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Thomas H. Boyle

Allotetraploid Z. angustifolia × Z. elegans hybrids (2 n =46) were reciprocally backcrossed to Z. angustifolia (2 n = 22 or 44) and Z. elegans (2 n = 24 or 48). Pollen germination and pollen tube penetration of the stigmatic surface were observed for all 8 cross combinations. At 14 days after pollination, the percentage of florets with embryos ranged from 0 to 69%, and some hybrid embryos exhibited developmental abnormalities. Seed-propagated backcross (BC1) populations were generated with Z. angustifolia (2 n =44)as ♀ or ♂, and Z. elegans (2 n =48) as ♀ BC1 progeny from these 3 crosses demonstrated low to high levels of resistance to bacterial leaf and flower spot (incited by Xanthomonas campestris pv. zinniae) and high levels of resistance to powdery mildew (incited by Erysiphe cichoracearum). BC1 hybrids derived from crossing allotetraploid hybrids as ♀ and Z. elegans (2 n =48) lines have commercial potential as disease-resistant, flowering annuals.

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Caihong Zhong, Shengmei Wang, Zhengwang Jiang, and Hongwen Huang

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Anusuya Rangarajan, A. Raymond Miller, and Richard Veilleux

Leptine (LP) glycoalkaloids have been demonstrated to confer natural resistance to the Colorado potato beetle (CPB) in Solanum chacoense (chc). Development of cultivated potatoes with natural resistance to CPB has the potential to reduce both costs and environmental impacts of production by reducing pesticide use. To introgress the genes conferring leptine production from chc into S. tuberosum (tbr), clones of chc have been crossed with clones of S. phureja. Leaf disks from eight hybrids were subjected to a CPB second instar feeding bioassay to determine if extent of feeding was related to LP levels. Most hybrids contained leptinidine (LD, the aglycone of LP) levels intermediate to chc and tbr, and insect feeding was suppressed 30% to 50% in hybrids containing >10 mg·g–1 DW LD. One hybrid displaying feeding suppression contained a very low level of LD, whereas another hybrid that contained higher levels of LD had higher feeding rates. The presence of LD at “threshold” levels in these hybrids will suppress feeding of CPB, but other factors affecting resistance are also present and need to be explored.

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James A. Schrader, Diana R. Cochran, Paul A. Domoto, and Gail R. Nonnecke

The popularity of grape (Vitis sp.) and wine production in the upper midwest region of the United States is increasing steadily. The development of several cold-climate, interspecific-hybrid grape cultivars (northern hybrids) since the 1980s has improved the probability of success for both new and established vineyards in this area of the country, but long-term data describing the performance of these cultivars in midwestern U.S. climates are needed to both aid growers in their choice of cultivars and to provide them with information about factors important in their management. We characterized the long-term winterhardiness and annual phenology of 12 cold-climate northern hybrid grape cultivars (two established cultivars, five newer cultivars, and five advanced selections) grown in a randomized and replicated field plot in central Iowa, an area that offers a warm growing season and very cold dormant season for grape culture. The established cultivars included in the study were Frontenac and St. Croix. The newer cultivars evaluated were Arandell, Corot noir, La Crescent, Marquette, and Petit Ami, and the advanced selections were MN 1189, MN 1200, MN 1220, MN 1235, and MN 1258. The grape trial was established in 2008, and vines were evaluated from 2011 through 2017 for annual timing of budbreak, bloom, veraison, and harvest, as well as winter survival of vines and primary buds. As a group, the northern hybrids in our trial showed good winterhardiness of vines but variable hardiness of primary buds across the six winters, which ranged from warmer than average to much colder than average. In Iowa climate, buds of northern hybrids were generally most vulnerable to cold temperature damage from late-winter (March) low-temperature events or from extreme midwinter low-temperature events. The bud hardiness of individual cultivars ranged from very hardy (Frontenac, Marquette, and MN 1235) to poor hardiness (Arandell, Corot noir, Petit Ami, and MN 1189), with all 12 cultivars showing good bud survival during Iowa winters that were warmer than average, but the less-hardy cultivars showing poor bud survival during winters that were colder than average. Evaluations of phenology revealed that heat accumulation measured in growing degree days with a threshold of 50 °F was not a reliable index for predicting the timing of annual developmental stages for the cultivars we tested. Our results indicate that northern hybrids rely on other factors in addition to heat accumulation for guiding annual development, and that factors such as photoperiod likely have a strong influence on phenological timing during seasons with unusual weather patterns. We determined that none of the cultivars were vulnerable to cold temperature damage to fruit before harvest in Iowa’s climate, but that three of the cultivars (Arandell, Marquette, and MN 1235) were highly vulnerable to shoot damage from spring freeze events, and four others (Corot noir, La Crescent, MN 1200, and MN 1220) were moderately vulnerable to cold damage to shoots in spring. An itemized summary of the relative hardiness, vulnerabilities, and timing of phenological stages of the 12 cultivars is provided to aid growers in selection and management of grape cultivars for Iowa climate. Based on hardiness and phenology, four of these cultivars (Frontenac, MN 1258, MN 1220, and MN 1200) have the lowest risk of issues related to cold temperatures.

