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  • Author or Editor: G. M. White x
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Previous work has shown that container grown landscape plants use, and likely need, much less water than is typically applied. Therefore, studies were conducted to quantify the relationships between water loss and water stress responses using several drought tolerant (Cassia corymbosa, Leucophyllum frutescens, Salvia greggii) and traditional landscape plants (Euonymus japonicus, Pyracantha coccinea). Water stress was induced by withholding water and water loss measured gravimetrically. The shape of the water loss curve was similar for all species being, Y = a + bx + cx2 (r2 > 0.95). The rate of ethylene production began to increase 24 hr after irrigation, reaching a maximum 36-48 hr after irrigation and then decreasing. Maximum ethylene production occured at 35-47% water loss irrespective of species or rate of water loss. Stress symptoms (wilting leaf discoloration and abscission) followed a similar pattern. The potential for monitoring gravimetric water loss to schedule container irrigation will be discussed.

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Previous work has shown that container grown landscape plants use, and likely need, much less water than is typically applied. Therefore, studies were conducted to quantify the relationships between water loss and water stress responses using several drought tolerant (Cassia corymbosa, Leucophyllum frutescens, Salvia greggii) and traditional landscape plants (Euonymus japonicus, Pyracantha coccinea). Water stress was induced by withholding water and water loss measured gravimetrically. The shape of the water loss curve was similar for all species being, Y = a + bx + cx2 (r2 > 0.95). The rate of ethylene production began to increase 24 hr after irrigation, reaching a maximum 36-48 hr after irrigation and then decreasing. Maximum ethylene production occured at 35-47% water loss irrespective of species or rate of water loss. Stress symptoms (wilting leaf discoloration and abscission) followed a similar pattern. The potential for monitoring gravimetric water loss to schedule container irrigation will be discussed.

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Abstract

Experiments were conducted to evaluate the response of carrots (Daucus carota L.) to target plant densities of 39, 59, and 79 plants per meter of band with various row arrangements (2 band/bed with 2, 3, or 4 seeded rows/band with 3.8 to 11.4 cm between rows) on a Landerhill muck soil. Marketable and total carrot yields increased linearly with increased plant density from 24 to 85 plants per square meter. In 2 of 3 experiments, row arrangement significantly influenced yield; greatest yields were obtained when spacing between rows in a band was greater than 3.8 cm, indicating some advantage to increasing the distance between rows. Mean length and diameter of marketable roots decreased linearly with increased plant density. Length and diameter of marketable carrots were influenced by row arrangement in one of the 3 experiments. Carrots grown in rows spaced more than 3.8 cm apart were longer and had a greater diameter than did carrots grown with 3.8 cm between rows.

Open Access

Abstract

‘Redhaven’ peaches (Prunus persica L. Batsch) were sprinkled from the end of rest, January 22, 1975, until the time check trees reached full bloom, April 18, 1975. Sprinkling delayed bloom by 15 days. Energy models predicted bloom one day before it occurred in the check trees. Wood temperatures were lowered as much as 6.5°C in sprinkled trees, but no significant difference in wood cold hardiness was observed. Sprinkled fruit buds were more cold hardy than non-sprinkled fruit buds until early March. Non-sprinkled buds were more cold hardy than sprinkled fruit buds in late March. Sprinkling reduced the number of viable buds/m by late March. Analyses of total and reducing sugars and protein showed no significant difference.

Open Access

Abstract

Root lengths of an adventitious root system (creeping bentgrass, Agrostis palustris Huds.) and a woody plant fiberous root system (Hetz juniper, Juniperus chinensis L. ‘Hetzii’) were estimated using an automated method employing a video camera and an area/length meter to count scanning line and root intersections. A grid method of root length estimation was used for comparison. Under- and overestimation was random when the automated method was used for creeping bentgrass samples (<80 cm) and the shorter group of juniper root samples (150-550 cm). However, these estimates were much closer to the actual root length, in the ranges evaluated, than the estimates from the grid method. The lengths of long juniper root samples (600-3000 cm) were underestimated consistently with the automated method. The magnitude of this underestimation increased with increasing length. However, the relationship between estimated and actual root length remained linear and was about 76% of the actual length. For the ranges of root length evaluated, this method was found to be useful for root length estimation.

