Miandoab) fields using a randomized complete block design. The irrigation method was furrow and irrigation periods, after two initial water for germination, was based on evaporation of 180 mm from the class A evaporation pan. Color, wilting and leaf senescence scores were evaluated in the middle of the growth season as well as the severity of disease to Rhizomania at harvest time. Root yield and sugar content were analyzed at harvest time. Water use efficiency (WUE) and superiority index (Pi) were calculated and evaluated. In these experiments, about 30% of water consumption decreased compared to control farms (irrigation based on evaporation of 80 mm from the class A evaporation pan.) .Aanalysis of variance showed that variety effect on sugar yield and water use efficiency (WUE) was significant (P˂ 0.01). It was confirmed that, in sugar beet, variety differences for water use efficiency are mainly due to differences in potential yield. The results showed that the ranking of the varieties differed in terms of the amount of sugar yield in infected conditions with non-infected conditions. In case of infection, the leaf color score and the severity index of the disease with sugar yield had a significant positive (R2= 0.44) and negative (R2= 0.39) correlation (P˂ 0.01), respectively. In non-infected conditions, the wilting and senescence score had a negative and significant correlation with sugar yield (r= -0.45* and -0.42*, respectively). However, in infected conditions with the disease, the correlation of sugar yield with the wilting score and leaf aging was negative but respectively, was not significant (r= -0.20, P> 0.05) and significant (r= -0.52, P