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- Author or Editor: J. Rodriguez-A. x
Twenty-six clones of pepino (Solanum muricatum Aiton) were evaluated for yield, fruit weight, fruit shape (length to width ratio), soluble solids concentration (SSC), titratable acidity (TA), and ascorbic acid concentration (AAC) over two growing seasons: autumn-winter (AW) and spring-summer (SS). Significant differences were found for the effects of clone, season, and clon× season interaction for all traits, except in the case of season for fruit shape. Mean values for yield, SSC, and AAC were higher in the AW than in the SS season, while mean fruit weight and TA were lower. Many clones (13 in AW and six in SS) had a yield higher than 30 t·ha-1. Substantial genotypic variation was found for all traits studied except for SSC. Clones stable for all traits were detected over both seasons, except for SSC, where the differences between seasons were very high. The significant clone × season interaction for all traits indicates that selection of genotypes adapted specifically to either AW or SS seasons would maximize the response to selection. Broad sense heritabilities were highest for fruit shape and yield (>0.70), while SSC had the lowest values (0.39 in AW, 0.17 in SS, and almost 0 when considering both seasons combined). For the AW season, significant fruit weight-SSC and fruit weight-AAC genotypic correlations were detected; for the SS season the significant genotypic correlations were yield-SSC, fruit weight-TA, fruit shape-TA, and SSC-TA. Results suggest there are ample opportunities for improving several traits in this crop using intraspecific variation for adaptation to specific environments.
The beneficial effects of early mycorrhizal inoculation with two arbuscular fungi, Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe and Glomus intraradices Schenck and Smith, were evaluated on Myrobalan 29 C (Prunus cerasifera × Prunus munsoniana Wight and Edr.) plum rootstock in soil infested or noninfested with the root lesion nematode Pratylenchus vulnus Allen and Jensen under microplot conditions. During this two year study, mycorrhizal colonization did not affect the number of nematodes per gram of root in plants infected with P. vulnus. In contrast, P. vulnus significantly decreased the percentage of mycorrhizal root colonization. Most elements were within sufficiency levels for plum by foliar analysis, although low P and deficient Fe and Cu levels were detected in P. vulnus treatments. Early mycorrhizal inoculation with G. mosseae favored plant growth after 20 months, but in soils infested by P. vulnus, only G. intraradices increased the tolerance of Myrobalan 29 C plum rootstock to damaging nematode levels by stimulating plant nutrition and vegetative growth.
Low-cost, sustainable wastewater treatment systems are needed for rapidly-growing communities of the southwestern United States. The objective of this study is to develop a practical management plan for land application of industrial wastewater on native Chihuahuan Desert vegetation. To assess environmental impact and create the management plan, wastewater effluent characteristics, soil physicochemical changes, and mineral uptake of the vegetation were monitored. The effluent was saline, ranging from 2500 to 6000 mg·L-1 of TDS and dominated by Na and Cl. Total N ranged from 10 to 40 mg·L-1. Soils sampled in Dec. 2002 (after 11 months and 64 cm of effluent irrigation) increased in salinity in the top 60 cm from 1.85 to 3.5 dS·m-1, and SAR in the top 30 cm was close to 15, but diminished with depth. Branch samples of the co-dominant perennial shrub vegetation members (Larrea tridentata and Prosopis glandulosa) harvested in July 2002 had elevated Na and Cl concentrations (0.4% to 2.1% of dry weight, respectively). By Oct. 2002, L. tridentata leaves contained comparable Na and Cl concentrations as those of P. glandulosa, yet removed 2 to three times more Na, Cl, and total N per branch, while maintaining their dry mass per branch. This raises the possibility of interspecific variation among the shrub species in salinity stress tolerance and capacity to remove wastewater contaminants. These data will aid in determining total vegetation removal of effluent components, preventing adverse environmental impact to the site, and developing a practical management plan suitable for small communities seeking cost-effective wastewater handling protocols.
