Future outlook for Pinus patula in South Africa in the presence of the pitch canker fungus (Fusarium circinatum)

Approximately 50% of the area planted to softwood trees in South Africa has been established with Pinus patula, making it the most important pine species in the country. More effort has gone into developing this species for improved growth, tree form and wood properties than with any other species. This substantial investment has been threatened in the last 10 years by the pitch canker fungus, Fusarium circinatum. The fungus infects and contaminates nursery plants and, once transferred to the field, causes severe mortality of young trees in the first year after establishment. Although nurserymen have some control of the disease, it is recognised that the best long-term solution to mitigate damage because of F. circinatum infection is to identify tolerant species, clones and hybrids for deployment in plantations in the future. Research has shown that alternative species such as P. tecunumanii, P. maximinoi and P. elliottii are suitable for warm sites. Pine hybrids, particularly between P. patula and the high-elevation sources of P. tecunumanii, appear to be a suitable replacement on subtemperate and temperate sites. Although these alternative species and hybrids are more sensitive to subfreezing temperatures than P. patula, their planting range can be increased by including cold tolerance as a selection criterion. Future breeding efforts will most certainly focus on improving the tolerance of pure P. patula to F. circinatum, which can be achieved by identifying specific family crosses and tolerant clones. The commercial deployment of disease-tolerant control-pollinated P. patula and hybrid families will most likely be established as rooted cuttings, which requires more advanced propagation technology. In the long term, new seed orchards comprised of P. patula clones tolerant to F. circinatum could be used to produce seed for seedling production.     

Variation in susceptibility of six pine species and hybrids to pitch canker caused by Fusarium circinatum

Six pine species or hybrids were tested for susceptibility to pitch canker caused by Fusarium  circinatum. Pinus  densiflora, Pinus  thunbergii, Pinus  x rigitaeda (Pinus  rigida × Pinus  taeda), P. rigida × P. x rigitaeda, Pinus  echinata and Pinus  virginiana were inoculated with three spore loads (50, 500 and 5000 per tree) of F. circinatum. External symptoms, lesion length, and the frequency of reisolation of the fungus were investigated. External symptoms were greatest in P. echinata, followed by P. virginiana, however, P. densiflora was not susceptible to F. circinatum. Based on mean lesion lengths, the six pine species or hybrids differed significantly (p < 0.01) in susceptibility to pitch canker. Pinus  echinata sustained the longest lesions, whereas P. densiflora sustained the shortest lesions. The effect of inoculum density was not significant among three spore treatments within species (p = 0.17), although lesion length was slightly greater at higher spore loads over all pine species. The fungus was reisolated from inoculated stems of all pine species tested, even on trees showing little or no damage from the disease. Additional studies are needed to further explore the basis for resistance to pitch canker.     

High genetic diversity of Fusarium circinatum associated with the first outbreak of pitch canker on Pinus patula in South Africa

The disease known as pitch canker results from infection of Pinus species by the fungus Fusarium circinatum. This fungus also causes a serious root disease of Pinus seedlings and cuttings in forestry nurseries. Pinus radiata and P. patula are especially susceptible to the pathogen, but there are no records of pitch canker on P. patula in established plantations. To date, only planting material of this tree species in nurseries or in plantations at the time of establishment have been infected by F. circinatum. Symptoms of pitch canker have recently emerged in an established P. patula plantation in South Africa and this study sought to determine whether the symptoms were caused by F. circinatum. Isolates from cankers were identified as F. circinatum using morphology and DNA-based diagnostic markers. Microsatellite markers were then used to determine the genetic diversity of a collection of 52 isolates. The entire population included 17 genotypes representing 30 alleles, with a greater number of genotypes collected from younger (three- to six-year-old) than older (12- to 19-year-old) trees. Both mating types of F. circinatum were present, but no evidence of sexual recombination was inferred from population genetic analyses. This is the first record globally of pitch canker on P. patula trees in managed plantations. It is of significant concern to South Africa, where P. patula is the most important Pinus species utilised for plantation forestry.     

