Interspecific Hybrid Cultivars Research Articles

A mixed model approach for evaluating yield improvements in interspecific hybrids of shrub willow, a dedicated bioenergy crop

Lignocellulosic bioenergy crops such as shrub willow (Salix spp.) are expected to have a significant role in climate mitigation strategies. Yield is perhaps the most important trait for genetic selection and development of biomass feedstocks, but the selection process is complicated by the strong influence that environmental factors has on cultivar performance. Understanding the genotype-by-environment interactions using regional yield trials of shrub willow will inform future breeding efforts and improve the ability to make regionally-specific cultivar recommendations. We analyzed two yield trial datasets containing genotypes from successive rounds of breeding using a series of mixed models. Stability variance parameters were used together with overall yields to identify genotypes with stable yields or specific adaptation. Analysis of the first dataset revealed a group of triploid interspecific hybrid cultivars with exceptional performance and specific adaptation to either poor or good quality environments. The best performing cultivar showed a 14% yield improvement over the mean of the check cultivars. In the second dataset, new selections were assessed along with the top performing cultivars from dataset 1. New triploid hybrids had yields 19 to 27% greater than the check cultivar and exhibited similar patterns of specific adaptation as some of the selections from the first dataset. Partial least squares regression analysis indicated that top-yielding genotypes were favored in environments with higher temperatures and greater growing degree days. This analysis demonstrates incremental improvements in yield with successive rounds of breeding through the development of interspecific triploid hybrids.

Infection and Colonization of Several Bermudagrasses by Ophiosphaerella korrae.

Bermudagrass (Cynodon spp.) is the most commonly used turfgrass in the southern United States where it is severely affected by spring dead spot (SDS) caused by Ophiosphaerella herpotricha, O. korrae, and O. narmari. In this study, infection of bermudagrass roots and stolons by O. korrae was characterized using a transformant that expressed the red fluorescent protein tdTomato. Roots of interspecific hybrid cultivars Midlawn and Tifway 419, C. transvaalensis accessions Uganda and 3200, and C. dactylon cultivar U3 were inoculated and observed from 2 to 14 days postinoculation (DPI) while stolons were observed from 2 to 22 DPI. For all five cultivars tested, a similar level of root colonization was observed; however, differences were observed in the rate of necrosis development. Necrosis of Tifway 419 and Midlawn tissues was evident at 2 DPI, in Uganda and 3200 at 8 DPI, and in U3 necrosis was often absent as late as 14 DPI. The fungus rapidly penetrated the root epidermis and colonized the cortex of all cultivars by 4 DPI. Colonization of stele tissues by O. korrae was rare in hybrid cultivars but common in C. transvaalensis and C. dactylon accessions. On intact stolons, the fungus did not penetrate the epidermis 22 DPI though epidermal necrosis was evident on the surface of only the hybrid bermudagrasses. Wounded stolons became necrotic in all cultivars. Infection and colonization of various bermudagrasses by O. korrae was found to be similar to that by O. herpotricha, suggesting that host genetic resistance may be used for effective management of SDS caused by both species.

Heat treatment and germination of seeds of interspecific hybrid between American oil palm (Elaeis oleifera (H.B.K) Cortes) and African oil palm (Elaeis guineensis Jacq.)

The oil palm (E. guineensis ) is the African origin and the world's leading source of vegetable oil. The interspecific hybridization of the African oil palm (E. guineensis) with American oil palm (E. oleifera) aims to improve resistance to diseases, to improve oil quality and lower plant height. EMBRAPA (Empresa Brasileira de Pesquisa Agropecuária, Brazilian Corporation of Agricultural Research) has developed the first Brazilian interspecific hybrid cultivar (HIE) between American oil palm and African oil palm. The procedures adopted for commercial seed germination assessment have shown an average germination rate of 32%. The objective of this work was to assess the effect of the period of heat treatment and seed water content that are ideal for breaking dormancy and obtaining maximum germination. A completely randomized design was adopted, in a 4 x 3 factorial design, with four ranges of moisture contents: 18-19; 19-20; 20-21 and 21-22%, and three periods of heat treatment: 55, 75 and 100 days, with three replicates of 500 seeds. The percentage of germination, the first count and the germination speed index were assessed. To break dormancy and germination, the hybrids seeds of HIE, oleifera versus guineensis, should have their water content adjusted to values between 19 and 22%, and be subjected to heat treatment at a temperature of 39 ± + 1 ºC and relative humidity of approximately 75% for 75 days.

