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- Author or Editor: Todd C. Wehner x
Downy mildew [Pseudoperonospora cubensis (Berk. & Curt.) Rostov] is an important disease in most cucumber (Cucumis sativus L.) production areas of the world. Resistant cultivars are available, but higher levels are needed if yield losses are to be avoided. The objective of this experiment was to test all available plant introduction accessions, cultivars, and breeding lines (collectively referred to as cultigens) of cucumber for downy mildew resistance under field conditions in North Carolina. Cultigens were tested in 2 years and two replications under natural field epidemics of the disease. Mean ratings for downy mildew leaf damage ranged from 1.3 to 9.0 on a 0 to 9 scale. The most resistant nine cultigens originated from the U.S., and were primarily adapted cultivars or breeding lines. The most-resistant cultigens, for which multiple-year data were available, were Gy 4, `Clinton', PI 234517, `Poinsett 76', Gy 5, `Addis', M 21, M 27, and `Galaxy'. The most-susceptible cultigens for which multiple year data were available, were PI 288995, PI 176952, PI 178886, and PI 211985. We classified 17 cultigens as highly resistant (1.3 to 3.0), 87 as moderately resistant (3.3 to 5.0), 311 as moderately susceptible (5.3 to 7.0), and 248 as highly susceptible (7.3 to 9.0) for the 663 cultigens with multiple-year data. No plant introduction accessions were found to be more resistant than the most-resistant elite cultivars and breeding lines tested.
The combining ability (hybrid performance) of breeding lines is often determined to measure selection progress for yield. Plant breeders utilize this information to develop breeding lines with higher combining ability. The objectives of this study were to measure the specific combining ability for yield traits over three selection cycles from four pickling cucumber populations with Gy 14, a popular pickling cucumber inbred; and to determine the change in specific combining ability for yield traits in four populations improved through recurrent selection. Four pickling cucumber populations, North Carolina wide base pickle (NCWBP), medium base pickle (NCMBP), elite pickle 1 (NCEP1), and hardwickii 1 (NCH1), were developed and improved through modified half-sib selection from 1983 to 1992 to improve yield per se and fruit quality in each population. Eleven families were randomly selected from each of 3 selection cycles (early, intermediate, advanced) from each populations and were hybridized to Gy 14. Plants were sprayed with Paraquat to defoliate them and to simulate once-over harvest. The experiment was a randomized complete-block design with 22 replications per population arranged in a split plot with the four populations as whole plots and the three cycles as subplots. The combining ability for fruit quality rating of NCWBP and NCMBP increased as the number of selection cycles increased. Conversely, selection for higher yield per se decreased the combining ability of the NCEP1 population for improved fruit quality. In most instances, the combining ability of each population exhibited a constant response over selection cycles for each measured yield trait.
Production of pickling cucumber (Cucumis sativus L.) requires a significant expenditure of labor and money. Those resources could be better managed if both yield and harvest date could be predicted for a given planting date and production area. The objective of this experiment was to develop a model to simulate growth and yield of pickling cucumbers under field conditions in North Carolina. Detailed measurements of leaf area, branching habit, flowering, fruiting, and dry weight distribution were obtained for the cultigens `Calypso', M 21, `Wis. SMR 18', and WI 2757 for 10 planting dates. Light interception, air temperature, and rainfall were also recorded. There were differences among cultigens and planting dates for time needed to reach certain growth stages. Number of days to reach a given stage generally decreased with later planting dates. Addition of nodes over time to the main stem was linear and the interaction of planting date by cultigen was significant. Number of staminate and pistillate flowers was affected by both cultigen and planting date.
