Association of seed‐borne Fusarium species on Pinus ponderosa with germination and seedling viability in Argentina

Pinus ponderosa seedlots from eight seed orchards in Western Patagonia, Argentina, were evaluated for the presence of Fusarium species, and isolates obtained were subjected to pathogenicity tests. The following species were isolated: Fusariumoxysporum, Fusarium equiseti, Fusarium verticillioides, Fusarium incarnatum, Fusarium acuminatum, Fusarium graminearum and Fusarium proliferatum. With the exception of F. proliferatum and F. graminearum all Fusarium species were recovered from P. ponderosa seedlings with symptoms of damping‐off. Five Fusarium species were re‐isolated from necrotic roots of seedlings showing chlorosis (F. oxysporum, F. equiseti, F. incarnatum, F. acuminatum and F. verticillioides). High damping‐off losses occurred in Fusarium‐contaminated seed of P. ponderosa and low disease incidence occurred on less contaminated seed. The role of seed‐borne inoculum in disease spread within forest nurseries is discussed.     

Seedborne Fusarium on Douglas-fir: Pathogenicity and seed stratification method to decrease Fusarium contamination

Twelve Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlots from coastal British Columbia were assayed for seedborne Fusarium. All of the seedlots were contaminated with Fusarium. Percent of nonstratified seeds from individual seedlots harboring Fusarium ranged from 0.3% to 95.4%. Sixty-seven percent of the seedlots had Fusarium on less than 2% of the seeds. Post-stratification seedborne Fusarium levels were significantly less for running water imbibition compared to standing water imbibition. However, seedling growth at a container nursery was not consistently different for stratified seed imbibed initially in standing or running water. Fusarium disease symptoms were not observed in the nursery environment. The species of Fusarium isolated from seed were F. acuminatum, F. avenaceum, F. lateritium, F. moniliforme, F. oxysporum, F. poae and F. sambucinum. Twelve Fusarium isolates, comprising six species, were assessed for pathogenicity. Disease symptoms were observed after four weeks incubation and Fusarium isolates ranged in virulence from low to high. Fusarium oxysporum isolates were the most pathogenic.     

Fusarium root infection of container-grown Douglas-fir: effect on survival and growth of outplanted seedlings and persistence of the pathogen

Greenhouse-grown Douglas-fir (Pseudotsuga menziesii var.glauca [Beissn.] Franco) seedlings with roots infected with eitherFusarium oxysporum Schlect. orFusarium proliferatum (Matsushima) Nirenberg were outplanted on a forest site in northern Idaho, U.S.A. No residentFusarium populations were detected in the forest soil.Fusarium persisted the first four years on roots initiated during the greenhouse phase, but occurred sparingly or was absent on roots that grew after outplanting. Height growth was unaffected, and mortality was not often associated withFusarium. A seasonal pattern ofFusarium activity was observed. Low levels (10–40%) of initial root infection apparently have little adverse effect on outplanting performance of Douglas-fir seedlings.University of Idaho, Idaho Forest, Wildlife and Range Experiment Station Contribution No. 640.     

Growth and water potential of j-rooted loblolly and eastern white pine seedlings over three growing seasons

The effects of j-rooting on water stress and growth of loblolly (Pious taeda L.) and eastern white pine (Pious strobus L.) were examined over three growing seasons in the field. Seedlings were planted in an area with severe herbaceous competition with either their roots planted straight or bent into a j shape. All seedlings were planted with their root collars placed at the soil surface. During the first year j-rooted seedlings consistently had lower water potentials but never statistically significant. Since both treatments were planted with the root collar at the soil surface, this trend was likely due to an initial shallower root system in j-rooted seedlings. In year three no differences in water potential were significant and no trends were evident. Growth did not differ significantly by treatment at any time but, by year three, j-rooted plants were consistently larger for both species.     

