A collection of collard (Brassica oleracea L., Acephala group) germplasm, including 13 cultivars or breeding lines and 5 landraces, was evaluated using randomly amplified polymorphic DNA (RAPD) markers and compared to representatives of kale (Acephala group), cabbage (Capitata group), broccoli (Italica group), Brussels sprouts (Gemmifera group), and cauliflower (Botrytis group). Objectives were to assess genetic variation and relationships among collard and other crop entries, evaluate intrapopulation variation of open-pollinated (OP) collard lines, and determine the potential of collard landraces to provide new B. oleracea genes. Two hundred nine RAPD bands were scored from 18 oligonucleotide decamer primers when collard and other B. oleracea entries were compared. Of these, 147 (70%) were polymorphic and 29 were specific to collard. Similarity indices between collard entries were computed from RAPD data and these ranged from 0.75 to 0.99 with an average of 0.83. Collard entries were most closely related to cabbage (similarity index = 0.83) and Brussels sprouts entries (index = 0.80). Analysis of individuals of an OP cultivar and landrace indicated that intrapopulation genetic variance accounts for as much variation as that observed between populations. RAPD analysis identified collard landraces as unique genotypes and showed them to be sources of unique DNA markers. The systematic collection of collard landraces should enhance diversity of the B. oleracea germplasm pool and provide genes for future crop improvement.
Samia Lotfy, Francois Luro, Françoise Carreel, Yann Froelicher, Delphine Rist, and Patrick Ollitrault
Somatic hybridization allows the creation of new patterns of nuclear, mitochondrial and chloroplastic association. It is therefore necessary to master cytoplasmic molecular markers to determine the genetic origin of both organelles of plantlets obtained from protoplasts fusion. In the case of Citrus and related genera, only southern blot hybridization and restriction fragment-length polymorphism (RFLP) techniques were used for this task until now. Here, we describe the use in the Aurantioideae subfamily, of a simple and non labeling cleaved amplified polymorphic sequence (CAPS) technique, to determine the cytoplasmic genome origin of intergeneric somatic hybrids. Mitochondrial and chloroplastic universal primers previously selected for population genetic studies in Quercus by Demesure et al. (1995) are used with some modifications. The variability of cytoplasmic genome among somatic fusion partners is detected by coupling amplification and restriction reactions. Digested DNA fragments are analyzed by agarose gel electrophoresis (PCR-RFLP). This technique has been applied for the analysis of the cytoplasmic constitution of somatic hybrids arising from intergeneric, intersubtribal and intertribal combinations. Systematic transmission of the mitochondria from protoplasts isolated from embryogenic callus parents was confirmed.
J.B. Magee, B.J. Smith, and Agnes Rimando
Control of muscadine diseases is necessary to minimize yield loss and is especially important for highest quality fresh-market berries. In a systematic disease control spray program, four fungicides registered for grapes were applied sequentially at 10- to 20-day intervals from early bloom until just before harvest to five muscadine cultivars. Objectives of the study were to: 1) determine the effects of the spray schedule on foliage and berry diseases; and 2) study the relationship between disease incidence and resveratrol content of the berries. Resveratrol, a phytoalexin, has shown potential value in prevention and treatment of cardiovascular disease and certain cancer processes. Foliar diseases were rated visually twice during the season. Berry disease ratings were made at harvest. All fungal foliage and berry diseases were significantly reduced by fungicide treatments. Resveratrol was determined separately on berry skins, seed and pulp/juice by gas chromatography/mass spectroscopy (GC/MS). Overall, resveratrol levels in berry skins from unsprayed vines were much higher than those of sprayed vines. Concentrations varied by cultivar and within cultivar by treatment. The relationship between resveratrol concentration in skins and total disease score or scores of specific diseases was not established. Seed resveratrol concentrations differed by cultivar but were not affected by the fungicide treatments. Resveratrol concentration of seed was lower than that of skins. Accumulation of resveratrol in juice/pulp was much lower than in skins and seeds.
