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  • Author or Editor: Todd C. Wehner x
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Gene linkage was investigated in 11 families using 18 genes in cucumber (Cucumis sativus L.). The genes studied were B (black spine), B-3 (Black spine-3), B-4 (Black spine-4), bi (bitterfree cotyledons), Bt (bitter fruit), Bt-2 (bitter fruit-2), D (dull fruit skin), df (delayed flowering), de (determinate habit), F (female sex expression), gl (glabrous foliage), lh (long hypocotyl), ns (numerous spines), pm-h [powdery mildew (Sphaerotheca fuliginea Schlecht.:Fr.) resistance expressed on the hypocotyl], ss (small spines), Tu (tuberculate fruit), u (uniform immature fruit color), and w (white immature fruit color). A major objective of this study was to measure linkages of genes for fruit bitterness (Bt and Bt-2), and spine color (B-3 and B-4) relative to previously studied loci: B, bi, D, de, df, F, gl, lh, ns, pm-h, ss, Tu, u, and w. The F2 progeny of LJ 90430 × PI 173889 segregated 13 bitter fruit: 3 nonbitter fruit, indicating that different genes are controlling fruit bitterness in these lines. Bt-2 is proposed as the gene controlling bitterness of fruit in LJ 90430. It is a separate locus from Bt, that causes bitter fruit in PI 173889. Several new gene linkages were found: biBt, (Bt-2)—de, D—(Bt-2), Dns, glF, ss—(Bt-2), Tu—(Bt-2), and u—(Bt-2). The Bt gene appears to be linked to bi and may be located on linkage group I. Bt-2 appears to be linked with several genes that could connect linkage groups I and IV. Bt-2 was linked to u, Tu, D, and ss, that are all on linkage group IV. Bt-2 was also found to be linked loosely to de, that is on linkage group I. No linkages were found between B-3 and B-4 and the genes evaluated in this study. Weak linkages (>25 cM) between several gene combinations [(Bt-2)-de, dens, dess, deTu, deu, nsF, and ssF] provided more evidence that linkage group I and IV may be linked. Due to the weak linkages, more information needs to be obtained using larger populations and more markers to confirm these findings.

Free access

Abstract

A detached-leaf test was used to screen a cucumber (Cucumis sativus L.) germplasm collection for antibiosis to the pickleworm (Diaphania nitidalis Stoll.). Data were collected on 1160 lines planted in the field in 1981. The 36 most resistant and 36 most susceptible lines were retested with improved methods, reducing the number of lines to 8 and finally to 6 based on leaf damage by pickleworm larvae. Selections were made within those lines to stabilize the resistant or susceptible reaction of each line in our test. In a final test, no significant differences were found among the selections, which included the most resistant and most susceptible lines identified in all studies. A heritability study was run on a population produced by intercrossing the 5 most resistant and 3 most susceptible lines identified in the initial field screening for 3 generations. Parent-offspring regression was used to estimate a narrow-sense heri-tablity of 0.03. Thus, there was little or no genetic variation in cucumber for antibiosis to pickleworm larvae, and other methods of control should be used.

Open Access

Abstract

A wide-base pickling cucumber (Cucumis sativus L.) population was formed by intercrossing all available cucumber lines (1063) and selecting for short fruit length. After intercrossing twice, 112 S0 plants and their half-sib progeny were evaluated for Rhizoctonia fruit rot resistance using a detached-fruit test. Parent-offspring regression indicated a narrow-sense heritability of 0.24, considered low to moderate. Gain from selection was calculated for 2 recurrent selection systems. Based on the heritability estimate, selection using replicated progeny rows was recommended for improving resistance to this trait.

Open Access

Abstract

Seedlings of 35 cucumber (Cucumis sativus L.) lines were evaluated for resistance to damping-off caused by Rhizoctonia solani Kuhn. Five variables were measured, with the corrected disease rating (a rating for disease severity including a correction for seed vigor) being the most useful. Differences in resistance occurred among the lines, with ratings varying from 1.5 to 5.9 on a 0 (no disease) to 9 (plant dead) scale. The ratings for damping-off resistance were compared with ratings collected previously for rhizoctonia fruit rot resistance. The correlations were low and nonsignificant (r = −0.19 to −0.10). Thus, the damping-off test would not be a good substitute for the fruit rot test.

Open Access

Abstract

Chemical defoliation of cucumber (Cucumis sativus L.) vines was evaluated as a method for rapid screening of breeding lines. Six chemicals (dinoseb, diquat, ethephon, glufosinate, glyphosate, and paraquat) were used at one or 2 rates on one pickling and one fresh-market cucumber cultivar (‘Calypso’ and ‘Poinsett 76’, respectively) in 1983 to determine speed of vine defoliation and amount of fruit damage. Of the chemicals tested, paraquat at 0.6 kg/ha provided the most rapid defoliation (85% to 91% defoliation one day after treatment) but caused some bleaching and chlorosis of the fruit. If the fruit were rolled 180° during evaluation, the damage was not noticeable. Chemical defoliation of vines for simulated once-over harvest provided a rapid, labor-saving method, requiring only 42% of the time to evaluate each plot compared to the conventional method. The chemical defoliation method is especially useful for initial evaluation of populations and breeding lines for fruit yield and other horticultural characteristics.