Responses of conifer species of the Great Lakes region of North America to inoculation with the pitch canker pathogen Fusarium circinatum

Five conifer species grown in the Great Lakes region of North America were examined for their susceptibility to Fusarium circinatum, (syns. Fusarium subglutinans f. sp. pini and F. moniliforme var. subglutinans), the causal agent of pitch canker. Three‐year‐old (3‐0) seedlings of red (Pinus resinosa), jack (P. banksiana) eastern white (P. strobus), Scots (P. sylvestris) and Austrian (P. nigra) pine were planted in 4 l pots in a greenhouse at Auburn University in November 1998. In April and June 1999, seedlings were inoculated by removing a needle fascicle approximately 5 cm from the terminal bud and placing a drop containing F. circinatum conidia on the wound. Resin production, canker length and seedling mortality were recorded 12 weeks later. Jack, Scots and eastern white pine were the most susceptible with Austrian and red pine more resistant to the fungus. F. circinatum was re‐isolated from 37% to 96% of inoculated seedlings. The susceptibility of jack, Scots and eastern white pine indicates a potential risk to these important species of the region if F. circinatum were to be introduced into the area.     

Pathogenic fungi associated with pre‐ and post‐emergence seedling blight of pine and cypress in Fars Province,Iran

Seed and root rot of pine and cypress seedlings cause heavy annual losses to forest nurseries in Fars Province. Root and crown samples of various species of conifers, such as Tehran pine (Pinus eldarica), brutia pine (Pinus brutia), Arizona cypress (Cupressus arizonica), Shirazian cypress (Cupressus sempervirens var. fastigiata), common cypress (C. sempervirens var. horizontalis) and oriental arborvitae (Thuja orientalis), showing chlorosis, necrosis, stunted growth, defoliation and root and crown rot symptoms were collected from pine and cypress nurseries across Fars province at various time intervals. Infected tissues were washed and cultured on acidified potato dextrose agar (PDA) and corn meal agar (CMA) amended with Delvocide and ampicillin, with and without surface sterilization, respectively, and incubated at 25°C for 3–5 days. Decaying seeds of all plant species were also collected from nursery seed stocks and cultured on PDA. Hyphal tip isolates were used for further studies. Species of Phytophthora, Pythium, Rhizoctonia and Fusarium were isolated from symptomatic seedlings of pine and cypress at different times during the growing season. Pathogenicity of isolates of Phytophthora, Pythium and Rhizoctonia was confirmed on seedlings of all plant species, whereas Fusarium sp. isolated from the seeds of Tehran pine was only pathogenic on seedlings of Tehran pine and Arizona cypress. Virulent isolates identified as Phytophthora nicotiana var. parasitica, Pythium ultimum, Pythium paroecandrum, Rhizoctonia solani and binucleate Rhizoctonia‐like fungus caused root and crown rot of pine and cypress seedlings. Pathogenic isolates of Fusarium identified as Fusarium proliferatum also caused pre‐emergence seed decay of pine and cypress. Isolates of Phytophthora and Pythium were the most virulent of these fungal isolates.     

Aggressiveness of Fusarium oxysporum and F. verticillioides isolates on stone and scots pine under greenhouse conditions

Scots pine (Pinus sylvestris) and Stone pine (Pinus pinea) are two important species used in re-forestation that are subject to damage by damping-off fungi in forest nurseries. Twenty-two isolates of Fusarium oxysporum and F. verticillioides from diseased seedlings of eight different hosts were tested for aggressiveness on seeds and seedlings of both pine species, including the effects on seedling emergence and mortality. Scots pine was more susceptible to damping-off than Stone pine, as indicated both by reduced seedling emergence and elevated seedling mortality. The impact of F. oxysporum and F. verticillioides on seeds and seedlings did not differ significantly for either pine species. Our findings support previous studies that found that these are damping-off pathogens on the studied pines. Whereas most isolates proved to be pathogenic, some isolates of both Fusarium species showed to be non-pathogenic.     

