Seedling survival and growth of Aquilaria malaccensis in different microclimatic conditions of northeast India

We studied seedling survival and growth of Aquilaria malaccensis in three different environmental conditions(homegardens,green house and in different canopy conditions) of northeast India.Results show that mean seasonal survival was highest in green house(95.53%±2.33),followed by homegardens(89.3%±1.89) and different canopy conditions(77.62%±6.73);the highest values were found during February to April for both the homegardens(96%±1.68) and green house(98% ± 0.88) and lowest during November to January(78%±2.99) in homegardens and May to July(90%±4.53) in green house.In case of transplanted seedlings in different canopy conditions,mean seasonal survival was highest during May to July(98%±1.92) and lowest during August to October(66%±12.81).However,mean seasonal growth of collar diameter was highest in different canopy conditions(23.99%±1.76) compared to green house(21.52%±2.70) and homegardens(12.44%±1.33) and it was highest during rainy season(May to July) and lowest during dry winter(November to January) in all the three experimental sites.These variations may be due to the different microclimatic conditions as well as nutrient status of the soil in all the three experimental sites.Although,seedling quality plays a great role in their survival and growth,based on the result of green house experiment,it can be concluded that maintenance of seedlings in green house conditions during their early growth period may improve both the survival and growth for large scale plantation of the species.Thus,the species can be reintroduced in its natural forest range to compensate the loss of natural population of this precious species in northeast India.     

Fungal inoculation induces agarwood in young Aquilaria malaccensis trees in the nursery

Fungi are often used to induce agarwood inAquilariatrees. This study was conducted to evaluate the effect of several fungi on agarwood formation over time in youngAquilaria malaccensis （Lam.） trees. Typical changes in the length and light intensity of the resulting discoloration were observed after three and six month periods following inoculation. Wood samples were observed microscopically and classified into several light intensity groups. The discoloration length was meas-ured longitudinally. The duration after inoculation affected the mean of discoloration length： the 6-month old sample （1.70 cm） had a wider discoloration zone when compared to the 3-month old sample （1.17 cm）. When measuring the discoloration intensity, a positive relationship with time was perceived. Digital images, captured using a camera-equipped microscope, revealed that wood samples collected after six months appeared to be 1.8-times darker than after three months. We concluded that time, not the species of any of the tested fungi, had significant effect on discoloration length and intensity. Gas chromatography/mass spec-trometry （GCMS） analysis of the 6-month old sample yielded some important agarwood compounds such as benzylacetone, anisylacetone, guaiene and palustrol. This demonstrates that the tested fungi have the ability to induce agarwood formation in nurseryA. malaccensis trees.     

Identification of chemical compounds in agarwood-producing species Aquilaria malaccensis and Gyrinops versteegii

Agarwood is a non-timber forest product found in tropical rain forests.It is a black and fragrant resin valued for the perfume industry and demand continues to increase.However,the Indonesian agarwood-producing species,Aquilaria malaccensis and Gyrinops versteegii do not automatically produce such quality resin.Bio-induction technology or inoculation using Fusarium solani is usually applied to these species to trigger resin production.This research aims to identify agarwood compounds formed in seedlings and trees of A.malaccensis and G.versteegii after these species were inoculated with the fungus F.solani.The chemical compounds were identified by comparing the patterns of mass spectra fragmentation in the sample and in previous studies.Five groups of agarwood compounds were identified:(1) sesquiterpen group—cisjasmone and aromadendrenepoxide;(2) chromones group—8-methoxy-2-(2-phenylethyl)chromen-4-one and newly-discovered chromone derivative,7-(benzyloxy)-5-hydroxy-2-methylchromone found only in G.versteegii;(3) aromatic group—benzylacetone,guaiacol,p-ethylguaiacol,phenol,syringaldehyde,vanilin,furfuryl alcohol,and furfural;(4) fatty acid group—palmitic acid,oleic acid,and lauric acid;and,(5) triterpen group—squalene.     

