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1.
The defoliating needle blight of pines caused by Dothistroma pini Hulbary (perfect state Scirrhia pini Funk & Parker) is severely damaging to plantations of Pinus radiata D. Don., P. ponderosa Laws, and P. nigra Am. Symptoms and studies on P. radiata are reported. Disease severity has a linear relationship to stunting in very young trees, and a sigmoidal relationship to losses of height and diameter increments in 3-year-old trees, the most rapid losses occurring at disease severities between 25 and 75% blighted foliage. Height, independently of age, reduces disease severity. Maximum infection occurs at 0–5 ft. above ground level, while above 18 ft. there is significantly less attack. Rainfall of less than 1/2 in. weekly has little effect on disease increase and a mean weekly temperature of 65° F. or greater seems to be necessary for large disease increases; but the general environmental relations are too complex to be explained entirely quantitatively from the present data.  相似文献   

2.
Twelve microsatellite markers were developed for population analyses of the fungal pathogen, Dothistroma septosporum. Intersimple sequence repeat polymerase chain reaction (ISSR-PCR) and an enrichment protocol (fast isolation by amplified fragment length polymorphism of sequences containing repeats [FIASCO]) were both used to identify 28 unique microsatellite regions in the genome. From 22 primer pairs designed, 12 were polymorphic. These markers, screened on two populations representing 42 isolates, produced 40 alleles across all loci with an allelic diversity of 0.09-0.76 per locus. Cross-species amplification showed variable success with Dothistroma rhabdoclinis and Mycosphaerella dearnessi and some sequence variation within isolates of Dothistroma pini. These markers will be used to further study the population structure and diversity of D. septosporum.  相似文献   

3.
Six related radiata pine (Pinus radiata) full-sib families were used to detect and independently verify quantitative trait loci (QTLs) for resistance to Dothistroma needle blight, caused by Dothistroma septospora. The detection families had from 26 to 30 individuals each, and had either a common maternal (31053) or paternal (31032) parent; one family (cross 4) consisted of progeny from both parents, 31053×31032. Approximately 200 additional progeny from cross 4 were clonally replicated and planted at two sites, with at least five to seven ramets of each individual per site. Marker segregation data were collected from a total of 250 RFLP and microsatellite markers, and single factor ANOVAs were conducted separately for each family and marker. A number of putative associations were observed, some across more than one family. Permutation tests were used to confirm expected probabilities of multiple associations based on chance alone. Seven markers representing at least four QTLs for resistance to Dothistroma were identified as being significant in more than one family; one of these was significant at P<0.05 in three families and highly significant at P<0.01 in a fourth. Further confirmation was obtained by testing those markers that were significant in more than one of the detection families (or highly significant in cross 4) in the clonally replicated progeny from cross 4. Four QTL positions were verified in the clonal populations, with a total percent variation accounted for of 12.5.Communicated by D.B. Neale  相似文献   

4.
Fungi possess genetic systems to regulate the expression of genes involved in complex processes such as development and secondary metabolite biosynthesis. The product of the velvet gene veA, first identified and characterized in Aspergillus nidulans, is a key player in the regulation of both of these processes. Since its discovery and characterization in many Aspergillus species, VeA has been found to have similar functions in other fungi, including the Dothideomycete Mycosphaerella graminicola. Another Dothideomycete, Dothistroma septosporum, is a pine needle pathogen that produces dothistromin, a polyketide toxin very closely related to aflatoxin (AF) and sterigmatocystin (ST) synthesized by Aspergillus spp. Dothistromin is unusual in that, unlike most other secondary metabolites, it is produced mainly during the early exponential growth phase in culture. It was therefore of interest to determine whether the regulation of dothistromin production in D. septosporum differs from the regulation of AF/ST in Aspergillus spp. To begin to address this question, a veA ortholog was identified and its function analyzed in D. septosporum. Inactivation of the veA gene resulted in reduced dothistromin production and a corresponding decrease in expression of dothistromin biosynthetic genes. Expression of other putative secondary metabolite genes in D. septosporum such as polyketide synthases and non-ribosomal peptide synthases showed a range of different responses to loss of Ds-veA. Asexual sporulation was also significantly reduced in the mutants, accompanied by a reduction in the expression of a putative stuA regulatory gene. The mutants were, however, able to infect Pinus radiata seedlings and complete their life cycle under laboratory conditions. Overall this work suggests that D. septosporum has a veA ortholog that is involved in the control of both developmental and secondary metabolite biosynthetic pathways.  相似文献   

