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  • Author or Editor: Frank Matta x
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Temperature is a major environmental factor governing the distribution of both wild and cultivated plant species. During acclimation and deacclimation plants undergo a series of metabolic changes that lead to cold hardiness or loss of hardiness. One of these changes is the accumulation of certain lipids. This research was conducted to compare hardiness among three pecan cultivars: `Desirable', `Jackson', and `Owens' growing under Mississippi condition and to determine the relationship between fatty acid levels and cold hardiness of pecan shoots. Differential thermal analysis (DTA), electrical conductivity, and tetrazolium tests were used to determine cold hardiness. Pecan stems were collected from September to March in 2002 and 2003 to determine cold acclimation and deacclimation. Fatty acid composition of pecan stems during this time period was determined by gas chromatography. DTA indicated that pecan stems acclimated in October and deacclimated in March. During cold acclimation, there was a shift in the fatty acid composition to more unsaturated fatty acids. The percentage of linoleic and linolenic fatty acids increased, while the percentage of palmitic and stearic fatty acids decreased. The correlation between unsaturated fatty acids and cold hardiness suggests that unsaturated fatty acid may play a role in membrane fluidity.

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Experiments were performed in 1995 and 1996 at the Mississippi State Univ. Agricultural Experiment Station, Pototoc Ridge, to investigate the effect of Accel and carbaryl sprayed 2 weeks postbloom on fruit set, yield, and plant nutrition of three apple cultivars (Empire, Jon-A-Red, and Braeburn). The treatments consisted of Accel 25 ppm, Accel 50 ppm, Accel 75 ppm, Carbaryl 0.05%, Carbaryl 0.1%, Carbaryl 0.2%, and an unsprayed control. Thinning trials using the two bioregulators conducted over 2 years indicated that Accel and Carbaryl consistently thinned the apple cultivars and increased the yields. Leaf mineral concentrations were affect by the treatments. In 1995, the treatments affected leaf concentrations of N, Ca, and Mg, while in 1996 the treatments affected the leaf contents of N, P, K, Ca, Mg, Fe, Mn, and Zn, but no copper. The treatments also affected the fruit flesh mineral concentration by increasing the contents of K, P, and Mg in 1996. It can therefore be concluded that, depending on apple cultivar, N content was reduced by the treatments while Ca and Mg were generally increased. Similarly, the fruit flesh contents of Fe, K, P, and Mg were also increased. The two bioregulators therefore thin apples, increase yields, and affect the fruit quality.

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Experiments were conducted in 1995 and 1996 to investigate the effect of Accel and Carbaryl sprayed 2 weeks postbloom on apple fruit yield and quality and to relate the degree of fruit set reduction to the yield of three apple cultivars (Empire, Jon-A-Red, and Braeburn). The treatments consisted of Accel 25 ppm, Accel 50 ppm, Accel 75 ppm, Carbaryl 0.05%, Carbaryl 0.1%, Carbaryl 0.2%, and an unsprayed control. Trials conducted over the 2 years indicated that Accel and Carbaryl reduced the fruit set of three apple cultivars as shown by the lower number of fruit per limb cross-sectional area on the sprayed trees compared to the unsprayed trees. Most effective concentrations in reducing the fruit set on apples were Accel 50 ppm, Accel 75 ppm, Carbary 0.01%, and Carbaryl 0.2%, with high yields and high fruit rates. Therefore, it was concluded that these are the best concentrations for thinning of apples. Other quality attributes, such as pH, sugar content, and percent fruit red were also increased by the treatments. The treatments did not influence the number of seeds in the fruit, fruit length, fruit diameter, and fruit length: diameter ratio.

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Experiments were conducted in 1995 and 1996 to investigate the effect of Accel and Carbaryl on apple fruit on three apple cultivars (Empire, Jon-A-Red, and Braeburn) at the Mississippi State Univ. Aricultural Experiment Station, Pontotoc. The treatments consisted of Accel 25 ppm, Accel 50 ppm, Accel 75 ppm, Carbaryl 0.05%, Carbaryl 0.2%, and an unsprayed control. Trials conducted over 2 years showed that Accel and Carbaryl consistently reduced the fruit set of three apple cultivars. There were interactions between the bioregulators and cultivars only in 1996. In all the bioregulators, treatments reduced fruit set, while in 1996, Carbaryl and Accel at all concentrations except Accel 25 ppm reduced the fruit set of `Empire', `Jon-A-Red', and `Braeburn'. Carbary 0.2% and Accel 75 ppm were the most-effective concentrations in `Empire', `Jon-A-Red', and `Braeburn', respectively, in 1996. The treatments generally increased yield and sugar content, while pH was either not affected, increased or decreased, depending on the apple cultivar.

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Abstract

Foliar sprays of dikegulac-sodium (sodium salt of 2,3:4,6-bis-0-(1-methylethylidene)-alpha-L-xylo-2-hexulofuranosonic acid) at 722 and 2888 ppm and hand-pinching significantly increased branching of chili pepper cultivars ‘Sandia’, ‘NM 6’, and ‘Espanola 1’ (Capsicum annuum L.). Both dikegulac-sodium concentrations were equally effective in increasing branching. Hand-pinching and dikegulac-sodium at 722 ppm did not influence plant height. Dikegulac-sodium at 2888 ppm significantly reduced plant height. Hand-pinching and dikegulac-sodium at 722 ppm delayed first harvest by 9 days. Dikegulac-sodium at 2888 ppm delayed first harvest by 34 days. Dikegulac-sodium at 5053 ppm resulted in death of treated plants. All concentrations of dikegulac-sodium decreased yield.

