Winter Wheat Seedling Emergence from Deep Sowing Depths

Abstract

Growers in low‐precipitation (<300 mm annual) dryland wheat‐fallow areas of the inland Pacific Northwest need winter wheat (Triticum aestivum L.) cultivars that emerge from deep sowing depths in dry soils. Stand establishment is the most important factor affecting winter wheat grain yield in this region. Despite poor resistance to disease, modest grain yield potential, and other problems, the outdated soft white winter wheat (SWWW) cultivar Moro is widely sown in these dry areas, due to its excellent emergence ability. All other SWWW cultivars are semidwarfs that carry emergence‐impeding Rht1 or Rht2 reduced‐height genes. From 12 sowing trials at 2 locations over 4 yr, we compared the emergence capability of Moro to (i) 8 SWWW cultivars and (ii) 16 SWWW advanced experimental Mororeplacement lines. Under both wet and dry soil conditions (soil water content in the seed zone ranged from 11 to 19 mm3 mm−3), seeds were sown deep, with 110 to 160 mm of soil cover. Moro always emerged fastest and achieved the best final stand compared with the semidwarf cultivars. The advanced experimental lines, which contained either no reduced‐height gene or a Rht1, Rht2, or Rht8 reduced‐height gene, had superior straw strength, disease resistance, and grain quality compared with Moro. The best‐emerging advanced experimental lines had coleoptile lengths >100 mm. Coleoptile length was associated with emergence capability among both cultivars (r2 = 0.71, P < 0.004) and advanced lines (r2 = 0.62, P < 0.001). From deep sowing depths in this study: (i) cultivars and advanced lines with Rht1 and Rht2 reduced‐height genes always emerged poorly compared with Moro; (ii) the Rht8 reduced‐height gene did not hamper emergence to the extent that Rht1 and Rht2 did; and (iii) several advanced experimental lines with long coleoptiles equaled or exceeded Moro for emergence.

Effect of Hormonal Priming (GA3) and Osmopriming on Behavior of Seed Germination in Wheat (Triticum aestivum L.)

“…Low seed zone water potential, deep planting depth and soil crusting due to rain before seedling emergence frequently impede winter wheat stands (Giri & Schillinger, 2003). So Farmers place seed as deep as 20 cm below the preplanting soil surface with deep-furrow drills to reach adequate water for germination and emergence (Schillinger et al, 1998). Seed zone water content is the controlling factor for wheat seedling emergence, but soil temperature and depth of soil covering the seed are also important (lindstrom et al, 1976;Kirby, 1993).…”

Coleoptile length and plant height of modern tall and semi-dwarf European winter wheat varieties

“…Soil conditions are so specific that only genotypes possessing very long coleoptiles can be grown, even they are agronomically out-dated. Most of the landraces grown in such areas possess a coleoptile length of about 10 cm [1,2]. Currently, semi-dwarf varieties prevail in the world due to intensive use of dwarfing genes Rht-D1 and Rht-B1 which shorten both plant height and coleoptile length.…”

Characterization for drought resistance at early stages of wheat genotypes based on survival, coleoptile length, and seedling vigor

“…Coleoptile length can also vary because of research or growth conditions. In addition, when we consider the coleoptile lengths reported as 49-119 mm by Schillinger et al (1998), 64-131 mm by Murphy et al (2008a), and 59-159 mm by Murphy et al (2008b), it can be stated that the coleoptile lengths of the bread wheat genotypes used in this study showed narrow variation. Moreover, the fact that the local cultivars and cultivars with old registration dates had longer coleoptiles than the modern and current cultivars took our attention.…”

“…In cases of hand-sowing (where it is difficult to adjust the sowing depth), no-till, and mulch tillage, coleoptile length is an important criterion for the emergence of shoots to the surface and for stand establishment. Short coleoptiles in seed beds that are unsuitable with respect to moisture and sowing depth decrease yield by extending the duration of emergence, decreasing the number of emergent seedlings, and resulting in smaller leaf area indices and weak seedlings (Richards, 1992;Schillinger et al, 1998). In order to suppress weeds and increase yield, the best practice is to select winter varieties having longer coleoptiles in regions having low rainfall (Murphy et al, 2008a).…”