5.
Summary Variation in leaf longevity of gymnosperms has received surprisingly little attention despite its likely adaptive significance. Pinus longaeva, a pine of arid, subalpine environments in the western United States, has the record among conifers for needle longevity, with a maximum dwarf shoot (needle fascicle) retention time of up to about 45 years. Most low elevation pines have dwarf shoot retention times (DSRs) of two to four years. Literature data for the 37 species of Pinus native to the United States and Canada and field data for eight taxa (21 populations) of pines growing at various elevations in California each show a strong positive correlation between elevation and DSR, respectively, r=+0.65, df=35, p<0.001 and r=+0.82; df=19, p<0.001. We propose that extended needle fascicle longevity represents an adaptation to arid and especially high elevation environments. Field data from native stands and common gardens indicate that differences between taxa in DSR relate to both genetic and environmental factors. When grown at the same sites certain species (eg, P. longaeva, P. monophylla) had much longer DSRs than others, indicating a genetic basis for differences in needle fascicle longevity. For six of seven taxa that were each studied at more than one elevation there was a statistically significant increase in DSR in going from the lowest to the highest elevation site, indicating strong environmental control of needle fascicle longevity.The physiological control of dwarf shoot senescence and abscission is poorly understood. For P. longaeva dwarf shoots of a particular age class are not shed simultaneously; rather there is a more or less gradual attrition of dwarf shoots from the long shoot. Although different types of long shoots of pines are known to differ physiologically, for P. longaeva there was no consistent difference in DSR on various types of lateral long shoots (eg, vegetative, pollen cone-bearing, seed cone-bearing), nor was there a statistically significant difference in DSR on trunks versus on their lateral long shoots. In addition, for P. contorta ssp. bolanderi and P. muricata needle fascicle longevity was not affected by the degree of edaphically induced dwarfing (ie, stunting) of the trees.  相似文献   

6.
Summary and Conclusions Leaf analyses have indicated that the dieback investigated was due to boron deficiency and this has been proved by field experiments. Incidence of boron deficiency is tentatively related to the weathered condition of the soils on which it occurs and a climatic regime which may be alternately too wet and too dry for optimum availability of soil boron. The best means of correcting the deficiency appears to be the application of a small amount of borax — 15 pounds per acre — to the soil towards the end of the rainy season.  相似文献   

7.
8.
A needle blight disease with brown spots was found on ornamental trees ofPinus thunbergii in Shimane Prefecture, Japan. The causal fungus was identified asLecanosticta acicola, known as causal fungus of brown spot needle blight of pines recorded in the Americas, Europe, and China.Pinus thunbergii was heavily infected following inoculation with the fungus in June, but only slightly infected following inoculation in September. The mycelia of the fungus were raised and produced conidial masses on potato-dextrose and Waksman agars. They grew well at 20–25°C within the range of 5 to 35°C.  相似文献   

9.
10.
The assembly of Mediterranean pines in the sense ofMirov is inhomogeneous in respect to morphological, geographical and evolutionary affinities. Considering new or neglected characters (vegetative and particularly reproductive, cone scales, apophyses, mucros, seeds: Figs. 1–3) in extant populations and fossils, three groups are recognized. The group of coast and island pines extends from the Canary islands to the Himalaya region and is closely related to Caribbean and C. American taxa. This complex evidently has originated from haploxyl ancestors of sect.Parrya during the Mesozoic (Upper Jurassic/Lower Cretaceous) in the NW. Tethys area (Fig. 13).P. rzedowskii can be regarded as an extant survivor of this first phase of differentiation. The extremely variableP. canariensis (together withP. roxburghii in sect.Sula) marks a transitional phase towards the more advanced diploxyl species of sect.Pinea (withP. pinea, P. halepensis &P. brutia, and subsect.Oocarpae) and sect.Pinaster (withP. pinaster, etc.) (Figs. 4–12).—The second group consists of diploxyl mountain pines from the areas surrounding the Mediterranean. They are classified as members of the Eurasiatic sect.Pinus subsect.Sylvestres, have differentiated along the northern Parathetys area, and exhibit close links with E. Asiatic taxa. The third group includes the haploxyl mountain pinesP. cembra andP. peuce which can be regarded as western outposts of the circumpacific centred sect.Strobus with a pre-Tertiary origin.—As an appendix, an improved classification scheme is presented for the pine groups discussed.  相似文献   