In many cases, measurement of cucumber fruit weight in small research plots involves more labor and resources than just counting the number of fruit per plot. Therefore, plant breeders are interested in an efficient method for estimating fruit weight per grade (early, marketable, and cull) based on fruit number and total fruit weight. We evaluated the cucumber germplasm collection of 810 plant introduction accessions (supplied by the U.S. Dept. of Agriculture, Regional Plant Introduction Station at Ames, Iowa) along with seven check cultivars for yield. Correlations were calculated for all pairs of fruit number and fruit weight combinations for each grade. In general, the lowest correlations were observed between the fruit weight of each grade (early, marketable, and cull) and total fruit weight or number per plot. High correlations were observed for fruit weight and fruit number within each grade (early, marketable, and cull). An efficient method for estimating fruit weight per hectare of early, marketable, and cull grades is to count total, early, and cull fruit, then measure total fruit weight. Our results showed that the fruit weight of each grade (early, marketable, and cull) was best estimated using the fruit number of that grade (early, marketable, and cull) along with the total fruit weight and total fruit number.
Eighteen cucumber (Cucumis sativus L.) cultivars (15 oriental trellis and three standard American slicers) were grown on trellis and flat-bed production systems during the spring and summer seasons of 1995. Vine, flower, fruit quality, keeping ability, and yield traits were measured. Vine length, incidence of powdery mildew, fruit shape, fruit quality, fruit firmness, yield of Fancy plus No. 1 grade slicer fruits, marketable yield, and percentage of culled fruits were all higher when cultivars were grown on trellis support. Anthracnose damage, fruit length, fruit diameter, average fruit mass, fruit color, overall impression, fruit shriveling, seedcell size, branch number, percentage of staminate nodes, and total yield were not significantly affected by production system. The best cultivars for marketable yield (mass of Fancy, No. 1 and 2 grade slicers) were `Summer Top', `Tasty Bright', and `Sprint 440' on trellis support and `Sprint 440' and `Poinsett 76' on flat bed. The cultivars with the best fruit quality were `Tasty Bright', `Summer Top', and `Sprint 440' on trellis and `Poinsett 76', `Sprint 440', and `Tasty Bright' on flat bed. The best cultivars overall on the trellis production system were `Sprint 440', `Summer Top', `Tasty Bright', and `89-211', and the worst were `Sky Horse', `Hongzhou Green 55', and `Fengyan'. The best cultivars overall on the flat bed were `Poinsett 76', `Sprint 440', and `89-211', while the worst cultivars were `Sky Horse' and `Hongzhou Green 55'.
Eighteen cucumber (Cucumis sativus L.) cultivars (15 oriental trellis and three standard American slicers) were grown on trellis and flat-bed production systems during the spring and summer seasons of 1995. Vine, flower, fruit quality, keeping ability, and yield traits were measured. Vine length, incidence of powdery mildew, fruit shape, fruit quality, fruit firmness, yield of Fancy plus No. 1 grade slicer fruits, marketable yield, and percentage of culled fruits were all higher when cultivars were grown on trellis support. Anthracnose damage, fruit length, fruit diameter, average fruit mass, fruit color, overall impression, fruit shriveling, seedcell size, branch number, percentage of staminate nodes, and total yield were not significantly affected by production system. The best cultivars for marketable yield (mass of Fancy, No. 1 and 2 grade slicers) were `Summer Top', `Tasty Bright', and `Sprint 440' on trellis support and `Sprint 440' and `Poinsett 76' on flat bed. The cultivars with the best fruit quality were `Tasty Bright', `Summer Top', and `Sprint 440' on trellis and `Poinsett 76', `Sprint 440', and `Tasty Bright' on flat bed. The best cultivars overall on the trellis production system were `Sprint 440', `Summer Top', `Tasty Bright', and `89-211', and the worst were `Sky Horse', `Hongzhou Green 55', and `Fengyan'. The best cultivars overall on the flat bed were `Poinsett 76', `Sprint 440', and `89-211', while the worst cultivars were `Sky Horse' and `Hongzhou Green 55'.
