Browsing by Author "Kushad, Mosbah M."

Now showing 1 - 13 of 13
  • Thumbnail Image
    Derivation, fertility and breeding value of doubled monoploids from the diploid potato species, Solanum phureja
    M'Ribu, H. Kabura (Virginia Tech, 1990-08-20)
    Thirty-two monoploids (2n = x = 12) derived by anther culture of ten diploid clones of Solanum phureja were used to generate doubled monoploids through in vitro shoot regeneration. Doubled monoploids were compared to the anther donor and progenitor monoploids for morphological characteristics, and were evaluated for fertility in the greenhouse and progeny performance under field conditions. Monoploids varied for frequency and earliness of shoot regeneration, number of shoots formed per explant and frequency of chromosome doubling among regenerated shoots. Regeneration was greater when stock plantlets were frequently subcultured (2- or 4-week intervals) and maintained under a 16 h photoperiod, and when explants were incubated at 20°C compared to 25°C. In addition, leaf explants regenerated at higher frequencies than stem explants. Significant high correlations between monoploids and their doubled monoploids were observed for 14 of 17 characters in the greenhouse. Doubled monoploids were significantly greater than monoploids for 15 characters, indicating a positive effect of increasing gene dosage from monoploid to diploid. The anther donor was not significantly greater than the mean of doubled monoploids for 10 characters; therefore, for specific characters, doubled monoploids without homozygote depression can be obtained. Doubled monoploids varied for nurnber of days to flower, duration of flowering, abundance of flowers, flower quality, fruit set and seed set; they had lower fruit and seed set than the anther donor. A few clones produced low levels of stainable pollen which had high 2n pollen frequency but did not germinate in vitro. Therefore, they were considered male-sterile for practical purposes. Used as female parents, doubled monoploids were able to transmit the 2n pollen trait to their progenies. Two of four doubled monoploids exhibited superior general combining ability over the anther donor under field conditions. This demonstrates the potential of passage of a heterozygous genotype through the monoploid sieve. The advantage of the monoploid sieve may be more or less evident depending on the combining ability of the crossing partner and variable performance can be expected among doubled monoploids from an unselected anther donor. The performance of unselected doubled monoploids demonstrates the potential for their utilization in breeding and warrants further research in the area.
  • Thumbnail Image
    Differential tolerance of corn hybrids to metolachlor and its regulation by the safener benoxacor
    Cottingham, Charles K. (Virginia Tech, 1991-06-05)
    Determining the basis of intraspecific herbicide tolerance was expected to be a useful way of revealing factors which are regulated by safeners in providing their protective effect. Differential tolerance to the chloroacetanilide herbicide metolachlor and the thiocarbamate herbicide EPTC was examined in 11 corn hybrids. Tolerance to one of these herbicides does not imply similar tolerance to the other. Detoxication of these herbicides in plants is mediated via conjugation with glutathione (GSH). GSH levels from 1.8 to 2.4 µmol/g fresh weight were determined for the eleven corn hybrids tested. There was no correlation between GSH content and herbicide tolerance. The monooxygenase inhibitor piperonyl butoxide (PBO) acted synergistically with EPTC on 8 of the tested corn hybrids. A Similar antagonism by the oxygen evolving compound calcium peroxide provided additional evidence for the importance of oxidative processes in EPTC tolerance which were not important in determining metolachlor tolerance. The more rapid absorption and greater accumulation of ¹⁴C-metolachlor by 'Northrup-King 9283' corn relative to 'Cargill 7567' corn at least partially explains the increased susceptibility of the former hybrid to metolachlor. The in vitro metabolism of ¹⁴C-metolachlor was similar for both hybrids. A lag in the expression of glutathione S-transferase (GST) activity during early seedling development of 'Northrup-King 9283' corn may be of additional significance in its limited tolerance to metolachlor. The safener benoxacor was effective in protecting 'Northrup-King 9283' and other susceptible corn hybrids from metolachlor injury. Benoxacor had no effect on metolachlor uptake or the rate of non-enzymatic conjugation of metolachlor. Seedlings of 'Cargill 7567' and 'Northrup-King 9283' treated with 1 µM benoxacor metabolized metolachlor to the GS-conjugate at a rate 1.7 times that of untreated seedlings. GST activity was stimulated by 35% by similar treatment. GST isozymes with metolachlor conjugating activity (GST-metolachlor activity) were found in the cytosol and microsomal fractions of corn extracts. At least two GST-metolachlor isozymes were separated by DEAE-Sepharose chromatography. The activity of both isozymes was increased by benoxacor treatment. It appears that benoxacor regulates metolachlor tolerance by inducing GST isozymes that consequently increase the rate of metolachlor detoxication.
