Crossability values within the slash-caribbeanPinus species complex

Summary Crossability values were calculated for (a) eight individual tree crosses betweenPinus elliottii Engelm. var.elliottii L. & D. andP. caribaea Mor. var.caribaea B. & G., (b) ten crosses betweenP. caribaea var.caribaea andP. caribaea var.hondurensis B. & G., and (c) twelve crosses betweenP. elliottii var.elliottii andP. caribaea var.hondurensis. Individual trees showed differences in ability to hybridize. Despite wide variation for each combination, the compatibility of the various combinations could be defined. It was high for (a), moderate for (b) and poor for (c). These results indicate the need for taxonomic review of theP. elliottii — P. caribaea species complex and suggest that hybridization within the complex might have economic value in Queensland forests.     

Intraspecific hybridization in Pinus caribaea var. hondurensis II. Genetic parameters

Genetic parameters of growth and stemstraightness to seven years of age wereestimated from two field populations ofpure Pinus caribaea var. hondurensis provenances and theirintraspecific hybrids, (Mountain Pine Ridge(MPR) × coastal provenances). There were noconsistent differences in the geneticparameter estimates obtained for theparental provenances compared to those fromthe MPR × coastal inter-provenance hybridcrosses. Narrow-sense heritabilities ofgrowth traits (0.06–0.33) andstraightness (0.21–0.50) were within therange of estimates that have beenpreviously reported for this species andother tropical pines. In general, additivevariance was found to be more importantthan dominance variance for growth andstraightness traits. There was no strongevidence to affirm that the superiority ofthe MPR × coastal hybrid could be caused bydominance variance. The low magnitude ofthe type-B genetic correlations within theMPR × coastal hybrid crosses suggested thatthe genotype-by-environment interactionmight be of practical importance inbreeding. For future hybridization of theMPR and coastal provenances, a recurrentselection scheme based on the utilizationof additive genetic variance of both parentpopulations is recommended.     

Unilateral cross compatibility in Vaccinium elliottii × V. arboreum, an intersectional blueberry hybrid

Vaccinium elliottii Chapmn., a diploid blueberry in Vacciniumsection Cyanococcus, was crossed with V. arboreum Marsh, a diploid blueberry insection Batodendron. The goal was toproduce hybrids that could be used toincorporate traits from these species intotetraploid southern highbush cultivars. The crosses were made reciprocally usingtwo clones of each species. A recessiveseedling marker gene for anthocyanin-freecotyledons in the V. elliottii clonesused as female parents permitted thetesting of mentor pollination. For thementor pollinations, V. elliottiiplants that were homozygous for therecessive marker allele were pollinatedwith a small amount of viable V.elliottii pollen carrying the recessivemarker mixed with a large amount of V.arboreum pollen carrying the dominantmarker. Thousands of intersectional hybridseedlings were obtained when V.elliottii was the seed parent, both withand without mentor pollination, but nohybrids were obtained from 2735 flowerspollinated in the reciprocal crosses. Theseeds that gave rise to hybrid embryos weresmaller than normal V. elliottiiseeds, but germinated well. Hybridseedlings grew slowly at first, buteventually produced some vigorous plants inthe field, although many plants remainedmuch smaller than normal seedlings of thetwo parental species. Some of the hybridsproduced numerous flowers during the 6years they were observed in the field, buteven with many diploid, tetraploid, andhexaploid section Cyanococcus blueberryplants growing nearby that could haveprovided pollen for their flowers, thehybrids produced no viable seed.     

