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  • Author or Editor: Robert M. Pool x
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Abstract

We previously reported a method for shoot tip micropropagation of the Vitis hybrid ‘Remaily Seedless’ (1, 2). In preliminary trials, rooting of subcultured shoots was erratic and shoots deteriorated after 2 weeks in culture. Herein we report the effects of sucrose and naphthaleneacetic acid (NAA) concentrations on the physical condition of subcultured shoots and subsequent root production in an attempt to increase the efficiency of grape micropropagation.

Open Access

Abstract

Girdling reduced, and gibberellic acid or 4-chlorophenoxyacetic acid treatment had no effect on, the incidence of internal browning in ‘Thompson Seedless’ grape berries stored at 0°C. There was a direct relationship between the soluble solids content of the berries and the percentage of berries which developed internal browning. Fruit susceptible to internal browning had high levels of polyphenoloxidase and low levels of dihydroxy-phenolic substrate.

Open Access

Abstract

The effect of 3 abscission-promoting compounds on flower and berry abscission in 4 varieties of Vitis vinifera grapes was studied. A cluster-dipping experiment with Ethrel, abscisic acid, and a morphactin at concentrations ranging from 0.1 to 1,000 ppm, was done using ‘Thompson Seedless’, ‘Carignane’, and ‘Muscat of Alexandria’, at 4 developmental stages. Stimulation of abscission by the growth regulators decreased as flowers and berries became older. The morphactin was the most effective and abscisic acid the least effective in promoting abscission. Spray treatments with the same compounds induced abscission on ‘Muscat of Alexandria’ and ‘Perlette’ at appropriate concentrations. Pretreatment of ‘Muscat of Alexandria’ clusters with 4-CPA eliminated the effectiveness of morphactin and, to some extent, that of Ethrel.

Morphactin at 1 ppm stimulated shoot growth of ‘Muscat of Alexandria’ but marked inhibition occurred at 100 and 1,000 ppm. Ethrel at 10 ppm stimulated shoot growth, but marked inhibition occurred at 100 and 1,000 ppm. With ‘Carignane’ only morphactin produced inhibition of shoot growth. Appropriate concentrations of these compounds applied as sprays thinned ‘Perlette’ grapes, but thinning was quite irregular both within and among clusters.

Open Access

Abstract

At a stage just after bloom, gibberellin (GA3) at 600 ppm induced maximum increase in berry size of ‘Thompson Seedless’ grapes. Seven days after fruit-set, only 25 ppm were required for maximum response. In both instances, regression lines of best fit between GA3 concentration and berry weight indicated a logarithmic response. At both late bloom and early fruit-set stages there was a large increase in berry size, but at a time halfway between these stages the response to GA3 was much less striking. After fruit-set there was a gradual decrease in response to GA3. Increase in berry size due to girdling, on both vines sprayed at bloom and fruit set with GA3 and on unsprayed vines was maximum when berry diameter was 3-10 mm at time of girdling. There was no interaction between berry response to girdling and to gibberellin application. At fruit-set, ‘Perlette’ berries generally responded to increases in GA3 concentration up to 600 ppm.

Open Access

Abstract

Application of ethephon at 200 to 2,000 ppm was made to the grape cvs. ‘Tokay’ and ‘Emperor’, and at 1,000 ppm to ‘Thompson Seedless’ and ‘Carignane’. The soluble solids were significantly increased in some fruits of ‘Carignane’ but not in the other cultivars. Ethephon treatment resulted in reductions in acidity in some fruits of all cultivars. This increased soluble solids to acidity ratios in some ethephon-treated fruits. An increase in anthocyanin content of the colored berries occurred, but not significantly so in ‘Tokay’. Optimum time for treatment was about 2 weeks after initiation of coloring.