  • Thumbnail Image
    Evaluation of yield and quality of five potato cultivars grown in Southwest Virginia
    Ajuoga, Okeyo James (Virginia Tech, 1992-10-07)
    Potato (Solanum tuberosum L.) cultivars Atlantic, BelRus, Kennebec, Superior, and Yukon Gold, grown at six locations in Southwest Virginia, were analyzed for yield, percent dry weight, specific gravity, soluble protein, and ascorbic acid. Thereafter. tubers were cold stored at 3 C for six weeks, reconditioned at 25 C for two weeks, and analyzed for percent dry weight, specific gravity, soluble protein, and ascorbic acid. Potato grown in one location was analyzed for glucose, fructose, sucrose, and total sugars. Another experiment was conducted to evaluate the effect of seed type and in-row spacing on yield and quality of Yukon Gold. Cultivar and location influenced yield and quality of potato at harvest, after cold storage, and following reconditioning. Kennebec, Atlantic, and Yukon Gold produced higher yield of US No. 1 tubers than Superior and BelRus. Atlantic and BelRus had higher percent dry weight and specific gravity than the other cultivars. Specific gravity increased during cold storage and following reconditioning. Percent dry weight increased during reconditioning but did not change during cold storage.
  • Thumbnail Image
    Expression of 3-hydroxy-3-methylglutaryl coenzyme a reductase in maize as influenced by light and bleaching herbicides
    Ji, Wan (Virginia Tech, 1991-05-05)
    The activity of the enzyme 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR, EC 1.1.1.34) is highly expressed in 4-day-old etiolated seedlings of normal ('DeKalb XL72AA'), dwarf (d₅), and albino (lw₃) maize (Zea mays L.). HMGR activity of maize seedlings appeared to be exclusively associated with the microsomal rather than the plastidic fraction of maize cells. Maize tissues with high meristematic activity such as germinating seeds, leaf bases, root tips, and the site of origin of lateral roots contained high levels of HMGR activity. The activity of HMGR extracted from leaf tips of normal, dwarf, and albino maize seedlings was regulated by light. HMGR activity from leaf tips of 4-day-old maize seedlings was inhibited significantly following exposure to strong light (600 μol/m²/s) for more than 10 h. In contrast, HMGR activity from leaf bases and root tips of maize was not inhibited by exposure to strong light. These results suggest that HMGR may play an important role in cell division and that light may regulate HMGR activity indirectly by increasing cell differentiation. Under conditions of strong light pretreatment with the bleaching herbicides clomazone, norflurazon, fluridone and acifluorfen stimulated by 4-to 7-fold the activity of HMGR extracted from 'Dekalb XL72AA' maize seedlings.
  • Thumbnail Image
    Floral initiation in Rudbeckia hirta: limited inductive photoperiod, polyamines and cytokinins
    Harkess, Richard Lee (Virginia Tech, 1993-01-15)
    This study examined floral initiation in Rudbeckia hirta at the biochemical, cellular, and whole plant levels. Histological and histochemical examination of floral initiation revealed that the pattern of initiation followed closely that described in other species. The primary difference was in the length of time over which initiation and differentiation occurred. When subjected to limited inductive photoperiods, R. hirta responded with a delay in flowering if the plants were returned to short days (SD) before bract initiation. Increased exposure to long days (LD) increased stem height and enhanced floral development. A limited induction period of at least 8 LD allowed enough of the floral stimulus to be translocated to the meristem to cause no interruption in development even upon return to non-inductive conditions. An inhibition of development occurred only when plants were returned to SD before periclinal divisions in the pith rib meristem commenced after approximately 8 LD. Axillary bud development and final plant height were dependent on the number of inductive LD received. Polyamines have been linked to floral initiation and, in this study, were strongly correlated to the stage of floral initiation. As initiation progressed, the observed increases in putrescine and spermidine were followed by a decrease after 16 LD, the observed onset of floral development. This was contrary to that previously observed in SD plants but followed a pattern similar to that reported for cytokinin behavior. Exogenous cytokinins have been used to stimulate floral initiation in several species but Rudbeckia hirta did not respond to benzyladenine (BA) applied at the onset of LD. Floral initiation has been found to begin after six to eight LD and, in most species, BA was most effective when applied during initiation. In an attempt to increase uptake, BA was dissolved in dimethyl sulfoxide (DMSO). This did not enhance the effects of BA and, in fact, DMSO was found to be toxic at concentrations of 25% or more.
