Phylogenetic relationships between the lettuce root rot pathogen Fusarium oxysporum f. sp. lactucae races 1, 2, and 3 based on the sequence of the intergenic spacer region of its ribosomal DNA

The genetic relationship between the vegetative compatibility groups (VCGs) and between physiological races of Fusarium oxysporum f. sp. lactucae (FOL), the causal pathogen of lettuce root rot, was determined by analyzing the intergenic spacer (IGS) region of its ribosomal DNA. A total of 29 isolates containing a type strain were tested: 24 Japanese isolates, 2 Californian isolates, and 3 Italian isolates. Three races (races 1, 2, and 3) were found in Japan, and race 1 was also distributed in California and Italy. Races 1, 2, and 3 each belonged to a distinct VCG: VCG-1, VCG-2, and VCG-3 (VCG-3-1, VCG-3-3), respectively. Phylogenetic (neighbor-joining) analysis of the IGS sequences revealed that races 1, 2, and 3 coincided with three phylogenetic groups (PG): PG-1, PG-2, and PG-3, respectively. These results indicate that the three races are genetically quite different and have a strong correlation with VCGs and phylogenetic groupings. The nucleotide sequence data reported are available in the DDBJ/EMBL/GenBank databases under the accession no. AB195218     

Assessment of morphological changes and determination of best cane collection time for 140 RU and 5 BB

This study was carried out to assess morphological changes in the canes of 140 Ru and 5 BB and to determine best time for cane collection. The first part of the study included the morphological assessment of the rootstock canes during the winters of 2003–2004 and 2004–2005. Canes collected in the second part of the study in 2005–2006 were grown in pots to relate the changes with the vegetative growth characteristics.     

Nitrogen nutrition of hedged stock plants of Loblolly Pine. I. Tissue nitrogen concentrations and carbohydrate status

Hedged stock plants of four full-sib families [27-2 × 27-5, 27-3× 27-1, 27-2 × 27-1, and 27-6 × 27-1 (designated B, G, R, andW)] of loblolly pine (Pinus taeda) were fertilized dailywith a complete nutrient solution containing N supplied fromNH₄NO₃ at either 10, 25, 40, 55, or 70mg·L^–1. In May (spring softwood), July(summer softwood), and January (winter hardwood) terminal stem cuttings weretaken for tissue analysis and rooting studies. Averaged over families, meantissue concentrations of N were higher in spring (1.8%) and summer (1.7%) thanin winter (1.3%). Concentrations of N increased linearly with increasing levelsof applied N. Concentrations of total nonstructural carbohydrates (TNC) inwinter (32.8%) were twice those in spring (17.1%) or summer (16.3%), but wererelatively unaffected by N application. In contrast, starch concentrations weresignificantly higher during spring and summer than winter. The greatest numbersof orthotropic shoots 9 cm in length were produced for thespring, followed by summer, and then winter hedgings. Number of shoots producedper hedge increased with increasing applied N rates, and family B producedsignificantly more shoots than the other three families at all applied N levels.Genetic differences among families were evident as several interactions with Nrates were observed.     

Regeneration and multiplication of Albizia procera Benth. through organogenesis

Vegetative propagation techniques are recognized as indispensable tools for mass multiplication of important multipurpose trees adopted in different agroforestry systems. Albizia procera, one among important species, is difficult to propagate commercially either by stem / root cuttings or layering. A study was undertaken to develop procedure for its in vitro regeneration through organogenesis. Explants collected from 15±2 yr-old mature plus trees and from 15 days old juvenile seedlings were regenerated with exogenous application of different hormones. Epicotyl and hypocotyl explants excised from juvenile seedlings showed higher callusing than axillary bud and shoot tip explants derived from mature trees. Benzylaminopurine (BA) at 3 μg/l was most effective, which induced hundred percent callusing in epicotyl and hypocotyl explants in 1/2 Murashige and Skoog (MS) medium. Callus originated from axillary buds and apical shoot tips of mature trees failed to form organs, however callus derived from epicotyl and hypocotyl explants proliferated and formed de novo shoots and leaflets. A concentration of 3 μg/l of BA was found effective for shoot proliferation. Shoots grew vigorously in 2 μg/l gibberellic acid (GA₃) treatment and rooted in 1/2 MS medium supplemented with indole-3-butyric acid (IBA) and indole-3-acetic acid (IAA). Rooting was most successful on medium supplemented with 6 μg/l IBA alone on which 93.3% of the shoots formed roots. Sand or vermiculite supplemented with 4 ml of yoshida solution proved as best hardening media, which recorded 70-80% survival of plantlets. One year old tissue culture raised plants had comparatively more height, collar diameter, biomass, and root shoot ratio than plants raised from cuttings and seeds of the same age. The procedures enumerated provide a basis for the development of in vitro techniques for rapid multiplication of A. procera. This revised version was published online in June 2006 with corrections to the Cover Date.     

Relationship of water to adventitious rooting in stem cuttings of Populus species

Populus species, characterized by fast growth and easy vegetative propagation, are widely used in agroforestry practices. The substantial water requirement of poplars make them interesting subjects for water balance studies. No information exists on soil moisture requirements for initial root and shoot growth of Populus cuttings. This study on leafless hardwood cuttings of Populus x euramericana (Dode) Guinier cv. Robusta examined the dynamics of water use during propagation, as influenced by two initial soil water potentials (–0.006 and –0.06 MPa). Differences in the initial water potential of the cuttings was achieved by three pretreatments i.e., fresh, soaked and dried. Initial _shoot was –1.45, –0.10 and –2.10 MPa in fresh, soaked and dried cuttings, respectively. Soil moisture had a major effect on rooting. Water-stressed cuttings took a longer time to root and had fewer roots. Pre-soaking of cuttings stimulated rooting, particularly under the drier soil moisture conditions. Initially the water potential of cuttings decreased with time and with the formation of roots it stabilized in all the pretreatments. The reduction in water potential of cuttings after planting was related to an increase in resistance to water flow in the xylem.This revised version was published online in November 2005 with corrections to the Cover Date.     