11.
The pinyon pines of southwestern North America hare been used by man as a source of food, firewood, medicinal compounds, and ceremonial materials for many centuries. The importance of these pines to contemporary inhabitants of the area has decreased markedly in recent years, and in some areas programs have been initiated to curtail the development of the juniper-pinyon association. These programs are aimed at increasing local water resources, but the long-range effects of the methods employed remain to be seen.  相似文献   

12.
Transpecific microsatellites for hard pines   总被引:4,自引:0,他引:4  
Microsatellites are difficult to recover from large plant genomes so cross-specific utilisation is an important source of markers. Fifty microsatellites were tested for cross-specific amplification and polymorphism to two New World hard pine species, slash pine (Pinus elliottii var. elliottii) and Caribbean pine (P. caribaea var. hondurensis). Twenty-nine (58%) markers amplified in both hard pine species, and 23 of these 29 were polymorphic. Soft pine (subgenus Strobus) microsatellite markers did amplify, but none were polymorphic. Pinus elliottii var. elliottii and P. caribaea var. hondurensis showed mutational changes in the flanking regions and the repeat motif that were informative for Pinus spp. phylogenetic relationships. Most allele length variation could be attributed to variability in repeat unit number. There was no evidence for ascertainment bias.  相似文献   

13.
Rapid expansion of microsatellite sequences in pines   总被引:9,自引:0,他引:9  
Microsatellite persistence time and evolutionary change was studied among five species of pines, which included a pair of closely related species (Pinus sylvestris and Pinus resinosa) in the subgenus Pinus, their relative Pinus radiata, and another closely related species pair (Pinus strobus and Pinus lambertiana) in the subgenus Strobus. The effective population sizes of these species are known to have ranged from the very small bottlenecks of P. resinosa to vast populations of P. sylvestris. This background allowed us to place the microsatellite evolution in a well-defined phylogenetic setting. Of 30 loci originating from P. strobus and P. radiata, we were able to consistently amplify 4 in most of the these pine species. These priming sites had been conserved for over 100 Myr. The four microsatellites were sequenced in the five species. Flanking sequences were compared to establish that the loci were orthologous. All microsatellites had persisted in these species, despite very different population sizes. We found a recent microsatellite duplication: a closely related pair of loci in P. strobus, where the other four species had just one locus. On two independent occasions, the repeat area of this same microsatellite (locus RPS 105a/b) had grown from a very low repeat number to 15 or 17 in the last 10-25 Myr. Other parts of the same compound microsatellite had remained virtually unchanged. Locus PR 4.6 is known to be polymorphic in both P. radiata and P. sylvestris, but the polymorphism in the two species is due to different motifs. The very large pine genomes are highly repetitive, and microsatellite loci also occur as gene families.  相似文献   

14.
15.
Climate-driven changes in biomass allocation in pines   总被引:8,自引:0,他引:8  
Future increases in air temperature resulting from human activities may increase the water vapour pressure deficit (VPD) of the atmosphere. Understanding the responses of trees to spatial variation in VPD can strengthen our ability to predict how trees will respond to temporal changes in this important variable. Using published values, we tested the theoretical prediction that conifers decrease their investment in photosynthetic tissue (leaves) relative to water‐conducting tissue in the stem (sapwood) as VPD increases. The ratio of leaf/sapwood area (AL/AS) decreased significantly with increasing VPD in Pinus species but not in Abies, Pseudotsuga, Tsuga and Picea, and the average AL/AS was significantly lower for pines than other conifers (pines: 0.17 m2 cm?2; nonpines: 0.44 m2 cm?2). Thus, pines adjusted to increasing aridity by altering above‐ground morphology while nonpine conifers did not. The average water potential causing a 50% loss of hydraulic conductivity was ?3.28 MPa for pines and ?4.52 MPa for nonpine conifers, suggesting that pines are more vulnerable to xylem embolism than other conifers. For Pinus ponderosa the decrease in AL/AS with high VPD increases the capacity to provide water to foliage without escalating the risk of xylem embolism. Low AL/AS and plasticity in this variable may enhance drought tolerance in pines. However, lower AL/AS with increasing VPD and an associated shift in biomass allocation from foliage to stems suggests that pines may expend more photosynthate constructing and supporting structural mass and carry less leaf area as the climate warms.  相似文献   

