Search Results
You are looking at 101 - 110 of 131 items for
- Author or Editor: Todd C. Wehner x
Abstract
Compressed air was injected into fruit of pickling cucumber (Cucumis sativus L.) to simulate the build-up of gas during brining. Four size grades were tested from 4 cultivars over 2 harvests and 2 seasons. Carpel adhesion, as measured by the air pressure required to separate the carpels, was negatively correlated with fruit size. Higher air pressure was required to separate the carpels of cultivars resistant to balloon bloating. The formation of balloon bloaters in cucumbers brined in commercial tanks was correlated with results from the compressed air test of carpel adhesion, especially with fruit 45 to 51 mm in diameter.
Abstract
The feasibility of testing the resistance of pickling cucumber (Cucumis sativus L.) cultivars to bloater damage was determined using a procedure of artificial carbonation at several concentrations of dissolved CO2 during brine storage of unfermented cucumbers. The use of grade 3-size fruit carbonated to saturation with CO2 during brine storage in 18-liter (5-gal) plastic pails appeared to be a simple, rapid (6 days), inexpensive, and reproducible method to test for cultivar differences in susceptibility to bloater damage. The method involves the use of a prescribed brine composition and sequential introduction of N2 and CO2 into the brined cucumbers. Thirty-five cucumber lines and cultivars were statistically separable using the method. Based on the data collected, it is recommended that 6 replications of 15 grade 3 fruit per cultivar or line be used, although good data can be obtained with as few as 2 replications of 5 fruit.
Abstract
Three rapid methods of measuring yield (small plots harvested at the green stage, and single plants harvested at the green or at the mature stage) were tested for correlation with yield from a replicated multiple-harvest yield trial to determine how well they predicted performance of 10 hybrids in 1981, and 18 lines and cultivars tested in 1982. Only 2 methods of measuring yield were evaluated in 1981, small plots harvested once-over at the green stage and the standard replicated multiple-harvest trial. In that year, the most efficient method for measuring yield, based on capacity of the method to handle lines and to predict multiple-harvest trial performance, was 2 or 3 replications of 3 m plots harvested once-over. Those methods had a calculated advantage (relative capacity × correlation coefficient) of 43% to 80% over the replicated multiple-harvest trial. The most efficient method for measuring yield, of the 4 tested in 1982, was single plots with 1, 2, or 3 replications harvested once-over at the green stage. The tests had a calculated advantage of 102 to 107% over the replicated multiple-harvest trial, respectively. It was concluded that 2 or 3 replications in the test would provide the best results by controlling environmental variability without using an excessive number of seeds per family. In addition, the best correlation with yield in the multiple-harvest test was obtained when all fruit from the plot were counted, rather than just those of marketable size (38 to 60 mm diameter).
Bottle gourd [Lagenaria siceraria (Molina) Standl.] is widely produced in some Asian and African countries as a fresh vegetable as well as for seed consumption. A major use of bottle gourd is for rootstocks in grafted watermelon production. There are several centers where bottle gourd genetic resources are maintained, with the U.S. Department of Agriculture (USDA) germplasm collection being one of the most important. There is little published information on the relationship between seed morphology and the early establishment of seedlings in bottle gourd. The objective of this study was to determine seed characterization, morphology, and cotyledon shape in 163 Lagenaria spp. accessions and measure any relationship between seed and cotyledon characteristics. In USDA Lagenaria germplasm, it has been determined that the common character in seeds was medium in terms of seed size (53% of accessions), intermediate in seed surface lustre (39% of accessions), brown in seedcoat color (89% of accessions), thin and uniform in seed margin (35% of accessions), and tan in seed margin color (64% of accessions). According to the research results, seed weight ranged from 0.11 g (PI 500820) to 0.36 g (PI 675112), seed length from 13.17 mm (PI 500820) to 23.68 mm (PI 675112), and seed width from 5.86 (PI 500808) to 11.21 mm (PI 491274). Cotyledon length ranged from 5.46 cm (PI 368640) to 2.47 cm (PI 381850). The widest cotyledon was 3.00 cm (PI 534552), and the narrowest was 1.50 cm (PI 381831). Interesting correlations were observed for seed weight with seed length (R 2 = 0.259), and cotyledon length with cotyledon width (R 2 = 0.547).