Impacts of fructification on biomass production and correlated genetic effects in Norway spruce (<Emphasis Type="Italic">Picea abies</Emphasis> [L.] Karst.)

For the period 2003–2006, fructification of Norway spruce (Picea abies [L.] Karst.) was recorded at the Kranzberg forest site in Southern Germany by employing a crane with access to the canopy of more than 266 trees. For each tree, stem diameter and growth parameters were assessed annually as well as biomass of cones and seeds, number of seeds per cone, and proportions of empty seeds for a total of 371 trees with cone crop. Genotypes at 19 enzyme coding gene loci of 110 trees were included in the study of correlations between morphological and genetic traits. Re-scaling the observed values for a virtual pure Norway spruce stand of 1 ha, cone biomass including winged seeds (oven-dried at 38°C) varied between 706.8 kg/ha in 2006 (average value per tree was 3.6 kg) and values close to zero in 2005. Corresponding values for vegetative biomass increment of the coning trees in 2006 were 9,273.0 kg/ha and 10.8 kg/tree. A significant higher biomass investment was determined for dominant trees in terms of absolute cone mass as well as in terms of cone mass relative to vegetative biomass and fructification frequency. No trade-off effects in decreased vegetative biomass growth were found in the fructification year, compared to trees that did not grow cones. Although the dominant trees invested proportionally considerable biomass in cones, they showed no significant reduction in vegetative biomass growth. In the following year no decrease in vegetative growth was detected. Based on logistic regressions and homogeneity tests, respectively, significant genetic effect became evident with respect to the gene loci AAP-B and AAT-C concerning fructification probability in the year with maximum generative biomass investment. These and closely related loci also have been found to be indicative for growth and viability, respectively, in other species.     

大豆生育期相关的QTL分析

采用来自Charleston×东农594的143个重组自交系(RILs),构建了1个含有20条连锁群的大豆遗传连锁图谱,对大豆营养生长期、生殖牛长期、发育期进行QTL分析,以期探索大豆生育期相关基因的遗传机理.结果表明:采用复合区间作图法共定位了 6个显著影响营养生长期的QTL位点,分布在A1、H、K、N连锁群上;定位了6个显著影响大豆生殖生长期的QTL位点,其中4个,reA1-2、reH、reK、reN也同时控制营养生长期的长短;在整个生育期定位到8个QTL位点,有5个位点能解释20%以上的表型变异.     

不同灌水量对水、旱稻营养生长和光合特性及其产量的影响

以中旱3号（常规旱稻）和汕优63（杂交水稻）为材料,研究5种不同灌水量处理对水稻和旱稻营养生长、光合特性以及产量的影响。结果表明,不同的灌水量处理明显影响水稻和旱稻的营养生长,光合特性以及产量。汕优63在处理A（灌溉水量为对照的25%）和处理B（灌溉水量为对照的43.75%）时,产量受到严重影响,分别比对照（处理E）减产80.58%和42.98%,差异极显著;在处理C（灌溉水量为对照的62.5%）和处理D（灌溉水量为对照的81.25%）时,与对照产量差异不显著。中旱3号在处理A时比对照减产68.42%,差异极显著;籽粒产量在处理B～E之间没有显著差异。这一特点在所有测定的其他营养生长和光合指标上也表现的非常明显。汕优63、中旱3号获得最高产量的灌溉需水量分别为每公顷7 500 m3和每公顷5 250 m3。超过此值,随着灌水量的增加,产量将有所下降。旱稻获得最高产量的灌溉水量比水稻约可节约30%,节水潜力巨大。在所有灌溉水量处理下,旱稻的产量比水稻的产量均低,有效穗数少是其主要原因。     

Key roles of leaves, stockplant age, and auxin concentration in vegetative propagation of two African mahoganies: Khaya anthotheca Welw. and Khaya ivorensis A. Chev

Leaf area, IBA concentration and age of stockplants were all found to be important factors for successful rooting for vegetative propagation using single-node cuttings of the two main African mahogany species: Khaya anthotheca and K. ivorensis. Cuttings with leaf area of 30–50 cm² had the best rooting percentage and cuttings with about 30 cm² had the most number of roots per cutting in K. anthotheca. Khaya ivorensis, cuttings with 10–30 cm² leaf area had the highest rooting percentage. Cuttings collected from 1-year-old stockplants recorded the highest rooting percentage and largest number of roots per cutting. Cuttings from 3-year-old stockplant of the same seeds sources had the lowest rooting suggesting aging negatively impacted rooting ability. The effect of auxin concentration, on rootability was examined with cuttings of K. anthotheca. An IBA concentration of 0.8% was the best exogenous auxin concentration for percentage rooting, number of roots per cutting and the length of the longest root per cutting.     

氮磷对菘蓝营养生长期根、冠生长的影响

通过盆栽试验,研究了不同的氮磷处理对菘蓝(Isatis indigoticaFort.)的株高、叶面积、叶绿素、可溶性蛋白、根、冠干物质积累、根长、根粗、根冠比等指标的影响。结果表明,氮对菘蓝的株高、单株叶面积、叶绿素的含量、干物质积累均具有明显的促进作用,且氮磷配合施用时效果更好;氮、磷均可以提高菘蓝可溶性蛋白的含量,单施氮肥降低了菘蓝的根冠比,而单施磷肥增大了菘蓝根冠比,以菘蓝根和叶同时采收为目的时,以处理6的效果最佳。