Wine Grape Cultivar Performance in the Four Corners Region of New Mexico in 2010–12

Commercial wine grape (Vitis sp.) production in northwestern New Mexico and the greater Four Corners region is now supported by four wineries. The challenges of growing grape vines in northwestern New Mexico include cold winter temperatures and killing spring frosts exacerbated by a semiarid climate and elevations exceeding 1700 m. Nineteen nongrafted European wine grape (Vitis vinifera) and interspecific hybrid wine grape cultivars were planted in 2007 and evaluated between 2010 and 2012. Among European wine grape cultivars, Agria, Malbec, Sangiovese, Viognier, Müller-Thurgau, and Sauvignon Blanc performed poorly or failed altogether. Interspecific hybrid cultivars Baco Noir, Kozma 55, Leon Millot, Chardonel, Seyval Blanc, Siegfried, Traminette, Valvin Muscat, and Vidal Blanc showed greater adaptability to a high-elevation intermountain western U.S. site, yielding on greater than 71% of their vines in each year (except Kozma 55 which only produced on 38% of its vines in 2012 due to severe spring frost damage). We speculate that fruit-bearing shoots on these vines arose from latent buds that survived when primary buds were killed from spring frost events. Once vines were established, grape berry sugar and pH appeared to be within acceptable ranges (3-year mean above 21% soluble solids and juice pH of 3.2), suggesting regional potential to produce favorable wines within acceptable commercial wine grape production ranges. Selection of sites without considerable frost risk and other mesoclimate variances is critical when considering vineyard establishment at high-elevation locations.

Inheritance of resistance to brown leaf spot disease in gentians

Brown leaf spot caused by Mycochaetophora gentianae is a serious disease on gentian in Japan. Previous studies revealed that Gentiana triflora cultivars were susceptible to M. gentianae and that G. scabra cultivars and their interspecific hybrid cultivars were resistant. We subsequently analyzed the mode of inheritance of resistance to M. gentianae in gentians using several populations derived from crosses between G. scabra and G. triflora. Parental G. scabra and G. triflora lines, F1 and BC1 plants were inoculated with a conidial suspension and assessed for susceptibility to M. gentianae. All tested F1 plants were resistant to M. gentianae, indicating that the resistance of G. scabra was inherited dominantly. Segregation ratios in backcross progenies using G. scabra line OK fit the Mendelian ratio of 1:1, showing the involvement of a single dominant locus. These results indicate that the resistance to M. gentianae in G. scabra line OK is controlled by a single dominant allele designated as gentian brown leaf spot resistance (GBLS-1). Finding this allele should facilitate future breeding efforts to develop resistant gentian cultivars.

Genetic diversity and population structure assessed by SSR and SNP markers in a large germplasm collection of grape

