Cucurbit Genetics Cooperative Report 1:14 (article 13) 1978
Pleiotropic Effects of the Glabrous Gene of the Cucumber
R. W. Robinson
New York Agricultural Experiment Station, Geneva, NY 14456
The glabrous (gl) gene of the cucumber was induced by thermal neutron seed treatment. It is a useful seedling marker gene, since the mutant is readily identified in the young seedling stage as well as at all later stages and its fertility is good. It is linked with yc, and segregates independently of B, m, l, and yg.
There has been interest in using this mutant in practical plant breeding programs because of one of its pleiotropic effects; fruit of the mutant lack spines and warts, and have a very smooth, attractive appearance. Efforts to breed cultivars with this gene, however, have not been successful. The primary problem has been the sensitivity of gl plants to stress conditions. Glabrous plants grow very well under optimal conditions, but often are adversely affected by stress. Glabrous plants in the field grew vigorously until the hot, dry conditions of midsummer, when their growth was stunted and they developed a mottle that was not associated with any virus. Glabrous plants in a greenhouse grew luxuriantly at 21°C (day) and 16°C (night), but when transferred to a growth chamber at constant 35°C the gl plants, unlike the normal plants, developed a severe chlorosis on all new foliage, similar to iron deficiency symptoms.
The spines and warts of the fruit are trichomes modified through evolution, and both are affected by the gene controlling trichome formation on the foliage. Still another apparently pleiotropic effect of this gene is on root hair development; gl plants have poorer root hair development than normal, accounting for the sensitivity of plants with this gene to extreme conditions of temperature, soil moisture, and mineral elements.