Mycoflora associated with slash-pine seeds from cones collected at seed orchards and cone-processing facilities in the south-eastern USA1

A diverse mycoflora was associated with slash-pine seeds from cones obtained at seed orchards and cone-processing facilities in the southeastern USA. Potentially pathogenic fungi, including Lasiodiplodia tbeobromae, Sphaeropsis sapinea, and Fusarium spp., were isolated from seeds of cones obtained at all locations. Fusarium proliferatum and F. semitectum were the Fusarium spp. most often associated with seeds; F. subglutinans was rarely isolated. Many other species of fungi were associated with seeds from all locations. Incidence of fungus-damaged seeds ranged from 2 to 11% among collection sites. Disease incidence was found to increase during cone storage. Types of fungi and the incidence of fungus-damaged seeds were similar for damaged/discoloured cones and apparently healthy cones. The potential for slash-pine seeds to become colonized by pathogenic fungi, such as S. sapinea and the various Fusarium spp., could have important implications for the establishment of these fungi in forest-tree nurseries, as well as their introduction into foreign countries.     

Effect of three species of bacteria on damping-off,root rot development,and ectomycorrhizal colonization of lodgepole pine and white spruce seedlings

Interactions between three species of bacteria (Burkholderia cepacia, Pseudomonas chlororaphis and Pseudomonas fluorescens), an ectomycorrhizal fungus (Paxillus involutus), and three root pathogenic fungi (Fusarium moniliforme, Fusarium oxysporum and Rhizoctonia solani) were studied. Burkholderia cepacia significantly reduced the in vitro mycelial growth of P. involutus, whereas, B. cepacia, Ps. chlororaphis, Ps. fluorescens and P. involutus reduced the mycelial growth of F. moniliforme, F. oxysporum and R. solani. Culture filtrates of B. cepacia, Ps. chlororaphis, Ps. fluorescens and P. involutus reduced conidial germination and increased the formation of chlamydospores of F. moniliforme and F. oxysporum. Burkholderia cepacia also reduced the formation of ectomycorrhizal short roots by P. involutus on lodgepole pine (Pinus contorta) and white spruce (Picea glauca) seedlings 2 months after inoculation. However, no significance difference in mycorrhizal short roots was observed after 4 months. The fungicide Anchor (a mixture of carboxine and thiram) significantly reduced root rot severity and increased the survival of lodgepole pine seedlings grown in a growth mix infested with F. moniliforme, F. oxysporum and R. solani. Control of the diseases of white spruce caused by these pathogens was not as successful. Treatment of seeds with either B. cepacia or P. involutus alone significantly increased the survival of seedlings grown in a mix that was inoculated with F. moniliforme and reduced the root rot severity caused by F. moniliforme and F. oxysporum, but not R. solani. Higher seedling survival and lower root rot severity were observed when conifer seeds were concomitantly inoculated with one of the bacterial species, P. involutus and Anchor.     

Root diseases in bareroot and container nurseries of the Pacific Northwest: epidemiology, management, and effects on outplanting performance

In forest and conservation nurseries in the Pacific Northwest USA, seedling production can be limited by root diseases caused by fungi in the genera Fusarium Link:Fr., Cylindrocarpon Wollenw., Phytophthora de Barry, and Pythium Pringsh. Fusarium, Cylindrocarpon, and Pythium are the most ubiquitous, whereas incidence of Phytophthora is mostly associated with coastal bareroot nurseries. All of these root pathogens are encouraged by water saturated soils or media. Seedlings infected with Fusarium, Phytophthora, or Pythium often appear chlorotic or necrotic with extensive root decay. Cylindrocarpon often causes serious root decay without shoot symptoms. The best approach to mitigate losses from these diseases is to use a holistic integrated pest management program. This program should combine chemical controls with cultural practices, particularly those that increase soil permeability and drainage and reduce potential sources of inoculum, especially by disinfesting seeds and containers reused for crops. In general, we found that seedlings meeting nursery specifications for outplanting on forest soil (proper height, root collar diameter, healthy shoot color, lack of disease symptoms) but having these disease organisms on their root systems perform as well as non-infected seedlings.     