The Sclerophomas associated with dieback of Douglas-fir

Two new species of Sclerophoma Höhn. are described from dieback of Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) in British Columbia, Canada, viz. S. xenomeria n. sp. (conidial Xenomeris abietis Barr), and S. semenospora n. sp. Morphological and cultural characteristics are compared with S. pithyophila (Corda) Höhn., another common species in the same disease syndrome.     

花椒枝枯病损失量与防治效益研究

通过对810株18年生绵椒枝枯病损失量及防治效益研究，得到了花椒枝枯病情指数（X）与花椒损失率（Y）的一元线性回归方程Y=0.8146X-9.3719(r=0.98098)；花椒枝枯病不造成经济损失的临界病情指数为11.50，花椒枝枯病防治的经济阈值为病情指数19，防治指标为病情指数30.50。     

Bacteria wilt of Casuarina equisetifolia in India

Pseudomonas solanacearum (Smith) was consistently isolated from the wilted plants of Casuarina equisetifolia. The isolate gave positive reaction to oxidase, catalase and gas production from nitrate and negative reaction for arginine dihydrolase and acid was produced from various carbohydrates. Wilt produced on tomato, egg plant and capsicum indicated that the pathogen belongs to Race I and Biovar III of P. solanacearum which is a new record from India.     

Phytophthora species associated with dieback of sweet chestnut in Western Turkey

Sweet chestnut (Castanea sativa) is an important tree species in the Marmara and Aegean regions of Turkey as these two regions produce the great majority of edible nuts, especially those used for marron glacé production. Chestnut forests and orchards in these regions showing severe dieback symptoms not associated with chestnut blight were investigated to determine the role of Phytophthora spp. in the decline syndrome. Soil samples were collected from around 108 symptomatic chestnut trees at 29 sites and Phytophthora spp. isolated using soil baiting technique and selective medium. Species isolated were identified by cultural characteristics and ITS sequencing. Phytophthora x cambivora was the dominant species detected in 13 sites, followed by P. cinnamomi (5 sites), P. plurivora (3 sites) and P. cryptogea (1 site). Phytophthora x cambivora was present in both regions, while P. cinnamomi was found only in the Marmara region in coastal areas around Istanbul. When inoculated at the stem bases of 3‐year‐old chestnut saplings, P. cinnamomi produced significantly longer necrotic lesions (7.8–12.0 cm) than P. x cambivora (2.6–6.3 cm) by 12 days after inoculation. Phytophthora plurivora was the least aggressive species causing only small lesions. Phytophthora cryptogea, which represents the first record on chestnut in Turkey, produced intermediate sized lesions in between P. x cambivora and P. plurivora. These results indicate that P. x cambivora and in some areas P. cinnamomi play major roles in the observed dieback of sweet chestnut in western Turkey.     

Oak mortality associated with crown dieback and oak borer attack in the Ozark Highlands

Oak decline and related mortality have periodically plagued upland oak–hickory forests, particularly oak species in the red oak group, across the Ozark Highlands of Missouri, Arkansas and Oklahoma since the late 1970s. Advanced tree age and periodic drought, as well as Armillaria root fungi and oak borer attack are believed to contribute to oak decline and mortality. Declining trees first show foliage wilt and browning, followed by progressive branch dieback in the middle and/or upper crown. Many trees eventually die if severe crown dieback continues. In 2002, more than 4000 living oak trees ≥11 cm dbh in the relatively undisturbed mature oak forests of the Missouri Ozark Forest Ecosystem Project (MOFEP) were randomly selected and inventoried for tree species, dbh, crown class, crown width, crown dieback condition (healthy: <5% crown dieback, slight: >5–33%, moderate: 33–66%, and severe: >66%) and number of emergence holes created by oak borers on the lower 2.4 m of the tree bole. The same trees were remeasured in 2006 to determine their status (live or dead). In 2002, about 10% of the red oak trees showed moderate or severe crown dieback; this was twice the percentage observed for white oak species. Over 70% of trees in the red oak group had evidence of oak borer damage compared to 35% of trees in the white oak group. There was significant positive correlation between crown dieback and the number of borer emergence holes (p < 0.01). Logistic regression showed oak mortality was mainly related to crown width and dieback, and failed to detect any significant link with the number of oak borer emergence holes. Declining red oak group trees had higher mortality (3 or 4 times) than white oaks. The odds ratios of mortality of slightly, moderately, and severely declining trees versus healthy trees were, respectively, 2.0, 6.5, and 29.7 for black oak; 1.8, 3.8, and 8.3 for scarlet oak; and 2.6, 6.5 and 7.1 for white oaks.     

