Highbush Blueberry Plants Research Articles

ESTABLISHMENT OF `GULFCOAST' SOUTHERN HIGHBUSH BLUEBERRY

In a 1989 field study, `Gulfcoast' southern highbush blueberry plants were subjected to irrigation [8 liters per week (low) and 30 liters per week (high)], mulching (none and 15 cm height), row height (level and raised 10-15 cm), and soil incorporated peat (none and 15 liters in each planting hole) treatments at establishment. Plants were grown on a well-drained fine sandy loam soil that contained < 1.0% organic matter. Plant volume was increased by either mulching, high irrigation, incorporated peat moss or level beds. Fruit yields were not significantly affected by irrigation levels but were highest with either mulching, level beds or incorporated peat moss. The bed height X mulching interaction indicated that mulching increased yield more with level beds than with raised beds. Plants grown with the combination of mulching, level beds, incorporated peat moss, and high irrigation levels yielded 1.1 kg per plant or approximately 10 times more than plants grown without mulch, with raised beds, without peat moss, and with the low rates of irrigation. Of the 4 establishment practices evaluated, mulching had the greatest influence on plant growth and fruiting.

Susceptibility of Blueberry to Infection by Agrobacterium tumefaciens

Table 1. Production of galls on blueberry seedlings after inoculation with various Agrobacterium fumefaciens strains. The ability to regenerate various plant species from leaf disks has provided opportunities for their genetic transformation by Agrobactetium tumefaciens (Horsch et al., 1985; Klee et al., 1987; McCormick et al., 1986). The regeneration of cultivated highbush blueberry plants (Vaccinium corymbosum L.) from leaf segments has been accomplished recently at several laboratories (Billings et al., 1988; Callow et al., 1989; Dweikat and Lyrene, 1988). Natural infection of blueberry by Agrobacterium is uncommon. Galls have been rarely observed on fieldand nursery-grown blueberry plants and rarely attributed to infection by A. tumefaciens (Demaree and Smith, 1952). The possible resistance of blueberry to infection by Agrobacterium may limit its usefulness for the transformation of blueberry leaf segments. In addition, the susceptibility of blueberry to infection by specific Agrobacterium strains commonly used in transformation experiments has not been previously determined. Therefore, the susceptibility of blueberry to infection by five Agrobactetium strains was investigated. Groups of six to eight seedlings (≈6 months old) were each inoculated with Agrobacterium strains T37, C58, A281, A518, or B6. Seedlings were from a cross between a V. corymbosum parent and a V. colymbosum x V. elliottii parent. Seedlings to be inoculated were brought into the laboratory and wounded once toward the base of the stem with a sterile scalpel. Ten microliters of 36-hr-old bacterial culture grown in YEP media (1% yeast extract, 1% peptone, 0.5% NaCl) was placed on each of the wounded sites. Plants were left in the laboratory 3 hr before being moved to the greenhouse. After ≈4 weeks, no gall

Histopathology of Blueberry Twig Blight Caused byPhomopsis vaccinii

Emerging flower buds or fully opened flower clusters of highbush blueberry plants were inoculated with a conidial suspension of Phomopsis vaccinii. Samples were taken 3 days and 1, 2, 3, 4, 6, 8, and 10 wk after inoculation for histopathological study. P. vaccinii penetrated succulent floral parts. Hypertrophy and hyperplasia occurred in response to infections on ovaries and floral axes, respectively, but did not prevent growth of the hyphae. Hyphae grew intercellularly through the cortical cells of the pedicel and into the intercellular spaces in the cortex of the floral axes by 1 wk after inoculation (...)

Prolonged Flooding Effects on Anatomy of Highbush Blueberry

Abstract Roots of flooded highbush blueberry (Vaccinium corymbosum L.) plants examined by light and scanning electron microscopy exhibited enlarged epidermal cells, compressed cortical cells, and disrupted vascular tissue. The stems of flooded plants showed disrupted epidermal tissue, condensed outer cortical cells, and large aerenchyma-like mid-cortical tissue. Leaves from flooded plants showed an increase in intercellular spaces in the spongy mesophyll and a disrupted palisade layer. There were no apparent differences in inflorescence bud anatomy, although inflorescences were small and delayed in development.