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Pachanoor S. Devanand, Jianjun Chen, Richard J. Henny, and Chih-Cheng T. Chao

Philodendrons (Philodendron Schott) are among the most popular tropical ornamental foliage plants used for interior decoration. However, limited information is available on the genetic relationships among popular Philodendron species and cultivars. This study analyzed genetic similarity of 43 cultivars across 15 species using amplified fragment length polymorphism (AFLP) markers with near infrared fluorescence labeled primers. Forty-eight EcoR I + 2/Mse I + 3 primer set combinations were screened, from which six primer sets were selected and used in this investigation. Each selected primer set generated 96 to 130 scorable fragments. A total of 664 AFLP fragments were detected, of which 424 (64%) were polymorphic. All cultivars were clearly differentiated by their AFLP fingerprints, and the relationships were analyzed using the unweighted pair-group method of arithmetic average cluster analysis (UPGMA) and principal coordinated analysis (PCA). The 43 cultivars were divided into five clusters. Cluster I comprises eight cultivars with arborescent growth style. Cluster II has only one cultivar, `Goeldii'. There are 16 cultivars in cluster III, and most of them are self-heading interspecific hybrids originated from R.H. McColley's breeding program in Apopka, Fla. Cluster IV contains 13 cultivars that exhibit semi-vining growth style. Cluster V has five cultivars that are true vining in morphology, and they have lowest genetic similarity with philodendrons in other clusters. Cultivated philodendrons are generally genetically diverse except the self-heading hybrids in cluster III that were mainly developed using self-heading and semi-vining species as parents. Seven hybrid cultivars have Jaccard's similarity coefficients of 0.88 or higher, suggesting that future hybrid development needs to select parents with diverse genetic backgrounds.

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Robert H. Bors and J. Alan Sullivan

Interspecific crosses with Fragaria moschata (6x) have been hampered by ploidy level differences, poor seed set, and extremely poor seed germination. Modification of pollination practices, embryo rescue, and use of several genotypes has allowed over 80 synthetic tetraploids to be created from 14 cross combinations. Germplasm for the experiment consisted of eight selections of F. moschata (6x), two of F. nubicola (2x), and two of F. viridis (2x). Both 2x × 6x and 6x × 2x crosses were performed. Initially, negligible seed set occurred on F. nubicola and F. viridis when multiple flowers per truss were pollinated. When only one cross was performed per truss, with other flowers removed, seed set was greatly enhanced. F. moschata was much more tolerant of multiple crosses per truss. The crossing combination of F. moschata × F. nubicola gave the worst seed production. Other species combinations were capable of producing good seed set with noticeable differences between individual selections. When achenes were halved, only 1% appeared normal, 2% were underdeveloped or shrunken, the remainder were empty. Many of the malformed and most of the normal embryos germinated using the cut achene method. Achenes were surface-sterilized, cut in half, and placed on MS media with activated charcoal (3g·L–1), sucrose (30g·L–1), and no hormones. Germination occurred only from achenes from fully ripened fruit. Viable hybrids were obtained from 2x × 6x as well as 6x × 2x crosses. Fragaria viridis–F. moschata hybrids closely resembled F. moschata while F. nubicola–F. moschata hybrids were more intermediate in leaf morphology.

