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Title: KERNEL GROWTH RESPONSES OF IN VITRO CULTURED WHEAT SPIKES FROM CULTIVARS WITH DIVERGENT SOURCE-SINK LIMITATIONS.

Author
item MA, YONG-ZHAN - UNIVERSITY OF KENTUCKY
item MACKOWN, CHARLES
item VAN SANFORD, DAVID - UNIVERSITY OF KENTUCKY

Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Kernel size (KS) is an important yield component of wheat. Interactions between source assimilate supply and kernel sink capacity affect KS. Compensatory kernel growth classifications range from no response to a 31% for field-grown wheat cultivars with partially degrained (DG) spikes. Source supply may limit KS of responsive cultivars, while KS of nonresponsive cultivars may be sink-limited. In vitro spike culture allow carbohydrate supply to be varied. In vitro culture was tested as a predictor of field performance of wheat cultivars with divergent responses to DG, and as a method to evaluate physiological limitations of kernel growth. Relative differences in KS among in vitro cultured cultivars were similar to those of field-grown plants at maturity. Field-grown plants produced larger kernels but had less vegetative soluble carbohydrate at maturity than in vitro cultured spikes. Smaller KS and abundant accumulation of vegetative soluble carbohydrate indicate that factors othe than carbohydrate supply limited KS of in vitro cultured spikes. Definitive evaluation of source and sink limitations among cultivars was not possible because KS of in vitro cultured spikes was suboptimal. Information about in vitro culture of wheat should prove valuable for further fundamental research by scientists studying source and sink interactions in cereals.

Technical Abstract: A 50% reduction in the main stem reproductive sink size of soft red winter wheat (Triticum aestivum L. em. Thell) elicits differential kernel size (KS) responses among cultivars. In this study, source levels were manipulated to evaluate cultivar source and sink limitations to kernel growth. Detached spikes of 'Arthur' (nonresponsive), 'Caldwell', 'FL 302', ,and 'Adena' (responsive) cultivars were cultured in vitro from 14 d after anthesis (during endosperm cell expansion stage) to maturity with sucrose levels of 25, 50, 100, and 200 mM. Relative differences in KS among cultivars for each sucrose level were similar to those of field-grown plants at maturity. The KS of all cultivars reached a maximum at 100 mM sucrose; however, these kernels were 11 to 21% smaller than those of field- grown plants. On average, kernels on spikes cultured in 100 mM sucrose grew at the same rate as kernels on field-grown plants, but for significantly shorter duration (22.7 vs. 31.7 d). Sucrose concentrations of peduncle and chaff tissues increased as sucrose levels increased. Compared to field-grown plants, peduncle and chaff tissues of cultured spikes averaged over all sucrose levels and cultivars had 4.6-fold higher water soluble carbohydrate concentration and 59% more tissue dry weight at maturity. Smaller kernels but abundant accumulation of water soluble carbohydrates in peduncle and chaff indicate that factors other than carbohydrate supply limited kernel growth of spikes cultured in vitro. The nonresponsive cultivar Arthur did not reach maximum KS at a lower sucrose concentration than the responsive cultivars. Thus, when cultured in vitro a limitation due to sink activity was not apparent for a cultivar nonresponsive to partial degraining.