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  • Author or Editor: Jack E. Staub x
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The inheritance and linkage relationships among isocitrate dehydrogenase, phosphogluconate dehydrogenase, and peptidase with phenyl-alanyl-proline were determined. Progeny segregations fit a model for a dimeric enzyme encoded by one disomic locus with two alleles. Linkage associations among the three loci were not detectable with recombination fractions ranging between 0.353 to 0.481 among these loci.

Open Access

Four cucumber (Cucumus sativus L.) inbred lines were intermated then bulked maternally to create four base populations denoted as cycle 0 (i.e., Pop.1 C0, Pop.2 C0, Pop.3 C0, Pop.4 C0). Each of these populations underwent phenotypic selection (PHE; open-field evaluations), selection by marker (MAS; genotyping at 20 marker loci), and random mating (RAN; no selection) for three cycles. The four traits under selection, multiple lateral branching (MLB), gynoecious sex expression (GYN), earliness (EAR), and fruit length to diameter ratio (L:D), are quantitatively inherited, controlled by relatively few (two to six) QTL per trait and are directly related to yield. Using the same C0 populations and selection scheme allowed a direct comparison of the effectiveness of MAS and PHE. Because each C0 population varied for any given trait, the response to MAS and PHE was not the same for each population. In general, C0 populations that were inferior for a trait either responded favorably to selection or remained constant, while those with superior trait values either did not change or decreased. Both MAS and PHE provided improvements in all traits under selection in at least one population, with the exception of MAS for EAR. MAS and PHE were equally effective at improving MLB and L:D, but PHE was generally more effective than MAS for GYN and EAR. When considering all traits, responses to PHE were superior in three of the four populations. The population for which MAS was superior, however, showed the only increase in yield (fruit per plant), which was not under direct selection. These results indicate that both MAS and PHE are useful for multi-trait improvement in cucumber, but their effectiveness depends on the traits and populations under selection.

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Plant improvement incorporating quantitatively inherited yield component traits is technically difficult, time consuming, and resource demanding. In melon (Cucumis melo L.), the inheritance of yield components is poorly understood. A unique highly branched fractal melon plant type has been developed by the U.S. Department of Agriculture (USDA) from exotic germplasm to improve yield of U.S. Western Shipping type melons (Group Cantalupensis). In order to more effectively develop useful germplasm for commercial use the genetic of components of yield must be clearly understood. Thus, the genetics of branching, an important yield component, was investigated. Melon progeny derived (F1, F2, F3, BC1P1, and BC1P2) derived from a cross between USDA line 846-1 (P1) and Top-Mark (P2) were used to evaluated in two locations (Wisconsin and California) to estimate of components of variance, and narrow-sense (h2N) and broad-sense (h2B) sense heritabilities. Lateral branch numbers among 71 to 119 F3 families were significantly different (P ¾ 0.01) regardless of test environment. Covariance analyses indicates that branching is moderately heritable (h2B = 0.62 to 0.76, h2N = 0.43 to 0.48), and conditioned by several additive factors (perhaps 2 to 4) that are highly additive. Although environment plays an important role in lateral branch development, family rankings over environments were relatively consistent, indicating that effective selection for this trait should be useful for incorporating the fractal plant habit into Western Shipping melon. The significant additive component underlying lateral branch number indicates that quantitative trait loci (QTL) conditioning this yield component might be identified for use in marker-assisted selection.

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A study was designed to determine whether temperature alone or temperature and relative humidity (RH) interactions affect the development of pillowy fruit disorder (PFD) in cucumber (Cucumis sativus L.). Fruit of `Calypso', `Flurry', `Carolina'? and inbred breeding line 39 were matured in four environments: cyclic and high (22 to 45C) and moderate (22 to 30C) temperatures at two RHs (35% and 75%). PFD symptoms were most severe at high temperature and RH; thus, both contribute to the development of this disorder. Line 39 had the highest PFD ratings, regardless of growing environment, a result indicating that cultigens respond differently to these imposed stresses.