  • Thumbnail Image
    Inheritance of protoplast culturability and improvement in pollen development by protoplast manipulation in solanum
    Cheng, Jianping (Virginia Tech, 1990-05-16)
    Genetic improvement of the potato through classical breeding has been limited by its tetraploid nature, the narrow genetic variability within cultivars, and interploidy barriers between tetraploid cultivars and diploid germplasm. Breeding at reduced ploidy levels has been proposed as a solution to these problems. Because of sterilities, somatic hybridization via protoplast fusion has been considered an alternative to sexual polyploidization for resynthesizing superior diploids from selected monoploids, and tetraploids from selected diploids and dihaploids. Successful application of somatic hybridization largely depends upon protoplast culturability and regenerability of a plant. The ability of callus formation and plant regeneration from protoplasts varies among plants. To understand the genetic basis for this variation, the mode of inheritance for protoplast culturability, defined as the ability to develop calli from cultured protoplasts, was studied in the diploid potato species, Solanum phureja. Based upon data from F₂ as well as from F₁ and backcross progenies, it was found that protoplast culturability in this potato species was controlled by two unlinked loci with dominant effect. In addition, there was quantitative variation for protoplast plating efficiency among culturable genotypes. Male sterility in cultivars of Solanum tuberosum ssp. tuberosum results from nuclear-cytoplasmic interactions. 'Donor-recipient' protoplast fusion and regeneration were conducted between a sterile S. tuberosum ssp. tuberosum cultivar, Russet Burbank, and fertile selections of S. tuberosum ssp. andigena which have a non-sensitive cytoplasm and were used as the cytoplasmic donor. Sixteen regenerated plants possessed nuclear background and chloroplast DNA of Russet Burbank. However, two of these regenerants had improved pollen stainability. The possible causes for the improvement of pollen stainability are discussed. In the last chapter, allelic polymorphism in a monoploid population derived from anther culture of a clone of S. phureja was assessed by isozyme electrophoresis. Fourteen monoploids and their anther donor were examined for six enzymes. No allozyme variation was detected in these plants. However, genetic variability among these monoploids was manifested by variations in some growth characters and general morphology. The limitation of enzymatic markers in detecting allelic polymorphism in these monoploids is discussed.
  • Thumbnail Image
    A Longer Marketing Life for Blackberry and Raspberry Fruit
    Kushad, Mosbah M.; Samtani, Jayesh (Virginia Cooperative Extension, 2020-12-07)
    Caneberries, which include blackberries and raspberries, must be picked when the berries are ripe or nearly ripe to ensure quality. Their thin fruit skin, high respiration rate, and high ethylene production make these berries extremely susceptible to postharvest losses. Although both raspberries and blackberries are considered 'soft' fruits, raspberries are slightly more perishable in nature.
  • Thumbnail Image
    A Longer Marketing Life for Blackberry and Raspberry Fruit
    Samtani, Jayesh B.; Kushad, Mosbah M. (Virginia Cooperative Extension, 2015-05-11)
    Discusses how to improve shelf life of blackberries and raspberries by choice of cultivars for fruits that are firm and have tough skin, harvest time, harvest time, packing, grading, transportation, and handling.