BackgroundThe economic importance of grapevine has driven significant efforts in genomics to accelerate the exploitation of Vitis resources for development of new cultivars. However, although a large number of clonally propagated accessions are maintained in grape germplasm collections worldwide, their use for crop improvement is limited by the scarcity of information on genetic diversity, population structure and proper phenotypic assessment. The identification of representative and manageable subset of accessions would facilitate access to the diversity available in large collections. A genome-wide germplasm characterization using molecular markers can offer reliable tools for adjusting the quality and representativeness of such core samples.ResultsWe investigated patterns of molecular diversity at 22 common microsatellite loci and 384 single nucleotide polymorphisms (SNPs) in 2273 accessions of domesticated grapevine V. vinifera ssp. sativa, its wild relative V. vinifera ssp. sylvestris, interspecific hybrid cultivars and rootstocks. Despite the large number of putative duplicates and extensive clonal relationships among the accessions, we observed high level of genetic variation. In the total germplasm collection the average genetic diversity, as quantified by the expected heterozygosity, was higher for SSR loci (0.81) than for SNPs (0.34). The analysis of the genetic structure in the grape germplasm collection revealed several levels of stratification. The primary division was between accessions of V. vinifera and non-vinifera, followed by the distinction between wild and domesticated grapevine. Intra-specific subgroups were detected within cultivated grapevine representing different eco-geographic groups. The comparison of a phenological core collection and genetic core collections showed that the latter retained more genetic diversity, while maintaining a similar phenotypic variability.ConclusionsThe comprehensive molecular characterization of our grape germplasm collection contributes to the knowledge about levels and distribution of genetic diversity in the existing resources of Vitis and provides insights into genetic subdivision within the European germplasm. Genotypic and phenotypic information compared in this study may efficiently guide further exploration of this diversity for facilitating its practical use.

Genetic variability and relationships among interspecific hybrid cultivars and parental species of Paphiopedilum via ribosomal DNA sequence analysis

The aim of the present study was to investigate genetic variability and relationships among several hybrid cultivars and parental species of Paphiopedilum for the purposes of further breeding. Genetic information was obtained by means of phylogenetic analysis, using nuclear ribosomal DNA (rDNA) nucleotide sequence data. Nuclear rDNA was derived from internal transcribed spacer (ITS) regions, and the 5.8S regions were amplified by polymerase chain reaction. The resulting nucleotide sequences were examined and compared for genetic variability, and the relationships were analyzed by pair-wise multiple alignment. ITS region analysis revealed the following lengths of the ITS1, ITS2, and 5.8S regions: 382–428, 207–215, and 170 bp, respectively. Sequence identity at the ITS site, including the 5.8S region, ranged from 75.9 % between P. emersonii and P. sanderianum, to 99.4 % between Paphiopedilum ‘Hamana Wave’ and Paphiopedilum ‘Kolosand’. Next, we investigated whether each of the analyzed hybrid cultivars could be identified and differentiated at the interspecies or intraspecies levels. Our phylogenetic tree revealed that hybrids derived from the subgenus Brachypetalum were clearly differentiated from those derived from the subgenus Paphiopedilum. Moreover, interspecific hybrids showed unique phylogenetic positioning among parental species, according to the ITS sequence.

Evaluating Grapevine Cultivars for Resistance to Anthracnose Based on Lesion Number and Length

Anthracnose is one of the most detrimental diseases of grapevines in humid regions. To lessen the risk of crop damage and to reduce fungicide application, resistant cultivars are needed. The resistance of grapevines to anthracnose caused by <i>Elsinoë ampelina</i> (de Bary) Shear was evaluated in two ways: the resistance against ingress was evaluated using the number of lesions and the resistance against colonization was evaluated using the lesion length. First, both forms of resistance in 13 cultivars were evaluated in a detached-leaf assay for three years using greenhouse-grown cuttings. Both lesion number and lesion length revealed a genetic component of the resistance, with greater phenotypic variation among interspecific hybrid cultivars than among <i>Vitis vinifera</i> cultivars. The detached-leaf assay revealed significant differences in lesion length among <i>V. vinifera</i> accessions; Exotic and Perlette showed moderate resistance. Lesion diameters were measured in a fungicide-free vineyard to evaluate the resistance of six cultivars, and significant differences were found among the cultivars. The lesion shape in susceptible cultivars was almost circular, whereas the shape in resistant cultivars was usually irregular. Results showed that evaluations based on the lesion number and length can reliably predict resistance to anthracnose without the need for large field trials and that some <i>V. vinifera</i> cultivars exhibited moderate resistance to this disease.