Growth and Survival of the Highbush Blueberry in Response to Root Zone Flooding

Abstract Flooded, 2-year-old highbush blueberry plants (Vaccinium corymbosum L. ‘Bluecrop’) survived 30 months of continuous flooding, but vegetative growth was suppressed after ≈4 months. Plants continuously flooded for 4 months and subsequently placed in the field recovered partially. The greatest number of plants died when flooding began in April and the least number when it was begun in December.

Plant Parasitic Nematodes Associated with Highbush Blueberry in Arkansas

Abstract Soil samples for a nematode assay were taken in 1983 within the root zone of highbush blueberry (Vaccinium corymbosum L.) plants in mature experimental and commercial plantings. Xiphinema americanum Cobb and Paratrichodorus christiei Allen were the predominant nematode species found. Nematode populations were not affected by cultivar. Mulched plots had significantly fewer P. christiei while X. americanum populations were similar in mulched and nonmulched plots.

Pruning Effects on Productivity and Vegetative Growth in the Highbush Blueberry

Abstract The effect of pruning was evaluated by removing varying amounts of different-sized canes from 15-year-old highbush blueberry plants. As much as 40% of a bush could be removed before yield was reduced. There was a significant correlation (P < 0.05) between percent base area removed and berry weight, suggesting a compensation for reduced basal area by increasing berry weight. The number of new canes also was significantly correlated with the number removed. The size of canes removed was less important than the percent basal area removed, except in the most extreme treatment (40% removed), where the removal of medium-sized (1-2.5 cm) canes had a greater effect than the elimination of large canes.

Irrigation Scheduling for Young Highbush Blueberry Plants in Arkansas

Abstract A moisture accounting method was used to schedule trickle irrigation on 3-year-old highbush blueberry plants (Vaccinium corymbosum L.) ‘Bluecrop’ planted in 140-liter barrels. Crop coefficients (K) of 1.00, 0.75, and 0.50 were used to relate Class “A” Weather Bureau pan evaporation to consumptive water use during three growth stages. No significant differences were found in yield, total berry number, average berry size, berry pH, titratable acidity, total soluble solids (TSS), TSS : acids ratio, and vegetative growth among the irrigation treatments. Significant differences in initiated flower buds were seen, but no trends were noted. An average water savings over the entire season of 57.0%, 67.7%, and 78.5% of the currently recommended irrigation rate of 3.8 liter·day−1 was observed when irrigation was scheduled using K values of 1.00, 0.75, and 0.50, respectively. A K value of 0.75 was considered to be the optimum crop coefficient for young highbush blueberries growing under Arkansas conditions.

Blueberry Red Ringspot Virus Detection in Crude Sap of Highbush Blueberry Plants

Blueberry Red Ringspot Virus Detection in Crude Sap of Highbush Blueberry Plants

Uptake, Translocation, and Metabolism of Hexazinone in Blueberry (Vacciniumsp.) and Hollow Goldenrod (Solidago fistulosa)

Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] toxicity, absorption, translocation, metabolism, and effect on photosynthesis were investigated with rooted cuttings of highbush blueberry (Vaccinium corymbosumL.), rabbiteye blueberry (V. asheiReade), and hollow goldenrod (Solidago fistulosaMiller # SOOFI). Highbush and rabbiteye blueberry plants were three times more tolerant to root applications of hexazinone than hollow goldenrod. Blueberry plants absorbed an average of 7.9% of root-applied14C-hexazinone and hollow goldenrod absorbed an average of 10.1%. An average of 6.8% of root-absorbed hexazinone (14C-label) was translocated from the roots of blueberry to stem and leaves. Radioactivity in hollow goldenrod was distributed equally between roots and shoots. The majority of radioactivity in both species was recovered as hexazinone. Root-absorbed hexazinone caused a rapid inhibition of photosynthesis in intact hollow goldenrod leaves. Root-absorbed hexazinone was capable of inhibiting photosynthesis in intact blueberry leaves; however, this occurred only when roots were exposed to high concentrations of hexazinone.

