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941.
The inheritance of resistance to Plum pox virus (PPV) has been studied in 1,178 apricot hybrids. Seven hundred and eighteen F1 hybrids, obtained from controlled crosses
between the susceptible Greek cultivar “Bebecou” and the resistant PPV cultivars of American origin (“Stark Early Orange,”
‘NJA2,” ‘Veecot,” “Sunglo,” “Harlayne,” and “Orangered”) were evaluated for resistance to the PPV-M (Marcus) strain, 8 years
after artificial inoculation. The inheritance of resistance to PPV has been additionally studied for the first time in a BC1 population of 95 apricot hybrids for four vegetative periods. Reaction of each hybrid to PPV-M was scored through visual
symptoms, indexing onto GF-305 and double-antibody sandwich enzyme-linked immunosorbent assay tests. Segregation within the
hybrids, determined by Chi-squared analysis, fits a 1:1 ratio (P ≤ 0.05) of the resistant vs susceptible, indicating that resistance to PPV is controlled by a single dominant gene locus
and that the above six resistant cultivars are heterozygous for the trait. Plants carrying this gene may initially develop
disease symptoms on leaves but eventually recover and no virus can be detected in leaves. Susceptible plants show similar
symptoms initially but remain symptomatic. Inheritance of resistance to PPV also has been studied in 365 F1 hybrids by crossing
the resistant cultivar “Stella” with the susceptible “Bebecou” and the resistant cultivars “Sunglo” and “NJA2,” for 8 years
after inoculation. The segregation ratio was 1:0 (resistant/susceptible) suggesting that “Stella” is homozygous for the resistance
trait. The purpose of this work was the enhancement of the knowledge of inheritance of resistance to PPV for the selection
of new cultivars. 相似文献
942.
Kitt G. Payn William S. Dvorak Bernard J. H. Janse Alexander A. Myburg 《Tree Genetics & Genomes》2008,4(3):519-530
Eucalyptus urophylla (Timor mountain gum) is an economically important plantation species that occurs naturally in a series of disjunct populations
on the volcanic slopes of seven islands in eastern Indonesia. Twelve microsatellite markers were used to investigate the distribution
of nuclear genetic diversity among 19 geographically defined E. urophylla populations. High levels of gene diversity were observed throughout the geographic range (H
E = 0.703 to 0.776). The level of genetic differentiation among populations was low (F
ST = 0.031), but the amount of differentiation increased with geographic distance. A phenogram produced by a neighbor-joining
analysis illustrated that populations clustered according to islands. However, a Bayesian clustering approach revealed a more
cryptic population structure comprising two genetically homogeneous groups. Gene flow among the populations is likely responsible
for the apparent weak influence of geographic insularity on the genetic diversity and structure of the island species. These
findings provide direction for conservation and breeding strategies in E. urophylla.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
943.
鱼类人工多倍体育种的研究进展 总被引:3,自引:0,他引:3
鱼类多倍体育种是鱼类育种最热的领域之一。本文概述了鱼类人工多倍体育种研究的进展情况,包括鱼类人工多倍体育种的方法和人工多倍体鱼类可育性等方面。鱼类人工多倍体育种的方法主要有物理、化学和生物学方法,三倍体鱼预期是不育的,四倍体是可育的,但目前两性可育的四倍体的报道还很少。本文还对人工多倍体鱼的生物学意义作了简单的阐述。本文旨在为对今后进一步开展鱼类人工多倍体育种研究提供参考。 相似文献
944.
Impact of severe dry season on net ecosystem exchange in the Neotropical rainforest of French Guiana 总被引:1,自引:0,他引:1
DAMIEN BONAL ALEXANDRE BOSC† STÉPHANE PONTON‡ JEAN-YVES GORET BENOÎT BURBAN PATRICK GROSS‡ JEAN-MARC BONNEFOND† JAN ELBERS§ BERNARD LONGDOZ‡ DANIEL EPRON¶ JEAN-MARC GUEHL‡ ANDRÉ GRANIER‡ 《Global Change Biology》2008,14(8):1917-1933
The lack of information on the ways seasonal drought modifies the CO2 exchange between Neotropical rainforest ecosystems and the atmosphere and the resulting carbon balance hinders our ability to precisely predict how these ecosystems will respond as global environmental changes force them to face increasingly contrasting conditions in the future. To address this issue, seasonal variations in daily net ecosystem productivity (NEPd) and two main components of this productivity, daily total ecosystem respiration (REd) and daily gross ecosystem productivity (GEPd), were estimated over 2 years at a flux tower site in French Guiana, South America (5 °16′54″N, 52 °54′44″W). We compared seasonal variations between wet and dry periods and between dry periods of contrasting levels of intensity (i.e. mild vs. severe) during equivalent 93‐day periods. During the wet periods, the ecosystem was almost in balance with the atmosphere (storage of 9.0 g C m?2). Seasonal dry periods, regardless of their severity, are associated with higher incident radiation and lower REd combined with reduced soil respiration associated with low soil water availability. During the mild dry period, as is normally the case in this region, the amount of carbon stored in the ecosystem was 32.7 g C m?2. Severe drought conditions resulted in even lower REd, whereas the photosynthetic activity was only moderately reduced and no change in canopy structure was observed. Thus, the severe dry period was characterized by greater carbon storage (64.6 g C m?2), emphasizing that environmental conditions, such as during a severe drought, modify the CO2 exchange between Neotropical rainforest ecosystems and the atmosphere and potentially the resulting carbon balance. 相似文献
945.