Characterization of fungal pathogens associated with grapevine trunk diseases in Arkansas and Missouri

Grapevine trunk diseases are a major concern to the wine- and table-grape industries worldwide, limiting both vineyard longevity and productivity. Field surveys conducted throughout the grape-growing regions of Arkansas and Missouri revealed the presence of three economically important grapevine trunk diseases including, Botryosphaeria canker, Eutypa dieback and esca. Morphological studies along with multi-gene phylogenetical analyses confirmed the identification of 15 different fungal taxa associated with different vascular symptoms. These include Botryosphaeria dothidea, Diatrypella sp., Diplodia seriata, Dothiorella americana, Eutypa lata, Eutypella vitis, Lasiodiplodia missouriana, Lasiodiplodia viticola, Neofusicoccum ribis, Neofusicoccum vitifusiforme, Pestalotiopsis sp., Pestalotiopsis uvicola, Phaeomoniella chlamydospora, Phomopsis viticola, Schyzophyllum commune, and Togninia minima. All of these represent new records on grapevines in Arkansas and Missouri. Dothiorella americana, L. missouriana and L. viticola are described as new species, and both N. ribis and N. vitifusiforme are first reported as grapevine pathogens in North America. Koch’s postulates confirmed the pathogenicity of all fungal species except S. commune in the interspecific hybrids Vignoles, Chambourcin, Norton, and Traminette. Lasiodiplodia spp., N. ribis, and P. viticola were the most virulent fungi, while D. americana, E. vitis and N. vitifusiforme were considered to be weak pathogens. This research highlights the importance that grapevine trunk diseases have on grapevine health in growing regions where, due to different climatological conditions, interspecific hybrid cultivars are predominantly grown.

Effects of Early Defoliation on Yield, Fruit Composition, and Harvest Season Cluster Rot Complex of Grapevines

Viticulture in Michigan is limited by a cool and humid climate and as a result, there is a problem of harvest season cluster rot, especially in cultivars with compact cluster morphology. Economically important wine grape varieties in eastern North America possess varying susceptibility to harvest season cluster rot. Some important cultivars that are susceptible are Pinot gris, Pinot noir, Riesling (Vitis vinifera L.) as well as Seyval and Vignoles (French–American hybrids or interspecific hybrid cultivars). A common characteristic of these cultivars is the compactness of the berries held on the cluster rachis. The aim of this work was to determine whether a quantified amount of leaf removal or a temporary reduction in carbon assimilation at the beginning of bloom would reduce fruit set and cluster compactness. Vines subjected to removal of four or six basal leaves had an average fruit set reduction of ≈45% from a non-treated control. Cluster weight and berries per cluster were similarly reduced with a greater effect on the basal than the apical cluster of the shoot. Reduced fruit set was associated with a reduction in cluster compactness and harvest season rot. This was also reflected in yield and basic fruit chemistry parameters associated with the importance of basal leaves to the developing cluster. Multiple applications of stylet oil at different time intervals resulted in significant reduction in net photosynthesis (Pn). A single application had no significant impact on Pn, whereas multiple applications reduced leaf assimilation rates. However, this reduction in Pn did not reduce fruit set or improve cluster compactness. There was a strong negative effect of early leaf removal in Year 1 on vine performance in Year 2; this carryover effect increased shootless nodes per vine, reduced the number of clusters per shoot and per vine, and dramatically reduced fruit set and consequently yield per vine.

Pathogenicity of Mycochaetophora gentianae, causal fungus of gentian brown leaf spot, as affected by host species, inoculum density, temperature, leaf wetness duration, and leaf position

When the influence of host species, inoculum density, temperature, leaf wetness duration, and leaf position on the incidence of gentian brown leaf spot caused by Mycochaetophora gentianae, was examined, the fungus severely infected all seven Gentiana triflora cultivars, but failed to infect two cultivars of G. scabra and an interspecific hybrid cultivar. Inoculum density correlated closely with disease incidence, and a minimum of 102 conidia/mL was enough to cause infection. In an analysis of variance, temperature and leaf wetness duration had a significant effect upon disease incidence, which increased with higher temperature (15–25°C) and longer duration of leaf wetness (36–72 h). No disease developed at temperatures lower than 10°C or when leaf wetness lasted 50% of conidia germinated at temperatures >15°C after 24-h leaf wetness. More appressoria formed at higher temperatures (15–25°C) with extended duration of leaf wetness (24–72 h). At 48-h leaf wetness, appressorium formation was 0, 8, 26, and 73% at 10, 15, 20, and 25°C, respectively. These results suggest that temperature and leaf wetness duration were important factors for infection of gentian leaves.

