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  • Author or Editor: J. G. Phillips x
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Eighteen New Guinea impatiens cultivars were evaluated for performance as bedding plants and for suitability as hanging basket plants. The cultivars were treated with three growth retarding chemicals (B-9, Sumagic and Cutless) to determine their effect on plant growth, branching and overall flower development. Two applications of 2500 ppm B-9 produced the most commercially acceptable plants. Height and spread were reduced by approximately 30 percent with no reduction in the number of flowers produced or the number of days to bloom. Cutless and Sumagic applications reduced growth approximately 50 percent and delayed blooming as much as 2 weeks when compared to the untreated control. Growth regulator treatment had no effect on the number of branches produced except with Sumagic which resulted in an overall reduction in branching.

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Abstract

Peach (Prunus persica (L.) Batsch) at 1157 and 868 trees per ha and trained as either palmette or hedgerow produced nearly twice as much fruit in the first 5 years as did trees trained to a modified central leader at 397 trees per ha at Jordan Station, Ontario, Canada. In addition to dormant pruning to shape the trees and restrict their size, the palmette and hedgerow plantings were pruned each year in midsummer when about half of the current year's growth was removed. Insects and mites were no greater problem, and brown rot was significantly less in the high- than in the low-density planting.

Open Access

Abstract

Fifty-eight cultivars of tomatoes were screened for the occurrence of high pH fruit. Although large differences in pH were found between and within cultivars, no pH values high enough to permit the growth of Clostridium botulinum were obtained. pH and titratable acidity were not highly correlated. Tomato acidity data obtained from 57 locations in 23 states for 356 cultivars and 212 breeding lines were compiled and analyzed to identify trends. These data show that small-fruited, light colored and “new” cultivars are not low in acid, as is commonly believed. A few high pH data points (pH ⩾ 4.7) were associated with specific cultivars, locations, and conditions (overripening). The response of some higher pH cultivars to acidulation with citric acid was determined; a linear relationship between pH and added acid was found. These data were used to evaluate several methods of acidulation recommended for home canners.

Open Access

Previous work suggests that `Beauregard' sweetpotato [Ipomoea batatas (L.) Lam.] has a much lower N requirement than other common cultivars. Over the past 10 years, `Beauregard' has become the premier sweetpotato cultivar grown in Virginia; however, N fertilizer recommendations have not been reassessed to consider the potentially lower N requirement of `Beauregard'. The objectives of this study were to evaluate the effects of N rate and application timing on root yield, quality, and N use efficiency for `Beauregard' sweetpotato production in Virginia. A field study was conducted each year from 2000 to 2002 at the Eastern Shore Agricultural Research and Extension Center, Painter, Va. Nitrogen fertilizer was applied at rates of 28, 56, and 84 kg·ha-1 either before transplanting, 2 to 3 weeks after transplanting (WAT), or 4 to 5 WAT. A check treatment that received no N fertilizer was also included. Optimum N rates varied annually; under normal precipitation, root yield was greatest at the 28-kg·ha-1 rate, while 56 kg·ha-1 was required for maximum yield in wet conditions. Of note is that this range of rates is considerably lower than the current N recommendation for Virginia sweetpotato production (56 to 84 kg·ha-1). Delaying N application until 2 to 3 WAT further increased marketable root yield compared with applying N before transplanting or 4 to 5 WAT. Crude protein and N uptake increased with increasing N rate up to 84 kg·ha-1; however, N use efficiency was highest (67%) when 28 kg·ha-1 was applied 2 to 3 WAT.

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Alternate cropping is a common physiological trait in several important apple cultivars, including spur-type ‘Delicious’. Alternate bearing usually develops slowly in apple trees as they mature, but may be dramatically induced by environmental or biotic stresses. We describe the native temporal and within-year variation of bloom and yield of a highly uniform spur-type ‘Delicious’/M.106 population (n = 95) over a period of 9 years. Crop load was adjusted by hand in the first year to establish a defined normal fruit population distribution. Thereafter, all trees received identical practices. Bloom density (BD) was rated (1 to 10) and yield and fruit size distribution were determined annually on an individual tree basis. Temporal profiles for bloom and yield had four periods above and below the general mean (GM). There were two 3-year periods of nonbienniality. Annual variation in BD ranged from 3.1 to 8.0 and in yield from 54 to 168 kg/tree. Variation in cropping was greater when expressed as percentage deviation from the GM. Annual mean fruit weight was inversely related to yield, but percentage of small- (51 to 64 mm) or large-diameter fruit (70 to 82 mm) was not consistently related to yield. The within-year cv ranged from ≈11% to 66% for BD and from 13% to 42% for yield. The degree of synchrony (within-year variation) was lowest in the year after crop adjustment (to normal distribution), became highly synchronized in ≈4 years, and then decreased. The relationship of native variation of individual trees to the population and to flower initiation and fruiting are discussed in relation to the alternate bearing cycle and significance in selecting trees for experimentation.

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Abstract

Increases in the darkness and redness of both thawed and cooked highbush blueberries (Vaccinium corymbosum L.), indicated by tristimulus measurements, were cultivar-related but not dependent on blueberry pH or anthocyanin content. Waxy bloom was retained in thawed berries but lost during cooking. Pigmented exudate appeared with some cultivars during thawing. Differences among cultivars in exudate formation and reddening during thawing are explained in terms of changes in epidermal cells, cuticle, and wax structure which were observed by light and electron microscopy. The color of blueberry cooking water depended primarily on the berry anthocyanin content, acidity, and the extent of leaching.

