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  • Author or Editor: William J. Martin x
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Abstract

The effect of temperature on ethylene evolution from ethephon-treated sour cherry (Prunus cerasus L. cv. Montmorency) leaves was determined subsequent to foliar application. The upper surface of uniform fully expanded leaves was treated in the field with 125 μg of ethephon, (2-chloroethyl)phosphonic acid. After 24 hours, leaves were detached and ethylene was measured during incubation at temperatures between 10 and 34°C. Ethephon degradation in buffered solutions was also monitored between 10 and 50° and over a range in pH from 3.0 to 7.0. The effect of temperature on rate of endogenous ethylene evolution was examined for sweet cherry shoots and sour cherry leaves, and was calculated for several other tissues and species from values found in the literature. The rate of ethylene evolution from both ethephon-treated leaves and buffered solutions was markedly temperature dependent, with an apparent energy of activation (Ea) of 30 to 32 kcal mole-1. There was no pH-temperature interaction affecting the Ea for buffered solutions. A generalized Ea for endogenous ethylene evolution was about 13 kcal mole-1.

Open Access

The time required to maintain plants on a standardized basis (effort) was investigated in 24 gardens of various plant composition over 5 years. Cluster analysis of data grouped gardens into five clusters based on magnitude and timing of effort. Plants grown in containers required up to 20 times more effort annually than plants grown in other gardens in ground beds. Gardens planted with annuals required about 80% less effort than container gardens but 75% more effort than other gardens evaluated. As the number of taxa in gardens decreased, effort decreased and was less variable throughout the year. Enumeration of effort in relation to garden composition should be used to project management cost for gardens.

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On-plant floret longevity and cutflower postharvest longevity (PHL) of Antirrhinum majus L., snapdragon, were evaluated using inbreds P1 (16 day PHL) and P2 (6 day PHL), F1 (P1 × P2), F2 (F1 self-pollinated), F2 × F2 (among and within PHL categories: long, 17 to 25 days; middle, 9 days; and short, 2 to 3 days), and F3 families (F2 self-pollinated). F2 on-plant floret longevity and PHL correlated to later generation PHL. Prediction of progeny PHL from F2 × F2 matings appears feasible if genotypic value for PHL of F2 is known. Selection for PHL is best based on evaluation of multiple cutflowers per genotype. Significant additive and dominant genetic variance components contribute to PHL.

Free access

Narrow-sense heritabilities and genetic correlations of ornamental quality traits of Antirrhinum majus (snapdragon) were evaluated with special reference to cut flower postharvest longevity (PHL). Inbreds P1 (16 days PHL) and P2 (3 days PHL) were hybridized to produce an F1 (P1 × P2) that was self-pollinated to produce an F2 population. The F2 were self-pollinated to produce F3 families and advanced through single-seed descent by self-pollination to the F5 generation. P1, P2, F1, F3, F4, and F5 were evaluated for ornamental quality traits. Quality traits were found to be quantitative and normally distributed. Narrow-sense heritability (h2) estimates were high and consistent across generations examined; PHL h2 ranged from 0.79 to 0.81 ± 0.06. Phenotypic and genotypic correlations revealed underlying physiological and pleiotropic interactions relevant to breeding programs aimed at simultaneous improvement of ornamental quality traits. PHL is inversely related to cut flower strength and days to flower, -0.44 ± 0.04 and -0.43 ± 0.44. Buds at discard is positively correlated to cut flower and plant diameter, cut flower weight and days to flower, 0.77 ± 0.05, 0.58 ± 0.06, 0.71 ± 0.06, and 0.77 ± 0.07, respectively. Gain from selection for quality traits of interest can be rapid.

Free access

Stomatal density during plant development and inheritance of the trait were investigated with the goal of utilizing stomatal density as a correlated trait to cutflower postharvest longevity in Antirrhinum majus L. Inbred P1 (stomatal index = 0.2) was hybridized to inbred P2 (stomatal index = 0.3) to produce F1 (P1 × P2), which was backcrossed to each parent producing BCP1 (F1 × P1) and BCP2 (F1 × P2). P1, P2, F1, BCP1, and BCP2 were used to examine changes in stomatal density with plant development and early generation inheritance. An F2 (F1 self-pollinated), and F3, F4, and F5 families, derived by self-pollination and single seed descent, were used to obtain information on advanced generation inheritance. Stomatal density was stable over time and with development of leaves at individual nodes after seedlings reached two weeks of age. Therefore, stomatal density can be evaluated after two weeks of plant development from a leaf at any node. Stomatal density is quantitatively inherited with narrow sense heritabilities of h2 F2:F3 = 0.47 to 0.49, h2 F3:F4 = 0.37 ± 0.06 to 0.60 ± 0.07, and h2 F4:F5 = 0.47 ± 0.07 to 0.50 ± 0.07.

