Several concentrations of mefluidide (Embark), a plant growth regulator; sethoxydim (Poast), a grass herbicide; and triclopyr (Rely) a nonselective herbicide, were evaluated to determine if italian ryegrass (Lolium multiflorum Lam.) growth could be suppressed. Ryegrass grows prolifically during the winter in states adjacent to the Gulf of Mexico and may serve as a living mulch for strawberry (Fragaria×ananassa Duch.) and other winter crops if its growth can be controlled. Different chemicals and concentrations were screened over 5 years for their efficacy to produce living mulch. Mefluidide produced good ryegrass control but was not evaluated after Study 1 because it is designed for industrial use and does not have an U.S. Environmental Protection Agency fruit crop label. Triclopyr, which has a label for several fruit crops, was studied only in the final year and it provided desired ryegrass control at the 0.016 and 0.030 mL·L-1 (parts per thousand) rate. Prime oil (paraffin base petroleum oil + polyol fatty acid esters) concentration affected results when sprayed with various sethoxydim rates. We concluded that 0.156 mL·L-1 sethoxydim plus 0.25 mL·L-1 prime oil will control ryegrass growth at the desired level (reduce growth by 40% to 50%) for living mulch. These rates are too low to cause much ryegrass browning. Chemical names used: N-[2,4dimethyl-5-[[(trifluoromethyl)-sulfony]amino]phenyl]acetamide, 2-[1-(ethoxylmino)buty1]-5-[2-(ethylthio)propy1]-3-hydroxy-2-cyclohexen-1-one), and ammonium-Dl-homoalanin-4-yl-(methyl) phosphinate.
A muscadine vineyard planted at McNeil, Miss., in 1990 included 23 cultivars and a planting in 1992 included nine cultivars. Each entry was evaluated for eight useful traits over 4 years. The regressions of certain traits on others were performed to determine relationships that might be useful in selecting for valuable traits such as phyto-chemicals in seed. Ranges among cultivars for the traits were: harvest date—20 days, yield—33 kg per vine, berry weight—11.2 g, percent dry scar—38, °Brix—5, pH—0.5, seed per berry—1.2 and seed weight—5.5 g. The best relationship was between berry weight and seed weight.
Annual ryegrass (Lolium multiflorum), which grows prolifically during the strawberry production season in the Gulf South, has the potential to serve as a living mulch if its growth is controlled. Sublethal dosages of Embark, a plant growth regulator, and the herbicides Poast and Rely were determined on ryegrass. Growth retardation was rated from 0 = none to 6 = dead. In 1993, all Poast dosages (1/8X – 1X, where X = 8 ml·L–1) were lethal. Embark regulated ryegrass growth, but its study was discontinued because of the unlikelihood that it could be labeled for use on strawberries. Results of the 1994 study suggested that prime oil in the spray may cause an inordinate amount of vegetative browning. In 1995, three levels of oil (1/256X, 1/64X, and 1/32X, where X = 8 ml·L–1) were used with each of four levels of Poast (0, 1/32, 1/64, and 1/128X). Increased levels of oil generally caused increased browning at each level of Poast, but no browning occurred where oil only was applied in the spray. In contrast to results in 1995, oil at 1/32X with no Poast caused considerable browning (score = 3.25) in 1996. The most desirable control (score = 2.75) was accomplished by a spray containing 1/128X Poast and 1/64X oil. The most desirable control by Rely (score = 3.25) was accomplished by 1/64 and 1/32X sprays. Rely is not labeled for strawberries although it is labeled for other fruit crops. Chemical names used: 2-[1-(ethoxylmino)buty1]-5-[2-(ethylthio)propy1]-3-hydroxy-2-cyclohexen-1-one (Poast); Paraffin Base Petroleum Oil + polyol Fatty acid Esters (Prime oil); N-[2,4dimethyl-5-[[(trifluoromethyl)-sulfony]amino]phenyl] acetamide (Embark); ammonium-Dl-homoalanin-4-yl-(methyl) phosphinate (Rely).