Open Access

Four subsets of apple (Malus Mill.) germplasm representing modern and old cultivars from the repository and apple genetics population of the Horticulture and Food Research Institute of New Zealand Limited were used in this study. A total of 155 genotypes randomly chosen from the four subsets were analyzed for random amplified polymorphic DNA (RAPD) variation. Nine decamer primers generated a total of 43 fragments, 42 of which were polymorphic across the 155 genotypes. Pairwise distances were calculated between germplasm subsets using the distance metric algorithm in S-PLUS, and used to examine intra-and inter-subset variance components by analysis of molecular variation (AMOVAR). A phenogram based on unweighted pair group method with arithmetic average (UPGMA) cluster analysis was constructed from the pairwise distances and a scatter plot was generated from principal coordinate analysis. The AMOVAR showed that most of the variation in the germplasm (94.6%) was found within subsets, suggesting that there is significant variation among the germplasm. The grouping of genotypes based on the phenogram and scatter plot generally did not reflect the pedigree or provenance of the genotypes. It is possible that more RAPD markers are needed for determining genetic relationships in apple germplasm. Nevertheless, the variation observed in the study suggests that the current practice of sublining populations in the first generation to control inbreeding may not be necessary in subsequent generations. If these results are confirmed by fully informative molecular markers, germplasm managers should reassess the structure of their genetics populations. There may be a need to combine sublines in order to capture the maximum genetic diversity available and to streamline breeding efforts.

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Potato (Solanum tuberosum) is an important agricultural crop for Florida. From 1996 to 2000, the winter and spring potato crop was grown on an average of 15,782.7 ha (39,000 acres) and valued at $117 million. Variety evaluation and selection is an important tool to improve production efficiency and increase the competitiveness of Florida growers. A red-skinned potato variety evaluation was conducted in northeastern Florida in 2002. The experimental design was a 4 (site) × 5 (variety) factorial with four replications at each site. The four sites were the University of Florida's Plant Science Research and Extension Unit and three local commercial farms. Potato varieties in the trial were `Red LaSoda', `LaRouge', B0984-1, B1145-2, and B1758-3. Marketable tuber yields were 36.3, 35.6, 30.2, 20.3, and 21.4 t·ha-1 (324, 318, 269, 181, and 191 cwt/acre) respectively, with tuber yields of the two named varieties significantly higher than the numbered entries. Specific gravity ranged from 1.060 (`Red LaSoda') to 1.070 (B0984-1). There were no significant differences among entries for total cull weight or the incidence of hollow heart, brown rot, or corky ringspot. However, a higher percentage of B0984-1 tubers showed symptoms of internal heat necrosis than all other varieties. Potato varieties ranked from lowest to highest in overall appearance were `LaRouge', `Red LaSoda', B1758-3, B0984-1, and B1145-2. Higher appearance ratings in the numbered entries were attributed to darkerred skin color, rounder tuber shape, and shallower eyes compared to `Red LaSoda' and `LaRouge'. `Red LaSoda' and `LaRouge' will continue to be recommended as the standard redskinned potato varieties for Florida. However, B0984-1 and B1145-2 had desirable characteristics and should be planted in larger plantings to further evaluate quality and production characteristics.

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Potato (Solanum tuberosum) is a high value crop in Florida. It consistently ranks in the top five valued vegetable crops produced in the state. The identification of new potato varieties that improve production efficiency is an imperative because of constantly evolving market and production demands. A chip potato variety evaluation experiment was conducted in northeast Florida in 2002 to compare the production characteristics of industry standards to advanced selections. The potato varieties evaluated in this experiment were bred specifically for processing by the potato chip industry. The experimental design was a four (site) by five (variety) factorial with four replications at each site. The sites were the University of Florida's research farm in Hastings, FL and three commercial farms in the surrounding area. Potato varieties were two seed sources of `Atlantic', as well as, `Snowden', B0564-8, and B0766-3. Marketable yield for each variety was 39.4, 33.4, 38.4, 33.6, and 33.6 t·ha-1 (351, 298, 343, 300, and 300 cwt/acre), respectively. Total yield of B0564-8 was statistically equivalent to an `Atlantic' standard at all four locations and similar to `Snowden' at three of four locations. Specific gravity of B0564-8 and B0766-3 was significantly lower than that of `Atlantic' from both sources but within acceptable range for chip potatoes. B0564-8 tubers had the highest overall appearance ratings and the most consistent size and shape. B0564-8 and B0766-3 tubers had a significantly lower percentage of hollow heart and internal heat necrosis than `Atlantic' tubers. This resulted in overall better chip ratings for the numbered entries compared to `Atlantic' tubers. A potential fit for B0564-8 and B0766-3 in northeastern Florida production may be as a late season chip variety when the potential for the development of internal heat necrosis increases.

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Intensive selection to improve vase life was performed on a sample population of Gerber ×hybrida Hort. from a broad source of germplasm. Progeny of a 5 × 5 diallel cross yielded estimates of narrow sense heritability (h2 = 0.28) and broad sense heritability (H2 = 0.28) for vase life based on a mean of 1.96 measurements per plant. Additive gene action is postulated to control this character since the difference between total genotypic variance and additive genetic variance components was small. Repeatability (r = 0.57) based on a single measurement per plant was moderately high. Heritability estimates were also determined based on 1, 2, 3, 5, and ∞ measurements per plant. Heritability ranged from 22% to 39%.

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