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Stomatal density is being investigated as a highly correlated trait to postharvest longevity (PHL) and subsequently may be used for selection in early generations of breeding germplasm. To this end, leaf imprints were created from Antirrhinum majus L. (snapdragon) P1, P2, F1, BC1 (F1×P1), BC2 (F1×P2), F2, and F3 plants and evaluated for stomatal densities. Cut flowers of P1, P2, F1, BC1 (F1×P1), BC2 (F1×P2), and F3 were harvested after the first five flowers opened and evaluated for PHL. Additionally, cut flowers from these lines were evaluated for leaf surface area. Populations for evaluation were grown in the greenhouse in winter and spring 1999-2000 in a randomized complete-block design according to standard forcing procedures. Twenty-five cut flowering stems of each genotype were held in the laboratory in deionized water under continuous fluorescent lighting at 22 °C for PHL assessment. The end of PHL was defined as 50% of the flowers drying, browning, or wilting. Data will be presented on the correlation between stomatal density and PHL.

Free access

Cut flowers of Antirrhinum majus L. (snapdragon) P1, P2, F1, F3, and F2 × F2 plants were harvested after the first five flowers were open and were evaluated for postharvest longevity to further evaluate genes conditioning postharvest longevity. F3 progeny evaluated were derived by selfing F2 selections of long keeping, mid-range, and short keeping types. F2 × F2 progeny evaluated were derived from crosses within and between postharvest longevity categories. Populations for evaluation were grown in the greenhouse in winter 1998-1999 in a randomized complete-block design according to standard forcing procedures. Thirty plants of each genotype were held in the laboratory in deionized water under continuous fluorescent lighting at 22 °C for postharvest assessment. The end of postharvest life was defined as 50% of the flowers drying, browning, or wilting. Data will be presented on postharvest longevity and allelic relationships within populations.

Free access

Abstract

Five compounds were evaluated for consistent promotion of sour cherry (Prunus cerasus L. cv. Montmorency) fruit abscission under field conditions: (2-chloroethyl)phosphonic acid (ethephon); 2-chloroethyl-tris-(2-methoxyethoxy)-silane (CGA 13586); 2-chloroethyl-methylbis-(phenylmethoxy)-silane (CGA 15281); 1,1,5,5-tetra-methyl-3-dimethylaminodithiobiuret (ER 3952), and beta-hydroxyethylhydrazine (BOH). The compounds were applied to mature trees at equimolar concentrations, and rates of ethylene evolution, effects of temperature on rates of ethylene evolution, and fruit removal forces were measured. Ethephon generated ethylene at adequate rates and was a good promoter of fruit abscission, but its activity was markedly affected by temperature. CGA 15281 promoted fruit abscission with minimal effect of temperature on ethylene evolution. ER 3952 was also a good fruit loosener, although it did not release ethylene directly. CGA 13586 and BOH were not effective in promoting fruit abscission and were poor ethylene generators.

Open Access

Abstract

Fruits of sour cherry (Prunus cerasus L. cv. Montmorency) were collected with pedicels attached during stage III of fruit development and were incubated with or without exogenous ethylene at temperatures between 15 and 35°C. Exogenous ethylene was supplied either by preincubation in 1.0 mm (2-chloroethyl)phosphonic acid (ethephon) or by incubating in ethylene-enriched (7 μ1 liter−1) air in a flow-through system. There was no detectable interaction between ethylene concentration and temperature in promoting fruit abscission, measured as fruit removal force. Thus, the ability of ethylene to induce this response appeared to be independent of temperature between 15 and 35°. Events which occur subsequent to induction by ethylene during fruit abscission layer development were slightly affected by temperature, with a mean Q10 of 1.20.

Open Access

Progeny of 158 F5 × F5 crosses of Antirrhinum majus (snapdragon) selected within and among cut flower postharvest longevity (PHL) categories (long = 12.6-16.8 days, middle = 9.3-12.1 days, and short = 4.8-8.9 days) were evaluated for PHL and quality traits. Results were compared with previous studies involving F2 × F2 progeny, and F3, F4, and F5 inbred lines. Heritability of PHL in F5 × F5 progeny (0.77 ± 0.11) agrees with that of inbred lines (0.79 to 0.81) but is higher than in F2 × F2 progeny (0.41). Therefore, selection for increased PHL should progress more rapidly and predictably through application of inbred lines rather than F2 individuals. Significant differences between F5 × F5 progeny PHL categories confirm PHL is heritable with a significant additive component. Heritabilities of quality traits in A. majus are high, suggesting selection for quality traits should progress without difficulty. Phenotypic and genotypic correlations of PHL with quality traits are not consistently significant across PHL studies in A. majus. Discrepancies between studies suggest most traits may not be correlated to PHL or are subject to strong environmental influence.

Free access