Hirofumi Terai, Alley E. Watada, Charles A. Murphy, and William P. Wergin
Structural changes in chloroplasts of broccoli (Brassica oleracea L., Italica group) florets during senescence were examined using light microscopy, scanning electron microscopy (SEM) with freeze-fracture technique, and transmission electron microscopy (TEM) to better understand the process of chloroplast degradation, particularly at the advanced stage of senescence. Light microscopy revealed that chloroplasts, which initially were intact and green, became obscure in shape, and their color faded during senescence. Small, colored particles appeared in cells as the florets approached the final stage of senescence and became full- to dark-yellow in color. Scanning electron microscopy showed that stroma thylakoids in the chloroplast initially were parallel to each other and grana thylakoids were tightly stacked. As senescence advanced, the grana thylakoids degenerated and formed globules. The globules became larger by aggregation as senescence progressed, and the large globules, called “thylakoid plexus,” formed numerous vesicles. The vesicles ultimately were expelled into the cytosol, and the light microscope revealed many colored particles in the senescent cells. These results indicate that the degradation of chloroplasts in broccoli florets progresses systematically, with the final product being colored particles, which are visible in yellow broccoli sepal cells.
Patrick J. Conner
Germination of muscadine seed has frequently been low and irregular in the University of Georgia breeding program. A systematic study was undertaken to determine the best seed treatments and germination conditions for muscadine seed. Open-pollinated seeds of ‘Fry’ muscadine were used for all treatments. Stratification of seeds was performed by placing dry seed in damp vermiculite at 4 °C for periods of 0, 30, 60, and 90 d. The 90-d stratification period gave the highest germination percentage, with successively lower germination in the shorter stratification treatments. Pretreatment of seeds before stratification with three rates (0.5, 1.0, and 2.0 M) of hydrogen peroxide (H2O2) and four rates (1, 2, 4, and 8 g·L−1) of gibberellic acid (GA3) were used in an attempt to promote germination. Low rates of H2O2 (0.5 M) and GA3 (1 g·L−1) were beneficial in some instances, whereas high rates of GA3 were detrimental. Nicking the seedcoats before stratification and soaking seeds in running water after stratification were ineffective in promoting germination. Germination temperatures of 32/22 °C (8 h/16 h) were superior to 22/22, 27/22, and 37/22 °C.
Yifei Wang, Stephanie K. Fong, Ajay P. Singh, Nicholi Vorsa, and Jennifer Johnson-Cicalese
The flavonoid and organic acid profiles of one cultivated tetraploid and six wild diploid blueberry species (Vaccinium spp.) were systematically investigated using high-performance liquid chromatography–electrospray ionization–tandem mass spectrometry (HPLC-ESI-MS-MS). Eighteen individual anthocyanins from five aglycone classes were characterized among species, with malvidin and delphinidin glycosides accounting for 31.4% and 29.1% of total anthocyanins. Twenty-three flavonol glycosides from six aglycone classes were identified, among which quercetin and myricetin glycosides accounted for more than 80% of total flavonols in most species. Both inter- and intraspecies differences in anthocyanin and flavonol composition were observed, as described by principal component analysis. Only B-type proanthocyanidins were found in blueberry species, and highly polymerized molecules with degree of polymerization greater than 10 appeared to be the most abundant fraction. Although overall proanthocyanidin levels varied from 27.7 to 146.3 mg/100 g fruit, all species exhibited similar proanthocyanidin composition. Citric, quinic, and shikimic acid were the major identified blueberry organic acids. However, their relative abundance varied across species. In certain species either citric acid (e.g., Vaccinium darrowii) or quinic acid (e.g., Vaccinium corymbosum) was lacking.