Comparison of greenhouse and environmentally controlled growthroom root growth potential testing of 2+0 eastern white pine seedlings

Two-year-old estern white pine (Pinus strobus L.) seedlings were measured for Root Growth Potential (RGP) in a hydroponic system over two years in both a greenhouse and an environmentally controlled growthroom. Analyses of variance showed no significant differences (alpha = 0.05) between testing environments for either year. This study demonstrates the validity of using greenhouse RGP testing for 2+0 eastern white pine.     

Fusarium species in declining wild apple forests on the northern slope of the Tian Shan Mountains in north‐western China

Wild apple forests in the Tian Shan Mountains in north‐western China have been adversely affected by an unknown disease in recent years. Symptoms attributed to this disease that affects wild apple trees include xylem browning and dieback which are suggestive of infection by Fusarium species. Therefore, the research team conducted the first survey for Fusarium in the afflicted wild apple forests. Twig samples with symptoms of xylem browning and dieback were collected in the Xinyuan, Gongliu, Yining and Huocheng Counties of Xinjiang Uighur Autonomous Region in China. Based on phylogenetic analyses and morphological observation, sixty strains of Fusarium accounted for 48% of the total number of fungi isolated from samples were subsequently classified into six species including twenty‐four F. avenaceum, seventeen F. solani, ten F. tricinctum, five F. proliferatum, two F. sporotrichioides and two unfamiliar Fusarium sp. 1. The five previously known species of Fusarium were then tested for pathogenicity to leaves and twigs in vitro. The results indicated that all of the species, except for F. tricinctum, can cause obvious lesions on the leaves of host plants and on the twigs of Fuji and wild apple. This is the first report of Fusarium species pathogenicity in Xinjiang wild apple forests, confirming a new host for these pathogens in this study.     

In vitro effects of four ectomycorrhizal fungi, Boletus edulis, Rhizopogon roseolus, Laccaria laccata and Lactarius deliciosus on Fusarium damping off in Pinus nigra seedlings

Species of Fusarium cause damping off of forest seedlings resulting in considerable losses and oftentimes fungicides are used to control the disease. Such chemicals may be detrimental to the environment. Protection of forest seedlings against this disease must be focused on integrated management for in which biological control is one of the most important tools. Mycorrhizal fungi may provide protection against pathogen invasion of seedlings. In this study, the interactions between the mycorrhizal fungi Boletus edulis, Rhizopogon roseolus, Laccaria laccata and Lactarius deliciosus and damping off pathogens (Fusarium oxysporum and F. moniliforme) were investigated in vitro and mechanisms involved in the protection of damping off in P. nigra seedlings are also discussed. The effect of filtrates from mycorrhizal species on spore germination of F. oxysporum varied throughout the tests. At the end of the assay, the inhibitory effect only could be observed in the L.␣deliciosus treatment. None of the filtrates reduced spore germination in F. moniliforme. Finally, three of the four mycorrhizal species grown for 2 months in the substrate, L. laccata, L.␣deliciosus and B. edulis, increased the survival of Fusarium inoculated P.␣nigra seedlings.     

Prevalence and incidence of the root-inhabiting fungi, Fusarium, Cylindrocarpon and Pythium, on container-grown Douglas-fir and spruce seedlings in British Columbia

Surveys were made at the end of the 1990 and 1991 growing seasons for root-inhabiting fungi in the genera Fusarium, Cylindrocarpon and Pythium from the roots of one year-old container-grown Douglas-fir and spruce seedlings grown under greenhouse conditions. In the 1990 survey of four nurseries, it was found that 61–97% of both Douglas-fir and spruce roots were colonized with Fusarium, Cylindrocarpon or Pythium. There were significantly (p0.05) more Douglas-fir roots than spruce roots colonized by Fusarium at all nurseries, however, there were significantly (p0.05) more spruce roots than Douglas-fir roots colonized by Cylindrocarpon and Pythium. Root colonization of Douglas-fir and spruce by the three fungal genera during 1991 varied from 0–82% at three nurseries, however, only at a south coastal nursery was there significantly (p0.05) more spruce than Douglas-fir roots colonized by Cylindrocarpon. Significantly more seedlings were infected in 1990 than in 1991. In 1991, there were few significant differences between Douglas-fir and spruce, in the percentage of seedlings with colonized roots and in the percentage of growth medium colonized by the fungi. However, there were significant differences between nurseries.     