Laetitia Mahé Marie-Christine Combes Vitor M. P. Várzea Claire Guilhaumon Philippe Lashermes 《Molecular breeding : new strategies in plant improvement》2008,21(1):105-113
Coffee leaf rust due to Hemileia vastatrix is one of the most serious diseases in Arabica coffee (Coffea arabica). A resistance gene (SH3) has been transferred from C. liberica into C. arabica. The present work aimed at developing sequence-characterized genetic markers for leaf rust resistance. Linkage between markers
and leaf rust resistance was tested by analysing two segregating populations, one F2 population of 101 individuals and one backcross (BC2) population of 43 individuals, derived from a cross between a susceptible and a SH3-introgressed resistant genotype. A total
of ten sequence-characterized genetic markers closely associated with the SH3 leaf rust resistance gene were generated. These included simple sequence repeats (SSR) markers, sequence-characterised amplified
regions (SCAR) markers resulting from the conversion of amplified fragment length polymorphism (AFLP) markers previously identified
and SCAR markers derived from end-sequences of bacterial artificial chromosome (BAC) clones. Those BAC clones were identified
by screening of C. arabica genomic BAC library using a cloned AFLP-marker as probe. The markers we developed are easy and inexpensive to run, requiring
one PCR step followed by gel separation. While three markers were linked in repulsion with the SH3 gene, seven markers were clustered in coupling around the SH3 gene. Notably, two markers appeared to co-segregate perfectly with the SH3 gene in the two plant populations analyzed. These markers are suitable for marker-assisted selection for leaf rust resistance
and to facilitate pyramiding of the SH3 gene with other leaf rust resistance genes. 相似文献
946.
四川南充市区火斑鸠的繁殖生态 总被引:5,自引:3,他引:2
20 0 2年 5~ 1 1月、2 0 0 3年 4~ 9月对南充市火斑鸠的繁殖生态进行了研究。结果表明 :4月下旬迁到 ,5月下旬开始繁殖 ;影响巢址选择的主要因素 6种 ;两性参与筑巢 ,营巢期 7~ 8d ;隔 2~ 3日产枚卵 ,窝卵数 ( 2 2 1± 0 0 9)枚 (n =1 9) ;雌雄轮流昼夜孵卵 ,日换孵两次 ,孵卵期 1 1~ 1 2d ,孵化率 92 86%;育雏可分三个时期 ,育雏高峰期每日 7:0 0、1 3 :0 0、1 8:0 0时左右 ,育雏期 1 7~ 1 8d ,雏离巢率 1 0 0 %,繁殖生产力1 86,种群育雏高峰期 7月和 8月上中旬 ;雏鸟于 1 7或 1 8日后离巢迁到郊外 ,9月下旬集群 ,1 0月中下旬迁飞。 相似文献
947.
Limits to gene flow in marine animals with planktonic larvae: models of Littorina species around Point Conception, California 总被引:1,自引:0,他引:1
PAUL A. HOHENLOHE 《Biological journal of the Linnean Society. Linnean Society of London》2004,82(2):169-187
Simulation models examined the process of gene flow in marine animals with planktonic larvae, and three factors that may influence it: ocean currents, planktonic period and spawning season. To focus on a realistic example, the models were based on measured ocean currents around Point Conception in southern California and the life histories of two intertidal gastropods, Littorina scutulata and L. plena . Results suggested that: (1) convergent ocean currents can create an effective barrier to gene flow that can be relaxed by temporal variation; (2) longer scales of temporal variation have a greater effect than shorter scales; (3) planktonic period has little effect above a minimum duration; and (4) an extended spawning season can eliminate gene flow barriers when currents vary seasonally. Failure of past studies to detect a phylogeographical boundary at Point Conception may be explained by extended spawning seasons and temporal variation at seasonal to millennial scales. These results fit a conceptual model of marine speciation in which short-lived, leaky barriers restrict gene flow, and divergence in a few genes may quickly produce reproductive isolation, resulting in cryptic sibling species. © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 82 , 169–187. 相似文献
948.