James L. Glancey, Edwin Kee, and Tracy Wootten
The vegetable industry is important to our nation as a provider of nutritious and safe food directly consumed by our citizens. It is also critical to a rich and vigorous national agriculture. During the 20th century, engineering innovations coupled with advances in genetics, crop science, and plant protection have allowed the vegetable industry in the U.S. to plant and harvest significantly more land with higher yields while using less labor. Currently, fresh and processed vegetables generate 16% of all U.S. crop income, but from only 2% of the harvested cropland. Yet, many of the challenges in production that existed a century ago still exist for many crops. Perhaps the most significant challenge confronting the industry is labor, often accounting for 50% of all production costs. A case study of the mechanized production system developed for processed tomatoes (Lycopersicon esculentum) confirms that systematic methodology in which the machines, cultural practices, and cultivars are designed together must be adopted to improve the efficiency of current mechanized systems as well as provide profitable alternatives for crops currently hand-harvested. Only with this approach will horticultural crop production remain competitive and economically viable in the U.S.
S.S. Miller, R.W. McNew, B.H. Barritt, L. Berkett, S.K. Brown, J.A. Cline, J.M. Clements, W.P. Cowgill, R.M. Crassweller, M.E. Garcia, D.W. Greene, G.M. Greene, C.R. Hampson, I. Merwin, D.D. Miller, R.E. Moran, C.R. Rom, T.R. Roper, J.R. Schupp, and E. Stover
Cultivar and planting site are two factors that often receive minimal attention, but can have a significant impact on the quality of apple (Malus ×domestica) produced. A regional project, NE-183 The Multidisciplinary Evaluation of New Apple Cultivars, was initiated in 1995 to systematically evaluate 20 newer apple cultivars on Malling.9 (M.9) rootstock across 19 sites in North America. This paper describes the effect of cultivar and site on fruit quality and sensory attributes at a number of the planting sites for the 1998 through 2000 growing seasons. Fruit quality attributes measured included fruit weight, length: diameter ratio, soluble solids concentration (SSC), titratable acidity (TA), flesh firmness, red overcolor, and russet. Fruit sensory characteristics rated included crispness, sweetness, and juiciness, based on a unipolar intensity scale (where 1 = least and 5 = most), and acidity, flavor, attractiveness, and desirability based on a bipolar hedonic scale (where 1 = dislike and 5 = like extremely). All fruit quality and sensory variables measured were affected by cultivar. The two-way interaction of cultivar and planting site was significant for all response variables except SSC, TA, russet, crispness, and sweetness ratings. The SSC: TA ratio was strongly correlated with sweetness and acidity sensory rating, but was weakly correlated with flavor rating. The results demonstrate that no one cultivar is ideally suited for all planting sites and no planting site is ideal for maximizing the quality of all apple cultivars.
Marissa Moses and Pathmanathan Umaharan
Capsicum chinense is commercially the most important pepper species grown in the Caribbean. It is popularly used to impart pungency and flavor to Caribbean cuisine. However, unlike Capsicum annuum, which is the most commercially exploited domesticated species internationally, C. chinense has not been methodically collected or characterized for systematic improvement through plant breeding. The objectives of the study were to assess the diversity of C. chinense and its structure within the Caribbean basin and to determine its phylogenetic relationship to groups within South America. DNA isolated from 201 accessions of C. chinense, representing geographical regions where the species is found, were amplified using arbitrary primers to generate 138 polymorphic and reproducible random amplification of polymorphic DNA (RAPD) markers. Nei’s and Shannon’s diversity indices for C. chinense (0.28 and 0.419, respectively) were higher in South America compared with Central America or the Caribbean, corresponding to its putative center of diversity. The study showed the existence of three phylogenetic clusters within C. chinense. The largest cluster consisted of accessions from the Upper Amazon region, the Guianas including Venezuela, and the Lesser Antilles of the Caribbean. The other major cluster was represented by accessions principally from the Lower Amazon region. Another distinct but small cluster consisted of samples solely from the Greater Antilles of the Caribbean. The discovery of the three phylogenetic clusters within C. chinense may have potential for exploiting heterosis in breeding. The implications of the findings to the understanding of the phylogenetic origin and distribution of C. chinense are discussed.
Christopher M. McGuire
1 Current address: Section of Ecology and Systematics, Cornell Univ., Ithaca, NY 14853. I thank Ian Merwin, John Ray, Marvin Pritts, and Mary Jo Kelly for advice and assistance, and my family for encouragement and