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Sixty accessions/genotypes (entries) of diploid Fragaria sp. were tested for susceptibility to Phytophthora cactorum in greenhouse tests. Four experiments, each with four to 35 entries, were conducted, and each entry was represented by 36 to 45 plants per experiment. The plants were graded according to the number of weeks of survival during the first 4 weeks and for plants surviving more than the first 4 weeks, scoring was based on amount of necrosis in the crown. Statistical analysis showed no significant difference among the four experiments. A majority of the accessions (48) were categorized as being resistant or moderately resistant to Phytophthora cactorum. The disease score for this group varied from 1.06 to 3.09. Five accessions with disease scores ranging from 6.25 to 7.43 were considered highly susceptible. Within F. vesca, a highly significant proportion of the total variation in disease scores (57.6%) was attributable to the differences between accessions and, hence, of genetic nature. There was no indication of any Fragaria species being more resistant or susceptible than others and no systematic differences resulting from geographic origin.
Garlic (cv California Late) was produced under four irrigation regimes (110% and 130% evapotranspiration with two water cut-off dates, 10 and 24 May 1999) in combination with three nitrogen fertilization levels (100, 250, and 400 lb total N). Bulbs were manually harvested mid-June, cured 3 weeks shaded at ambient temperatures and the outer whorl of cloves manually peeled. Samples were freeze-dried, and carbohydrate (fructan and free sugars) and alliin (substrate for alliinase activity and indicator of potential pungency) concentrations were determined by HPLC. The percent dry weight was not affected by the irrigation treatment, but was reduced with increased N rate (41.3% to 39.0%). Alliin concentrations varied from 8.3 to 13.8 mg/g DW for 110% and 130% Eto irrigation treatments. Alliin concentrations were not affected by N fertilization (average = 11.5 mg/g DW). Fructan concentrations were affected by N fertilization treatment, with the highest content (802 mg/g DW) associated with the lowest N level, and the lowest (717 mg/g DW) content in samples from the highest N rate. Sucrose concentrations increased with increased N, but glucose and fructose concentrations did not vary with N fertilization. Fructan as percent of total carbohydrate remained constant across irrigation treatments (96.6% + 0.2%) and across N fertilization treatments (96.6% + 0.3%).
Abstract
Preharvest application of (2-chloroethyl)phosphonic acid (ethephon) to muskmelon (Cucumis melo L., Reticulatus group) significantly reduced the soluble solids content and the sucrose concentration of fruits harvested at the full-slip stage. Texture and flavor ratings were also reduced. During 5 days at 20°C, the flesh of fruits from treated plants softened more rapidly and was more aromatic than the fruits from untreated plants.
Abstract
Extracts from freshly harvested tubers of potato (Solanum tuberosum L.) held at different temperatures and extracts taken from stored tubers were examined by starch gel electrophoresis. Storage of tubers at 10°C for up to 70 days or storage of extracts at −60° for 70 days did not affect isozyme banding patterns. Storage of fresh extracts for 14 days at 5° produced blurring of alkaline phosphatase (AKP) bands, altered isozyme mobility of malic enzyme, and added a band to glucosephosphateisomerase (GPI) zymograms. It did not affect the mobility or resolution of 6-phosphogluconate dehydrogenase. Addition of 0.1 m mercaptoethanol did not restore original resolutions or mobilities.
A participatory, on-farm research and extension program has been established around 16 demonstration comparisons of biologically integrated soil building–pest management systems and conventionally managed systems within the West Side row crop area of California's San Joaquin Valley. In each of the biologically integrated parcels, cover crops and composted organic materials are integrated into rotations wherever appropriate, whereas in the conventionally managed parcels, mineral fertilizer applications are made. Pest management practices are evaluated and biologically and informationally intensive alternatives are developed through a participatory process. Indices of soil quality including nutrient status, water stable aggregates, organic matter content, and phospholipid fatty acids are routinely monitored. Information related to the objectives, structure and monitoring activities of this project during the establishment phase will be discussed.
Abstract
A table is presented from which the percentage distribution of a crop into various maturity classes can be estimated for an optimizing or non-optimizing harvest day. Two or three characteristics of the crop must be known or guessed for predictive or speculative purposes. The use of the table throws light on the type of information which must be at hand in order to work intelligently toward a once-over harvest in those perishable crops which at present are not well adapted for it.
In Fall 1995, 12 row crop farmers in conjunction with Univ. of California, NRCS and private agency advisors established the West Side On-Farm Demonstration Project to conduct demonstrations of soil and pest management options aimed at sustained profitability and environmental stewardship in the western San Joaquin Valley of California. Monitoring of soil physical, chemical, and biological properties is done in side-by-side on-farm comparisons of plots amended with organic inputs and unamended plots. Intensive monitoring of beneficial and pest insects is carried out within each comparison block, and the data generated is used to guide pest management decision-making at each site. Yields and soil characteristics of the amended plots did not differ from those of unamended plots after the first year. The on-farm context and the cooperative farmer–scientist interactions of this project facilitate the development of timely and relevant research directions to be pursued beyond the core set of monitoring activities.