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W.A. Erb, A.D. Draper, G.J. Galletta, and H.J. Swartz

Data from a four-parent diallel, involving one highbush (Vaccinium corymbosum L.) clone and three interspecific hybrids grown on mineral soil unamended with organic matter, were analyzed to determine combining ability effects for six traits: plant size, berry size, the number of days between flowering and fruiting (# DBF&F), the ratio of total fruit weight to canopy volume (TFW: CYV), days to fruit ripe, and yield. General combining ability effects were significant for all characters tested, except yield and berry size in 1984. Specific combining ability effects were significant for plant size in 1983, #DBF&F in 1984, TFW: CYV in 1984, and berry size in 1985. Vigorous and productive highbush cultivars can be developed for mineral soils by using the interspecific clones from this study and their selected recombinant to combine the genes for plant vigor with the high-quality fruit traits of highbush cultivars.

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Winston Elibox and Pathmanathan Umaharan

Modern-day anthurium cultivars are complex interspecific hybrids between Anthurium andraeanum Linden ex André and other species belonging to the section, Calomystrium, and are collectively referred to as A. andraeanum (Hort.) ( Kamemoto and

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Mark J. Bassett

A new gene for flower color pattern, designated white banner (WB), appeared in material derived from the cross `Harvester' snap bean (Phaseolus vulgaris L.) × Plant Introduction (PI) accession 273666 of scarlet runner bean (P. coccineus L.). The WB character has a white banner petal and pale violet wings (veronica-violet 639/2). The inheritance of the mutant was studied in crosses involving dry bean breeding line 5-593, which has bishops-violet (wild-type) flowers, and genetic stocks v BC2 5-593 (white flowers) and blu BC2 5-593 (blue flowers). Segregation in F2 and F3 progenies from the cross v BC2 5-593 × WB supported the hypothesis that WB is controlled by a single recessive gene that is nonallelic with the V locus. An allelism test with blu BC2 5-593 gave evidence that WB is not allelic with the blu locus. The gene symbol wb is proposed for the gene producing WB.

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Mi-Young Chung, Jae-Dong Chung, Jaap Van Tuyl, and Ki-Byung Lim

Intergenomic F1 hybrids between L. auratum and L. henryi were made and backcrossed to Oriental hybrids to produce BC1 progenies. The F1 intergenomic hybrids produced a relevant frequency of 2n-gamete and fertile pollen. Analyses of pollen size, viability, and germination ability were checked under microscopic observation. GISH analysis confirmed that F1 intergenomic hybrids possess a set of chromosomes from both parents and showed an intermediate morphological phenotype. Twenty BC1 plants were generated by in vitro embryo rescue technique, and analyzed for genome composition by GISH. All plants were triploid, showing 12 from female parent (2× Oriental) and 24 from male (2× F1 hybrid). Based on the GISH analyses, 19 BC1 plants were derived from FDR 2n-gamete and only one plant was derived from IMR 2n-gamete of F1 hybrid. The genome composition of 19 BC1 plants from FDR 2n-gamete possess 12 Orientals + 12 L. auratum + 12 L. henryi chromosomes with some extent of homoeologous recombination between L. auratum and L. henryi. However, one plant from IMR 2n-gamete origin contains an odd number of parental chromosomes from F1 hybrid, showing 12 Oriental + 14 L. auratum + 10 L. henryi chromosomes. In this case, two L. auratum chromosomes recombinant with L. henryi chromosome segments were added and L. henryi counterpart chromosomes were deleted, respectively.