Differential responses of Central American and Mexican pine species and Pinus radiata to infection by the pitch canker fungus

Seedlings from a wide array of 23 species, varieties,and geographic races were screened for resistance topitch canker using artificial inoculation in agreenhouse. Seed to represent these taxa weregenerally collected in natural stands. In addition,seedlings from 79 families of P. radiata fromcommercial populations from Chile and New Zealand werescreened in a separate experiment. There was littlevariation in resistance among the commercial P.radiata families, with over 98% mortality. Similarresults were obtained with native P. radiatapopulations. All close relatives of P. radiata(sub-section Patula) were very susceptible. However,a number of closed-cone pine species (specifically,from sub-section Oocarpa) were generally veryresistant, with survival approaching 100%. Inaddition, in P. oocarpa, P. jaliscana, and P. tecunumanii from low elevation provenances anextremely high frequency of trees suffered no apparentdamage from the pathogen (92%, 85% and 80%,respectively).     

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.     

Development and evaluation of a real‐time PCR seed lot screening method for Fusarium circinatum,causal agent of pitch canker disease

Fusarium circinatum is a serious pathogen of Pinus spp. worldwide, causing pitch canker disease. F. circinatum can contaminate seeds both internally and externally and is readily disseminated via contaminated seed. Many countries require screening of pine seeds for F. circinatum before they can be imported. The currently accepted screening method is based on culturing the pathogen on a semi‐selective medium and identifying it using morphological traits. This method is time‐consuming and does not allow for accurate identification of the pathogen to the species level. A bulk DNA extraction and real‐time PCR procedure to screen seeds for the presence of F. circinatum were developed in this study. The real‐time PCR method resulted in the detection of F. circinatum in 5 of 6 commercial seed lots tested and has a lower detection limit of 1 × 10^?5 ng of F. circinatum DNA per PCR. The culture‐based method detected Fusarium spp. in four of six of the same seed lots. The real‐time PCR method can be used to screen multiple seed lots in 2 days, whereas the culture‐based method requires a minimum of 1–2 weeks. This new real‐time PCR seed screening method allows for fast, sensitive and accurate screening and can be adapted to handle larger volumes of seeds.     

Selection of Pinus spp. in South Africa for tolerance to infection by the pitch canker fungus

The increasing threats from pests and diseases demand that the South African forest industry explores options to deploy alternative pine species in plantation development. This is especially true for species, such as Pinus patula Schiede and Deppe ex Schltdl. and Cham., which are highly susceptible to the pitch canker fungus Fusarium circinatum. Losses due to F. circinatum have been confined mostly to nurseries and at field establishment resulting in a significant cost to the industry. Although, the fungus has not as yet resulted in stem and branch infections on established P. patula in South Africa, it has caused pitch canker on other, more susceptible species such as P. radiata D. Don., and P. greggii Engelm. ex Parl. As alternatives to P. patula, on the warmer and cooler sites in South Africa, families of P. elliottii Engelm var. elliottii, P. tecunumanii (Schw.) Eguiluz and Perry, P. maximinoi H. E. Moore and P. pseudostrobus Lindl. were screened for tolerance to infection by F. circinatum in greenhouse studies. Seedlings were wounded and inoculated with spores of F. circinatum. Lesion development following inoculation was used to differentiate the levels of tolerance between families. The results showed that P. maximinoi, P. pseudostrobus, and the low elevation variety of P. tecunumanii are highly tolerant to infection with very little family variation. The narrow sense heritability estimates for these species were less than 0.06. In contrast, P. elliottii showed good tolerance with some family variation and a heritability of 0.22, while the high elevation source of P. tecunumanii showed a high degree of family variation and a heritability of 0.59. These results provide the industry with valuable information on pine species tolerant to F. circinatum that could be used as alternatives to P. patula in South Africa.     

