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M.B. Fiely and T.E. Morelock

Spinach (Spinacia oleracea L.) varies in tolerance to saturated soil conditions. Plant vigor was assessed for plants flooded in autoclaved and nonautoclaved field soil. Decline of vigor was more rapid for plants flooded in nonautoclaved field soil, indicating that flooding tolerance may be influenced by soil borne pathogens.

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M.B. Fiely and T.E. Morelock

Spinach (Spinacia oleracea L.) varies in tolerance to saturated soil conditions. Plant vigor was assessed for plants flooded in autoclaved and nonautoclaved field soil. Decline of vigor was more rapid for plants flooded in nonautoclaved field soil, indicating that flooding tolerance may be influenced by soil borne pathogens.

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C.H. Becker and T.E. Morelock

Southernpea (Vigna unguiculata) is a popular home garden, fresh-market, and processing vegetable in the southeastern United States. Processing schedules are normally controlled by planting the same variety at different dates. Difference in genetic maturity would allow growers to stagger harvest dates by planting different maturity peas on the same day and allow genotype to alter harvest dates. This procedure would allow growers to better utilize available soil moisture and optimum planting dates. Ten southernpea varieties and breeding lines representing early, medium, and late maturity were planted in Kibler, Ark., during the summers of 1994 and 1995. Five different planting dates were used. Flowering dates and days to maturity were recorded and plots were harvested for yield. Results indicate that relative days to maturity can be significantly shortened or lengthened by the time of planting. Varieties planted in early June or early August took longer to mature then when they were planted in late June or early July.

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T.E. Morelock, P.W. Simon and C.E. Peterson

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T.E. Morelock, J.C. Correll and L.P. Brandenberger

Downy mildew (Blue mold) is probably the most common spinach disease in most parts of the world, and it can be a problem in the mid-South. Frequently, other diseases such as white rust and fusarium cause major crop loss. The Arkansas breeding program was initiated 25 years ago to address white rust and fusarium, as well as other diseases that destroy spinach crops. Since single gene resistance is not available for most spinach diseases, it was necessary to utilize polygenic resistance to develop varieties that are resistant to most of the common spinach diseases that occur in the Arkansas River Valley of Arkansas and Oklahoma. Highly resistant genotypes have been developed by using disease nurseries and field screening, so frequent selections are made based on the reaction to 3-4 diseases.

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L.P. Brandenberger, T.E. Morelock and J.C. Correll

Spinach germplasm (707 accessions) from collections from six countries were screened for resistance to race 4 of the downy mildew pathogen Peronospora farinosa f. sp. spinaciae; these collections contained germplasm that originated from 41 countries. The predominant species examined was Spinacia oleracea L., however, eight accessions of S. turkestanica Iljin and two accessions of S. tetrandra Stev. were also tested. About 40 seedlings of each accession were inoculated. The cultivar St. Helens was included as a susceptible control in each test. The majority of accessions tested (>98%) were susceptible to race 4. Nine accessions exhibited some resistance to race 4 (9% to 38% of the seedlings within an accession were resistant), and two accessions, CGNO 9546 and SPI 82/87, exhibited a high level of resistance (60% and 80% resistant, respectively). Resistance identified in several of the accessions in this study may be useful for breeding for race 4 resistance.

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J. M. Al-Khayri, F. H. Huang and T. E. Morelock

Regenerated spinach (Spinacia oleracea L.) maintained under a 10-h photoperiod (65 uE m-2 s-1) after an incubation period on a GA-containing medium were induced to flower in vitro. The plantlets were regenerated from callus initiated on MS medium with 2.0 mg L-1 kinetin and 0.5 mg L-1 2,4-D and were subsequently transferred to a medium containing 2.0 mg L-1 kinetin, 1.0 mg L-1 GA, and 0.01 mg L-1 2-4,D. While on the regeneration medium, the cultures were exposed to a long-day photoperiod. Regenerants were transferred to an IBA-containing medium for rooting, after which flowering was observed. In vitro flowering plantlets exhibited male and female flowers depending on the sex of the explant donor. Female plantlets developed seeds in the culture vessels. This method of seed production from regenerants can eliminate time-consuming steps in acclimation, transplanting to soil, and plant maintenance.

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L.P. Brandenberger, T.E. Morelock and J.C. Correll

Field observations indicate that polygenic resistance to downy mildew (Peronospora farinosa f. sp. spinaciae) was observed during the course of a breeding program to develop polygenic resistance to white rust (Albugo occidentalis). Field studies were initiated using five cultivars and one breeding line to quantify the level of resistance to downy mildew and white rust. Separate plots were inoculated with each pathogen at a specific spore concentration and then subjected to a minimum dew period of 12h. Infection was quantified by measuring latent period, lesion number, lesion size, sporulation and percent leaf area infected.

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L.P. Brandenberger, T.E. Morelock and J.C. Correll

Field observations indicate that polygenic resistance to downy mildew (Peronospora farinosa f. sp. spinaciae) was observed during the course of a breeding program to develop polygenic resistance to white rust (Albugo occidentalis). Field studies were initiated using five cultivars and one breeding line to quantify the level of resistance to downy mildew and white rust. Separate plots were inoculated with each pathogen at a specific spore concentration and then subjected to a minimum dew period of 12h. Infection was quantified by measuring latent period, lesion number, lesion size, sporulation and percent leaf area infected.

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T.E. Morelock, D.R. Motes and A.R. Gonzalez

Southernpea (cowpea), Vigna ungiculata L. Walp, is an important processing and fresh-market vegetable in the southern United States. While many of the newer varieties are early maturing, there is still a need for late-maturing, high-yielding varieties. Arkansas 92-552 fills this niche. It is a bush plant that produces silver pods in the upper portion of large plants that are free of basal runners. The seed are medium size with a bright pink eye. Maturity is 5 to 7 days later than `Coronet' under Arkansas conditions. The variety processes well and canned peas have been rated equal to `Coronet' by consumers panels. The yield potential is high and it has produced higher yield than `Coronet' in replicated trials in Arkansas. 92-552 is also resistant to rootknot nematode.