Early identification of waxflower (Chamelaucium) hybrids using RGAP markers

Waxflower is one of Australia's major native cut flowers for the export market. A number of interspecific hybrid cultivars such as the ‘Pearl’ series bred by the Department of Agriculture and Food, Western Australia have increased the competitiveness of waxflower on world markets. To improve the breeding efficiency, resistance gene analog polymorphisms (RGAP) are investigated as molecular markers for the early identification of interspecific hybrids between Chamelaucium uncinatum and C. megalopetalum. The results show that RGAP can be effectively applied to generate DNA markers to identify true waxflower hybrids. The RGAP marker system provides a reliable, simple, fast and inexpensive approach for hybrid identification in waxflower breeding.

GENETIC CONTROL OF TENDRIL DISTRIBUTION IN A GRAPEVINE ROOTSTOCK HYBRID POPULATION

Grapevine tendril distribution is a characteristic of varieties and species. We examined the tendril distribution on a population of seedlings from a 161-49C x (V. labrusca x V. mustangensis) hybridization. 16149C is a V. riparia x V. berlandieri hybrid that ordinarily bears tendrils in a discontinuous pattern. Although the V. labrusca x V. mustangensis parent frequently demonstrates more than two tendrils in sequence, it does show nodes without tendrils and as such cannot be described as strictly continuous in its tendril distribution. Grapevine tendrils and clusters (inflorescences) are found at the node opposite a leaf. Cultivars and spe cies exhibit some variation in tendril distribution, the phyllotactic patterning of which nodes have tendrils (or clusters) and which do not. Most Vitis species and cultivars have two nodes with tendrils followed by a node without a tendril (Mullins et al., 1992; Gerrath et al., 1998). This pattern is called intermittent tendril distribution. However, in the North American species V. labrusca and some V. labrusca interspecific hy brids, a tendril is found at every node (continuous tendril distribution). Some interspecific hybrid cultivars have an intermediate tendril distribution, with more than two nodes in a row bearing tendrils, but with occasional tendril-free nodes. Cousins et al. (2005) reported exploratory studies in the genetic control of phyllotactic patterning. Here we report in-depth analysis of a population segregating for tendril distribution patterns.

Differential Resistance Among Crape Myrtle (Lagerstroemia) Species, Hybrids, and Cultivars to Foliar Feeding by Adult Flea Beetles (Altica litigata)

Field (choice) and laboratory (no choice) studies were conducted to evaluate the susceptibility of 12 crape myrtle (Lagerstroemia) cultivars, representing two species and their interspecific hybrids, to feeding damage by the flea beetle (Altica litigata Fall). The results indicate that as a group, the L. indica L. cultivars were more susceptible to attack and significant herbivory damage by Altica beetles, whereas all the L. fauriei Koehne cultivars and most of the interspecific L. indica × fauriei hybrids were resistant. Significant differences in feeding damage were observed between the new and older leaves in the susceptible hybrid ‘Biloxi’ and L. indica ‘Whit IV’, but not in the rest of the cultivars. Mineral nutrient content differences were observed between species with L. indica cultivars having a significantly contrasting nutrient status profile compared with the L. fauriei and interspecific hybrid cultivar groups. The results indicate that the factors influencing Altica flea beetle-feeding preferences and damage are inherited and therefore will allow the implementation of pest management practices that minimize damage and optimize chemical control strategies. In addition, opportunities may exist for breeding and selection efforts that could lead to superior cultivars with insect resistance.