Ectomycorrhizal development on pine by Pisolithus tinctorius in bare-root and container seedling nurseries

Vegetative inoculum of Pisolithus tinctorius (Pt) produced by Sylvan Spawn Laboratories (C:N 50) and by research methods (IMRD), spore-encapsulated seeds, spore pellets, and sprayed spores were compared for efficacy in forming Pt ectomycorrhizae on pines in operational bare-root nurseries in South Carolina, Florida, and Indiana and in microplots and containers in Georgia. Two rates of application (0.33 and 0.16 liter/m² of soil) of both sources of vegetative inoculum were similar in effect and formed abundant Pt ectomycorrhizae (Pt index > 50) and fruit bodies in all studies. Spore treatments formed consistently fewer Pt ectomycorrhizae than vegetative inoculum. The most effective spore treatment was spore encapsulated seeds. These results indicate that at a bed density of 270 seedlings/m², 0.6 to 0.7 liter of vegetative inoculum is needed to obtain Pt indices > 50 on 1,000 pine seedlings.     

Identification of mangrove endophytic fungus 1403 (Fusarium proliferatum) based on morphological and molecular evidence

A mangrove endophytic fungus 1403 isolated from the South China Sea Coast, which is able to produce griseofulvin and anthracenediones under submerged fermentation, was compared with Fusarium genus with the similar morphological characters such as elongated, microconidium-producing conidiophores, ovoid microconidia and straight to slightly curved macroconidia. It was found that the fungus 1403 resembles pathogenic F. verticillioides (teleomophy Gibberella moniliforme) in the production of false head or chains and abundant microconidia on the aerial mycelium, but different in the occasional formation of polyphialides with relatively long as well as short monophialides, in its typical coiled hyphae and mycelia fusion. Through maximum Parsimony and Bayesian analyses, the fungus 1403 was further compared with some similar Fusarium species. The results indicated that this endophyte was identified as Fusarium proliferatum based on the analyses of partial 18S and 28S rDNA genes, ITS region, and EF-1α gene. Foundation project: This research was supported partly by the Guangzhou Natural Science Foundation (Grant No. 2007Z3-EO581), the Guangdong Provincial Natural Science Foundation (Grant No. 2007A0200300001-7; 05003268), the Chinese High-Tech 863 Project (Grant No. 2006AA09Z422), and the National Natural Science Foundation of China (Grant No. 20572136)     

Nursery soil cover influences germination of Thujopsis dolabrata var. hondai seeds

We examined the influence of nursery soil cover on germination of Thujopsis dolabrata var. hondai. Seeds were sown under seeding bed conditions: (1) nursery soil (andosol) without soil cover, (2) Kanuma pumice without soil cover, (3) nursery soil with nursery soil cover, and (4) nursery soil with sterilized sand cover. Germination percentages were compared between these conditions. The germination percentage (8.8%) at 10 weeks after sowing under condition 3 was significantly lower than under conditions 1, 2, and 4 (56.8%, 52.0%, and 47.2%, respectively). Of the nongerminated seeds under condition 3, 75.0% were decayed and several fungi were isolated from decayed seeds. An inoculation test of isolated fungi Cylindrocarpon tenue, Cylindrocarpon sp., Fusarium oxysporum, and Botrytis sp. to seeds showed that these fungi caused seed decay. Our results indicated that nursery soil cover may not be suitable for T. dolabrata var. hondai seeds sown in nursery soil because of seed decay by pathogens.     