J.B. Magee and C.L. Gupton
The organic acid composition of blueberries of three highbush (Vaccinium corymbosum) cultivars, three rabbiteye (V. ashei cultivars and nine southern highbush (V. corymbosun hybrids) cultivars or selections was determined by HPLC. Species means off the individual acids (citric, malic, succinic, and quinic), expressed as a percentage of total acid, formed profiles or patterns that are thought to be characteristic of the species. Citric (75%) was the predominant acid in highbush fruit with lesser percentages of succinic (13%), quinic (9.6%), and malic (2.7%). The percent composition of rabbiteye berries [quinic (49%), succinic (39%), citric (6.7%), malic (5%)] was distinctly different from highbush. The acid profile of southern highbush fruit reflected their V. corymbosum heritage with an acid profile similar to that of highbush. When related to a clone's pedigree, these results suggest that organic acid profiles may be a useful screening tool for studying the contribution of southeastern native species such as V. darrowi or V. ashei to the inheritance of organic acids.
C.L. Gupton and J.M. Spiers
To determine if high Zn concentrations contribute to chlorosis in blueberry, plants of rabbiteye `Climax' and southern highbush `Bladen' were fertilized in sand culture with 30, 60, 90, and 120 ppm Zn solutions at 4, 4.5, 5, 5.5, 6, and 6.5 pH. Only Zn levels significantly affected the degree of chlorosis in plant leaves. No interaction among cultivars, pH, or Zn concentration was significant. The linear response to Zn levels was significant (P = 0.0001), but quadratic and cubic responses were not significant. Cultivars and Zn fertilization levels affected Zn and Mn accumulation; however, no difference in chlorosis rating was observed between cultivars. An inverse relationship existed between Zn fertilization levels and leaf Mn content so that the total concentration of the two minerals was about the same for each fertilization level, suggesting that Mn toxicity would not be expected at high levels of Zn fertilization. We concluded that high levels of Zn may induce chlorosis in rabbiteye and southern highbush blueberry.
S.L. Noffsinger, A.D. Draper and C.L. Gupton
Although southern highbush (Vaccinium sp.) is replacing rabbiteye (Vaccinium ashei L.) blueberry, rabbiteye will continue to be grown on marginal soils of the southeastern United States. Dwarfism or short, compact growth habit is a trait that could be used to reduce labor costs in rabbiteye blueberry production. Parental backgrounds, and flowering and fruit traits were studied in seven Mississippi (MS) and five Georgia (T) selections. Six of the MS selections are available for propagation and bloom late enough that cold damage should not be a problem. Four (MS63, MS454, MS546, MS891) of the six have acceptable fruit quality and will be used in breeding. Ethel and MS134 were the only known dwarf ancestors, with Ethel, Myers, Black Giant, and Tifblue (Ethel × Clara) dominating the parental background. Based on the variation in growth habit and ancestries, it would appear that Ethel has several genes for dwarfism and multiple allelic interactions are involved, similar to what Garvey and Lyrene found (1987). Future breeding will include crosses of MS63, MS454, MS546, and MS891 with germplasm outside of the common ancestors, to broaden the genetic base of the dwarf rabbiteyes.
G.J. Galletta, B.J. Smith and C.L. Gupton
C. L. Gupton, J. M. Spiers and A. D. Draper
Eight clones with various Vaccinium species in their background were evaluated to determine their potential for improving fruit characteristics in the southern highbush blueberry. One clone was crossed with each of the others to produce seven sets of progenies which were evaluated with the parent clones. Heritability estimates were computed as the regression of progeny on parental means for each character. The progenies ranged from small to average berry size and weight, were above average for picking scar, and were generally less than average for color, firmness, and flavor. Mean of progenies was not significantly different from the parental mean for any character. Very high (0.45-0.85) heritability estimates were found for each character except berry firmness (0.22). These results suggest that considerable improvement in each character except possibly berry firmness should result from phenotypic recurrent selection in a broad based population involving these parents.