Response of Genotypes of Three Brasica Species to Delayed Planting in Rainfed Conditions of Gonbad Region in Iran

To study the effect of planting date on genotypes of three species of Brassica، an experiment was conducted at Agricultural Research Station of Gonbad in Iran in 2008-09 and 2009-10 cropping seasons. Three separate experiments were carried out using randomized complete block design with three replications. Two mustard (Bard-1 and J-98-102/51-5)، two turnip (Rainbow and Candle)، three oilseed rape (Hyola401، RGS003 and Shiralee) genotypes and Select4 (a cross between canola and mustard) were studied in each planting date. The planting dates were Nov. 12، Dec. 10 and Jan. 09 in 2008، and Nov. 17، Dec. 19 and Jan. 09 in 2009، respectively. The mean air temperature in in Nov. 12، Dec. 10 and Jan. 09 in 2008 was 8. 0، 11. 6 and 5. 5 ºC، and in Nov. 17، Dec. 19 and Jan. 09 in 2009 was 13. 9، 14. 7 and 11. 0 ºC، respectively. With delay in planting date seed yield decreased considerably. The mean seed yield in first، second and third planting dates was 2362، 2227and 1939 kg ha-1، respectively. Seed yield of oilseed rape genotypes decreased more with delay in planting date as compared with mustard and turnip genotypes. Hyola401 hybrid had the highest seed yield and harvest index mainly due to higher seed number pod-1 and 1000-seed weight. The mean seed yield of Hyola401 hybrid in first، second and third sowing dates was 2851، 2524 and 2173 kg ha-1، respectively. Results of this study showed the superiority of oilseed rape genotypes when compared with genotypes of other Brassica species for seed yield and agronomic traits.