Several mutations are known to alter the normal progression of meiosis and can be correlated with defects in microtubule distribution. The dv mutation affects the spindle organization and chromosomes do not converge into focused poles. Two Brachiaria hybrids presented the phenotypic expressions of dv mutation but exhibited many more details in the second division. Bivalents were distantly positioned and spread over a large metaphase plate and failed to converge into focused poles. Depending on the distance of chromosomes at the poles, telophase I nuclei were elongated or the chromosomes were grouped into various micronuclei of different sizes in each cell. The first cytokinesis occurred. However, when there were micronuclei, a second cytokinesis immediately took place dividing the prophase II meiocytes into three or four cells. In each meiocyte, meiosis progressed to the second division. Slightly elongated nuclei or micronuclei were recorded in telophase II. After a third cytokinesis, hexads or octads were formed. Pollen grains of different sizes were generated. One of these hybrids presented a higher frequency of abnormal cells than when previously analyzed. The fate of these hybrids as genitors or as candidates for cultivars in the Brachiaria breeding program is discussed. 相似文献
949.
Abstract. In heavily altered landscapes, where vegetation is not natural and where people are the main source of ignitions, relationships between fire occurrence and climate conditions may be unclear. The objective of this study was to evaluate to what extent territories with similar Potential Natural Vegetation (PNV) in peninsular Spain differ in their forest fire characteristics. From 1974 to 1994, more than 174 000 fires occurred. We used (1) the Spanish data base of forest fires, (2) a PNV map and (3) a land use map. Separate fire characteristics, based either on the number of fires occurred or the area burned, were obtained for each of the ca. 5000 grid‐cells (10 km × 10 km) into which peninsular Spain is divided in the UTM projection. Also, meteorological conditions at the time of fire ignition, cause of ignition and present forest cover were referred to the same grid‐cells as external factors potentially determinant of fire occurrence. The relationships between fire regime characteristics and PNV units were explored with Principal Components Analysis (PCA). The role of the three sets of external factors in the fire characteristics was evaluated with Redundancy Analysis (RDA). Groups of similar PNV types were clearly segregated, suggesting a gradient of fire characteristics. Higher fire incidence (higher frequencies and spatial incidence of fires, but lower proportions of grid‐cells affected by large fires) was associated with Atlantic, warm territories with deciduous forests as PNV. Intermediate fire frequency and rotation period, but with a higher relative incidence of medium and large fires occurred in Mediterranean PNV units, dominated by sclerophyllous oak forests. Low fire frequency and long rotation periods, with strong seasonal and yearly variability occurred for PNV units in the cold uplands (Fagus, Pinus, Abies, Juniperus) or in the semi‐arid, shrubby PNV units. The cause of ignition best explained the patterns of forest fire characteristics, followed by weather conditions. Our results indicate that, even in human influenced regions, climate and soil conditions exert control on the resulting forest fire characteristics, as indicated by the high segregation of the PNV types. However, the role of man was crucial in shifting the patterns of fire incidence. This was so that highest fire incidence occurred in regions that, otherwise, would be expected to have a much lower one, thus posing a serious threat for such areas. PNV maps, by providing a phytogeographical framework for characterizing forest fires, could be valuable tools for applying research results to forest fire management policies, taking properly into account the underlying determinant factors. 相似文献
950.
The aerobiological behaviour of Urticaceae in Trieste and the correlations with the meteorological parameters were examined. Airborne pollen was collected from 1990 to 1999 using a Hirst type spore trap (Burkard) and the data interpretation was performed according to the standard method adopted by the Italian Aeroallergen Network. The main pollen season of Urticaceae in Trieste goes from mid-April to mid-September. The highest values occur in May and June. Although different seasonal patterns are found every year, the main peak occurs on average at the beginning of May, followed by other decreasing peaks until September. Thecumulative counts vary greatly over the years, with a mean value of 18.315 p/m3. The maximum annual total pollen grains was registered in 1996 and the minimum in 1991. Spearman's correlation was used to establish the relationship between the daily pollen counts and the daily meteorological data both considering their original quantitative values and transformed values according to their day by day changes. Daily pollen concentrations present usually positive correlation with temperature, negative with rainfall and wind speed and no correlation with humidity. Better results were obtained with transformed values. 相似文献