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Experiments were performed to determine the effect of Accel and carbaryl on the fruit set, yield, quality, and leaf mineral composition of three apples cultivars: `Empire', `Jon-A-Red', and `Braeburn'. The treatments used were Accel at 25, 50, and 75 ppm; carbaryl at 0.05%, 0.1%, and 0.2%. There were significant increases in length: diameter ratio, weight of fruit per tree, pH, and percent red color. Mean fruit weight, percent N, K, and Mg as the rates of Accel and carbaryl increased. Sugar content in the fruit and the levels of P, Ca, Mn, Fe, Cu, and Zn in the leaves were not affected. We conclude that the increased fruit weights were due to increased cell numbers and the few fruit that remained after thinning, thereby leading to increased amounts of assimilates directed to the developing fruit. The increase in percent red color is indicative of the effect of the treatments on the degree of ripening.

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Greenhouse-grown purple passion fruit (Passiflora edulis Sims) were harvested mature-green 55 or 60 days after anthesis (DAA) and stored for 10 days at 10C. After storage, half the fruit were treated with 10 μl ethylene/liter for 35 hours and then stored at 21C for 48 hours. Juice of treated and nontreated fruit was analyzed for comparison with juice of vine-ripened fruit (harvested 70 to 80 DAA). Sucrose concentration decreased and fructose and glucose concentrations increased after storage, regardless of ethylene treatment. Fruit harvested 55 or 60 DAA, with or without ethylene, had the same sugar and soluble solids concentrations and pH as vine-ripened fruit. Ethylene treatment enhanced surface purple pigmentation of fruit harvested mature-green.

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A study of spur-type apple scion cultivars on semi-dwarf and dwarf apple rootstocks was conducted to evaluate and identify suitable scion/stock combination for Mississippi. Fruit weight varied among scion/stock combinations. `Royal Gala' on MM111 and MM106 and `Ultra Gold' on MM106 yielded the heaviest fruit. `Jon-A-Red' on Mark produced the lightest fruit. Fruit length diameter ratio (L/D) was the highest for `Blushing Golden' on M7A and MM111, and `Ultra Gold' on MM111. The L/D ratio of `Royal Gala' was not affected by rootstock. Scion cultivars on M7A and M26 tended to have more red fruit than on the remaining rootstocks. `Ultra Gold' on M26 and `Braeburn' on Mark and MM111 had the firmest fruit. Overall, trees on M7A and Mark rootstock tended to produce firm fruit. Juice pH was significantly affected by scion-stock combination. In general, `Royal Gala', regardless of rootstock, had the highest juice pH, whereas `Ultra Mac' and `Jon-A-Red' produced the lowest pH. `Blushing Golden' on MM111 and `Royal Gala' on M26 had the highest soluble solids concentration (SSC). Soluble solids concentration of scion cultivars on MM106 did not differ.

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This study was established to determine the influence of scion/stock combination on leaf area, yield efficiency, and fruit quality attributes in effort to identify the most suitable scion/stock combination for Mississippi. Twenty-nine scion/stock combinations were grown at the Pontotoc Ridge-Flatwoods Research and Extension Center, North Mississippi. The treatments were arranged in a completely randomized design (CRD) with six single tree replications. `Jon-A-Red' on Mark produced the smallest leaf area, while the largest leaf area was produced by the combination of `Royal Gala' on MM106 and `Blushing Golden' on M7A. Scion/stock combinations significantly affected yield efficiency, fruit yellow pigment dvelopment, firmness and fruit mineral composition. Scion cultivars on Mark resulted in the highest yield efficiency, except `Empire'. `Ultra Gold' and `Braeburn' on Mark and `Blushing Golden' on MM111 led to yellow pigmentation in the highest category. Meanwhile, `Braeburn' on Mark was among the scion/stock combinations that produced the firmest fruit. And fruit from trees on Mark consistently had high calcium (Ca) levels. After 7 years, `Royal Gala' on Mark produced the highest yield efficiency. `Braeburn' on Mark resulted in both the firmest fruit and the highest fruit Ca concentration.

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Maturity indices such as fruit size, firmness, fresh fruit weight, soluble solids content, titratable acidity, and juice pH of `Earligold'/EMLA 7, `Jonagold'/EMLA 111, `Improved Golden'/EMLA 7, `Improved Golden'/EMLA 111, `Scarlet Gala'/EMLA 7, `Jonafree'/Mark, `Macspur'/M 7A, `Royal Gala'/MM 111, and `Williams Pride'/M 7A were monitored. Based on maturity indices analysis, the optimal harvest time for each scion rootstock combination was determined. `Scarlet Gala'/EMLA 7, `Williams Pride'/M 7A, and `Earligold'/EMLA 7 were early cultivars, while `Jonagold'/ /EMLA 111, `Improved Golden'/EMLA 7, `Improved Golden'/EMLA 111, and `Macspur'/M 7A were late cultivars. After harvest, all cultivars were stored for 3 months under controlled conditions. Changes in fruit appearance, flavor, sweetness, tartness, and firmness were recorded. Fruit size, firmness, fresh fruit weight, soluble solids content, and juice pH were influenced by the cultivar/rootstock combination. Results of the sensory evaluation indicated that medium and late cultivars were preferred by panelists compared to the early harvested cultivars. `Improved Golden'/EMLA 7, `Royal Gala'/MM 111, and `Jonagold'/EMLA 111 combinations maintained quality during storage, compared with the remaining cultivars/rootstock combinations, and had a longer storage life.

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