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- Author or Editor: Keith Patterson x
Five year old 'Bluecrop' blueberry plants were subjected to five irrigation regimes over a two year period to determine the influence on yield, berry weight, and plant growth. The plants were in 140 liter open-ended barrels to isolate different rates of moisture application. Ten plants/treatments were utilized in this study, with each plant considered a rep. Total yields did not follow a predictable pattern. Plants receiving 12 and 16 liters of water 3x per week produced larger berries, and resulted in larger dry weights at termination of this study. Plants receiving 20 liters 1x per week produced smaller berries than other treatments, lower yields in year 2, and smallest dry weight at end of the study.
Regulated deficit irrigation (RDI) is a management strategy that on grape can improve shoot/fruit ratio, water efficiency, and wine quality but has the potential to reduce yield. As part of a study on the influence of RDI on leafhopper density, we evaluated the effects on grape yield, berry size, berry soluble solids, and wine color. The studies were conducted at commercial vineyards in the San Joaquin Valley and in the Paso Robles region, CA, with Cabernet Sauvignon as the cultivar. Water deficits were imposed at either 50% (moderate deficit) or 25% (severe deficit) of standard irrigation (the control) for a period of 3 or 6 weeks and initiated at berry set, leafhopper egg hatch, or veraison. Deficit irrigation decreased berry weight by 16.1% at the San Joaquin Valley site (Aliso) and 11.7% at one of the Paso Robles sites (Frankel) but did not differ at the other site (Steinbeck). Yield was decreased by the deficits by 18.1% at Aliso, 26.7% at Frankel 2001 (but not 2002), and 24% at Steinbeck. Wine color density was increased by 21.8% at Aliso, 34.4% at Frankel 2001 (but not 2002), and did not differ at Steinbeck. Soluble solids did not differ among treatments at any site. There was no difference in berry weight, yield, or color between the moderate and severe deficits. It appears that in central California, RDI such as these are likely to reduce yield but are only one factor among many variables affecting quality such as wine color.
Canopy management and ethephon application (100 mg·liter-1 2 weeks after veraison) were investigated for 2 years as possible ways to improve color and overall quality of `Reliance' grapes (Vitis spp.). Canopy management consisted of leaf removal, shoot positioning, and cluster thinning. Grapevines were subjected to one of two levels of leaf removal and one of two levels of preharvest ethephon spray and were either thinned to a basal cluster or nonthinned. Thinning and ethephon advanced harvest dates by 5 to 8 days and 2 to 3 days, respectively. In 1989, berry weight was increased by thinning but was not affected by leaf removal or ethephon. Leaf removal (direct sun exposure) of thinned and nonthinned treatments increased “L” values (lighter colored fruit) in 1989. In 1990, leaf removal, ethephon, and thinning resulted in higher “L” values. The “a” values were significantly increased by leaf removal in 1989 and 1990 and by thinning in 1989, a result indicating increased skin redness. Exposed clusters of nonthinned treatments had significantly higher “b” values due to more yellow fruit in 1989 than in 1990. Ethephon increased “b” values in thinned and nonthinned treatments. In 1990, leaf removal increased “b” values. Thinning resulted in more evenly colored, redder fruit. Leaf removal caused a lightening and yellowing of the skin. Juice from leaf removal treatments in 1990 had significantly higher “L”, “a”, and “b” values. Ethephon significantly increased the “a” value of juice in 1989, and leaf removal significantly increased the “b” value in 1989. The percent soluble solids of juice was generally decreased by ethephon and increased by leaf removal and thinning. Titratable acidity was decreased by leaf removal and ethephon and increased by thinning in both years. Leaf removal decreased berry pH in 1990. Thinning increased coloration, and direct exposure to light decreased coloration. The results with ethephon were not conclusive. Chemical name used: 2-chloro-ethyl-phosphonic acid (ethephon).
A green house experiment was conducted to study growth response of strawberry seedlings inoculation to mycorrhizal fungi. Seeds of strawberry cultivar `sweetheart' were planted in trays of 25cm × 25cm × 5cm which were inoculated with Glomus intraradices. Spore densities of 0, 750, 1500, 3000, 7500, 12000 per plant were used. Results indicated that total dry wts. of plants inoculated with highest spore density significantly differed from the other treatments as well as from the controls. Moreover, total dry wts. of all treatments significantly differed from controls. The highest infection (71%) was seen at the 12000 spore density. Plant heights were variable at first two measurement dates. However, at the 3rd date, the 12000 spore density treatment significantly increased over all treatments except the 3000 level.
Grape clusters were subjected to one of two levels of leaf removal, one of two levels of preharvest ethephon spray, and either thinned to a basal cluster or left unthinned. Ethephon was applied at a concentration of 100 ppm two weeks after veraison. Affects on soluble solids content (SSC), titratable acidity (TA), pH, hue, chroma, and L, a, b values were not consistent. In 1989, light exposed clusters of thinned vines had significantly higher SSC. In 1990, when ethephon was applied to non-thinned vines, light-exposed clusters had higher SSC values than non-exposed clusters. Light, ethephon, or thinning in 1989 and light or ethephon in 1990 significantly increased TA. Ethephon in 1989 and light in 1990 significantly higher pH in 1989, and ethephon-treated clusters from thinned vines had significantly lower pH in 1990. Juice from light treatments in 1990 had significantly higher L, a, b, and chroma values. Ethephon significantly increased the “a” value of juice in 1989, and light significantly increased the “b” value. Hue was significantly different for light and ethephon treatments in 1989.
