Effect of Planting Date on Cold Tolerance of Winter, Spring and Facultative Growth Types of Wheat Genotypes

Early autumnal and late spring frosts usually impose damages to wheat production in North-West of Iran. In order to investigate cold tolerance of wheat genotypes, two laboratory and field experiments were carried out at three planting dates of 12 Oct. and 1 and 21 Nov. 2007 in Saatlu Agricultural Research Station on 15 genotypes with winter, facultative and spring-growth types. Arrangement of the greenhouse and field experiments were completely randomized design and randomized complete blocks design, respectively. Results showed that spring and facultative- growth types had the highest and lowest ion leakage. At 6-leaf stage (60 days after planting), autumn-growth type genotypes including Saison, Marton, Gascogen, C-82-12, C-81-14, along with facultative-growth type genotypes of Alvand, Mahdavi and Zarrin were in vegetative growth stage, but Shiraz, Pishtaz, M-79-7, M-81-13 and Kavir spring-growth type genotypes, with two facultative-growth type genotypes of Marvdasht and Tus entered the reproductive stage and were susceptible to cold stress. Spring-growth type genotypes had the minimum grain yield and yield components. Facultative-growth type genotypes had more total dry matter and were taller. The C-82-12 genotype had minimum ion leakage, needed minimum survival temperature of -35 ْC for 50% of the plants, and had maximum grain yield and total dry matter. In contrast, the M-79-7 genotype had maximum ion leakage, highest standard deviation for grain yield and dry matter, and needed minimum survival temperature of -30 ْC for 50% of the plants. Number of spike per m2 had positive correlation with grain yield. In general, negative correlation of ion leakage with total dry matter and grain yield could be used as an indirect criterion for screening of cold tolerant wheat genotypes.