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  • Author or Editor: Yosef Burger x
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The use of grafted vegetables as one of the alternatives to soil disinfestation with methyl bromide is increasing in Israel. Watermelon (Citrullus lanatus) and melon (Cucumis melo) plants are grafted mainly onto Cucurbita rootstocks for lessening losses due to soil-borne pathogens. The contribution of the rootstock to the grafted plant's resistance depends on the nature of the disease. In general, damage caused by non-specific root-rot pathogens such as Rhizoctonia solani, Macrophomina phaseolina, Monosporascus cannonballus, and Pythium spp. are effectively reduced by using Cucurbita rootstocks. However, these rootstocks provide only partial protection from vascular diseases such as fusarium wilt, in which case better protection can be achieved by grafting susceptible melons onto monogenic fusarium-resistant melon rootstocks. The performance of the grafted plants depends not only on the rootstock but also on the scion response to pathogens and on the effect of the environment on disease development. The response of grafted and non-grafted melons of different cultivars to sudden wilt disease caused by the fungus Monosporascus cannonballus was evaluated in field trials conducted in the fall and spring growing seasons. Significant differences in disease incidence were found among cultivars, between grafted and non-grafted plants, and between seasons. Grafting reduced plant mortality in the spring and fall experiments but prevention of yield losses was more effective in the spring. More emphasis should be given to finding suitable rootstocks and adjusting agrotechniques for successful commercial cultivation of grafted melons in the fall.

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The relationship between sugar accumulation and sucrose metabolism enzyme activities was studied among seven genotypes of Cucumis melo L., covering the broad genetic range of sucrose accumulation found in the species. The primary determinant correlated with sucrose levels was the genetic variation for developmental loss of soluble acid invertase (AI) activity. Sucrose accumulation in the developing fruit began only when AI activity declined to less than an experimentally determined threshold value, and continued until removal of the fruit from the plant. In addition, the activities of sucrose phosphate synthase (SPS), sucrose synthase (SuSy), and neutral invertase (NI) were all positively correlated with sucrose accumulation among the genotypes. The low-sucrose-accumulating genotypes were characterized by low activities of each of the three enzymes, irrespective of their invertase activities. Final sucrose content was best predicted for each genotype by the number of days the fruit remained attached to the plant while characterized by “sucrose accumulation metabolism,” which was characterized primarily by AI activity less than threshold values, together with SPS, SuSy, and NI activities higher than threshold levels.

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Abstract

Gene B of Cucurbita pepo L. conditions precocious yellow-fruit pigmentation and is incompletely dominant to its allele, B + (3). This gene is found in representatives of several C. pepo cultivar groups, including ornamental gourd, zucchini, straightneck, pumpkin, and acorn. In addition to its primary effect, gene B can have a number of secondary effects, such as yellow spotting of leaves, decreased fruit size, reduced yields, bright orange flesh color, increased carotene content of the flesh, and improved flavor. The extent to which a particular secondary effect is manifested is dependent upon the genetic background.

Open Access

Abstract

Precocious Caserta is a summer squash (Cucurbita pepo L.) of the vegetable marrow type. Unlike other vegetable marrows, its fruit are yellow with yellow broken stripes, and the flesh is bright golden yellow. Plant characteristics resemble those of ‘Caserta’, but leaves may exhibit much yellow spotting.

Open Access

Abstract

The effects of paclobutrazol (cultar, PP333) on yield and fruit quality of muskmelon (Cucumis melo L. var. reticulatus Naud. cv. Galia) were examined in a series of field experiments, in the spring at Newe Ya’ar (northern Israel) and in autumn at Biq’at HaYarden (lower Jordan Valley, eastern Israel). In the spring experiments, paclobutrazol applied at 2 and 4 mg·liter−1 as a drench to the media-mix of muskmelon transplants increased total fruit yield 15% to 20% at various plant populations and in combination with ethephon and/or chlorflurenol, but tended to decrease the early yield. Yield increase was due to an increase in fruit weight rather than number. Paclobutrazol, in general, tended to improve marketable yield, yield concentration, and netting index. In the autumn experiment, paclobutrazol was applied at 250 mg·liter−1 as a spray from flowering through fruit maturation and compared with benzyladenine (BA), and N, P, and K fertilization. Paclobutrazol reduced early leaf-yellowing symptoms, but was not as effective as BA. Paclobutrazol in the autumn experiment did not affect yield or yield components, but soluble solids content was significantly increased and keeping-quality was unaffected. Chemical names used: β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-l ethanol (paclobutrazol); (2-chloroethyl)phosphonic acid (ethephon); (methyl-2-chloro-9-hydroxyfluorene-(9)-carboxylate) (chlorflurenol); benzyladenine (BA).

