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  • Author or Editor: J. G. Rodriguez x
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Recently observed hybrid populations of peach [Prunus persica (L.) Batsch] provide evidence for the presence of a single gene suppressing red skin color. The fruit of seedling populations of FL90-48C and FL90-37C × FL84-18C, FL90-50CN × FL92-2C, FL90-48C × FL91-12, FL91-8 × FL88-6, and open-pollinated or selfed populations from unselected seedlings of `Contender' × PI65977 (`Giallo di Padova') and `Mexico Selection' × `Oro A' were rated for normal quantitative vs. no anthocyanin skin color at maturity. At this stage of development, anthocyaninless phenotypes displayed no red color over the entire surface of the fruit. Instead they were characterized by a bright yellow ground color that stood out visually in the seedling rows, and which was dubbed highlighter. The two crosses with FL84-18C yielded populations that approximated a 1:1 segregation ratio for quantitative red:no red skin color. All other crosses produced populations that closely approximated a 3:1 segregation ratio for quantitative red to no red. These data are consistent with the hypothesis that the highlighter phenotype is a single gene recessive trait. We propose the gene symbols of h and H for the recessive no red (highlighter) and dominant normal quantitative red (wild-type) alleles, respectively.

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Abstract

Backcrosses and outcrosses of mite resistant strawberry selections and combinations of resistant selfed lines were made. Backcrosses to the resistant parents resulted in intermediate progeny means but they were closer to that of the less resistant parent. Backcrosses to the susceptible parent also resulted in intermediate progeny means but they were close to that of the more resistant parent. Outcrosses gave progenies similar to those of backcrosses but with less spread in resistance. Crosses of certain resistant selfed selections showed almost complete dominance for mite resistance.

Open Access

The influence of long and short daylengths on twospotted spider mite (TSSM) (Tetranychus urticae Koch) resistance of strawberry (Fragaria ×ananassa Duch.) foliage was studied. Photoperiods of 8 hours (short daylength) and continuous light (long daylength) altered the seasonal change in susceptibility of `Redchief' strawberry foliage to TSSM. Plants exposed to continuous light rapidly became resistant, those exposed to short daylength remained relatively susceptible, and plants under natural daylength exhibited the seasonal change of slowly increasing resistance. Plants resistant to TSSM under long daylength became susceptible 19 days after being switched to a short daylength. Plants that were switched from short to long daylength changed from TSSM susceptible to resistant. Field-grown plants of `Redchief', a short-day sensitive cultivar, and `Tribute', a day-neutral cultivar, exhibited increasing resistance to TSSM from 2 weeks before bloom until 2 weeks into harvest when greatest resistance was observed. These results suggest that TSSM resistance in strawberry is influenced by daylength and that this effect may be independent of daylength effects on strawberry reproductive development.

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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.

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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.

Open Access

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.

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