Effects of plant growth regulators,carbon sources and pH values on callus induction in Aquilaria malaccensis leaf explants and characteristics of the resultant calli

The endangered tropical tree, Aquilaria malaccensis, produces agarwood for use in fragrance and medicines. Efforts are currently underway to produce valuable agarwood compoundsn tissue culture. The purpose of this study was to develop an optimal growth medium, specifically, the best hormone combination for callus suspension culture. Using nursery-grown A. malaccensis, sterilized leaf explants were first incubated on basic Murashige and Skoog(MS) gel medium containing 15g/L sucrose and at pH 5.7. Different auxin types including 1-naphthaleneacetic acid(NAA), 2,4-dichlorophenoxyacetic acid(2,4-D), and indole-3-butyric acid(IBA), were tested at various concentrations(0.55, 1.1 and 1.65 μM) using the basic medium. Leaf explants were incubated for 30 days in the dark. Callus induced by 1.1 μM NAA had the highest biomass dry weight(DW) of 17.3 mg; however the callus was of a compact type. This auxin concentration was then combined with either 6-benzylaminopurine(BAP) or kinetin at 0.55, 1.1, 2.2 or 3.3 μM to induce growth of friable callus. The 1.1μM NAA + 2.2μM BAP combination produced friable callus with the highest biomass(93.3mg DW). When testing the different carbon sources and pHs, sucrose at 15g/L and pH at 5.7 yielded highest biomasses at 87.7mg and 83 mg DW, respectively. Microscopic observations revealed the arrangement of the friable cells as loosely packed with relatively large cells, while for the compact callus, the cells were small and densely packed. We concluded that MS medium containing 15 g/L sucrose, 1.1 μM NAA + 2.2 μM BAP hormone combination, and a pH of 5.7 was highly effective for inducing friable callus from leaf explants of A. malaccensis for the purpose of establishing cell suspension culture.     

Temporal evolution of collar lesions associated with ash dieback and the occurrence of Armillaria in Belgian forests

Ash dieback, caused by the fungus Hymenoscyphus fraxineus, has been observed in Europe for several years. In Belgium, the disease was first reported in 2010. Besides crown defoliation and dieback, collar lesions have sometimes been reported. To evaluate the prevalence and the progression of collar lesions and crown defoliation in ash dieback‐affected stands of various ages, a survey was conducted in 2013 and 2014 on 268 ash trees (Fraxinus excelsior) originating from 17 Walloon forest stands. The results showed that the proportion of trees with collar lesions greatly increased between June 2013 and September 2014 and that there appeared to be no significant link between a tree's diameter‐at‐breast height (DBH) and collar lesion occurrence. The mean percentage of defoliation increased in each forest stand across time, with observations conducted in September 2013 and 2014 showing a positive correlation with the mean percentage of trees with collar lesions. Molecular tests were carried out on 103 additional trees originating from 12 of the 17 stands to evaluate the occurrence of H. fraxineus and Armillaria spp. at the collar level. Most of the trees (98%) were infected by H. fraxineus. In contrast, only 41% of the samples were infected with Armillaria spp., most commonly A. gallica and A. cepistipes. This study discusses the role of Armillaria spp. and the rapid increase in the number of trees with collar lesions within the context of the evolution of ash dieback in Europe.     