Open Access

Abstract

An Oriental pickling melon (Cucumis melo var. conomon) was crossed with a hermaphroditic melon, and the hermaphroditic form also was crossed with a birds-nest-type melon, with the goal of producing pickling melon breeding lines possessing a concentrated yield. Hermaphroditic and birdsnest breeding lines derived from these crosses produced markedly more fruits per plant and per unit area in a once-over harvest than did the pickling cucumber cultivars tested.

Open Access

Excess of boron and salinity in soil and irrigation water can limit the production of melons (Cucumis melo). A greenhouse study was conducted in order to compare the responses of grafted and non-grafted melon plants to combinations of high levels of boron and salinity. Boron levels were 0.25, 0.8, 2.5, 5.0, 10.0 mg·L-1 and salinity levels were 1.8 and 4.6 dS·m-1. Foliar injury caused by boron was more severe in the non-grafted than in the grafted plants. Likewise, boron accumulation in leaf tissue from non-grafted plants was higher than in grafted plants. High salinity led to decreased boron accumulation in the leaves. Fruit yield was decreased only at a boron concentration of 10 mg·L-1, and the decrease in grafted plants was smaller than that in non-grafted plants. A negative correlation was found between boron accumulation in leaves and fruit yield. The results showed that melon plants grafted on Cucurbita rootstock are more tolerant than non-grafted ones to high boron concentrations, and this can probably be explained by the decrease in boron accumulation caused by the rootstock.

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Abstract

Two precocious yellow-fruited zucchinis (Cucurbita pepo L. cvs. Goldy and Gold Rush) and a green-fruited control, ‘Burpee Hybrid Zucchini9, were compared for yield and yield quality in a series of 6 trials conducted in Israel. Overall, ‘Goldy’ and ‘Burpee Hybrid Zucchini’ produced a similar number of fruits and yield of “Grade A’’ fruits, but ‘Gold Rush’ produced significantly less. Yield quality, expressed as the percentage of “Grade A” fruits, was higher in ‘Goldy’ and ‘Burpee Hybrid Zucchini’ than in ‘Gold Rush’. Off-color fruit production was the most important parameter which reduced yield quality in ‘Gold Rush’.

Open Access

Abstract

‘Benning’s Yellow Tint’ is a summer squash (Cucurbita pepo L.) of the scallop or patty-pan cultivar group that has uniformly light yellow exterior color and excellent quality.

Open Access

The sweet cultivars of Cucumis melo are characterized by high sucrose levels, together with low acid levels in the mature fruit flesh. The trait of high sugar accumulation in C. melo fruit is determined by a single recessive gene, suc. High acid content, conferred by a single dominant gene, So, is found only in C. melo varieties that do not accumulate high levels of sugar and are used for nondessert purposes. We combined the genetic traits of high acid content (low pH) and high sugar levels by crossing the nonsweet, high acid C. melo var. flexuosus, `Faqqous' (So/So, Suc/Suc), with high sugar, low acid C. melo genotypes (so/so, suc/suc) and generating the recombinant genotype So/—, suc/suc. Segregating F2 populations derived from the cross between `Faqqous' and a standard high sugar, low acid line showed that the traits of high sugar and low pH were inherited independently of each other. The accumulation of acid and sugar in the developing fruit of a recombinant high acid, high sugar breeding line, A6, were also temporally independent, with acid accumulation preceding the rise in sucrose levels. The low pH of A6 was correlated with the developmental increase in titratable acidity and particularly of citric acid levels. The combination of increased acidity and high sugar provides the melons with a unique taste due to a sugar to acid ratio not present in sweet C. melo cultivars. These results are discussed in terms of the evolution under domestication of C. melo.

Free access