First leaf emergence force of three deep-planted winter wheat cultivars

Authors: LUTCHER, L - Oregon State University; Wuest, Stewart; Johlke, Tami

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/29/2018
Publication Date: 2/14/2019
Citation: Lutcher, L.K., Wuest, S.B., Johlke, T.R. 2019. First leaf emergence force of three deep-planted winter wheat cultivars. Crop Science. 59(2):772-777. https://doi.org/10.2135/cropsci2018.08.0495.
DOI: https://doi.org/10.2135/cropsci2018.08.0495

Interpretive Summary: In some of the driest wheat growing regions of the Pacific Northwest, USA, wheat is planted deep in order to reach enough soil moisture to germinate before cold weather arrives in the fall. If the soil crusts before the wheat emerges, the plants often cannot emerge and the field might need to be replanted. Some winter wheat varieties have a reputation of being better at emerging under difficult conditions than others, so we devised a method for measuring the force a seedling can exert against a soil crust using an electronic load cell. We compared three varieties and were able to detect statistically significant differences in force. We also made measurements and examined micrographs to look for potential differences in anatomy, which might explain why one variety might have better emergence success than another. These force measurement could prove useful to farmers looking for varieties with superior emergence from deep seeding, or to breeders looking for superior traits.

Technical Abstract: Late summer planting of winter wheat (Triticum aestivum) into tilled fallow is necessary for production of maximum yield in many areas of the low precipitation (< 30 cm; annual) zone of the inland Pacific Northwest region of the United States of America. Farmers plant deep to reach moisture adequate for germination and emergence. The first leaf emerges from a deep planting depth after protruding through the tip of the coleoptile. Emergence may be jeopardized by below-surface buckling. Buckling is a sudden collapse, deformation, and folding of the leaf that impedes its elongation toward the soil surface. Buckling of the first leaf occurs when its exerted force cannot overcome the strength or weight of overlying soil. Small, single-point load cells were used to measure force exerted by the first leaf of three cultivars (Farnum, Finley, and Norwest 553) as it emerged from a deep planting depth in a small containerized volume of soil. The average maximum before buckling emergence force (BBEF) of Norwest 553 and Finley was 12.2 and 11.6 g, respectively. The corresponding value for Farnum (10.9 g) was statistically similar to the BBEF of Finley and less than that of Norwest 553. The measured difference between Farnum and Norwest 553 may be a consequence of variation in the diameter of coleoptiles or the size of the tip of first leaves. Maximum diameter measurements of 1.6 to 1.7 mm were made near the base and in the middle of the Norwest 553 coleoptile. Scanning electron microscope images provide preliminary evidence of phenotypic diversity in the surface area of the foremost tip of the first leaf.