Genetic variation in survival,growth, and stem form of Pinus leiophylla in Brazil and South Africa and provenance resistance to pitch canker

Pinus leiophylla is a relatively common pine that occurs in the mountains of western and central Mexico. Between 1987 and 1990, Camcore, North Carolina State University, sampled 11 populations and 309 mother trees of the species to determine patterns of genetic variation in survival, growth and stem form. Fifteen provenance/progeny trials were established in southern Brazil and South Africa across a wide range of sites and assessed at 3, 5 and 8 years of age for height, diameter and stem form. Results indicated that average productivity ranged from 5 to 19m³ ha^?1 y^?1 depending on the site and that performance was not as competitive as P. patula (South Africa) and P. taeda (Brazil) controls. Provenances from central Mexico (Michoacán) were statistically better in productivity than those from the southern part of the country (Oaxaca), which in turn were superior to those from the northern part of the country (Durango). However, provenances from northern Mexico exhibited superior survival to seed sources from other locations in Mexico when grown on cold sites (winter minimums –10 to 5°C) in South Africa and superior stem form across all locations. Seedlings from the original 11 provenances were screened for resistance to the pitch canker fungus (PCF; Fusarium circinatum). Results indicated that generally P. leiophylla is as susceptible to PCF as P. patula (stemkill = 85%) with the exception of two fast-growing, moderately resistant populations from Michoacán, La Pinalosa (stemkill = 44%) and Ario de Rosales (stemkill = 73%). The future potential of P. leiophylla might be in hybrid combination with P. patula in the seasonally dry areas of southern Africa where fires are common and pitch canker is a problem.     

Life cycle and in vitro sporulation dynamics of Corinectria constricta,the causal agent of Pinus radiata stem canker,in Chile

In 2008, a canker disease caused by the fungus Corinectria constricta was detected in southern Chile. The causal agent was previously identified as Neonectria fuckeliana (now Corinectria fuckeliana), which has been associated with stem cankers in Pinus radiata plantations in New Zealand since the 1990s. Many basic aspects of the life cycle of C. constricta remain unknown. The current study aimed to (a) document the periods during which C. constricta fruiting bodies are present in P. radiata plantations and associated factors; (b) determine the C. constricta life cycle in P. radiata plantations in southern Chile; and (c) evaluate, under in vitro conditions, the sporulation dynamics of ascospores. The first and second aims were carried out by evaluating affected plantations every 15 days, identifying asexual and sexual fungal structures, and recording the time periods when the structures were present. The third aim was achieved with in vitro tests in Petri dishes simulating humidity chambers. The life cycle was characterized by the presence of sporodochia from the Cylindrocarpon‐like (asexual form of C. constricta) morph during the autumn of 2012 (March–May). Subsequently, perithecia began to form on the sporodochia during April of 2012, taking approximately 3 months to mature (May–July), persisting for the rest of the year and providing inoculum to infect new trees. The development of perithecia in winter demonstrates that this is the most important period for dispersal and infection. In terms of sporulation dynamics, perithecia can release ascospores up to eight days following a wetting event; without this event, the spores are not released.     

Damage caused by Lygus rugulipennis Popp. (Heteroptera,Miridae), to Pinus sylvestris L. seedlings

The tarnished plant bug (Lygus rugulipennis) and occasionally L. punctatus were found to feed on pine seedlings in central Finland. Both the nymphs and adults of Lygus bugs injured the apical meristem of the seedlings. This led to the death of the apex, and the opening of the lateral buds, resulting in a seedling with multiple leaders. L. rugulipennis may also oviposit on pine seedlings and the development from egg to adult on pine alone is possible. In laboratory experiments it was shown that the main factor in the apical meristem injury is the mechanical damage caused by the bug's stylet. The feeding damage and artificial mechanical damage caused by needles to the apical meristem of pine seedlings resulted in increased numbers of multiple‐leader seedlings and reduced shoot length and dry weight of the shoot and root.     

