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Genetic relationships among 42 grape accession of at least 15 species were estimated and compared using RAPD and isozyme techniques. These accessions were either hybrids or wild collections of the Asiatic species, the American species, the European grape (V. vinifera), and muscadine grape (V. rotundifolia). A total of 196 RAPD fragments were generated from twenty 10-mer primers. The pairwise similarities among the accession ranged from 0.46 to 0.94. A dendrogram was generated based on the RAPD similarity coefficients. Species/accessions were basically grouped together in accordance with their geographic origins. The similarities and dendrogram resulted from the RAPD analysis were consistent with the ones generated from the isozyme data, and also consistent with the known taxonomic information. This result suggest that the RAPD method, like isozyme, is an useful tool for studying grape genetic relationship/diversity and origination.
Economic and environmental concerns over nitrogen (N) fertilization of turfgrasses are prompting serious considerations of how to best use various N pools in turf-soil ecosystems. Nitrogen in clippings is receiving special consideration but information on how large and variable this N source might be for different turfgrasses is limited. Therefore, a field study investigated growth of and N recovery in clippings from 10 cultivars each of kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.), and tall fescue (Festuca arundinacea Schreb.) turf at the University of Rhode Island Turfgrass Research Station, Kingston, during 1990 and 1991 growing seasons. All turf had been established in 1985, 1986 or 1987 on an Enfield silt loam (Coarse loamy over sandy skeletal, mixed, mesic, Typic Dystrochrepts) and maintained under N fertilization rate of 147 kg N ha/year. Daily clipping growth rate (DCG), leaf blade N concentration (NC), and daily N recovery rate (DNR) in clippings were compared across species and cultivars. Seasonal clipping yields ranged from 5152 kg dry weight/ha for tall fescue to 3680 kg·ha–1 for perennial ryegrass. Significant species differences in the amount and seasonal pattern of N recovery were identified. Cultivar differences in N recovery were greatest for kentucky bluegrass but much less for perennial ryegrass and tall fescue. Total N recovery in clippings ranged from 260 to 111 kg N/ha/year generally exceeded N supplied as fertilizer, thus emphasizing potential importance of clipping N in turf management.
Growth and mineral nutrient content of creeping bentgrass [Agrostis stolonifera (L.) var. palustris (Huds.) Farw.] in response to salinity and humic acid (HA) application were investigated, and the effects of HA application on salinity tolerance was evaluated. Bentgrass plugs were grown hydroponically in one-quarter-strength Hoagland's nutrient solution containing HA at 0 or 400 mg·L-1 with salinity levels of 0, 8.0, or 16.0 dS·m-1. Clipping dry weight (DW), tissue water content, and net photosynthesis (PN) were measured weekly for 1 month. Maximum root length, and root DW from 0 to 10 cm and >10 cm root zones were determined 31 days after treatment (DAT). The turfgrass plugs were mowed three times weekly, with clippings collected and dried for mineral nutrient analysis. Salinity was inversely related to clipping DW, tissue water content, PN, and maximum root length. Salinity had less effect on root growth than top growth. HA treatment did not affect tissue water content, PN, or root growth of salt-stressed turf. Salinity decreased uptake of N, P, K, Ca, and S; increased uptake of Mg, Mn, Mo, B, Cl, and Na; and had no influence on uptake of Fe, Cu, and Zn. Application of HA at 400 mg·L-1 during salinity stress neither increased uptake of the mineral nutrients inhibited by salinity, nor decreased uptake of nutrients which were excessive and toxic in the salinity solution. In general, application of HA did not improve salinity tolerance of creeping bentgrass.
The genetic diversity among Cucumis sativus var. sativus (commercial cucumber) (1), var. anatolicus (2), var. cilicicus (3), var. europaeus (4), var. falcatus (5), var. indo-europaeus (6), var. irano-turanieus (7), var. izmir (8), var. sikkimensis (9), var. squamosus (10), var. testudaceus (11), var. tuberculatus (12), var. vulgatus (13), and var. hardwickii (14) were assessed using 7 morphological characteristics and 9 isozyme loci to determine their potential use for plant improvement. Results of morphological comparison below. Isozyme and morphological analysis did not result in similar dendrogram depictions. Varieties 13 and 3 might have potential in plant improvement based on yield performance.
Packaged salad-cut lettuce (Lactuca sativa L.) for food service and salad mixes is an increasingly important component of the lettuce industry. The product is highly perishable; cold storage and modified-atmosphere (MA) packaging are used to extend its shelf life. Given the importance of this market, lettuce cultivars, breeding lines, and populations should be selected for increased shelf life in MA environments. The objectives of this research were to determine the genetic variation in lettuce for shelf life in low-O2 MA environments and to develop rapid evaluation methods suitable for a lettuce breeding program. Lettuce was processed from field-grown plants of 33 romaine and three crisphead cultivars over 2 years. Shelf life was evaluated after storage in MA bags and in CO2-free controlled-atmosphere (CA) chambers with gas ratios of 0.2% O2:99.8% N2, 1.0% O2:99.0% N2, or 5.0% O2:95.0% N2. Deteriorated leaf blade tissue was water soaked and wilted with a dull to dark or black color, and midrib tissue and heart leaves were water soaked with a translucent to dark brown color. Genetic variation for shelf life was detected using MA bags or CA chambers, and the results from both years and testing methods were significantly correlated. Oxygen concentration did not affect shelf life in the CA chamber experiment, which indicated that the observed symptoms in the majority of cultivars were probably not from low O2 damage or CO2 injury, although multiple mechanisms of deterioration may be involved. Selection for lettuce cultivars, breeding lines, and populations with extended shelf life is possible using MA bags or CA chamber testing methods and could facilitate a consistent release of germplasm with stable shelf life in MA environments.