Field survival of containerized red and jack pine seedlings inoculated with mycelial slurries of ectomycorrhizal fungi

Red pine and jack pine seedlings growing in styroblocks were inoculated 8 wk after sowing with mycelium/agar slurries of 3 mycorrhizal fungi (Laccaria bicolor, Scleroderma citrinum, and an unidentified basidiomycete), and one suspected mycorrhizal fungus (Cantharellula umbonata). Seedlings inoculated with L. bicolor developed mycorrhizae earlier and in greater numbers than the other inoculation treatments, with red pine out-performing jack pine in both respects. At 34 wk following sowing, seedlings were outplanted on a cleared xeric site in Baraga Co., in Michigan's Upper Peninsula. Seedlings inoculated with C. umbonata failed to form mycorrhizae and were not outplanted. Inoculation treatments did not affect shoot or root weight at outplanting. Red pine inoculated with L. bicolor averaged 21% and 19% greater survival compared with control seedlings after one and two years in the field, respectively. Other inoculation treatments failed to increase seedling survival for either tree species. Jack pine demonstrated higher overall survival than did red pine for both years in all corresponding inoculation treatments.     

Different development of pine wilt disease in artificially infectedPinus thunbergii seedlings potted together with different tree species

To evaluate the effect of adjacent tree species on the susceptibility of Japanese black pine (Pinus thunbergii) to pine wilt disease, an inoculation experiment was conducted usingP. thunbergii seedlings potted with seedlings of six tree species,i. e. Alnus sieboldiana, Eurya japonica, Lespedeza bicolor formacutifolia, Pinus thumbergii, Robinia pseudo-acacia andSarothamus scoparius. About ten months after planting, they were inoculated with the pinewood nematode (Bursaphelenchus xylophilus) in early July 1992. After that, the proportion of pine seedlings with completely discolored foliage increased more quickly when the seedlings were potted withR. pseudo-acacia, S. scoparius orA. sieboldiana than when potted withP. thunbergii, L. bicolor orE. japonica. At the end of the study period, 17 weeks after inoculation, it reached 90.6%, 90.0%, 87.5%, 72.7%, 63.3%, and 59.4% when the pine seedlings were potted withR. pseudo-acacia, S. scoparius, A. sieboldiana, P. thunbergii, L. bicolor andE. japonica, respectively. This indicated that the susceptibility ofP. thunbergii seedlings to pine wilt disease was influence by the species of adjacent trees.     

Adventitious root formation of two <Emphasis Type="Italic">Abies</Emphasis> species on log and soil in an old-growth subalpine forest in central Japan

We assessed stem burial and adventitious root formation of two late-successional species, Abies mariesii and A. veitchii, in central Japan. In a plot (5 × 5 m), all seedlings between 8 and 24 cm tall were excavated: six A. mariesii seedlings in soil, and six and four A. veitchii seedlings in soil and on logs, respectively. For each sampled seedling, the number of terminal bud scars (TBS) was counted on the aboveground and belowground stems. Stem length was measured, and divided into aboveground and belowground stems. Among the three groups (A. mariesii seedlings in soil and A. veitchii seedlings in soil or on logs), there was no significant difference in height or total root weight (sum of adventitious roots and primary roots), but diameter at ground level and number of TBS were significantly different. Counting TBS on the aboveground stem of seedlings in soil underestimated seedling age, whereas the estimate was much closer to the true age for seedlings on logs. Seedlings in soil formed more adventitious roots than seedlings on logs. A large proportion of the stem was buried in humus for seedlings in soil, while most of the stem was not buried in humus for seedlings on logs. These results suggest that substrate affects adventitious root formation, the formation of which is important to shade tolerance. Thus, our preliminary results suggest that consideration of adventitious root formation is necessary to understand seedling bank dynamics and estimate seedling ages of these Abies species in spatially heterogeneous old-growth subalpine forests.