Open Access

Abstract

Fourteen methods of calculating heat units from planting to harvest were applied to daily maximum and minimum air temperatures taken in a standard weather shelter for 2 growing seasons (spring and summer) over 5 years of cucumber (Cucumis sativus L.) plantings in North Carolina. The coefficient of variation (cv) was used to determine which of the methods was most reliable in predicting day of first harvest. The best method was to sum over days from planting to harvest the difference between the daily maximum and a base temperature of 15.5°C; but if the maximum exceeded 32°, it was replaced by 32° minus the difference between the maximum and 32°, before subtracting the base. This method had a cv of 3%, compared with 10% for the standard method—numbers of days from planting to harvest.

Open Access

Abstract

Details are provided for construction of an extractor to be used in recovering seed from cucumber fruit (Cucumis sativus L.). The extractor is best-suited for handling seed lots from areas of less than one hectare, but having more than 25 to 50 fruit. The machine handles about 100 fruit per minute and recovers 98% of the seed that would be extracted by hand.

Open Access

Abstract

Source-sink ratios were modified in cucumber (Cucumis sativus L.) by defoliation and defruiting to investigate the role of assimilate supply and demand in regulating fruit growth. Plants of the cultivar Calypso were subjected to 0%, 25%, 50%, and 75% defoliation levels. Each level was applied by three different methods of defoliation involving removal of whole or half leaves or a combination of the two. Plants in the 0% defoliation treatment (control) were divided into two groups: defruited and pollinated. Defoliation treatments were begun at fruit set and maintained throughout growth. Defoliation of the plants significantly decreased total plant weight and the fresh and dry weight of the fruits relative to the fruited control. An increase in the level of defoliation caused an increase in accumulation of dry weight in the leaves and a decrease in the dry weight of the fruits. Defoliation of 50% or 75% was followed by an increase in carbon exchange rates determined 7 days after defoliation. Vegetative controls had equal plant dry weight but only half as much fresh weight as the fruited controls. Carbon exchange rate was significantly reduced in defruited compared to fruited plants 16 days after defoliation.

Open Access

A new trait, twin fused fruit, was discovered in gynoecious cucumber (Cucumis sativus L.) line B 5263. Plants with the twin fused fruit trait had two fruit fused into a single unit. In addition to having the twin fused fruit trait, line B 5263 had fruit with necks, large tubercles (warts), and dark green skin. The inheritance of twin fused fruit was studied in populations resulting from crosses between gynoecious line B 5263 (twin fused fruit) and monoecious line B 5404 (single fruit). Research was done in 1999 to 2001 in the greenhouses of the Research Institute of Vegetable Crops, Skierniewice, Poland. The F1 progeny developed single fruit in all cases. The observed distribution of plant phenotypes in the F2 fitted the expected ratio of 3 with single fruit: 1 with twin fused fruit. The observed distribution of plant phenotypes in the BC1A fitted the expected ratio of 1 with single fruit: 1 with twin fused fruit. Twin fused fruit occurred only in gynoecious plants, and never in monoecious plants of the cross. In the F2 progeny, the ratio of twin fused fruit within gynoecious plants fitted the expected ratio but the gene was not expressed in monoecious plants. In the F2 generation, the observed distribution of plant phenotypes fitted the expected ratio of 9 gynoecious single: 4 monoecious single: 3 gynoecious twin fused: 0 monoecious twin fused, indicating that there was epistasis, with twin fused fruit hypostatic to monoecious. The new gene will be named tf (twin fused fruit).

Free access

Cucumber (Cucumis sativus L.) and horned cucumber (C. metuliferus Naud.) germplasm were evaluated for their resistance to root-knot nematodes (Meloidogyne spp.). All 24 C. metuliferus cultigens evaluated were resistant to all root-knot nematodes tested-M. incognita (Kofoid and White) Chitwood race 3, M. arenaria (Neal) Chitwood race 2, and M. hapla Chitwood. All 884 C. sativus cultigens (cultivars, breeding lines, and plant introduction accessions) tested were resistant to M. hapla and few to M. incognita race 3. Only 50 of 884 C. sativus cultigens evaluated were somewhat resistant to M. arenaria race 2 and M. incognita race 3. A retest of the most resistant C. sativus cultigens revealed that LJ 90430 [an accession of C. sativus var. hardwickii (R.) Alef.] and `Mincu' were the only cultigens that were moderately resistant to M. arenaria race 2. LJ 90430 was the only cultigen, besides the two retested C. metuliferus cultigens, that was resistant to M. javanica (Treub) Chitwood. All C. sativus cultigens retested, including LJ 90430, were highly susceptible to M. incognita races 1 and 3. The two C. metuliferus cultigens retested were highly resistant to all root-knot nematodes tested-M. arenaria race 2, M. incognita races 1 and 3, and M. javanica.

Free access