Phosphorus (P)-containing starter fertilizers are often recommended for establishing new turf, regardless of P levels indicated by the soil test. However, few field studies have been conducted to determine the effects of P in starter fertilizer on the rate of turf establishment. The primary objective of this study was to determine if P in starter fertilizer enhances tall fescue groundcover and growth during establishment on silt loam soil. This 2-year field study was conducted on silt loam soil tilled with a rototiller or core-aerated and vertically sliced. Mehlich-3 P levels ranged from 38 to 270 mg·kg−1. Experiments were conducted during late summer and fall, and all tests were seeded with ‘Bullseye’ tall fescue (Festuca arundinacea Schreb.). Treatments included 49 and 73.5 kg·ha−1 of nitrogen (N) without P, 49 kg·ha−1 of N plus three different rates of P (24.5, 49, and 73.5 kg·ha−1), and a nonfertilized control. Comparisons between groups that received treatment with 49 kg·ha−1 of N without P and treatments with 49 kg·ha−1 N with P revealed few significant groundcover responses to the addition of P. Of 12 groundcover assessments performed during four experiments, contrasts revealed only one instance of a higher percentage of groundcover in response to the addition of P. This occurred during an experiment having a pretreatment Mehlich-3 P level of 38 mg·kg−1. Comparisons indicated greater clipping yields in response to the addition of P in one of the four experiments. This occurred in soil that was core-aerated and sliced with an initial Mehlich-3 P level of 66 mg·kg−1. In most cases, Mehlich-3 P levels at the end of each experiment increased as the P application rates increased. The only instance in which comparisons between treatment with 49 kg·ha−1 N without P and treatments with 49 kg·ha−1 N with P demonstrated a significant leaf tissue response to P during the experiment with soil that was core-aerated and sliced with a pretreatment Mehlich-3 P level of 66 mg·kg−1. When individual treatments were compared, the 73.5 kg·ha−1 N treatment without P produced similar or higher groundcover and clipping yields than all other treatments during all four experiments. This study revealed few groundcover and variable tall fescue clipping yield responses to P additions when applied at rates used for starter fertilizer applications on silt loam soil during late summer and fall. Groundcover and growth responses due to P in starter fertilizers do not appear to be solely related to soil test P levels, and other factors such as the method of establishment (tilling soil vs. core-aerating and slicing the soil surface), environmental conditions, and the N content of soil may be involved.
Abstract
Initial fruit set in 6 ‘Italian’ prune orchards for 2 years was markedly influenced by post-bloom temperature. In the warm year initial sets ranged from 36 to 64%; in the cool year initial sets were 1 to 13%. Visible frost damage occurred in only 1 orchard and was not responsible for the general failure in the cool year.
Embryo sacs were studied in pistils from the same orchards in the 2 years. The cause of erratic fruit setting in ‘Italian’ prune is attributed to its genetically determined sensitivity to cool weather in the post-bloom period. Cool temperature delays pollen tube growth, fertilization, and early embryo and endosperm development so long that the ovule begins to degenerate. Ovule breakdown begins in the nucellus at the chalazal end, so that even if fertilization is finally accomplished, fruit set is not stimulated.
Abstract
An inheritance study of 2 dwarf mutants in watermelon showed that dwarfness in each form is due to single, non-allelic, recessive genes designated dw-1 and dw-2. Dwarfness in dw-1 and dw-2 plants was primarily attributed to reduced length of internodes, but there was also some reduction in the number of internodes in the dwarfs compared to the normal plants. The shorter internodes in dw-1 dwarfs were due to both fewer and shorter cells than in the internodes of vine forms. In the dw-2 dwarf most of the reduction in internode length was due to fewer cells.
Abstract
Erratic fruitfulness, reputedly characteristic of ‘Italian’ prune in many areas, was pronounced in this 2-year study. Supplemental pollination with self-pollen and with pollen of 2 other cultivars did not increase fruit set over that of open-pollination in any orchard regardless of whether yield was high or low. Controlled self- and cross-pollinations established that ‘Italian’ is self-fertile. The lack of differences in fruit set on caged trees with and without bees as well as the failure to increase set with supplemental self-pollinations demonstrated that bees are not necessary to transfer the self-fertile pollen. It was concluded that inadequate pollination, in terms of quantity or quality, is not responsible for the sporadic poor yields of this cultivar.
Abstract
A study of vegetative growth and flowering was conducted on normal and 3 dwarf segregants, dw-1, dw-2 and dw-1:dw-2 (extreme dwarf) of watermelon [Citrullus lanatus (Thunb.) Matsumura and Nakai]. Con pared to normal segregants, stem elongation was reduced by about 50% in dw-1 segregants, 80% in dw-2 segre gants and 90% in extreme dwarfs. The primary effect of the dwarf genes was an additive reduction in internode length. The rate of leaf initiation was reduced in dw-2 and extreme dwarfs, but not in dw-1 dwarfs.
Extreme and dw-2 dwarfs flowered at an earlier node number than either dw-1 or normal segregants. However, due to slower growth and abortion of early pistillate flowers, particularly in dw-2 and extreme dwarfs, the dwarf segregants displayed a temporal delay in flowering. Hence, the late-flowering characteristic of the dwarf segregants, especially in dw-2 and extreme dwarfs, imposes serious limitations on their usefulness for breeding early maturing dwarf cultivars.