Factors contributing to the resistance of Pinus densiflora (Sieb. and Zucc.) and susceptibility of Pinus rigida × radiata to Fomes annosus

Water, ethanol, ethyl acetatc and chloroform extractives of Pinus densiflora and P. rigida×radiata were made. The ethanol extractives from P. densiflora were most inhibitory in bioassays using two F. annosus strains. Thcse cxtractives werc scparated into acid, base, and ncutral parts. Fractions were collected from the neutral part and bioassays conducted to determine which contained activc fungitoxic compounds. Thin layer diromatography revealed the number of compounds in each fraction.     

激素、钙、水杨酸和铵诱导马尾松、黑松抗松材线虫病的研究

诱抗试验结果表明：（１）ＩＢＡ、乙烯、ＩＢＡ＋乙烯对马尾松的诱抗效果达６０％，而ＩＢＡ＋乙烯对黑松苗的诱抗效果为１２５％。（２）Ｃａ２＋＋ＩＢＡ对黑松苗的诱抗效果为３６６７％。（３）除Ｓａ＋ＩＢＡ对黑松苗的诱抗效果为１６７％外，其余Ｓａ的各处理效果均不明显。（４）铵的单用、混用或与Ｃａ２＋混用对马尾松诱抗效果均可达６６８％～１００％。     

Screening for resistance to cypress canker (Seiridium cardinale) in three Greek provenances of Cupressus sempervirens

A test involving field-inoculation of three year-old cypress seedlings was evaluated to find clones resistant to Seriatim cardinale. A satisfactory proportion of resistant trees was found, but it was significant different among three provenances and also among families. Best results were obtained from the provenance of Sames, followed in decreasing order by the provenances of Rhodes and Krete.     

Regeneration of pitch pine (Pinus rigida) stands inhibited by fire suppression in Albany Pine Bush Preserve,New York

The Pine Barrens in New York State are dominated by pitch pine(Pinus ridgida) and scrub oaks(Quercus ilicifolia and Q. prinoides). With fire suppression over the last 90 years or so, P. rigida regeneration has become sparse, even in areas set aside to preserve this type of vegetation. We evaluated the effects of fire and an alternative disturbance(mechanical removal of vegetation)for increasing P. rigida regeneration in the Albany Pine Bush Preserve in eastern New York State. By comparing cover, diameter and height of P. rigida, Q. ilicifolia, Q.prinoides, and Vaccinium spp.(blueberry) growing on the sites with a known fire history, we documented structural and compositional changes in the vegetation since its establishment. We also compared sites on which Quercus sprouts were controlled through mechanical removal. In the years following a disturbance, height and cover of Q. ilicifolia increased continuously and the species became increasingly competitive. Both the density of P. rigida seedlings and Vaccinium cover decreased significantly as the diameter and height of Quercus increased. Our results confirmed that the dominance by P. rigida could be attributed to periodic fires at intervals of 20–25 years. We conclude that removing Q. ilicifolia can favor P. rigida dominance on the barren without fire by releasing pine seedlings from competition.     

Susceptibility of cork oak (Quercus suber) to canker disease caused by Diplodia corticola: when time is of the essence

New Forests - Cork is a renewable resource mainly produced in Mediterranean countries thanks to sustainable management of cork oak (Quercus suber) stands. The infection caused by the ascomycete...     

Possible altitude and temperature limits on pine wilt disease: the reproduction of vector sawyer beetles (Monochamus alternatus), survival of causal nematode (Bursaphelenchus xylophilus), and occurrence of damage caused by the disease

Pine wilt disease is caused by the pine wood nematode [Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle]. In East Asia, an important vector of the nematode is Monochamus alternatus Hope. We determined the tolerance and reproductive ability of sawyer beetles and the nematode to altitude and temperature at elevations between 850 and 1,450 m on Mt. Fuji in Japan. The number of emergent adults decreased markedly along the altitudinal gradient, but the beetle could still reproduce at 1,050 m (8.2 °C annual mean temperature). Beetles with a 2-year life cycle increased rapidly in number with increasing altitude. The pine wood nematode survived through winter at all altitudes tested (850–1,450 m). The beetle population decreased between 950 (9.1 °C) and 1,150 m (8.3 °C). Therefore, the beetle population seems to be stable at 850 m (10.2 °C) and lower altitudes (higher temperatures) but cannot be maintained from 950 (9.1 °C) to 1,150 m (8.3 °C) without constant immigration of beetles from lower altitudes. The beetles could not reproduce at altitudes above 1,150 m (lower than 8.2 °C). From the mean and effective cumulative temperatures, we concluded that the beetle (and its population) can endure temperatures lower than those previously reported. Pine wilt disease also occurred at lower temperatures and higher altitudes than expected. We have summarized the principal strategies for controlling the disease at high altitudes based on these results.     