南方红豆杉人工林培育模式对生物量及其分配格局影响

本研究通过了解南方红豆杉生长、干形变化、生物量积累与分配格局的培育模式响应机制,为南方红豆杉林下栽培体系提供理论基础,在福建明溪对林下套种与纯林培育模式12年生南方红豆杉的生长、干形、生物量积累与分配进行调查。结果表明,培育模式对南方红豆杉树高、胸径、冠幅、单株材积、高径比和生物量有显著性影响,林下套种显著促进南方红豆杉生长,改良干形品质,利于南方红豆杉构件生物量及总生物量积累;不同培育模式中南方红豆杉生物量分配比大小顺序均为干＞枝＞叶;培育模式对南方红豆杉生物量分配比与构件生物量比有着显著性影响,林下套种南方红豆杉增加枝、叶、干等地上生物量分配比,降低根系生物量分配比;林下套种的生物量更趋向地上部分、干和叶的分配;南方红豆杉人工林林下套种较纯林培育模式促进生物量高效积累与有效分配。     

Relationships between African species of the genus Cucumis L. Estimated by the production,vigour and fertility of F1 hybrids

Summary The production, vigour, and fertility of F₁ hybrids between nine African species of the genus Cucumis L. were studied as a measure of the relationships between the species. Hybrid plants were obtained from 29 out of the 72 possible cross combinations. Two F₁ hybrids died as seedlings, and 27 hybrids were raised to maturity. Pollen production and stainability varied greatly amongst these hybrids, as did fruit and seed set following self pollination and backcrossing with either parental species. The fruit shape of the hybrids was always intermediate between that of both parental species.Two species appeared to be closely related: C. prophetarum L. and C. anguria var. longipes A. Meeuse. Most other species produced highly to moderately fertile F₁ hybrids with at least one other species. C. metuliferus Naud. produced only sterile hybrids with C. zeyheri Sond. 2x. The results sustain the recent taxonomic classification of the genus (Jeffrey, 1980).     

Morphological variation of Medicago sativa subsp. falcata genotypes and their hybrid progeny

Semi-hybrid alfalfa cultivars offer the possibility of capturing non-additive genetic variation. Medicago sativa subsp. falcata and subsp.sativa have been shown to form a heterotic pattern for biomass yield. Objectives of this study were to examine morphological variation in a broad range of falcate germplasm and to determine how falcate morphological variation per se is related to the performance of falcate germplasm in hybrid crosses with subsp. sativa. Falcata genotypes from 40 populations spanning the subspecies native range were selected and biomass yield, plant width, plant height, growth angle, biomass density, plant maturity, and regrowth after cutting were measured on the genotypes and their hybrid progeny three times throughout the growing season. In addition weekly plant heights were measured and growth rates were determined with a Gompertz function. Falcata parental genotypes exhibited a full range of phenotypes for plant width, plant height, growth angle, density, and maturity. Heterosis was not only observed for biomass yield but also for plant width, plant height, and more erect growth habit. The top yielding sativa-falcata hybrids had increased plant width, plant height, and plant density. European germplasm was taller and had faster regrowth than Asian material. Sativa-falcata hybrids produced biomass yield superior to the mid-subspecies mean only after two to three weeks of growth prior to first and third harvests. Prior to second harvest, biomass production was inferior to the mid-subspecies mean for 30 days. Hybrids using falcata as one parent are not currently adapted to intensive harvest management due to their slower regrowth. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intraspecific hybridization in Pinus caribaea var. hondurensis I. Performance for growth and form traits

Inter-provenance hybrids of Pinuscaribaea var. hondurensis wereprogeny tested in Queensland, Australia inorder to assess the feasibility ofincorporating some desirable traits intothe local breeding population, consistinglargely of a single upland provenanceMountain Pine Ridge (MPR). Data onphenotypic traits up to seven years fromplanting revealed that an inter-provenancehybrid, MPR × coastal had greater diameter,straightness and wind-firmness, and fewerramicorns than the MPR control provenance.The data were mostly consistent for twowidely separated sites, and also whenpooled across those sites (p <0.05). In addition, hybrid vigor for treevolume was apparent (p < 0.05).Trees of coastal × Guanaja Island, and purecoastal provenances were as large as thoseof the MPR provenance but had fewerramicorns. Even though the coastal ×Guanaja provenance seemed to produce treesthat were more crooked than the MPRprovenance, there was evidence at leastwithin one site to suggest that the hybridtrees were superior in terms ofwind-firmness (p < 0.01). Breedingfor hybrid vigor and pedigree selection ofthe priority hybrid, MPR × coastal aresuggested as future measures. Pureprovenance populations of coastal andGuanaja island are to be bred as sublinesto the MPR breeding population for futureuse in inter-provenance hybridization andfor gene conservation.     

