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Nine heat-tolerant tomato [Lycopersicon esculentum (Mill.)] breeding lines, four heat-tolerant cultivars, and four heat-sensitive cultivars were evaluated in the greenhouse under high temperature (39C day/28C night) and in the field. Criteria for heat tolerance included flowering, fruit set, yield, fruit quality, and seed production. Under high-temperature conditions, the group of heat-tolerant lines, the heat-tolerant cultivars, and the heat-sensitive cultivars produced, respectively, the following per plant: flowers, 186, 94, and 55; fruit set 70%, 52%, and 30%; yield, 410, 173, and 11 g; and normal mature fruit, 72%, 37%, and 7%. Yields of heat-tolerant lines under high temperature in the greenhouse ranged from 118% to 31% of their respective yields in the field. Yields of heat-tolerant cultivars were 62% of those in the field. In contrast, yields of heat-sensitive cultivars under high temperature were < 1% of their respective yields in the field. High temperature induced flower abscission, reduced fruit set and yield, and increased the incidence of abnormalities. Major fruit abnormalities with high temperatures included cracks, blossomed rot, watery tissue, and small, immature fruits. Production of viable seeds under the high-temperature regime was severely reduced or totally inhibited regardless of the heat-tolerance level exhibited by the line or cultivar. The failure of heat-sensitive and most heat-tolerant cultivars or lines to produce viable seeds under such a high temperature suggests that a lower level of heat stress than that applied in these experiments could allow the production of enough seeds to test the relationship between heat tolerance in a genotype and its ability to produce viable seeds under high temperature. The results indicate that certain lines have high tolerance to heat and, therefore, could provide valuable sources of plant material for physiological studies to establish the physiological and molecular bases of heat tolerance. Some of the heat-tolerant lines might also serve as excellent germplasm sources in breeding heat-tolerant tomato cultivars.

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A sample of 210 cultivars of Prunus persica (L.) Batsch, with a wide range of fruit and plant characteristics, was studied for variability using nine polymorphic amplified fragment length polymorphism (AFLP) primer combinations. Forty-seven AFLPs allowed identification of 196 (93%) different genotypes, 187 of which could be distinguished with three primer combinations. Eleven cultivars with the same AFLP phenotype corresponded to known somatic mutations (sports), but from the four sports of the `Springcrest' group, two (`Maycrest' and `Queencrest') differed at three AFLPs from the others (`Starcrest' and `Early Maycrest'). Cluster analysis allowed differentiation of most cultivars with nonmelting fruit flesh, generally used for canning, from the melting-flesh peach and nectarine cultivars used for fresh consumption.

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Backpropagation neural networks (BPNNs) were used to distinguish among 10 olive (Olea europaea L.) cultivars, originating throughout the Mediterranean basin. Identification was performed on the basis of 17 phyllometric parameters resulting from image analysis. Different BPNN architectures were attempted and best performance was achieved using a 17 × 20 × 10 BPNN. Networks were tested with sets of phyllometric parameters not involved in the training phase. Results enabled identification with certainty all cultivars tested.

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Cranberry (Vaccinium macrocarpon Ait.) has the opportunity to partition resources into sexual and/or asexual (stolons) modes of reproduction. Nitrogen status has been shown to impact the degree of stoloniferous growth. To determine whether there is a genotypic response to varying nitrogen levels, six hybrid and four native cultivars were treated with three annual rates of nitrogen fertilizer (17, 34, or 67 kg·ha-1) for 4 years. Fruit yield was determined each year and asexual vegetative growth (stolons) weight was removed and measured in all but the first year of the experiment. Cultivars exhibited different patterns of yield and stolon weight response over the three nitrogen rates. Not all cultivars exhibited significant yield decreases at the high N levels. Vegetative growth (stolon weight) generally increased with increasing N, however, not all cultivars responded similarly over three N rates. Partitioning between yield and stolon production favored fruit yield at the lower N rates in three of the four native cultivars studied (`Cropper', `Early Black', and `Howes'). Yield over N rates was more stable for four of the six hybrid cultivars, which may be the result of greater heterozygosity in hybrids than natives, and/or genetic gain from one breeding and selection cycle, offering increased tolerance to nitrogen stress. This study indicates that genetic variation exists for yield, yield stability, and stolon production relative to nitrogen level, and that genetic gain in cranberry is possible for these traits. Future studies involving cranberry physiology and nutrition should consider the genotypes used.

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DNA amplification fingerprinting (DAF) was used to study genetic relationships between closely related chrysanthemum cultivars (Dendranthema grandiflora Tzvelev.). Twenty-one cultivars were examined that belonged to the Anne, Blush, Boaldi, Charm, Davis, and Pomona series (families). The genetic variability of cultivars within and between series was evaluated using eleven arbitrary octamer primers. A few polymorphic characters uniquely identified closely related cultivars within each of the series. In contrast, many DNA polymorphisms were observed between members of the different series. Phenetic patterns were established by unweighted pair group cluster analysis using arithmetic means (UPGMA) and principal coordinate analysis (PCO). The average distance between series was 10-fold greater than between cultivars within a series. DNA from all cultivars belonging to a series were also bulked to generate profiles containing unique amplified products for each series. Cluster analysis and PCO of bulked DNA clearly grouped Charm and Pomona together. However, series grouping did not correspond to morphology of inflorescence types. The results demonstrate the utility of the DAF technique in distinguishing clonal materials and its potential use for patent protection, phylogenetic studies, and for identifying useful markers in breeding applications.