The lack of persistence of Ophiostomataceae fungi in Pinus radiata 3 years after damage by the bark beetle Hylastes ater,and the subsequent colonisation by Sphareopsis sapinea

A survey established in 2002 of 1-year-old Pinus radiata seedlings in New Zealand confirmed the presence of a number of members of the Ophiostomataceae family within the seedlings following damage. The persistence of fungi in P. radiata trees for extended periods following prior damage to the seedlings by the bark beetle Hylastes ater was studied subsequently as is reported herein. A random selection of the remaining P. radiata trees from the original sites were destructively sampled in 2005, approximately 3 years after the initial study. The diameter of each tree was measured, visual observations of any damage to tree were noted and any potential sapstaining fungal species were isolated. Sphareopsis sapinea was isolated from 6 to 16% of trees, despite not being isolated from any trees in the first study. With the exception of Ophiostoma setosum isolated from a single tree, no members of the Ophiostomataceae family were isolated this second time from the trees. The present study highlights that Ophiostoma species initially inhabited P. radiata seedlings following bark beetle attack, but their presence was not sustained over the three year period, showing that they were not endophytes in P. radiata. The asymptomatic persistence of S. sapinea in seedlings and larger P. radiata trees, however, is of significant concern for the forest industry.     

四川阿坝辐射松引种长期森林健康风险初步评估

Pinus radiata was introduced to the summer rainfall environments of Sichuan Province, China in the 1990s as a part of an afforestation pmgram for soil and water conservation in the arid and semi-arid river valley area of Aba Prefecture. Within this region a total area of 26 000 ha have been identified through climate matching as suitable and a further 63 000 ha potentially suitable for environmental plantings of P. radiata. The plantations are being established in widely separated small patches on steep and degraded slopes along the dry river valley The newly introduced P. radiata are exposed to two kinds of forest health risks： they may be attacked by （a） indigenous pathogens and pests against which they may not possess any resistance or （b） by inadvertently introduced foreign pests or pathogens. This paper presents a survey of the potential damaging pests and a preliminary assessment of forest health risks facing the P. radiata plantations over a much longer timeframe than the initial phase of introduction and early plantation establishment. An empirical appmach was adopted to evaluate forest health risks by a combination of literature review, examination of historical records of pest and disease outbreaks in the surrounding conifemus forests, field surveys and inspections, specimen collection and identification, and most importantly, expert analysis of the likelihood of attack by specific pests and pathogens and the subsequent impact of such attacks. The assessment identified some specific forest health risks to the long-term success of P. radiata introduction in this area. These risks are closely associated with the indigenous pests and pathogens of the two native pine species, P. tabulaeformis and P. armondii since these pests and pathogens are considered more likely to establish on P. radiata over time. Exotic pests and pathogens are of a quarantine concern at present. Based on the results of assessment, recommendations are pmvided to improve forest vigour and to reduce the forest health risks pos     

抗松材线虫病马尾松无性系种子园营建技术

松材线虫病是危害松属树种的毁灭性病害,危害严重、防治困难。安徽省从2001年开始从疫区和非疫区的马尾松林分中选择324株抗病优树以及部分广东、广西种源,通过嫁接繁殖和人工接种松材线虫的方法进行无性系抗病性测定。2011年利用筛选出的68个家系的89个高抗无性系营建了1.6 hm2抗松材线虫病马尾松无性系种子园。各家系成活率90.9%～100%,平均成活率93.6%。