Interspecific hybridization in sexual diploid Allium senescens var. minor× apomictic tetraploid A. nutans and sexual diploid A. senescens var. minor× apomictic hexaploid A. senescens

Fourteen interspecific hybrids in sexual diploid Allium senescens var. minor× apomictic tetraploid Allium nutans L. crosses, and eight interspecific hybrids in sexual diploid A. senescens var. minor× apomictic hexaploid A. senescens L. crosses were produced. The number of chromosomes was 2n= 24 in interspecific hybrids of diploid × tetraploid, and 2n= 32 in diploid × hexaploid crosses. Triploid and tetraploid interspecific hybrids showed intermediate parental morphological characteristics. Tetraploid interspecific hybrids of A. senescens var. minor×A. senescens crosses formed two groups based on leaf colour and leaf width. Seeds were formed in 11 out of 14 triploid interspecific hybrids under natural conditions. In cytological observations of parthenogenesis, three out of 12 triploid interspecific hybrids and five out of eight interspecific tetraploid hybrids were observed. Parthenogenesis ranged from 26.0% to 86.0% in five tetraploid interspecific hybrids. Non-parthenogenesis to parthenogenesis segregated in a 3:5 ratio in A. senescens var. minor×A. senescens crosses.     

Characterization of fall and spring plantings of Galician cabbage germplasm for agronomic, nutritional, and sensory traits

Twenty one landraces of cabbage (Brassica oleracea var. capitata L.) and two of Tronchuda cabbage (B. oleracea var. tronchuda Bailey) from Galicia (north–western Spain) along with five commercial hybrids of cabbage and one commercial variety of Tronchuda cabbage were evaluated in this study in two planting dates, autumn/winter for an early harvest and spring/summer for a late harvest. Data were recorded on morphologic, agronomic, nutritional, and sensory traits. The objectives were to assess the characteristics of the Galician cabbage landraces and to compare their agronomic value with that of the commercial hybrids available in local markets, at two planting dates. Four cabbage landraces and the two Tronchuda cabbage landraces showed no head formation. At the autumn/winter season, commercial hybrids showed poor adaptation, with more plants lost after transplanting, less early vigor, and yield than the head forming landraces. However, for characters related to crop uniformity (head appearance, days to harvest, and synchrony of production), commercial hybrids did better than landraces. Regarding the sensory and nutritional values, in the autumn/winter season, accessions were tenderer, sweeter, had a better flavour, and showed higher levels of crude protein and less of crude fibre than in the spring/summer season. Landraces had higher calcium contents compared to commercial varieties. Local landraces MBG-BRS0425, MBG-BRS0452, MBG-BRS0536, and MBG-BRS0537 stood out for the most interesting traits in the autumn/winter season growing period and they could be included in breeding programs to obtain hybrids suitable to grow in this planting period.     

Selection for adaptation in multipurpose trees and shrubs for production and function in agroforestry systems

Summary With the greater uniformity in site conditions in cultivated fields and higher levels of inputs (soil amendments and labour) for modern agroforestry systems, selection and breeding for optimal tree adaptation to site conditions and management practices call for strategies radically different from those for plantation forestry. Furthermore, specific requirements for the most efficient growth resource sharing arrangements between the tree and its companion crop call for evaluation both above-ground and below-ground tree growth characteristics in much greater details than has been the case for forestry practice.Specific adaptations in tree-soil relations are highlighted. Tree ideotype profiles are defined for a valuable fodder species (Calliandra calothyrsus) and a valuable timber species (Grevillea robusta). Results from half-sib progeny testing experiment on C. calothyrsus in alley farming system indicate differential adaptedness to frequent cutting for fodder production among the families after 6 cutting cycles (over a period of 2 years). If this differential response to frequent cutting among genotypes is confirmed, phyllomorphs which are more tolerant to this management practice could be selected for further improvement research.Excavation of 2 trees per family within G. robusta half-sib progeny testing experiments at two locations in Kenya provided the base for studying (a) variations in root growth patterns and (b) correlations between stem and root growth patterns in the background of efficient soil resource sharing strategies and of potentials for indirect selection for root growth characteristics. Analyses based on 7 categories of root growth and 7 categories of stem growth patterns involving 94 families selected in Australia and 60 families selected from landraces in Kenya indicate (a) insignificant variation among families in root growth patterns and (b) non existent or weak correlations between stem and root growth pattenrs.     

