Mechanisms for Differential Interference among Cucumber (Cucumis sativus L.) Accessions

Competitive and allelopathic characteristics of a cucumber cultivar `Pioneer' were compared with those of a wild accession PI 169391, which demonstrated respective weak and strong interference abilities. Leachates collected 0-9 days after imbibition from PI 169391 suppressed 10-day seedling dry weight by 40% and percentage of germination by 46% in proso millet (Panicum miliaceum L). Leachates collected from PI 169391 10 days after imbibition to fruiting, as well as all Pioneer leachates, were nontoxic. Growth analyses conducted during the growth period associated with biochemical interactions indicated that the allelopathic PI 169391 did not exceed the net assimilation rate or relative growth rate of Pioneer. Leaf area ratios indicated that PI 169391 may have a greater competitive shading advantage than Pioneer. Although competitive parameters are always present, there was no indication that strong interspecific competition was present during seedling emergence. Allelopathy appears to be more important than competition during the early seedling growth stages of PI 169391.