Root-knot caused by Meloidogyne spp. is the primary disease of cucumber (Cucumis sativus L.) in North Carolina, causing an annual yield loss of approximately 12 %. All cucumber cultivars we have tested are resistant to M. hapla, but none are resistant to any of the four important nematodes found on cucumber in North Carolina: M. incognita, M. arenaria races 1 and 2, and M. javanica. However, we are preparing to release three cucumber inbreds with resistance to four out of five of those nematodes. `Marion' (NC-44), `Shelby' (NC-45), and `Lucia' (NC-46) are high yielding, monoecious pickling cucumber inbreds that have resistance to M. arenaria races 1 and 2, M. javanica, and M. hapla. Length: diameter ratio was 3.4, 3.0, 3.9 for `Marion', `Shelby', `Lucia' (`Calypso' was 2.9 in the same trial), respectively. Thus, different length requirements for the pickling industry can be met with the three cultivars. Based on the 1995 North Carolina stage 1 pickle trial, performance (as % of `Calypso') for `Marion', `Shelby', and `Lucia' respectively was 79%, 94%, and 115% for total fruit number/ha; 71%, 96%, and 113% for marketable fruit number/ha; and 102%, 84%, and 97% for fruit quality rating. Therefore, nematode resistant cultivars are available that match the performance of the gynoecious hybrid check cultivar for the region.
Plant breeders often measure selection progress for yield by measuring the hybrid performance (combining ability) of a breeding line. This information is used to develop breeding lines with higher combining ability. The objectives of this study were to measure the specific combining ability for yield traits over three selection cycles from four slicing cucumber populations with `Poinsett 76', a popular slicing cucumber cultivar; and to determine the change in specific combining ability for yield traits in four populations improved through recurrent selection. Four slicing cucumber populations, North Carolina wide base slicer (NCWBS), medium base slicer (NCMBS), elite slicer 1 (NCES 1), and Beit Alpha 1 (NCBA1), were developed and improved through modified half-sib selection from 1983 to 1992 to improve yield per se and fruit quality in each population. Eleven families were randomly selected from each of three selection cycles (early, intermediate, advanced) from each population and were hybridized to `Poinsett 76'. Twenty-three seeds from each cross were planted in 1.2-m plots in Spring and Summer 1995. When 10% of fruit were oversized (>50 mm in diameter), plants were sprayed with paraquat to defoliate them and to simulate once-over harvest. The experimental design was a randomized complete block with 22 replications per population arranged in a split plot with the four populations as whole plots and the three cycles as subplots. The combining ability for early and marketable yield of NCWBS and NCBA1 increased as the number of selection cycles increased. Conversely, selection for higher yield per se decreased the combining ability of the NCES 1 population for early and marketable yield. The NCBA1 population exhibited the largest gain (131.2%) from cycle 0 to 8 averaged over all traits. Early yield exhibited the largest gain (60.8%) averaged over all populations.
Root knot, caused by Meloidogyne spp. is the most important disease of cucumber (Cucumis sativus L.) in North Carolina, causing an average annual yield loss of 12 %. A greenhouse study was conducted 10 screen 924 cultigens (728 accessions, 136 cultivars and 36 breeding lines of C. sativus, and 24 accessions of C. metuliferus Naud.] for resistance to 3 species of root knot nematodes, M. incognita r. 3, M. arenaria r. 2 and M. hapla, Plants were grown from seed in 150-mm diameter clay pots. Two-week-old seedlings were inoculated with 5000 nematode eggs per plant, then evaluated for resistance 9 weeks later. All cultigens evaluated were resistant to M. hapla. Little resistance was found in the cultigens of C. sativus to M. incognita r. 3 and M. arenaria r. 2. Most of the cultigens evaluated were susceptible to both. `Southern Pickler' was resistant to both nematodes (1 % average galls). `Green Thumb and LJ 90430 were resistant to M. arenaria r. 2, Two check cultigens, `Sumter' and Wis. SMR 18, had an average of more than 50% galls. All C. metuliferus cultigens evaluated were resistant to all root knot nematodes tested. PI 482452 was most resistant (1 % average galls), and PI 482443 was least resistant (5% average galls) of the C. metuliferus cultigens tested.