Open Access

Abstract

Samples of 45 cranberry clones (Vaccinium macrocarpon Ait.) were analyzed for factors relating to fruit quality and processability to develop selection procedures for breeding programs. High correlations were obtained between tristimulus reflectance measurements on whole or pureed cranberries and the juice color, determined by spectrophotometric or tristimulus transmission measurements. Differences between cranberry samples in the proportions of individual anthocyanins were small and not correlated with berry or juice color. A 3-stage sequence of simple measurements, entailing minimal sample preparation, was developed for selection. First- and second-stage selections were based on the application of discriminant analysis to tristimulus reflectance data obtained with whole and pureed cranberry samples, respectively. In the third stage, selections were based on analytical measurements performed on juice prepared from samples selected in the preceeding stages.

Open Access

Abstract

The effect of cultivar on cranberry (Vaccinium macrocarpon Ait.) fruit size and composition was investigated. ‘Ben Lear’, ‘Crowley’, ‘Early Black’, and ‘Franklin’ berries contained about twice the anthocyanin of the other clones. Based on projections of analytical data, potential gain could be enhanced by increasing the proportion of berries that attain high anthocyanin content, seen in individual fruits within samples, as compared to the alternative strategies of breeding for improved anthocyanin content, for small berries, or for synchronous ripening.

Open Access

Small-sieve snap beans (Phaseolus vulgaris L.) are an important source of income for smallholder farmers in East Africa. In this region as well as in other tropical and subtropical environments, common bean rust, caused by Uromyces appendiculatus (Pers.:Pers.), and heat stress reduce the yield and quality of snap beans. Small-sieve rust-resistant snap beans and that are heat-tolerant were developed using heat-tolerant snap bean breeding lines that had broad-spectrum rust resistance conditioned by the combination of the Andean Ur-4 and Mesoamerican Ur-11 genes. The Ur-4 and Ur-11 rust gene combination confers resistance to 90 races of the hypervariable pathogen from different parts of the world, including East Africa, that are maintained at Beltsville, MD. Four breeding lines each having the combination of the two rust genes were crossed in a 4 × 5 diallel mating design with five susceptible small-sieve cultivars to give 20 F1 hybrids. The hybrid combinations were advanced through the F2, F3, and F4 generations with selection for heat tolerance, rust resistance, and pod quality to develop lines combining these traits. Twenty F5 breeding lines that had the combination of these traits were selected and evaluated in East Africa at four field sites selected on the basis of differences in altitude, climate, and virulence diversity of the bean rust pathogen and in Puerto Rico at a field site characterized by high temperatures. There was a significant positive correlation between ranks of heat stress influenced yield components (seeds per pod and total yield) at the hot field site and the controlled high-temperature (32/27 °C) greenhouse. Four of the breeding lines developed, L5, L9, L13, and L17, combined heat tolerance and rust resistance in the desired plant type with high yield and good pod quality. These lines are the first known small-sieve snap beans with the combination of traits for heat tolerance and broad-spectrum rust resistance conferred by the Ur-4 and Ur-11 genes. These results demonstrate ability to combine heat tolerance and rust resistance as important traits for adaptation of specific market classes of common bean to tropical and subtropical environments through targeted selection of multiple traits in controlled environments.

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Common bean rust disease (caused by Uromyces appendiculatus) and high temperatures (heat stress) limit snap bean (Phaseolus vulgaris) production in many tropical and temperate regions. We have developed snap bean lines combining broad-spectrum rust resistance with heat tolerance for tropical agroecosystems. Eight breeding populations were developed by hybridizing BelJersey-RR-15 and BelFla-RR-1 (each possessing the Ur-4 and Ur-11 rust resistance genes) and the heat-tolerant snap bean breeding lines HT601, HT603, HT608, and HT611. F2–F4 generations of the populations were evaluated under greenhouse conditions and selected for heat tolerance while simultaneously selecting for the rust resistance genes Ur-4 and Ur-11. Three heat-tolerant F5 lines, which were homozygous for Ur-4 and Ur-11 genes, were selected together with a rust-resistant but heat-sensitive control. These and 12 cultivars adapted to different geographical regions were evaluated for their reaction to rust and yield at six contrasting field sites in eastern Africa and their response to high temperature verified in Puerto Rico. Rust incidence and severity was high at three of the trial sites in eastern Africa. Two of the 12 cultivars were resistant to rust at most of these sites, and three of the four breeding lines were resistant at all sites. The Ur-11 gene effectively conferred rust resistance at all sites. Yield in Puerto Rico was strongly correlated (R 2 = 0.71, P < 0.001) with that of the hottest site in eastern Africa, highlighting the similarity in genotypic response to high temperatures at the two distinct sites. The newly developed rust-resistant and heat-tolerant breeding lines showed stable yield at the eastern Africa sites with contrasting mean temperatures compared with the cultivars presently grown in the region. Two of these lines, HT1 and HT2, were confirmed to be homozygous for Ur-4 and Ur-11 and with high heat tolerance under both greenhouse and field environments. This research validates the effectiveness of targeted rust resistance gene combinations for tropical environments and the effective selection of high temperature tolerance traits correlating across multiple environments. The breeding lines HT1 and HT2 developed in this research could be used to improve snap beans for the tropics and other environments with similar constraints.

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