Wheat Seedling Emergence from Deep Planting Depths and Its Relationship with Coleoptile Length

Abstract

Successful stand establishment is prerequisite for optimum crop yields. In some low-precipitation zones, wheat (Triticum aestivum L.) is planted as deep as 200 mm below the soil surface to reach adequate soil moisture for germination. To better understand the relationship of coleoptile length and other seed characteristics with emergence from deep planting (EDP), we evaluated 662 wheat cultivars grown around the world since the beginning of the 20th century. Coleoptile length of collection entries ranged from 34 to 114 mm. A specialized field EDP test showed dramatic emergence differences among cultivars ranging from 0–66% by 21 days after planting (DAP). Less than 1% of entries had any seedlings emerged by 7 DAP and 43% on day 8. A wide range of EDP within each coleoptile length class suggests the involvement of genes other than those controlling coleoptile length. Emergence was correlated with coleoptile length, but some lines with short coleoptiles ranked among the top emergers. Coleoptiles longer than 90 mm showed no advantage for EDP and may even have a negative effect. Overall, coleoptile length accounted for only 28% of the variability in emergence among entries; much lower than the 60% or greater reported in previous studies. Seed weight had little correlation with EDP. Results show that EDP is largely controlled by yet poorly understood mechanisms other than coleoptile length.

First Leaf Emergence Force of Three Deep‐Planted Winter Wheat Cultivars

“…Data were obtained from 10-d-old seedlings propagated in the dark, in folded and moistened 25-cm ´ 38-cm, heavy-grade germination paper (Anchor Paper Company), and at constant temperature (22°C) (Mohan et al, 2013). A 100-mm-thick layer of moist (15% gravimetric water content) soil was placed on top of the plastic and packed, using a wooden dowel, to an approximate Diameter measurements in the middle of the coleoptile were made at a point equidistant from 5 mm above the base and 5 mm below the tip.…”

“…A 100-mm-thick layer of moist (15% gravimetric water content) soil was placed on top of the plastic and packed, using a wooden dowel, to an approximate Diameter measurements in the middle of the coleoptile were made at a point equidistant from 5 mm above the base and 5 mm below the tip. Data were obtained from 10-d-old seedlings propagated in the dark, in folded and moistened 25-cm ´ 38-cm, heavy-grade germination paper (Anchor Paper Company), and at constant temperature (22°C) (Mohan et al, 2013). Data were collected during five runs.…”

“…Emergence from deep planting is affected by coleoptile length (Mohan et al, 2013). Coleoptile length is an inherited trait positively correlated to plant height.…”

“…Wheat breeders now use a coleoptile length screening protocol to evaluate germplasm of predominantly tall lines targeted for the low precipitation zone. There is a limit to what can be accomplished from this kind of protocol, however, as coleoptile length accounts for only 28% of the variation in emergence from deep planting depths (Mohan et al, 2013).…”

Genome-wide association mapping reveals novel genes associated with coleoptile length in a worldwide collection of barley

“…Geminating seedlings of monocotyledons have a coleoptile, which is a sheath-like tissue covering the primary leaf to protect the emerging shoot as it breaks through the soil to the surface. The coleoptile is essential for early crop establishment and its length determines the maximum depth at which the seed can be sown [28,33,38,39,50]. If seeds are sown at a depth greater than their coleoptile length, it may result in lower emergence rate, reduced early growth, fewer tiller numbers, and decreased grain yield [11,38,43].…”