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Bell pepper (Capsicum annuum L.) cultivars were grown in nine Florida environments to evaluate phenotypic stability of marketable fruit yield (t-ha-') and mean fruit size (g/fruit). A stable cultivar excelled for a particular trait when grown in either favorable or unfavorable environments. A stable cultivar for a given trait was defined as one with an individual mean greater than the grand mean (mean of all cultivars) (x > X), a regression coefficient (b1) ≤ 1 (individual genotypic mean regressed against environmental means), nonsignificant deviation mean squares from regression (S2d), coefficient of linear determination (R2) > 0.50, and coefficient of variation (cv) < the pooled cv. `Ssupersweet 860', `Whopper Improved', and `Ranger' were stable for mean marketable fruit weights and fruit size, and `Ssupersweet 860' and `Whopper Improved' were stable for mean fruit size. Bell pepper cultivars were differentiated for phenotypic stability of yield and fruit size or adaptability to diverse environments. Therefore, through stability analyses, bell pepper plant breeders can identify cultivars or select advanced breeding lines that express adaptability for fruit yields or size to diverse environmental conditions or cultural practices.

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Field corn (Zea mays L. var. mays) cultivar heterosis could improve sweet corn (Zea mays L. var. rugosa Bonaf) heterotic patterns. Two Spanish field corn (Su) and two sweet corn (su) heterotic patterns have been reported previously. The objective of this study was to determine which sweet × field corn crosses could be used to improve sweet corn heterotic groups. A diallel among three sweet corn cultivars (`Country Gentleman', `Golden Bantam', and `Stowell's Evergreen') that are representative of the variability among modern sweet corn cultivars, and three field corn synthetic cultivars [`EPS6(S)C3', `EPS7(S)C3', and `EPS10'] representing the heterotic patterns involving Spanish field corn, was evaluated for 2 years at two locations in northwestern Spain. Differences in heterosis effects (h jj') and average heterosis (h) were significant for all traits except grain moisture. Differences for cultivar heterosis (h j) and specific heterosis (s jj') were significant for grain yield, plant height, and kernel row number. `EPS6(S)C3' had lower s jj' for yield in crosses to `Golden Bantam' than to `Stowell's Evergreen', while `EPS7(S)C3' had higher s jj' in crosses to `Golden Bantam' than to `Stowell's Evergreen'. The best crosses to establish enhanced sweet corn heterotic patterns involving Spanish maize would be `Golden Bantam' × `EPS6(S)C3' and `Stowell's Evergreen' × `EPS7(S)C3'. New sugary 1 cultivars would require preliminary cycles of intrapopulational recurrent selection for agronomic performance and flavor prior initiating an interpopulational recurrent selection program to enhance heterosis.

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Abstract

Seventy-nine cultivars and lines of cabbage Brassica oleracea L. (Capitata group) were analyzed for 11 glucosinolates to provide a data base of the levels of these potential toxicants. Aglucon hydrolytic products of glucosinolates from fresh cabbage (mean of 79 cultivars) include 24 ppm allyl isothiocyanate, 45 ppm 3-methylsulfinylpropyl isothiocyanate, 18 ppm SCN ion, 17 ppm 4-methylsulfinylbutyl isothiocyanate, and 4 ppm goitrin. Composition of the cultivars are summarized by type (red, white, savoy) and by end use (market, storage, kraut). Glucosinolates with a 3-carbon aglucon (excluding the sinolate carbon) predominate over 4-carbon glucosinolates in white and savoy types. Four-carbon glucosinolates (including goitrin precursor) predominate in red cabbages. Savoy cabbages are high in glucosinolates yielding SCN ion. Distinctions between market, storage, and kraut cultivars are less well defined. No differences could be seen between open pollinated and hybrid cultivars. Year-to-year variation for 12 cultivars is discussed.

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hybridization is an important breeding strategy that has been used for many ornamental crops ( van Tuyl and Lim, 2003 ); in addition, it has been a common strategy for cultivar development of Hibiscus with novel phenotypes ( Ha et al., 2014 , 2015 ; Klips

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As fall-sown onions are seeded earlier, an increase in premature seedstalk (bolting) incidence is observed for bolting-susceptible cultivars. The mechanism of resistance for bolting-resistant cultivars is not well known. Four fall-sown cultivars (Daybreak, NuMex Mesa, NuMex Sweetpak, Texas Early White), that differed in their bolting susceptibility, were seeded on four separate dates in September, each one week apart, in Las Cruces, N.M., to observe their growth and performance at each seeding date. Plant height and leaf number were measured monthly throughout the growing season from 10 plants in each plot. Prior to harvest, the number of plants that bolted were counted. When 80% of the plants in a plot were mature, the bulbs were harvested and the maturity date, disease resistance, bulb yield, and percentage of single centers were recorded. In general, earlier seeding dates resulted in larger plants with more leaves than later seeding dates when compared early in the growing season. By harvest time, plants from later seeding dates were comparable in height and had produced more leaves than earlier seeded plants. Plant height of `NuMex Mesa' (bolting resistant) was less than the plant height of bolting-susceptible cultivars. Bolting-resistant and bolting-susceptible cultivars produced similar numbers of leaves throughout the season. The mechanism of bolting resistance for `NuMex Mesa' may be a smaller plant size and/or a greater plant size required for receptivity to bolting-inducing temperatures as compared to bolting-susceptible cultivars. In general, cultivars exhibited less bolting, later maturity dates, and an increase in bulb yield with a delay in seeding.

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