Open Access

Abstract

Gibberellin was applied at bloom to the seeded grape cvs. Zinfandel and Tokay. With ‘Zinfandel’ concn from 5 to 20 ppm caused increasing reductions in wt of fruits per vine and in ‘Tokay’ gibberellin at 10 and 20 ppm reduced fruit wt. Gibberellin applications successfully thinned the compact ‘Zinfandel’ and ‘Tokay’ clusters. Formation of unsightly shot berries was not a serious problem on ‘Tokay’. With ‘Zinfandel’, applications at the end of bloom were more effective than those at initiation of bloom.

A comparison of objective methods of measuring cluster compactness revealed that both number and wt of berries per cm of rachis are adequate indicators of the degree of compactness.

Open Access

Abstract

The growth of excised grape shoots in the absence of roots was investigated using asceptic culture. Sustained shoot development was observed only when cytokinins were present in the media. We used ‘Concord’ (Vitis labruscana Bailey) in most experiments, but the response was observed in other cultivars including those of Vitis vinifera L. Better response was obtained with cytokinin ribosides than with free bases. If roots developed, the requirement for an exogenous source of cytokinin was nullified.

Open Access

Abstract

Differential thermal analysis was evaluated as a means of determining the cold hardiness of excised dormant buds of Vitis vinifera L. cv. Chardonnay grapevines. The manner in which buds were excised and cooled affected the freezing characteristics of bud primordia. Buds excised with 1 to 2 mm of subjacent nodal tissue exhibited both high temperature exotherms (HTEs) and low temperature exotherms (LTEs). HTEs apparently resulted from freezing of supercooled moisture in bud scales and/or in the subjacent nodal tissue and occurred at inconsistent temperatures. Cooling similarly excised buds on a water-saturated substrate caused HTEs to occur at −4° to −8°C and did not affect the occurrence of LTEs, which were consistently associated with primordia death. Median LTEs associated with primary bud death were 1.5° to 2.0° warmer than LT50s derived from temperature/survival freezing tests of similar buds. Buds killed by freezing did not supercool appreciably when refrozen. Bud cold hardiness increased when single-node cuttings were exposed to a step-wise cooling cycle; however, the ability to detect exotherms decreased under these conditions. The decreased detection of exotherms was due to increased bud death and, presumably, a decrease of freezable (and thus detectable) moisture in the supercooled primordia of viable buds. DTA provides a useful and reliable means of determining grapevine bud cold hardiness when conducted in a standardized fashion.

Open Access

Abstract

Thermal and differential thermal analysis (DTA) are used to detect exotherms that result from the freezing of supercooled tissues (4). They provide a convenient and rapid means of assessing the hardiness of tissues that supercool, such as the floral primordia of Prunus spp. (3) and the compound buds of Vitis spp. (2). The inability to process a large number of tissue samples simultaneously, however, has been a major limitation of DTA. Ashworth et al. (3) described a computer-assisted data-logging system for recording thermal analysis data generated when Prunus flower buds were frozen. Multiple cooper-constantan thermocouples were used to increase the number of buds monitored on a given channel of a multichannel data-logger. Copper-constantan thermocouples, however, were not adequate with our instrumentation to discriminate exotherms generated by the freezing of individual shoot primordia of compound grapevine buds. Furthermore, anatomical barriers to ice propagation may be negated if thermocouples are inserted into buds to increase exotherm detection (5).

Open Access

Abstract

A factorialized thinning level/shoot density experiment which was started in 1980 demonstrated that ‘Seyval blanc’ grapes benefits from cluster thinning in terms of vine size maintenance, cane ripening, berry weight, and Brix. Reducing shoot density led to increased cane ripening. Concomitant increases in cluster exposure improved fruit composition and led to higher berry weights. However, maintaining reasonably high shoot densities (4 shoots/30 cm of row or more) also was essential to maintain yield and vine size, even when crop was controlled by thinning. Levels of 4 shoots/30 cm of row and 17 clusters/500 g cane prunings are recommended to maximize yield and maintain reasonable fruit quality and vine size. Postbloom cluster thinning was found to reduce the incidence of bunch rot and to reduce the production of 2nd crop in 1982, without affecting any parameters of yield or fruit composition.

Open Access