Flooding, gas exchange and hydraulic root conductivity of highbush blueberry

Highbush blueberry plants (Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO2 and O2 concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO2 levels on carbon assimilation less for flooded than unflooded plants after short‐(i‐2 days), intermediate‐(10–14 days) and long‐term (35–40 days) flooding. A reduction in O2 levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO2 fixed (mol CO2)−1. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O2, averaging 0.005 mol CO2 fixed (mol CO2)−1. Apparent quantum yield decreased from 2.2 × 10−1 mol of CO2 fixed (mol light)−1 for unflooded plants to 2.0 × 10−3 and 9.0 × 10−4 for intermediate‐ and long‐term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.

Split-root Water Application to Highbush Blueberry Plants

Abstract Watered split-root portions of 2-year-old plants of ‘Bluecrop’ blueberry (Vaccinium corymbosum L.) exhibited significantly greater shoot dry weight, shoot thickness, shoot length, mean number of shoots, and leaf dry weight than nonwatered portions. Watered portions blossomed, produced fruit, and set new flower buds while existing flower buds died and no new flower buds formed on the nonwatered portions.

Effect of soil amendments and sawdust mulching on growth, yield and leaf nutrient content of highbush blueberry plants

The effects of soil amendments (elemental S, peat, crushed pine bark or crushed pine bark plus elemental S) mixed into the planting hole, with or without a sawdust mulch over the soil surface, on the early growth and yield of highbush blueberry bushes ( Vaccinium corymbosum L., ‘Bluecrop’) grown in a mineral soil were investigated in a 3-year field study. Plant growth and yields were increased by additions of all amendments and generally followed the order: bark plus S > bark = peat = elemental S > control. The reasons for the positive growth responses probably differed among the treatments. In the control treatments, growth appeared to be limited by Mn and possibly Fe deficiency. For the S treatment, a decrease in the soil pH with a concomitant increase in levels of Mn and Fe probably stimulated the response. However, concentrations of both leaf Al and Mn were very high in the S treatment, and toxicities of these elements may have been limiting a further growth response. For the peat amendment, the growth response was probably related to both a decrease in soil pH and an improvement in soil physical conditions. For the bark amendment, the growth response is likely to have been pricipally related to improved physical conditions and also to the reasonably high Mn content of the bark itself. For the bark plus S treatment, the additional effect of reduced pH provided for an even greater response than that for bark alone. It was concluded that additions of organic matter and an acidifying agent to the planting hole can greatly increase early growth and yields of blueberries in mineral soil.

Nitrogen and Plant Spacing Effects on Growth and Fruiting of Potted Highbush Blueberry

Abstract Increasing the rate of N application and the spacing distance between potted 3-year-old highbush blueberry (Vaccinium corymbosum L.) plants ‘Earliblue’ increased fruit production and promoted early ripening. The increased N rate was associated with increased vegetative growth and berry size, whereas the increased plant spacing was associated with an increase in flower bud formation and flower number.

The effects of pH and of form and rate of applied iron on micronutrient availability and nutrient uptake by highbush blueberry plants grown in peat or soil

SummaryThe effects of pH (4.5 or 6.5), growing medium (peat or soil) and of two rates of iron as iron sulphate or iron chelate (Fe-EDTA) on the growth and leaf nutrient content of young highbush blueberries were investigated in a greenhouse study. Plant dry matter production was greater at pH 4.5 than at 6.5 in both media, although the difference was more marked in the peat. From the leaf nutrient contents it appears that at pH 4.5 growth in soil was likely to have been limited by Mn and Al toxicities whereas at pH 6.5 growth in peat was possibly limited by deficiencies of Fe and Mn. Dry matter production was unaffected by Fe treatments at pH 4.5, but at pH 6.5 the high rate of chelate addition reduced plant growth in both media. The reduced growth was associated with lowered levels of leaf Mn but levels of other nutrients were unaffected. Extractable micronutrients showed different trends with pH, depending upon the medium, the extractant used and the element being assayed. In general, EDTA did not appea...