Comparison of stand dynamics after dieback caused by pine wilt disease among pine forests with different management regimes in western Japan

In pine forests damaged by pine wilt disease, in western Japan, the effect of protection regimes of pine trees on the stand dynamics were examined in the following four stands: (1) lightly damaged stand (age 30–40 years) with no procedure in operation for protecting pine trees; (2) severely damaged stand (age 30–40 years) with no procedure in place for protecting pine trees; (3) severely damaged stand (age 50 years) with a selective cutting of infected trees; (4) severely damaged stand (age 30–40 years) with a selective cutting of infected trees. All the stands had been abandoned before the pine wilt disease damage. The understory structure of the severely damaged stand with no protection procedure was similar to that of the lightly damaged stand. Frequent invasion by tree species and acceleration in the growth of understory trees occurred after the dieback in the selective cutting stand. These results suggest that a deficiency in the canopy layer caused by the dieback resulted in low disturbance intensity in the early stages after the dieback, but the selective cutting increased the intensity by the reduction in the understory as well as the canopy layer. The intensity of the disturbance in the selective cutting stands was larger in the younger stand because it had a higher density of selectively cut pine trees. The different stand structure of pine forests occurred after the dieback because the intensity of the disturbance varied as a result of the selective cutting operation and the stand age.     

The identification and pathogenicity of Fusarium oxysporum causing acacia seedling wilt disease

Wilt disease with unknown etiology causes mass mortality in commercial Acacia mangium nurseries in South Sumatra. This pathogen induces symptoms of chlorosis in...     

Xyleborus glabratus attacks and systemic colonization by Raffaelea lauricola associated with dieback of Cinnamomum camphora in the southeastern United States

Laurel wilt, caused by Raffaelea lauricola, is responsible for extensive mortality of redbay and other American members of the Lauraceae in the southeastern United States. Raffaelea lauricola is a mycangial symbiont of the redbay ambrosia beetle (Xyleborus glabratus), and the beetle and fungus were accidentally introduced from Asia. Branch dieback of camphortree (Cinnamomum camphora), an Asian member of the Lauraceae, has been occasionally observed in areas where laurel wilt has decimated redbay populations, and R. lauricola was isolated from such camphortrees. However, the role of X. glabratus and R. lauricola in this branch dieback remains unclear. Examination of camphortrees on Jekyll Island, Georgia showed that healthy‐appearing trees and those with branch dieback had been attacked by X. glabratus, but the trees with branch dieback had four times as many beetle attacks. Raffaelea lauricola was routinely isolated from discoloured xylem near beetle tunnels in healthy trees and those with dieback. Single‐point inoculations with R. lauricola on stems of mature, healthy camphortree trees failed to induce wilt‐like symptoms or branch dieback, although areas of discoloration were scattered throughout the xylem, and R. lauricola was reisolated irregularly at various heights in some inoculated trees. In growth chamber experiments, single‐point inoculations with R. lauricola resulted in systemic colonization but no wilt symptoms or branch dieback in camphortree saplings. In contrast, inoculations at multiple points along the stem (simulating multiple attacks by the vector) caused branch dieback and wilt‐like symptoms, including a brownish, diffuse discoloration of the xylem. Camphortree appears to be more resistant than American species of Lauraceae to the vascular wilt caused by R. lauricola. The fungus does colonize camphortrees systemically, however, and can apparently cause branch dieback. This suggests that the fungus may provide brood material for X. glabratus in Asia as it does in the southeastern United States.     

Chalara fraxinea sp. nov. associated with dieback of ash (Fraxinus excelsior) in Poland

A new species of the hyphomycete genus Chalara is described. It has been frequently isolated from stems and branches and sometimes also from roots of wilting and dying Fraxinus excelsior in Poland. It differs from previously described species of Chalara by its small, short cylindrical phialoconidia extruded in chains or in slimy droplets, morphological features of the phialophores and by colony characteristics. It is non‐tolerant to cycloheximide.     

