Challenges of breeding for longer coleoptile in bread wheat ( Triticum aestivum L.)

Bread wheat cultivars with longer coleoptile are desired for cultivation in drought prone environments where moisture is available in the deeper layers of the soil. Although there exist several studies about coleoptile length, its relations with important agronomic traits are not clear. In the present research, a diallel mating was generated of seven Iranian and overseas wheat cultivars to evaluate coleoptile length, yield and yield related traits during 2 years, and assess relationships between coleoptile length and important agronomic traits. Roshan, Iranian landrace containing Rht8 , had the longest coleoptile length (8.81 cm). High narrow sense heritability (0.53 and 0.66 in 2016 and 2017, respectively) of coleoptile length indicated strong additive genetic control of this trait. Selection for longer coleoptile indirectly increased plant height (r = 0.75**), biological yield (r = 0.56**), fertile tiller numbers (r = 0.37*), days to flowering (r = 0.57**) and awn length (r = − 0.64**). Except for days to flowering and awn length, these indirect responses are appropriate in drought stress condition. Coleoptile length of gibberellic acid sensitive cultivars possessing Rht8 and Rht13 were 42% longer than gibberellic acid insensitive cultivars containing Rht1 and Rht2 .