16.
Noncoding chloroplast DNA variation in Mexican pines   总被引:2,自引:0,他引:2  
Universal primers were used for PCR amplification of three noncoding regions of chloroplast DNA in order to study restriction site variation in 12 Mexican pine species. Two length mutations were identified that are of diagnostic value for two subgenera or sections of the genus. Phylogenetic analysis of the restriction site and length variation showed patterns of variation largely consistent with previous arrangements of these pines, except for the position of Pinus nelsonii, indicating that Pinus section Parraya Mayr, as circumscribed by Little and Critchfield (1969) and later authors, is not a monophyletic group.  相似文献   

17.
The polyketide toxin dothistromin is very similar in structure to the aflatoxin precursor, versicolorin B. Dothistromin is made by a pine needle pathogen, Dothistroma septosporum, both in culture and in planta. Orthologs of aflatoxin biosynthetic genes have been identified that are required for dothistromin biosynthesis in D. septosporum. In contrast to the situation in aflatoxin-producing fungi where 25 aflatoxin biosynthetic and regulatory genes are tightly clustered in one region of the genome, the dothistromin gene cluster is fragmented. Three mini-clusters of dothistromin genes have been identified, each located on a 1.3-Mb chromosome and each grouped with non-dothistromin genes. There are no obvious patterns of repeated sequences or transposon relics to suggest recent recombination events. Most dothistromin genes within the mini-clusters are co-regulated, suggesting that coordinate control of gene expression is achieved despite this unusual arrangement of secondary metabolite biosynthetic genes.  相似文献   

18.
19.
Trees at timberline in the high Alps are exposed to a variety of climatic conditions. Most climatic stresses occur during winter and spring, when frost, occasionally low snow cover, and high irradiation interact. In this study, we follow reactions of photosynthesis from high winter to spring in two dominating tree species of the alpine timberline, which may indicate the status of stress response to a changing environment. The results indicate a level of physiological stability in trees, which are important for stabilising natural high mountain ecosystems. Trees of Pinus cembra and of Pinus mugo were selected at altitudes between 1850 m a.s.l. and 1950 m a.s.l. near innsbruck, Austria. At six sampling times from January to May, fast chlorophyll fluorescence was measured in the field and twigs were collected for further investigation in the laboratory. The following measurements were taken: photosynthetic oxygen formation, needle chlorophyll and carotenoid determination, and kinetic studies of the xanthophyll cycle. In general, both tree species showed similar results in most parameters studied. P. mugo seems to have some advantages if winter precipitation is high, when, because of its growth habitus, most needles will be snow covered. Primary photochemistry (trapping per reaction centre) in PS II does not change with sampling dates despite the fact that temperature and light are changing. However, first events in electron transport and whole needle photosynthesis are strongly affected by light and temperature conditions during the days before sampling. The kinetics of the xanthophyll cycle indicate not only light, but also strong temperature effects. P. mugo photosynthesis seems to have a higher stability under changing weather. Both tree species are well prepared to start with photosynthesis in winter, if favourable conditions, like foehn events, occur.  相似文献   

20.
Homologs of aflatoxin biosynthetic genes have been identified in the pine needle pathogen Dothistroma pini. D. pini produces dothistromin, a difuranoanthraquinone toxin with structural similarity to the aflatoxin precursor versicolorin B. Previous studies with purified dothistromin suggest a possible role for this toxin in pathogenicity. By using an aflatoxin gene as a hybridization probe, a genomic D. pini clone was identified that contained four dot genes with similarity to genes in aflatoxin and sterigmatocystin gene clusters with predicted activities of a ketoreductase (dotA), oxidase (dotB), major facilitator superfamily transporter (dotC), and thioesterase (dotD). A D. pini dotA mutant was made by targeted gene replacement and shown to be severely impaired in dothistromin production, confirming that dotA is involved in dothistromin biosynthesis. Accumulation of versicolorin A (a precursor of aflatoxin) by the dotA mutant confirms that the dotA gene product is involved in an aflatoxin-like biosynthetic pathway. Since toxin genes have been found to be clustered in fungi in every case analyzed so far, it is speculated that the four dot genes may comprise part of a dothistromin biosynthetic gene cluster. A fifth gene, ddhA, is not a homolog of aflatoxin genes and could be at one end of the dothistromin cluster. These genes will allow comparative biochemical and genetic studies of the aflatoxin and dothistromin biosynthetic pathways and may also lead to new ways to control Dothistroma needle blight.  相似文献   

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