Growth characters and number of strobili in clonal seed orchards of Pinus sylvestris

Observations were made on six grafts for each of 25 clones in three Scots pine (Pinus sylvestris) seed orchards in Turkey. The characters studied were number of female and male strobili, height below and above the longest branch, total height; diameter at base and breast height, crown diameter, and number of branches. Variation, broad-sense heritability (H ²) and correlations between characters were estimated. Variation among clones was lower than among grafts within clone for all characters. The genetic variation for number of strobili varied between 0 and 17% of total variation, while that for growth characters values varied between 2 and 13%. The number of female strobili appeared more variable among trees than the number of male strobili. H ² was not consistently high for any character or seed orchard. The number of strobili increased with the size of the tree, but not dramatically. Correlations between measures of tree size (both on clone level and individual graft level) and the number of strobili were in the magnitude r ≈ 0.3. Diameter at breast height seems a reasonable predictor for number of strobili.     

Variation in Nicotine Content of Cultured Cell Lines of Nicotiana Species and their Somatic and Sexual Hybrids

Several Nicotiana species, their intergeneric sexual and somatic hybrids were compared for their in vitro growth rate and nicotine content. Cell yield on a dry weight basis and HPLC analysis of their nicotine content revealed a very high variation within each cell line from parental, sexual and somatic hybrids for the two traits analyzed. The trigeneríc sexual hybrids (N. rustica × N. debneyi) × N. tabacum and only two of the N. rustica × N. tabacum somatic hybrid lines show a positive heterosis in nicotine content in vitro The in vitro growth rate and nicotine content did not demonstrate a statistically significant correlation.     

Unreduced pollen frequencies versus hybrid production in diploid-tetraploid Vaccinium crosses

Summary Reciprocal crosses were made between highbush Vaccinium corymbosum L. cultivars (4X) and high, medium and low frequency diplandroid pollen producing diploid clones of V. elliotti (Chapm.) and diploid pubescent forms of V. corymbosum. Pollination of 3,342 flowers produced 15 hybrids-11 tetraploids and 4 triploids. All V. elliottii hybrids were tetraploid while each successful diploid-tetraploid V. corymbosum cross produced at least one triploid. The ratio of tetraploid hybrids to 100 pollinations (H: 100P) was considered to be the best criterion for assessing crossability. Vaccinium elliottii produced a total of 8 4X hybrids while 2X V. corymbosum only produced 3. Vaccinium elliottii was more successful as a female parent and diploid V. corymbosum only produced hybrids as male parents. High frequency diplandroid clones showed a lower mean crossability as pollen parents (H: 100P=0.2) than medium frequency diplandroid clones (H: 100P=0.8). As predicted, 0% diplandroid clones wer unsuccessful as pollen parents. Unreduced pollen production was essential for tetraploid hybrid production in 4X×2X crosses. There appeared to be no consistent, inherent pattern between 2n pollen and 2n egg production in a clone nor was a tetraploid genotype effect on crossability consistently observed.Paper No. 10781 of the Journal Series of the North Carolina Agricultural Research Service, Raleigh, NC., 27695-7601     

Tetraploid bahiagrass hybrids: breeding technique,genetic variability and proportion of heterotic hybrids