Abstract
Five clones of strawberries varying in degree of resistance to the two-spotted spider mite, Tetranychus urticae Koch, were grown at four nutrient levels. Foliage samples were analyzed for minerals, amino acids, total sugar and total starch. The plants were infested with this mite and were rated for injury. Nitrogen of clones and treatments showed significant correlation with mite injury at the 0.05 and 0.01 levels respectively. Phosphorus of clones was significantly correlated with mite injury. Mite injury and treatments, but not clones, were significantly correlated when the amino acids classified as non-essential to Tetranychus urticae were considered. Total starch and total sugar of treatments had significant negative correlations with mite damage.
The application of plastic mulches, row cover or a combination of the two were evaluated from 1987 to 1991 for reducing early blight of tomatoes and Alternaria leaf spot of okra. Early blight on early season tomatoes (TU-80-130, New Yorker and Floradade) was significantly reduced by the application of black plastic mulch (BM) or BM plus spunbonded polyester row cover (RC) compared to bare soil. Early blight evaluation of late season tomato (Better Boy) showed that BM significantly reduced the incidence and number of lesions per leaf on the fruit clusters compared to bare soil, but the spunbonded polyester RC treatment didn't improve disease reduction of the BM. Alternaria 14 spot of Clemson Spineless okra in 1989 was severe on plant grown in bare soil compared to those grown on BM, BM plus VisPore row cover, clear plastic mulch (CM) and CM plus VisPore RC treatments. These soldier indicted that the application of agriplastic techniques could be used as a new crop management option in an IPM program to reduce the application of foliar fungicides or application of biological control agents.
The evergreen (EVG) peach, first described in Mexico, was used as a parent with deciduous (DE) peaches to develop F1 and F2 hybrid populations in Mexico, Florida, Georgia, and West Virginia. F1 trees were DE and F2 plants segregated 3 DE: 1 EVG. In West Virginia, the most temperate location, the heterozygous class could be distinguished in the first few years of growth by late leaf abscission in the fall. Segregation ratios suggest that the EVG trait is controlled by a single gene, evg, the EVG state being homozygous recessive. Evergreen trees were characterized by insensitivity of shoot tips to daylength and failure of terminal growth to cease growth until killed by low temperature. Lateral buds of EVG trees went dormant in the fall. Deep supercooling occurred in both EVG and DE trees, but it appeared later in EVG trees, was of shorter duration, and occurred to a lesser extent. Evergreen germplasm may be useful in developing peach cultivars for frost-free subtropic and tropical areas. It also presents a useful system for studying dormancy and cold hardiness.
Combinations of solarized soil (SBS), bare soil control (BS), black plastic mulched soil (BM), row cover (RC), fungicide (chlorothalonil) and biological treatments (Bacillus cereus) were evaluated. SBS vs. BS treatments were main plots, mulch and row covers splitplots and foliage treatments split-splitplots. Application of either foliar treatment was superior to BS. Using a 1/2 rate of fungicide on plants from solarized soil treatments showed equal or comparable reduction of the disease when compared to tomatoes grown in BS with high rates of the fungicide. Combined treatments of solarized + BM, BM with or without RC and low rate of fungicide or biological agent, were the most effective when compared to BS + fungicide, indicating that integration of plasticulture and biological strategies can reduce early blight below the levels of commercial fungicide applied to tomatoes grown on BS.
The yellow passionfruit (Passiflora edulis f flavicarpa Degener), a perennial vine grown in the tropics and subtropics, was successfully grown as an annual crop in a temperate zone. Fruit maturity was hastened by ethephon treatments to allow harvest before the mean date of the first killing frost. Maturity was advanced in a linear manner with application rates of 150, 300, and 600 ppm ethephon. Total yield was not affected by ethephon treatment; however, cull fruit producing no juice increased with increasing rates of ethephon, thereby reducing marketable yields. Soluble solids and ascorbic acid contents of the juice were not affected by ethephon treatment. Purple passionfruit (Passiflora edulis Sims) did not produce blossoms.