ancestors as a result of random selection of parents that go unreported or deliberate open-pollination. Despite the important role of wide hybridization in blueberry breeding, we know little about its effects on DNA polymorphism. SHB are assumed to be
Patricio A. Brevis, Nahla V. Bassil, James R. Ballington, and James F. Hancock
Timothy F. Wenslaff and Paul M. Lyrene
Two diploid yellowleaf Vaccinium elliottii Chapmn. clones were pollinated with pollen from the tetraploid southern highbush cultivar `Misty' (largely V. corymbosum L). These interspecific crosses, which normally yield few hybrids because of a triploid block, were made with and without the use of V. elliottii mentor pollen mixed with V. corymbosum pollen. Mentoring had no effect on the number of hybrids produced when V. elliottii `Silverhill' was the seed parent, but when V. elliottii `Oleno' was the seed parent, no hybrids were produced unless mentor pollen was utilized. The difference was postulated to be a greater ability to produce one-seeded berries in `Silverhill' than in `Oleno'.
Paul M. Lyrene
females ( Table 1 ). At least two V. stamineum plants (not shown in Table 1 ) thought to be tetraploid based on pollen size gave few or no seeds when crossed onto highbush. After reviewing many experiments in wide hybridization of plants, Darwin (1859
Sandra M. Reed, Keri D. Jones, and Timothy A. Rinehart
D. febrifuga than to other Hydrangea L. species ( Rinehart et al., 2006 ). Morphological investigations support a close relationship between these two species ( Hufford, 2001 ; Soltis et al., 1995 ). Wide hybridization has resulted in a number
James W. Olmstead, Hilda Patricia Rodríguez Armenta, and Paul M. Lyrene
.R. Hancock, J.F. 2008 Impact of wide hybridization on highbush blueberry breeding J. Amer. Soc. Hort. Sci. 133 427 437 Brooks, S.J. Lyrene, P.M. 1998a Derivatives of Vaccinium arboreum × Vaccinium section Cyanococcus : I. Morphological characteristics J
Hirotoshi Tsuda, Hisato Kunitake, Mai Yamasaki, Haruki Komatsu, and Katsunori Yoshioka
cultivated highbush blueberry HortScience 46 563 566 Lyrene, P.M. Ballington, J.R. 1986 Wide hybridization in Vaccinium HortScience 21 52 57 Lyrene, P.M. Olmstead, J.W. 2012 The use of inter-sectional hybrids in blueberry breeding Intl. J. Fruit Sci. 12 269
Jason D. Lattier and Ryan N. Contreras
studies, as demonstrated by Liu et al. (2013) . Though interseries crosses and in vitro germination failed to achieve hybrids, the quantity of seed produced combined with several seed that germinated in vitro provides evidence that future work on wide
Sylvia J. Brooks and Paul M. Lyrene
Morphological characteristics of many derivatives from Vaccinium arboreum Marsh × Vaccinium section Cyanococcus crosses were studied. The purpose of the study was to determine if V. arboreum traits were being inherited and expressed in hybrid progeny and to identify characteristics that would enable hybrid field identification. This study focused on the F1 hybrids of V. darrowi Camp × V. arboreum (F1 hybrids) and the open-pollinated progeny of the F1 hybrids [mother is known (MIK)]. Also included in the study were the parents: V. darrowi, V. arboreum, and V. corymbosum L. (pollen parent of the MIKs). Many leaf, flower, and fruit characteristics were measured for all five taxa. Leaf characteristics included length, width, and presence or absence of stalked glands, pubescence, and marginal bump glands. The floral characteristics measured were corolla length and width, corolla aperture, pedicel length, peduncle length, bracteole length and width, and the presence or absence of anther awns and bracteoles. Berry and seed mass were the fruit characteristics investigated. Four unique V. arboreum traits were found to be expressed in the F1 and MIK hybrid populations. These were the presence of anther awns, large seed size, bracteole shape, and marginal glands. These traits should permit field identification of hybrid plants.
John R. Stommel
Solanum ochranthum Dunal is a nontuber bearing wild relative of the cultivated tomato (Lycopersicon esculentum Mill.), and a potential source of new genes for disease and pest resistance. Because S. ochranthum is sexually isolated from tomato, somatic hybrids between tomato (PI 367942; L. esculentum Mill. var. cerasiforme (Dunal) A. Gray VFNT cherry × L. peruvianum (L.) Mill. backcrossed to VFNT cherry) and S. ochranthum (LA2117) were developed previously to overcome these crossing barriers. Attempts to backcross these hybrids to tomato have been unsuccessful. Pollen fertility and mitotic and meiotic studies in tomato + S. ochranthum somatic hybrids determined the cause of the sterility of the somatic hybrids and identified hybrids with moderate fertility. Chromosome counts of dividing root tip cells delineated tetraploid (2n = 4x = 48) and hexaploid (2n = 6x = 72) genotypes and aneuploidy in these hybrids. Meiotic analysis of developing microspores confirmed the presence of precocious division and laggard chromosomes at anaphase in both hexaploid and tetraploid hybrids. Bridges were observed in hexaploids at anaphase I and II and multivalent configurations were observed at diakinesis. Multivalents and univalents were evident in nearly all cells examined, proving that the two genomes are homoeologous. Aberrant microsporocytes with five to six developing microspores were noted in hexaploid hybrids. The occurrence of homoeologous pairing between chromosomes of both fusion parents is advantageous to effect recombination between these isolated species. However, the negative effects of multivalent formation and univalents likely contributed to observed sterility in these first generation fusion hybrids. Low to moderate levels of pollen fertility (0% to 52%) were found in tetraploid hybrids, while little or no viable pollen (0% to 4%) was observed in hexaploid somatic hybrids.
Diploid plants in Vaccinium section Cyanococcus, including plants of V. darrowi Camp, V. atrococcum. Heller (diploid V. corymbosum L.), a V. atrococcum × V. darrowi F1 hybrid, and a V. atrococcum × V. elliottii Chapmn. F1 hybrid, were hand pollinated in a greenhouse with pollen from diploid V. arboreum Marsh. (Section Batodendron). The resulting seeds were germinated and the seedlings were transplanted to a high-density field nursery. Forty of these F1 intersectional hybrids were selected after 2 1/2 years and transplanted to a 1.5 × 4-m spacing. Most of these plants were vigorous and flowered heavily in subsequent years, but only a small percentage of the flowers produced fruit. In 1990, however, >4000 berries were harvested from the 35 surviving plants. Open-pollinated seed from a much smaller number of berries was planted in Dec. 1987; these seeds produced ≈200 seedlings, some of which had moderate to high fruit set in a field nursery in 1989. Six of these seedlings, which were selected for high vigor, high fruit set, and characteristics intermediate between section Cyanococcus and section Batodendron, had fruit set ranging from 19.4% to 92.7% when pollinated with pollen from tetraploid V. corymbosum cultivars. One of the six seedlings was highly self-fruitful, and some intercrosses among the six seedlings produced much viable seed. Large-scale introgression of V. arboreum genes into tetraploid highbush cultivars likely will be possible by the methods used in this study.