Presence of defeated qualitative resistance genes frequently has major impact on quantitative resistance to Melampsora larici-populina leaf rust in P. × interamericana hybrid poplars

Qualitative resistance to Melampsora larici-populina leaf rust inherited from North American species Populus deltoides did not allow for durable control of this pathogen in interspecific hybrid cultivars. Despite significant levels of strain-specificity, quantitative resistance would exert lower selection pressures on the pathogen populations, and hence could be more durable. Previous studies restricted to a large P. × interamericana (i.e., P. deltoides × Populus trichocarpa) F1 family revealed that the presence of R1, a segregating defeated qualitative resistance gene inherited from P. deltoides, had major beneficial effects on quantitative resistance. The present study was based on 14 F1 families from a 4 × 5 P. deltoides × P. trichocarpa factorial mating design where at least four defeated qualitative resistances segregate 1:1. Even though quantitative resistance assessments were conducted in the laboratory with a M. larici-populina strain able to overcome these qualitative resistances, their presence had a significant effect on the mean level and on the genetic variability for quantitative resistance. One unprecedented result is the identification of a defeated qualitative resistance which presence is associated with lower levels of quantitative resistance. Possible inferences on the nature of the genetic relationship between both resistance types are discussed.

BIOGEOGRAPHY AND ORIGIN OF LILIUM LONGIFLORUM AND L. FORMOSANUM I - INTERSPECIFIC ISOLATING MECHANISMS AND POPULATION GENETIC STRUCTURE

BIOGEOGRAPHY AND ORIGIN OF LILIUM LONGIFLORUM AND L. FORMOSANUM I - INTERSPECIFIC ISOLATING MECHANISMS AND POPULATION GENETIC STRUCTURE

Genotypic and Environmental Variation in Antioxidant Activity, Total Phenolic Content, and Anthocyanin Content among Blueberry Cultivars

Dietary antioxidants may have a role in preventing some of the chronic diseases in humans resulting from free radical oxidation of lipids and other cellular components. Blueberries (Vaccinium L. sp.) are considered one of the best fresh fruit sources of antioxidants, and there is the potential to increase the antioxidant activity further through breeding. Thus, the variability of fruit antioxidant activity (AA) was examined among a set of 16 highbush and interspecific hybrid cultivars grown at locations in Minnesota (MN), Michigan (MI), and Oregon (OR) over 2 years (1998 and 1999) to determine effects of genotype, year, and location. Nine cultivars were common to all three locations in both years. Antioxidant activity, total phenolic content (TPH), and total anthocyanin content (ACY), were determined in triplicate samples from each genotype. Cultivars differed significantly (P ≤ 0.05) in AA, TPH, and ACY both within and over locations. The single location mean AA for all cultivars changed significantly between the 2 years in OR and in MI, while the single location mean for TPH differed between the 2 years in MN and MI. Changes in cultivar rank were significant for AA, TPH, and ACY between years within each location. Significant changes in rank for TPH and ACY were also noted between pairs of locations as well. Pearson's correlation for AA (based on cultivar means) appeared highest between MN and OR (r = 0.90) and MN and MI (r = 0.69) in 1998; correlations between locations for the combined years were 0.74 for MN and OR, 0.55 for MN and MI and 0.45 for MI and OR. For the group of nine cultivars, AA correlated well with TPH within each location, with r ranging from 0.67 to 0.95 for data from individual and combined years. Correlation of AA with ACY at each location was lower than that for AA with TPH, in both individual and combined years. This study demonstrates significant genotype× environment interaction for AA in blueberry.

