Emergence, stand establishment and vigour of deep-sown Australian and CIMMYT wheats

The short coleoptile of the majority of released Australian wheat cultivars, is well-documented to increase time to emergence and reduce stand establishment. We examined the effect of seeding depth on coleoptile length and seedling characteristics of 36 CIMMYT wheats, bred for their ability to emerge from deep sowing, relative to 14 Australian cultivars in controlled and field environments. Coleoptile length of one of the CIMMYT lines, Berkut, exceeded that of Vigour 18 when grown in the dark in a controlled environment. In a second experiment in controlled conditions, this time with a regular day/night cycle, seedlings of 4 CIMMYT and 4 Australian cultivars emerged from 5 and 8 cm sowing depths, but only 50% of the Australian wheats emerged from 11 cm, compared with 100% for the CIMMYT wheats. In a third experiment, 6 cultivars were sown at depths of 5, 8 and 11 cm at 2 field sites with different soil types ( a sandy loam duplex and a red clay) at Kukerin, Western Australia. Field site and sowing depth interacted for emergence time, stand establishment and coleoptile length, with higher values of each at the clay site. The first internode elongated at both field sites, but to a lesser extent on the clay soil, where the response was only observed with deep sowing. CIMMYT wheats Parus/Pastor and Berkut were notable for rapid emergence, a long sub-crown internode and coleoptile, and above-average leaf area in controlled and field environments, in comparison with Australian cultivars. These lines hold promise as genetic sources of improved stand establishment and early vigour in wheats for use in Australia and similar environments.