Manipulating apomixis for fixing tetraploid bahiagrass (Paspalum notatum Flüggé) hybrids exhibiting superior agronomic characteristics would be a valuable tool for the genetic improvement of this species. The objectives were to create a second generation of hybrids by crossing sexual first-generation tetraploid hybrids (FGTH) and unrelated apomictic FGTH or ecotypes, determine the segregation for mode of reproduction, and estimate the resulting genetic variation and heterosis for several agronomic characteristics. The segregation for mode of reproduction was analyzed using mature embryo sac observations. Field measurements and visual ratings were used to evaluate the growth habit, production of inflorescences, cool-season growth and freeze resistance of hybrids. A ratio of 4.6:1 between sexual and apomictic hybrids was observed. Only 3% of the progeny was classified as highly apomictic. The low proportion of highly apomictic progeny restricts the feasibility of this breeding approach. Large genetic variation was observed among hybrids for growth habit, cool-season growth and freeze resistance. The proportion of hybrids exhibiting heterosis was high for plant height, cool-season growth, and freeze resistance. The tetraploid bahiagrass germplasm contains a large diversity for traits of agronomic importance that can be exploited for the genetic improvement of this species.     

Interspecific hybrids in the genus Elaeis II. vegetative growth and yield of F1 hybrids E. guineensis x E. oleifera

Summary Yield and morphology of F₁ hybrids E. guineensis x E. oleifera are discussed. Yield of the hybrids in terms of total fruit weight is promising but the oil content of the mesocarp is intermediate between the parental species and lower than in E. guineensis. E. oleifera has a marked tendency towards the production of parthenocarpic fruits. This character is fully dominant in the hybrid. Because of this the percentage fruit per bunch in the hybrids therefore tends to become higher than in E. guineensis partly offsetting the lower percentage oil on mesocarp.The oil composition of the parental species and hybrids are compared.Height increment of the hybrids is substantially lower than of E. guineensis but annual frond production is approximately the same. There is some hybrid vigour for frond area. For most morphological, vegetative and reproductive characteristics E. oleifera exhibits complete dominance over E. guineensis.     

Identification of somatic hybrids of dihaploid Solanum tuberosum lines and S. brevidens by species specific RAPD patterns and assessment of disease resistance of the hybrids

Summary Symmetric somatic hybrids were produced by electrofusion of protoplasts of two dihaploid tuber-bearing potato (Solanum tuberosum L.) lines and Solanum brevidens Phil., a diploid non-tuber-bearing wild potato species. A total of 985 plants was obtained. Verification of nuclear hybridity of putative hybrids was based on additive RAPD patterns, general morphological characteristics and chromosome counts. 53 (90%) calli regenerated into plants which were identified as somatic hybrids. Most of the hybrids were aneuploids at the tetraploid (4×) or hexaploid (6×) level. The 20 hybrids tested expressed a high level of resistance to potato virus Y (PVY ^N ) characteristic of the S. brevidens parent. Resistance to late blight (Phytophthora infestans (Mont.) de Bary) varied between hybrids, but was on average better than that of the fusion parents. Resistance of hybrids to bacterial stem rot (Erwinia carotovora subsp. atroseptica (van Hall) Dye) was not superior to that of commercial potato cultivars.     

Moisture Stress Effects on the Yield and Water Use of Sorghum Hybrids and their Parents*

Little is known of the relationship between hybrids and parental material with respect to water use and drought resistance. Responses of sorghum (Sorghum bicolor [L.] Moench) F₁ hybrids to moisture deficits are partially determined by parental material. The yield and water use of six sorghum hybrids and their respective male and female parents were evaluated under stressed and well irrigated conditions during 1980 and 1981 at Tucson, Arizona. The soil was Comoro loamy sand (coarse-loamy, mixed, calcareous, thermic typic Torrifluvent) with an average available soil moisture of 16 % at field capacity. Changes in soil moisture were monitored semi-weekly by neutron modulation. Meteorological data were collected daily. The 1980 season had higher maximum temperatures and pan evaporation than the 1981 season. Differences in cumulative water use among entries were apparent within the same water treatments during 1981. Mean cumulative evapotranspiration (ET) for the stressed treatment was 248 and 281 mm for 1980 and 1981, respectively, and ET under well irrigated conditions was 419 and 528 mm for 1980 and 1981, respectively. Hybrids produced greater grain yield than their parents under both water treatments. This was due to greater seed number for hybrids. Seed numbers were more stable for hybrids over both treatments than for parents. Hybrids four and seven had the greatest grain yield in 1980 and 1981, respectively, under stressed conditions. Water use efficiency (WUE) was significantly different within water treatments but was not so between the irrigated and stressed treatments. Hybrids WUE was generally greater than that of parents except for hybrid five under irrigated conditions in 1981. Hybrids with WUE and stable yields were not necessarily reflective of parental material under stressed and non-stressed environments.     