Effects of Flower Bud Density on Vegetative and Reproductive Development and Carbohydrate Relations in Southern Highbush Blueberry

Vegetative budbreak and subsequent canopy development in some southern highbush blueberry (Vaccinium corymbosum L. interspecific hybrid) cultivars are delayed and/or reduced as flower bud density increases. This delay/reduction in vegetative growth has been correlated with decreased weight and soluble solids of individual fruit. In the present study, the effects of flower bud density (FBD) on vegetative budbreak and canopy development, starch reserves, and whole-canopy net CO2 exchange rate (NCER) were assessed to determine how FBD affected the source supply for fruit development. A range of flower bud densities was established in two cultivars of containerized southern highbush blueberry during dormancy. Vegetative budbreak was delayed and vegetative budbreak, leaf area, and leaf area to fruit ratios decreased as FBD increased. In general, increasing FBD increased the rate of root and cane starch depletion during the first four weeks after bloom. Whole-canopy NCER was similar across the range of FBD during early fruit development, but between four weeks after bloom and fruit ripening, NCER decreased as FBD increased. Although FBD explained only a small proportion of the variability observed in carbohydrate concentration and NCER, the data suggest that both the rapid depletion of starch reserves early in fruit development and the decrease in whole canopy NCER later in fruit development contribute to the detrimental effects of increased FBD on fruit development.

583 Field performance of Grafted Chestnut Cultivars and their Seedlings

We planted grafted and seedling chestnuts of six cultivars in Lansing, N.Y., in April 1995 to evaluate performance of the different cultivars in our region and to compare grafted and seedling trees. We used the following cultivars: the Chinese chestnut cultivar Mossbarger (Castanea mollissima) and five interspecific hybrid cultivars [Douglas 1A (C. mollissima × C. dentata), Eaton [C. mollissima × (C. crenata × C. dentata)[, Skioka (C. mollissima × C. sativa), Layeroka (open-pollinated daughter of `Skioka'), and Grimo 142Q (an open pollinated daughter of `Layeroka')]. Growth was not significantly different between cultivars. There were no notable correlations between trunk cross-sectional area at planting and any measurement after the first year. Significant differences between cultivars were found for mortality, yield, and yield efficiency. `Eaton' had the lowest mortality rate (2%) of all cultivars. `Grimo 142Q' and `Layeroka' had the highest dry weight yields and the greatest yield efficiencies, although `Grimo 142Q' had significantly larger nuts than `Layeroka'. In 1998, the largest nuts (5.2 g) were harvested from `Mossbarger' and `Eaton trees'. `Skioka' had the highest mortality (48%), lowest yield, lowest yield efficiency, and smallest nut size. In the first 2 years, most grafted trees showed significantly higher yields and greater yield efficiency than seedling trees. By the third year, differences in yield between grafted and seedling trees were no longer significant for most cultivars. Over the 3 years most grafted trees revealed higher mortality and slower growth than seedlings of the same cultivar. Seedlings did not show more variability in measurements than grafted trees of the same cultivar.

Tracing the Parentages of Some Oriental Hybrid Lily Cultivars by PCR-RFLP Analysis.

PCR-RFLP analysis was applied to some interspecific hybrid cultivars of lily to verify their probable parentage. Six Lilium species, L. auratum var. platyphyllum, L. japonicum, L. speciosum, L. nobilissimum, L. auratum and L. rubellum, were analyzed with four pairs of primers and 22 restriction enzymes ; among them PCR-RFLP markers, characteristic to each species, were detected. L.×formolongi, L. speciosum and their artificial hybrids derived by embryo culture confirmed that the PCR-RFLP markers in a chloroplast gene of the female parent were inherited by all hybrids, whereas the markers in a nuclear rRNA gene of the hybrids possessed a combined band pattern of the female and pollen parents. Hence, we utilized PCR-RFLP analysis for tracing the parents of interspecific hybrid cultivars. PCR-RFLP gel patterns were analyzed to trace parents of six lily hybrid cultivars called Oriental hybrids, 'Star Gazer', 'Le reve', 'Casa Blanca', 'Summer Dress', 'Pink Pearl', and 'Marco Polo'. The data indicate that the cytoplasm of 'Casa Blanca', 'Summer Dress', and 'Pink Pearl' was transmitted from L. speciosum, whereas that of 'Star Gazer', 'Le reve', and 'Marco Polo', was inherited from L. auratum var. platyphyllum or L. japonicum. The pollen parents of these hybrids were not completely identified because genetic segregation may have occurred at gametogenesis if pollen parents were interspecific hybrids.