Powdery mildew has been reported on Citrullus lanatus in Africa and Europe for the past 9 years, and in the United States for the past 6 years. During this time, it has occurred in the main watermelon production areas in the U.S. and has been documented in nine states (South Carolina, Georgia, Florida, Oklahoma, Texas, Maryland, New York, Arizona, and California). This is of great concern to the watermelon industry since powdery mildew is difficult to control and can have a severe impact on yield and fruit quality due to loss of photosynthetic area and sunscald. Finding resistant C. lanatus germplasm is needed for the development of commercial varieties containing this resistance. This report summarized the status of an ongoing project to screen the entire USDA–ARS C. lanatus germplasm collection. Currently, the collection is being screened for race 1 and race 2 Podosphaera xanthii (syn. Sphaerotheca fuliginea auct. p.p.), the causal agent of powdery mildew in C. lanatus in the United States. Resistance genes appear to exist for both races and the genes conferring resistance to race 1 appear to be different than race 2 resistance genes. Allelism tests are currently in process to determine the number of resistance genes present.
Powdery mildew has been reported on Citrullus lanatus in Africa and Europe for the past nine years, and in the United States for the past 6 years. During this time, it has occurred in the main watermelon production areas in the U.S. and has been documented in nine states (South Carolina, Georgia, Florida, Oklahoma, Texas, Maryland, New York, Arizona, and California). This is of great concern to the watermelon industry since powdery mildew is difficult to control and can have a severe impact on yield and fruit quality due to loss of photosynthetic area and sunscald. Finding resistant C. lanatus germplasm is needed for the development of commercial varieties containing this resistance. This report summarized the status of an ongoing project to screen the entire USDA–ARS C. lanatus germplasm collection. Currently, the collection is being screened for race 1 and race 2 Podosphaera xanthii (syn. Sphaerotheca fuliginea auct. p.p.), the causal agent of powdery mildew in C. lanatus in the United States. Resistance genes appear to exist for both races and the genes conferring resistance to race 1 appear to be different than race 2 resistance genes. Allelism tests are currently in process to determine the number of resistance genes present.
Cucumber (Cucumis sativus L.), melon (Cucumis melo L.), watermelon [Citrullus lanatus (Thunb.) Matsum. & Nakai], and luffa (Luffa aegyptiaca Mill) accessions were exchanged between scientists of the United States and the People's Republic of China. Exchanges were made during a July 1994 visit of cucurbit research institutions in Shanghai, ZhengZhou, Yangling, Urumqi, Turpan, ChiangJi City, Tianjin, and Beijing. The trip was coordinated by the Office of International Cooperation and Development, USDA. Chinese scientists received elite American accessions with useful traits, and the American scientists received classic accessions that will be preserved for use in the future by interested researchers. Accessions to be included in the USDA germplasm collection were 50 cucumbers, 30 melons, 51 watermelons, and 15 luffas. As a result of the visit, cucurbit scientists in the two countries learned about the programs of their counterparts, and are planning cooperative research for the future.
Aquaporin proteins are part of an ancient family that functions as water transporting facilitators in all organisms. Phylogenetic and physiological analyses have revealed that plant aquaporins consist of two groups: the plasma membrane intrinsic proteins (PIPs) and the tonoplast intrinsic proteins (TIPs). Using the conserved asparagineproline-alanine (NPA) to NPA motif regions, we studied the evolution of 35 plant aquaporins that included nine of our newly cloned cucumber aquaporins and 26 from the GenBank database. Results indicated that NPA repeated regions were effective for phylogenetically characterizing the plant aquaporin family, and to accurately localize the introns. Phylogenetic analysis showed that 35 plant aquaporins fell into two distinct groups (except for the Arabidopsis gene AtMip)—PIPs and TIPs. The nine cucumber aquaporins belong to the PIP group that were localized further into two different sub-groups. The intron analysis showed that introns of plant aquaporins mainly consist of two types. Eighteen PIPs shared identical intron positions localized in connecting loop C between amino acids 95 and 96. Nine TIPs shared the other identical intron positions localized in connecting loop D between amino acids 44 and 45. Cucumber aquaporins CRB9 and CRB10 (with no intron in the repeated NPA regions) may be the result of intron loss events, while intronless rice (Orzya sativa) Os-TIP1 and Os-TIP2 may have resulted from other intron loss events. PIP11 and Os-PIP do not have the same amino acid number as major PIP members, but combined phylogenetic analysis results along with intron positions and phases showed that they belong to the PIP group. The phylogenetic tree and intron position information suggest that AtMip was mis-annotated as a member of aquaporin, and is a homologue of the glycerol facilitator-like protein. Introns share identical positions and phases within the PIP group (except PIP13) or the TIP group, but differ between the plasma and the tonoplast membrane aquaporins matching the phylogenetic analysis results. Intron positions of the repeated NPA regions of plant aquaporins that have stable inheritance can act as molecular markers for phylogenetic studies.