Growth and nutrient uptake by highbush blueberry plants in a peat medium as influenced by pH, applied micronutrients and mycorrhizal inoculation

The effects of pH, micronutrient additions and mycorrhizal inoculation from two sources on the growth and leaf nutrient content of young highbush blueberry plants ( Vaccinium corybosum L. ‘Blueray’), grown in a peat medium, was investigated in a greenhouse study. Levels of extractable Fe, Mn, Zn and Cu in the peat were also measured. Dry-matter production was very much greater at pH 4.5 than at 6.5. Plants grown at the high pH had lower levels of leaf Fe, Mn and Al and higher levels of leaf Ca, K, Na and Zn, whilst levels of leaf N, P, Mg and Cu were unaffected by pH. Deficiencies of Mn and Fe and the predominance of NO 3 −-N in the rooting medium were suspected of restricting plant growth at pH 6.5. Percentage mycorrhizal infection was considerably greater at pH 4.5 than at 6.5, and greater from inoculation with Pezizella ericae than with a commercial inoculum. At pH 4.5 there was a small positive growth response to inoculation with P. ericae, but inoculation with a commercial inoculum had no effect on plant growth. For plants grown at pH 4.5, mycorrhizal infection increased levels of leaf Mn, but Mn levels in control (uninfected) plants were well above the critical level. Mycorrhizal infection had no effect on levels of leaf N, P, K, Ca, Mg, K, Na, Zn, or Cu. Levels of HCl- and EDTA-extractable Fe, Mn, Zn and Cu in the peat were increased by increasing rates of micronutrient additions at both pH values. Levels of HCl-extractable Fe, Mn and Cu were lower at pH 6.5 than at 4.5, whilst levels of EDTA-extractable Fe and Mn were higher at the high pH and levels of HCl-extractable Zn and EDTA-extractable Zn and Cu were unaffected by pH.

Effects of soil acidification on the chemical extractability of Fe, Mn, Zn and Cu and the growth and micronutrient uptake of highbush blueberry plants

The effects of soil acidification and micronutrient addition on levels of extractable Fe, Mn, Zn and Cu in a soil, and on the growth and micronutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L. cv. Blueray) was investigated in a greenhouse study.

Effects of liming on the extractability of Fe, Mn, Zn and Cu from a peat medium and the growth and micronutrient uptake of highbush blueberry plants

Levels of extractable micronutrients in a peat and the growth and nutrient uptake of young highbush blueberry plants (Vaccinium corymbosum L cv. Blueray) were studied in a greenhouse experiment in response to liming and two rates of addition of Fe, Mn, Zn and Cu. Levels of extractable micronutrients showed different trends with liming depending upon the extractant used and the element being considered. Levels of 0.05M CaCl2-extractable Fe, Mn and Zn decreased as the pH was raised whilst those of Cu first decreased and then increased again. There was a general decline in 0.1M HCl-extractable Fe, Mn and Cu with increasing pH but levels of Zn were not greatly affected. Levels of 0.005M DTPA extractable Fe, Mn Zn and Cu generally declined but those extractable with 0.04M EDTA were either unaffected or increased as the pH was raised. Levels of CaCl2-extractable Mn and Zn were the same order of magnitude as those extractable with HCl, DTPA and EDTA. In contrast, the latter reagents extracted considerably more Fe and Cu than did CaCl2. Dry matter yields of plants were increased as the pH was raised from 3.9 to 4.3 but then decreased markedly as the pH was raised further to 6.7. With increasing pH, concentrations of plant Fe generally increased those of Mn were decreased and those of Zn and Cu were not greatly affected except for a marked decline in plant Cu at pH 6.7.

Split-root Fertilizer Application to Highbush Blueberry Plants

Abstract Fertilized portions of 1-year-old plants of ‘Berkeley’ blueberry (Vaccinium corymbosum L.) displayed significantly greater shoot dry weight, shoot thickness, leaf dry weight, and mean number of shoots than unfertilized portions. Fertilized portions blossomed and produced fruit while flower buds on the unfertilized portions died.

Yield component analysis of winter damage and flower buds in highbush blueberry

Potential components of winter damage and flower buds to cane tips of mowed high-bush blueberry plants ( Vaccinium corymbosum) were analysed using multiple regression analysis. Thick, highly-branched canes were most conducive to high yields of flower buds and low incidence of winter injury. Winter damage may have influenced the yield of flower buds.