Cucurbit Genetics Cooperative Report 15:17-18 (article 7) 1992
The Significance of Some Traits and Their Combinations in the Usage of U.S. Cucumber
Henry M. Munger
Department of Plant Breeding, Cornell University, Ithica, NY 14853
The excellent history of U.S. cucumber improvement by Wehner and Robinson (1) prompts me to make some corrections and add some thoughts about the importance of the right combination of traits as contrasted with improvement in a single trait. The slight corrections involve the Cornell releases 'Tablegreen' and 'Marketmore' which contrary to this history (1), did not become important as open-pollinated varieties and perhaps not as parents of F1 hybrids either. Soon after 'Tablegreen' was released, it became clear that its susceptibility to scab (Cladosporium cucumerinum Ell. & Arth.) negated much of the value of its high cucumber mosaic resistance (CMR). Because of this, the release of 'Marketmore' was delayed until the addition of scab resistance was completed, and this resistance should be added to its traits in Table 1 of the history (1). The scab resistant version of 'Tablegreen' was named 'Tablegreen 65' and became much more important than the original 'Tablegreen'.
Along with high CMR, another novel trait of 'Tablegreen' was its uniform fruit color. It apparently was the first U.S. Variety to carry the u gene, which came from 'Chinese Long', the source of CMR. Lack of the u gene limited the use of 'Marketmore' because the fruit color became too light at high temperatures. The u gene was transferred from 'Tablegreen' by backcrossing and the resulting 'Marketmore 70' achieved far more usage than 'Marketmore'. It still, however, lacked the powdery mildew resistance of 'Tablegreen'. This was corrected by adding a higher level of PMR from 'Spartan Salad' and releasing 'Marketmore 76'.
Dating back to the first commercial trials of the scab susceptible 56-388, the recurrent parent of 'Marketmore', growers commented on its high yield and high percentage of marketable fruit. This trait was reflected in the name, and because of the difficulty of identifying it in segregating material, the backcross method has been particularly appropriate as a means of retaining it while improving other features. This is probably the principal trait that has made 'Marketmore 76' far more useful than 'Tablegreen 65' which is so similar in other respects. "High marketable yield" might well be added to the list of 'Marketmore 76' (CMR, SR, PMR, uniform color, and high marketable yield), not one could be omitted without seriously impairing the usefulness of the variety.
The listing of "fruit type" as the trait of interest for 'Marketer' (1) does not make it clear why that was the dominant slicing cucumber variety for many years. Consequently an anecdote about the development of 'Marketer' may be worth recording. Dr. Floyd Winter, Asgrow's director of research at that time told of a meeting in which company salesmen requested better slicing cucumbers. Invited by Winter to give their specifications, they agreed on a cylindrical fruit with blunt ends. One of Asgrow's breeding stations proceeded to breed such a cucumber. A trial sample resulting from this effort planted at Cornell in 1943 was impressively cylindrical and promptly used in crosses in the Cornell CMR program. In the same trial, a second unnamed slicer bred independently at another Asgrow station had tapered ends and got little attention. The variety bred to specifications was subsequently named 'Cubit' and soon disappeared. The one with tapered ends was named 'Marketer' and became the leading slicer. Their reasons for this unexpected outcome are not entirely clear, but we observe din later trials that 'Cubit' produced many more cull fruits if conditions were less than ideal. 'Cubit' fruits were said to have a tendency to "jumbo" (become oversized) whereas 'Marketer' remained of marketable size for a longer time. In short, shape itself had less influence on success of the variety than did marketable yield.
'Poinsett 76' may deserve listing in a history of U.S. varieties because it so rapidly and completely replaced the extremely important 'Poinsett'. Bred primarily for scab resistance, the u gene for color was incorporated at the same time, and a slight increase in fruit length demonstrated that the earlier linkage between scab resistance and short fruit had been broken. Since scab is not important in most areas where 'Poinsett' was adapted and the difference in length is not great, it is likely that improved color was the main reason for the success of 'Poinsett 76'. Only a few years after its introduction, slicers lacking the u gene disappeared from U.S. supermarkets.
- Wehner, T.C. and R.W. Robinson. 1991. A brief history of the development of cucumber cultivars in the U.S. Cucurbit Genetics Coop. Rpt. 14: 1-4.