Most gynoecious hybrid cucumbers (Cucumis sativus L.) grown in the U.S. require pollination for proper fruit set. Early flowering pollenizers may help yield, earliness, or quality. Two experiments were run to measure the value of early pollenizers using fields isolated from other cucumbers by at least 1 km. The first experiment used `Armstrong Early Cluster' and `Sumter' as the early and normal pollenizer, with 30 and 35 days to flower, respectively. Gy 2, Gy 3, Gy 4, and Gy 14 were used as the gynoecious pickling cucumbers. The experiment was run in 2 years (1994, 1995) and seven locations in North Carolina with two pollenizers and the four gynoecious inbreds. There were four replications of plots within each whole plot to help control variability inherent in an experiment where treatments are in separate fields. The second experiment had only 1 year (1996), but the same seven locations, four replications, and four gynoecious inbreds, but only one pollenizer (`Sumter') planted at the same time, or 2 weeks earlier than the gynoecious lines. Plots were harvested once when 30% of the fruits were >50 mm diameter. None of the differences in either experiment were significant (F-ratio test, 10% level). Therefore, it does not appear that use of early flowering pollenizers in blends with gynoecious pickling cucumbers will have a large effect on the yield, earliness, or internal quality of the crop.
Cucumber (Cucumis sativus L.) breeders have provided growers with many useful cultivars since production began in the U. S. in the 1600s. The objective of this study was to determine how much breeding progress has been made for yield, earliness, quality, and anthracnose resistance. The experiment was a split-split-split plot in a randomized complete block with 3 replications. Treatments were 2 years (1989, 1990), 2 seasons (spring, summer), 2 production systems (stress, elite), and 14 cultivars (2 important ones from each of 7 time periods, from 1786 to 1982). Plants were grown at Clinton, N. C. using recommended cultural practices, except for the stress treatment, which received half the recommended amount of fertilizer, irrigation, and pesticides. Total yield over 8 harvests increased from approximately 20 Mg/ha for the old cultivars to 30 Mg/ha for the new cultivars. Similar increases were measured for marketable and early yield. Fruit quality (rated 1 to 9) also was improved by breeding, with shape improved 2, and fruit color improved 3 rating points. Part of the improvement in yield was probably due to improved anthracnose resistance. However, improved yield also was obtained in the spring season where anthracnose was absent. In conclusion, the relatively small cucumber breeding effort produced large gains for most traits measured.
Cucumber (Cucumis sativus L.) populations often are intercrossed after each selection cycle using bees in isolation blocks. Previous research showed the rate of natural outcrossing in monoecious cucumber inbreds was 36%. The objective of this experiment was to determine whether the rate of natural outcrossing could be increased using hormones, plot size, and node of fruit for seed harvest. The experiment was run with 2 years (1997, 1998), two hormones (treated, none), two plot sizes (hills, small plots), two nodes of harvest (2, 8), and four replications. Each treatment combination consisted of four plots or hills planted in 1.5-m rows in one isolation block. Plots or hills were planted to white-spined `Sumter', and were surrounded by rows of black-spined `Wis. SMR 18'. Treatment combinations receiving hormones were sprayed at the cotyledon stage and 1 week later. Plots or hills received ethrel to make them gynoecious, and surrounding rows received silver nitrate to make them androecious. Unsprayed isolation blocks remained monoecious. At maturity, fruit were harvested from nodes 2 or 8 from the white-spined plants in each isolation block. Node of harvest had no effect on outcrossing rate. However, hormones and plot size had a significant effect. Sprayed plots, sprayed hills, and unsprayed hills had high outcrossing rates relative to unsprayed plots. Therefore, if families are to be intercrossed in isolation blocks, they should be sprayed with hormones for maximum outcrossing among families.
Agricultural workers in many developed and developing countries are interested in collecting, evaluating, and maintaining germplasm of the crop species used in their particular agricultural production systems. However, opportunities to collect germplasm from centers of origin are being reduced as land is developed for agriculture, roads, housing, and other uses. Of the 240,000 angiosperm species thought to exist currently, it is estimated that 50,000 will become extinct by the year 2000 (2). The urgency to collect accessions of useful or potentially useful plant species is driving many germplasm institutions to expand. Thus, administrators of germplasm institutions are worried about their ability to maintain accessions unchanged for use in solving future problems (1). With such a large effort involved in the areas of germplasm collection and maintenance, it is important to use efficient collection methods, as well as proper means to preserve accessions.