思茅松种源/家系苗期选择研究

为了能够筛选出苗期表现优良的思茅松家系和进行苗期选择研究,笔者对收集的5个种源191个思茅松优株家系苗期生长指标进行了测定和分析。巢式数据方差分析结果表明：苗高、地径和高径比3个生长指标在种源和家系间均具有显著差异;而发芽率在种源和家系间差异未达显著水平。在对聚类分析结果与种源分类间关联性进行了分析后,发现聚类分析可用于优良家系筛选,并筛选出24个表现相对优良家系。     

Transfer of resistance to Verticillium dahliae Kleb. from Solanum torvum S.W. into potato (Solanum tuberosum L.) by protoplast electrofusion

Summary Interspecific somatic hybrid plants were regenerated after electrofusion of mesophyll protoplasts with the objective of transferring resistance to Verticillium dahliae from Solanum torvum into potato. Early selection of the putative hybrids was based on differences in cultural behaviour of the parental and hybrid calli (particularly the ability of the latter to regenerate early) in combination with morphological markers. Four putative hybrids were recovered from hundreds of calli, probably resulting from complementation of the two parental genomes. The regenerates were tetraploids (2n=4×=48 chromosomes) and exhibited intermediate traits including leaf form, plant morphology and the presence of anthocyanin. The hybrid nature of the four selected plants was confirmed by examining isoenzyme patterns for isocitrate dehydrogenase (Idh), malate dehydrogenase (Mdh), phosphoglucoisomerase (Pgi) and 6-phosphogluconate dehydrogenase (6-Pgd). While the hybrid plants rooted readily and grew vigorously under in vitro conditions, in the greenhouse their development and growth were retarded by difficulties in rooting. When grafted on potato or S. torvum rootstocks, the hybrid plants recovered normal development and growth. Again, they exhibited intermediate morphological traits. Tests for resistance realized in vitro with medium containing 50% Verticillium wilt filtrate showed that all the somatic hybrids were resistant to the fungus filtrate.     

不同立地条件下东方杉等沿海防护林树种的生长生态特性研究

为了筛选出适宜浙南沿海盐碱地和潮滩盐土的树种,笔者进行耐盐、抗风树种的广泛收集、引进和区域试验,结果表明：沿海土壤条件复杂,新围垦海涂的土壤盐度随土层加深逐渐加大;1‰~3‰盐度下候选树种36个,3‰~5‰盐度下候选树种28个,5‰~8‰盐度下候选树种16个;无柄小叶榕、东方杉等19个树种表现为具有较强的抗风性,且随林木年龄的增长,风倒率下降;不同龄级防护林树种的冠径/树高的比值在0.45~1.13之间,以无柄小叶榕、大叶黄杨、夹竹桃最高,夹竹桃、大叶黄杨等相对冠长值大,需与其他树种配合才能发挥较好的防护作用;几个高抗性树种的高生长速率排序为：邓桉（1.18 cm/a）＞木麻黄501（1.16 cm/a）＞东方杉（1.08 cm/a）＞无柄小叶榕（1.07 cm/a）＞乌桕（0.92 cm/a）;径生长速率排序为：无柄小叶榕（1.58 cm/a）＞邓桉（1.35 cm/a）＞木麻黄501（1.15 cm/a）＞东方杉（1.06 cm/a）＞乌桕（0.93 cm/a）。