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J. Creighton Miller Jr. and Douglas C. Scheuring

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Tyann Blessington, Douglas C. Scheuring and J. Creighton Miller Jr.

Potatoes are stored to ensure a continuous supply; however, losses due to shrinkage and sprouting can be large. It is believed that ionizing irradiation will become more prominent for sprout inhibition due to the increasingly higher operating costs of low-temperature storage and possible phase-out of chemical sprout inhibitors. The effects of storage and ionizing irradiation (gamma and electron beam) on antioxidant activity (AOA), phenolic content, and carotenoid content were analyzed using the potato cultivar Atlantic. Tubers were subjected to 0, 75, and 200 Gy γ-irradiation doses, stored at 20 °C, and analyzed after 0, 10, 20, 75, and 110 days. Tubers from another harvest were subjected to a surface dose of 0 or 200 Gy e-beam irradiation, stored at 20 °C, and analyzed after 0, 10, 20, 75, and 110 days. AOA was measured via the DPPH method; phenolic content via the Folin-Ciocalteau method and individual phenolics via HPLC; and carotenoid content via absorbance at 445 nm and individual carotenoids via HPLC. During early storage, higher doses resulted in higher AOA, while, during longer storage, lower doses produced greater AOA. Phenolic content increased in storage during the γ-irradiation study, but decreased in the e-beam study, partly due to increases in chlorogenic acid in the former and decreases in caffeic acid in the latter. The e-beam dose of 200 Gy resulted in significantly greater total phenolics than 0 Gy. Total carotenoids and lutein decreased with storage, but were not affected by irradiation. Storage exerted a much greater influence on AOA, phenolic content, and carotenoid content than either irradiation treatment.

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M.N. Nzaramba, Douglas C. Scheuring and J. Creighton Miller Jr.

Antioxidants are important to human health, as they are responsible for reduced risk of diseases such as cancer, hence motivating researchers to examine crop plants for available antioxidant compounds. There is also increasing interest in the use of antioxidants from plants instead of synthetic products. In order to evaluate variability of antioxidant activity (AOA) in cowpea, 697 cowpea accessions from the U.S. Cowpea Core Collection obtained from the Regional Plant Introduction Station, Griffin, Ga., were analyzed for AOA expressed as μg trolox equivalents/gdw. Two grams of dry seed from each accession were ground, extracted in methanol and analyzed for AOA using the free radical, 2,2-Diphenyl-1-picrylhydrazyl (DPPH), method. A large variation in AOA within the core collection, ranging from 1859 μg·g–1 dw (PI 180355, pigmented seed coat) to 42.6 μg·g–1 dw (PI 583100, cream seed coat), was observed. A least significant difference of 131.5 (p =0.05) was obtained. Higher AOA was manifested by accessions with pigmented seed coats. Accessions that were speckled, striped or had a pigmented eye were moderate in AOA, while the cream types were generally low. Variability in AOA observed among cowpea accessions suggests that breeding for high AOA can be successfully conducted. Accessions with high AOA could also be used to extract antioxidants for industrial purposes. Some accessions were a mixture of various colors and patterns, making it difficult to classify them into a particular category. Therefore, there is need to ensure purity of these accessions by ascertaining whether the mixtures are physical, i.e., combination of different varieties, or are composed of segregating material.

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Armando Campos Cruz, Douglas C. Scheuring and J. Creighton Miller Jr.

The effect of Biozyme™, a commercial germination stimulant, on emergence of bean and sweet corn seeds, treated with four levels of Carbofuran and Chlorothalonil, and grown under suboptimal field temperatures, was evaluated. Half the seeds from each treatment were treated with Biozyme™ Two planting dates were selected to provide suboptimal temperatures during emergence. Pesticide overdoses caused significant detrimental effects to all emerging seedlings. These effects were magnified under the low temperatures of the first planting. Biozyme™ treatment significantly improved emergence rate, percent emergence, final stand and number of ears of sweet corn in the first planting, and the percent emergence final stand, plant dry weight, and number of ears in the second planting. In beans, however, Biozyme™ treatment significantly reduced emergence rate, percent emergence. and final stand in the first planting, while significantly increasing percent emergence, plant dry weight, and seed dry weight in the second planting. The beneficial effects of Biozyme™ appeared to be independent of the negative effects of pesticide overdoses.

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Douglas C. Scheuring, J. Creighton Miller Jr. and David W. Walker

Two cowpea cultivars, Pinkeye Purple Hull and Royal Blackeye, were evaluated for their ability to produce a ratoon crop. Dry weight and pod yield were measured following harvest from two different cutting heights (second and fourth node), and stages of pod maturity (green and dry). The cultivar Royal Blackeye produced more green manure or returned biomass following ratooning than did Pinkeye Purple Hull. Cutting height and sampling at different pod maturities influenced ratooning potential. These results suggest that cowpea ratooning appears to be economically feasible and that further screening of cowpea cultivars for ratooning ability is warranted.