  • Thumbnail Image
    A Longer Marketing Life for Bramble Fruits
    Stiles, Herbert D.; Kushad, Mosbah M. (Virginia Cooperative Extension, 2009)
    Discusses how to improve shelf life of blackberries and raspberries by choice of cultivars for fruits that are firm and have tough skin, harvest time, harvest containers, packing, grading, transportation and handling.
  • Thumbnail Image
    De novo morphogenesis on tomato thin cell layers and variation for genetic recombination among plantlets regenerated from tissue culture
    Compton, Michael E. (Virginia Tech, 1990-05-15)
    De novo shoots, roots, and flower buds were regenerated on thin cell layer explants excised from pedicel tissue of tomato. Direct shoot organogenesis was greatest when media contained 10µM kinetin and 0.001µM indole-3-acetic acid (IAA); however, shoot regeneration was increased in subsequent experiments by substituting 10 µM zeatin or 10 µM benzyladenine for kinetin. Root formation occurred when media contained higher (0.1 and 10µM) auxin concentrations. Flowers were formed on elongated shoots with several leaves when media contained 10µM IAA and 0.1µM kinetin. Competence for de novo shoot morphogenesis was tested on thin cell layers of eleven tomato cultivars. All tomato cultivars formed shoots directly on thin cell layer explants at varying frequencies (29%-63%). The mean number of shoots per explant was greatest for 'Large Red Cherry', 'Ohio 7814' and 'BL 6807', and poorest for 'Campbell 1327' and 'Red Alert'. Active cell divisions were observed in subepidermal cells during the first week of culture, and meristematic centers of dividing cells were evident after 2 weeks. Well developed shoot apices were observed on 50% of the explants 4 weeks after culture initiation. Shoot morphogenesis was compared among tomato plants placed into micropropagation, callus, and thin cell layer tissue culture systems. More shoots were produced on thin cell layer explants than on cotyledon calli, or micropropagated shoot tips. Genetic recombination rates and map distances were compared among hybrid plants grown in the greenhouse and regenerated from the aforementioned tissue culture systems. Increased recombination rates and map distances were detected between the sunny (sy) and baby leaf syndrome (bls) genes on chromosome 3, and between the white virescence (wv) and anthocyanin reduced (are) genes on chromosome 2. The percent change in the former ranged from 4.5%-5.9% for micropropagated shoot tips, 3.7%-8.5% for plants from cotyledon calli and 2.8%-5.9% for plants from thin cell layers. The percent change between the wv and are loci ranged from 4.5%-6.1% for micropropagated shoot tips, and 3.2%-5.0% and 3.9%-5.7% for plants from cotyledon calli and thin cell layers, respectively. Conversely, a decreased map distance was observed between bls and the solanifolia (sf) locus which is more distal to the centromere on the same arm of chromosome 3 as bls. Changes in recombination rates among plants regenerated from tissue culture may result from an influence of the tissue culture process on meiosis of regenerated plants.
  • Thumbnail Image
    Physiological studies of bitter pit in apple
    Witney, Guy W. (Virginia Polytechnic Institute and State University, 1989)
    In a series of related experiment: some aspects of the histology and physiology of the disorder bitter pit in apple (Malus domestica Borkh.) were studied. A two year field study was conducted to induce consistent bitter pit development in type ’Delicious’ (D) and ’Golden Delicious’ (GD) apple fruit. Multiple spray treatments of CaCl₂ and MgCl₂, combined with paper bag fruit covers, were applied and subsequent bitter pit development examined. The main effect of bags in both cultivars was increased pit development, decreased Ca in fruit and increased fruit K. CaCl₂ sprays resulted in less pit development, increased Ca in fruit, and less fruit Mg. MgCl₂ sprays resulted in increased bitter pit, decreased fruit Ca, and increased fruit Mg. Overall, field treatments provided a wide range of bitter pit incidence after storage, from 100% (bag and MgCl₂ spray combined) to 3% (CaCl₂ spray alone) in both D and GD. The cellular morphology of pitted apple fruit from field trees was examined using transmission and scanning electron microscopy. The overall tissue morphology of both cultivars was similar, but in pitted tissues differences were observed in tannin localization, starch hydrolysis, and cell wall morphology. Cation levels in the tissues were examined using X-ray microanalysis. High Mg levels were localized in pit cells, while K levels were similar in both healthy and pitted cells. Ca levels in both tissue types were too low to be detected by this method. Using ’Golden Delicious’ fruit from the field study, the relationship between pyruvate kinase activity, fruit cation concentration and bitter pit was investigated. Pyruvate kinase activity during early fruit growth was higher in fruit which developed 100% bitter pit after storage (MgCl, spray + bag), than in fruit that developed 3% bitter pit (CaCl₂ spray). Fruit with a high bitter pit incidence had a lower Ca: Mg + K ratio than fruit with a low level of the disorder. There was a strong positive correlation between enzyme activity early in the season and bitter pit incidence alter storage. An assay for pyruvate kinase may be valuable for early prediction of postharvest bitter pit development. Finally, the qualitative electrophoretic patterns of soluble fruit proteins from each treatment were examined starting early in the season and continuing until termination of fruit storage. Patterns from all treatments were almost identical throughout the season.