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During winter months, a substantial volume of various horticultural products are imported to the United States from the Caribbean and Central and South America. United States cucumber (Cucumis sativus L.) processors who market fresh-pack and refrigerated products require raw product daily to meet consumer demands. Mexico serves as a single-source supplier to all United States processors during this period, and thus Mexican production represents certain price risks. United States processors would consider other growing regions to reduce these risks if financially attractive alternatives could be identified. Therefore, a project was initiated to acquire information on production and export costs in Hispaniola (Dominican Republic and Haiti), and to compare those to Mexican and United States production and transport costs. Experimentation lead to the identification of the critical influences of market prices, costs and conditions for the financial feasibility of establishing a processing cucumber industry on Hispaniola. Comparative evaluation indicated that significant variation in total cost was caused by fluctuations in transport, tariffs, and labor cost components. The causes of variation in transportation costs were distance, method (sea, air, truck), competitive demand (volume), and shipping frequency, consistency, and capacity.

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Development projects in developing countries are generally considered to be speculative investments. Potentially significant returns on investment opportunities are often overlooked by assuming that investment risks in developing countries are greater or less manageable than the risks of investment in developed countries. An import purchasing-risk evaluation identified the costs associated with the production and export of processing cucumbers (Cucumis sativus L.) from Hispaniola (Haiti and the Dominican Republic) to the United States. Although production and export analyses suggested that Hispaniola might not replace Mexico as the primary source of cucumbers for processing in the United States between November and April, Hispaniola affords the U.S. processing industry with an alternative investment option for reducing single-sourcing raw product risk. Therefore, an import diversification evaluation was conducted using Monte Carlo simulation to define a investment-risk model. Monte Carlo simulations of the means and variances of the components of cost andprice were used to assess investment risk under various investment strategies. This model identified sources of cost variation which were then used to characterize export risks derived from growing processing cucumbers on Hispaniola. It was determined that U.S. processors can reduce overall purchasing-risk by diversifying Mexican production to Hispaniola. Through the creation of a strategic transportation alliance between the U.S. and Hispaniola project participants, the export-import costs were such that the investment-risk model identified the allocation of 80% of the production in Mexico and 20% in Haiti as the most favorable diversification strategy. This strategy offered less risk and greater potential long-term returns than purchasing cucumbers solely in Mexico.

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A fruit anomaly, pillowy (P), has been identified in processing cucumber This physiological disorder has been shown to be accelerated by water stress.

A series of experiments were conducted to determine postharvest handling procedures which minimize the appearance of pillowy after induction by water stress. Isogenic lines evaluated in RCB design with 3 replications where subjected to water stress during fruit enlargement. Fruits were then subjected to various storage temperatures and times before hydrocooling to 8°C. Cucumbers were then fresh pack processed and evaluated for % pillowy after 12 weeks,

The postharvest control treatmcnt (2 days, 26°C, 60% RH) produced 32%P to 51%P in fruit subjected to stress and 23%P to 39%P in unstressed fruit. In the optimal postharvest treatment (1 day, 26°C, 60% RH, then hydrocool to 8°C, 2 days, 15°C, 85% RH) fruits from stress plants exhibited 23%P to 39%P and those from nonstress plants showed 13%P to 26%P. Fruits from miniature leaf lines exhibited higher percent (37%) P ratings when compared to normal leaf lines.

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The cucumber (Cucumis sativus L.) germplasm collection of 924 cultigens (accessions, breeding lines and cultivars) was evaluated for resistance to anthracnose (Colletotrichum orbiculare (Pass.) Ell. & Halst) in the field and greenhouse. The field test was run using 1 m plots grown in 4 environments (year-location combinations). The field was inoculated 3 weeks after planting using a backpack sprayer. A susceptible spreader cultivar (Wis. SMR 18) was planted every 5th row, and plots were overhead-irrigated 3 times/week. Plots were rated 1 and 2 weeks after inoculation. The greenhouse test was run using seedlings grown in flats of vermiculite, and inoculated with 104 spores/ml on one cotyledon. Plants were rated using the size of the chlorotic halo surrounding the lesion. There was no correlation (r=0.04 to 0.17) of seedling test with field test ratings, nor between any of the 4 field test environments. Correlations were significant among field tests when only cultivars and breeding lines were evaluated. We concluded that diversity within accessions resulted in the lack of correlation among tests. The cultigens that had high resistance in all tests were `Slice', NCSU M 21, Gy 14A, `Addis' and PI 164433 (India). Most susceptible were PI 175696 (Turkey) and PI 285606 (Poland).

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