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Tyann Blessington*, Anna L. Hale, Douglas C. Scheuring and J. Creighton Miller Jr.

We have demonstrated that potatoes contain significant levels of antioxidants important to human health; however, since potatoes are not consumed raw, it is important to determine the effects of cooking/processing on these levels. Therefore, the changes in phenolic and carotenoid content and total antioxidant activity in potatoes were investigated using combinations of storage and cooking methods. Fresh and stored tubers (110 days at 4 °C) of 17 potato cultivars, both raw and cooked (microwaved, boiled, baked, fried), were analyzed for antioxidant activity using the DPPH method. In addition, carotenoid levels were determined for each treatment based on the absorbance of the methanol extraction (oxygenated phenolics and carotenoids) at 445 nm and the hexane extraction (non-oxygenated carotenoids) at 450 nm. Total antioxidant activity as well as carotenoid levels were significantly affected by both genotype and cooking method. Across extraction methods, the microwave and fry cooking treatments were generally highest in antioxidant activity, while boiling was the lowest. Oxygenated carotenoids were significantly affected by storage, while the non-oxygenated carotenoids were unaffected.

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Lavanya Reddivari*, Anna L. Hale, Douglas C. Scheuring and J. Creighton Miller Jr.

In recent years, much emphasis has been placed on functional/antioxidant properties of various fruits and vegetables and their contribution to human health. Since average per capita consumption of potatoes in the United States is about 137 pounds, even moderate levels of antioxidants could be viewed as an important human health benefit. Variation in antioxidant activity has not been extensively investigated for colored potatoes (specialty selections). Therefore, the objective of this study was to evaluate antioxidant activity of specialty selections from the Texas Potato Variety Development Program and identify elite lines to use in breeding for improvement of this trait. Potato tubers were also assessed for their outer appearance, skin color, flesh color, spoilage and yield characteristics. Specialty potato selections (320 lines) were screened for total antioxidant activity using the 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay. After an initial screening, the top 10 % of selections were reevaluated in the following year. Significant (P ≤ 0.01) differences were found among selections and, for some selections, differences were found between seasons. Total antioxidant activity ranged from 27 μg/gfw to 832 μg/gfw. The specialty selection CO112F2-2 (purple flesh) had the highest antioxidant activity (832 μg/gfw) irrespective of season. In most cases, purple flesh selections produced the highest antioxidant activity, probably due to the presence of anthocyanins, followed by yellow selections.

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H.M. Cortinas-Escobar, Douglas C. Scheuring, Thomas J. Gerik and J. Creighton Miller Jr.

Dry bean (Phaseolus vulgaris L.) cultivars differ in their response to iron deficiency when grown on calcareous soils. This response is influenced by environmental factors such as soil pH, soil texture, presence of bicarbonates, organic matter, and temperature. The objective of this study was to investigate the genetic basis for resistance to iron deficiency in beans. Crosses between nine resistant and three susceptible cultivars/lines were made in the greenhouse during Spring 1994, and F2 seeds from 12 different crosses were obtained in the summer. Seed of the parental and F2 generations were planted near Temple, Texas, during Fall 1994. The color (greenness) of 1482 F2 plants was measured using a chlorophyll meter (Minolta SPAD-502) 35 days after planting. Chi-square analysis showed a good fit to a 15:1 ratio of resistant: susceptible plants. The F2 segregation suggests that two dominant genes are involved in the response to iron deficiency in dry beans, and when either dominant gene is present, resistance is expressed to some degree.

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H.M. Cortinas-Escobar, Douglas C. Scheuring, Thomas J. Gerik and J. Creighton Miller Jr.

Cowpea [Vigna unguiculata (L.) Walp.] cultivars differ in their response to iron deficiency when grown on calcareous soils. This response is influenced by environmental factors such as soil pH, soil texture, presence of bicarbonates, and temperature. The objective of this study was to determine the genetic basis for resistance to iron deficiency in cowpea. Crosses of `Texas Pinkeye Purple Hull' (resistant) and `Pinkeye Purple Hull' (susceptible) were made in the greenhouse during Spring 1994, and F2 seeds were obtained in the summer. Reciprocal crosses were made in order to test for maternal effects. Seed of the parental, F1, and F2 generations were planted near Temple, Texas, during Fall 1994. The color (greenness) of 1031 F2 plants was measured using a chlorophyll meter (Minolta SPAD-502) 35 days after planting. Chi-square analysis showed a good fit to a 3:1 ratio of susceptible: resistant plants. These results suggest simple inheritance of the response to iron deficiency in cowpea. Similar segregation of the reciprocal crosses indicated absence of maternal inheritance.