The relationship between canopy manipulation to improve solar penetration and ethephon application was studied on field-grown Vitis aestivalis L. `Norton' grapevines. Canopy manipulation involved removal of nonfruitful shoots, topping, and application of ethephon (750 mg·liter-1) at two intervals. Vines that were shoot-positioned and topped were not significantly different from control in soluble solids accumulation, but were superior to both ethephon treatments. Potassium levels in grape berries were lower in all treatments than in the control, but malate was significantly reduced only in the 2nd year of the 2-year study. Ethephon successfully controlled vine size and lateral development and thus increased solar penetration into the fruiting zone. Chemical name used: 2-chloroethyl phosphonic acid (ethephon).
Growth of strawberry (Fragaria ×ananassa Duch. `Sweetheart') seedlings inoculated with six spore levels ranging from 0 to 12,000 spores/plant of the mycorrhizal fungi Glomus intraradices Schenck and Smith was studied in the greenhouse and with greenhouse plants subsequently moved to the field. Plant height, leaf area, and number of leaves increased significantly with inoculum spore densities ranging from 750 to 12,000 spores/plant in relation to control plants in the greenhouse and field. In the greenhouse, there was a linear relationship between percent infection and spore density, although the relationship was cubic in the field. In the field study, control plants were infected with indigenous mycorrhizae, but inoculated plants produced more runners than the control plants, and foliar Cu and Ca increased linearly with increased spore density. Inoculated plants contained significantly more dry matter than the controls. For inoculated plants, root dry weight increased linearly with increased spore density. We conclude that a minimum spore density of 750 spores/plant is sufficient for a positive growth response.
Phytophthora root rot is a severe disease on blueberry (Vaccinium corymbosum L.) in poorly drained soils. The objective of the study was to determine the frequency of water-logged conditions on disease severity of blueberry. Phytophthora cinnamomi was grown on rice hulls and incorporated into the soil at the rate of 10% v/v. Water logging conditions were inflicted for 48 hr on mulched and non–mulched blueberry plants at 1-, 2-, and 4-week intervals. Non-water logging conditions were used on both mulched and non-mulched control plants. There was a significant linear relationship between disease severity of shoots and roots and the frequency of water-logging conditions. Disease symptoms were low in control plants, but disease ratings were high in mulched and non-mulched plants that were treated with water-logging conditions every week. There was also a linear trend between shoot dry weight and root dry weight of plants with frequency of water logging. Higher dry weights were seen on control plants. There was a significantly higher shoot, root dry weight and number of leaves of mulched plants than non-mulched plants. The percentage of infection on roots were high with frequent water logging. The study revealed high disease incidence with frequent water loggings. However, growth of mulched blueberry plants were comparable in control plants and plants that were subjected to water logging at 4-week intervals.
Strawberry (Fragaria ×ananasa Duch. `Chandler') tips containing only root initials were inoculated with mycorrhizal fungus Glomus intraradices and were fertilized with rockphosphate levels of 1, 2, 4 and, 6 mg·cm–3 to study root growth and mycorrhizal infection. The addition of rockphosphate at >2 mg·cm–3 decreased mycorrhizal infection. Root dry weight of mycorrhizal strawberry plants increased significantly over the controls with addition of rockphosphate, and mycorrhizal infection significantly decreased the shoot: root ratio. Foliar P levels decreased in mycorrhizal plants fertilized with up to 4 mg·cm–3 of rockphosphate and a quadratic relationship was seen between rockphosphate levels and foliar P. In nonmycorrhizal plants, the highest foliar P level was with rockphosphate at 1 mg·cm–3. The study revealed rockphosphate at 1 to 2 mg·cm–3 is beneficial for greater root growth with mycorrhizal inoculation.
The highbush blueberry cultivar Bluecrop was inoculated with potential plant growth-promoting (PGPR) candidates, including bacterial inoculants Pseudomonas fluorescens (Migula) (strains Pf 5, PRA 25, 105, or 101), Bacillus pumilus (Mayer and Gottheil) (strain T4), Pseudomonas corrugata (Roberts and Scarlett) (strain 114), and fungal isolates Gliocladium virens (Miller et al., Von Arx) (strain Gl.21) and Trichoderma harzianum (Rifai) (strain T 22). Addition of G. virens to pasteurized soil increased leaf area and the number of leaves produced in a 4-month growth period, as well as shoot content of P, Zn and Cu in 1997. Treatment with P. fluorescens Pf 5 increased leaf area and stem diameter. In nonpasteurized soil, plants inoculated with G. virens had greater leaf area, stem diameter, shoot and root dry weight, and more leaves per plant. These results demonstrate the potential of G. virens for increasing growth when used to inoculate blueberry plants in the nursery or at transplanting.