  • Thumbnail Image
    Physiology and control of apple scald
    Kamath, Osler C. (Virginia Tech, 1990-02-05)
    The effect of controlled atmosphere (CA) storage, and antioxidant treatment on polyphenoloxidase (EC 1. 1418.1:PPO), peroxidase (EC11.11.1.7:POD), and superoxide dismutase (EC 1.15.1.1:S0D) activities and superficial scald and soft scald development in 'Virginiagold','Stayman', and 'Rome' apples (Malus domestica Borkh.) was investigated. 'Virginiagold' apples treated postharvest with an aqueous solution of diphenylamine (DPA) + 1,2, dihydro -6- ethoxy -2,2,4-trimethylquinoline (ethoxyquin) and stored in CA exhibited lower soft scald incidence and higher firmness than comparable fruits stored at O°C in air storage. Fruit firmness and titratable acids (TA) decreased continuously, while ethylene increased in storage. Titratable acids and firmness were positively correlated, while TA and ethylene and firmness and ethylene were negatively correlated. 'Stayman' and 'Rome' apples analyzed during storage showed increase in levels of λ±-famesene and its oxidation products conjugated trienes. During storage fruits showed an increase in the activities of polyphenoloxidase (PPO), peroxidase (POD), and superoxide dismutase (SOD), which reached a maximum when scald symptoms in 'Stayman' were observed. Our results indicate that 'Stayman' apples exhibited scald and 'Rome' did not, because 'Stayman' apples had a ten fold higher PPO activity than 'Rome.'
  • Thumbnail Image
    Production and postharvest quality maintenance of single unit and bunching broccoli in Virginia
    Jett, Lewis W. (Virginia Tech, 1990-11-05)
    Broccoli (Brassica oleracea L. var. italica) has become an increasingly popular vegetable with American consumers. Much of the attractiveness of fresh broccoli is derived from this vegetable's high nutrition and excellent organoleptic properties. In a consumer response survey, Virginia Master Gardeners indicated a preference for broccoli that has less stalk and more florets by weight. The objectives of this research were to produce single unit broccoli, and to examine vacuum and shrink-film wrapping of single unit and bunching broccoli as alternatives to the standard post harvest practice of top icing in order to preserve post harvest quality attributes: vitamin C, color, odor, and turgidity. Broccoli cv. 'Symphony' was direct seeded and transplanted at two sites in Virginia (within row spacing 20 cm , .9 m centered, 3 row bed). Single unit broccoli was classified as broccoli with head diameters greater than or equal to 20 cm (i.e., equivalent to one bunch of broccoli). Single unit and bunching broccoli for post harvest experimentation was vacuum or shrink-film wrapped with plastic film wraps of varying gauges. The broccoli was held in cold storage from 12 to 22 days with no supplemental ice. Single unit broccoli was produced successfully at one site only. The yields, however, were a fraction of total bunching broccoli yields. There was no significant difference in marketable yields with either planting method (direct seeded vs transplanting) at site 2. Transplants, however, out yielded the direct seeded broccoli at site 1. Vacuum and shrink-film wrapping proved to be very effective in preserving organoleptic attributes of single unit and bunching broccoli even when never receiving ice. Vitamin C and chlorophyll retention were not influenced by wrapping.