Effects of associated fungi Sclerophoma pythiophila and Cenangium ferruginosum on Gremmeniella abietina dieback in Spain

The interactions between Gremmeniella abietina and either Sclerophoma pythiophila or Cenangium ferruginosum, fungi frequently isolated from diseased twigs along with G. abietina, were studied under laboratory (dual cultures) and greenhouse conditions (double‐inoculations). Virulence of each species was also evaluated in greenhouse experiments by means of single‐inoculations. In vitro interactions were assessed on Petri dishes containing malt agar with pine needle extract, and greenhouse experiments were performed on 1‐year‐old Pinus halepensis seedlings. In vitro growth of G. abietina was inhibited by both fungi when grown in dual culture. In single‐inoculations, G. abietina caused the greatest necrosis length on P. halepensis seedlings, followed by S. pythiophila, whereas C. ferruginosum did not cause significant necrosis. In double‐inoculations, C. ferruginosum was able to reduce the length of necrosis caused by G. abietina on the P. halepensis seedlings. In contrast, necrosis length was greater in seedlings inoculated with both S. pythiophila and G. abietina than in those inoculated with G. abietina alone. Therefore, S. pythiophila seems to play a role in disease expression caused by G. abietina on P. halepensis in Spain.     

Aboveground biomass and carbon stock in the largest sacred grove of Manipur,Northeast India

Aboveground biomass and carbon stock in the largest sacred grove of Manipur was estimated for trees with diameter [10 cm at 1.37 m height.The aboveground biomass,carbon stock,tree density and basal area of the sacred grove ranged from 962.94 to 1130.79 Mg ha~(-1),481.47 to 565.40 Mg ha~(-1) C,1240 to 1320 stem ha~(-1) and79.43 to 90.64 m~2 ha~(-1),respectively.Trees in diameter class of 30–40 cm contributed the highest proportion of aboveground biomass(22.50–33.73%).The aboveground biomass and carbon stock in research area were higher than reported for many tropical and temperate forests,suggesting a role of spiritual forest conservation for carbon sink management.     

In silico annotation of five candidate genes associated with pathogenicity in Fusarium circinatum

The Pine Pitch Canker disease caused by the pathogenic fungus Fusarium circinatum is one of the most devastating diseases in pine forests, afforestation and nurseries around the world. Despite the importance of this phytopathogen, only a little is known about the genes that drive the infection traits and the virulence factors. In this work, five candidate genes (i.e. Fcfga1, Fcfgb1, Fcac, Fcrho1 and FcpacC) were in silico annotated using the whole genome of F. circinatum as reference. The similarity of these proposed genes at nucleotide and protein levels with genes previously described in other Fusarium species was > 90% of identity and > 90% query coverage in all cases. In addition, the gene ontology of each candidate gene was also investigated.     

Pathogenicity of fungi associated with ash dieback symptoms of one‐year‐old Fraxinus excelsior in Montenegro

In addition to Hymenoscyphus fraxineus, two fungi identified as Diaporthe eres aff. and Fusarium sambucinum aff. were also isolated from necrotic bark lesions on declining one‐year‐old Fraxinus excelsior in a forest stand in Montenegro. To examine their involvement in ash decline, a pathogenicity test was performed using under bark inoculations on one‐year‐old Fraxinus excelsior. Hymenoscyphus fraxineus was included as comparison. All three fungal species proved highly pathogenic towards one‐year‐old seedlings although lesion sizes differed significantly between the different species. Hymenoscyphus fraxineus was most aggressive, followed by F. sambucinum aff., while D. eres aff. caused the smallest lesions. This study demonstrates for the first time the ability of isolates in the D. eres and F. sambucinum species complexes to cause decline on one‐year‐old common ash seedlings.     

Biocontrol potential of Pseudomonas azotoformans,Serratia marcescens and Trichoderma virens against Fusarium wilt of Dalbergia sissoo

Wilt disease caused by Fusarium solani is a serious constraint to Dalbergia sissoo (shisham) plantations in northern India. In this study, the antagonistic potential of 40 bacterial isolates recovered from rhizophere soil of healthy shisham trees, and a well‐characterized Trichoderma species (Trichoderma virens) were tested for their possibility as biocontrol agents for F. solani. Two promising isolates (S1 and S15) were identified which inhibited pathogen growth, caused chitin degradation, produced siderophores and solubilized phosphate in vitro. Isolate S15 scored highest for hydrogen cyanide (HCN) production while isolate S1 was a non‐HCN producer. These two isolates were identified as Serratia marcescens (S1) and Pseudomonas azotoformans (S15) following sequence analysis of 16S rDNA. In dual culture assays, T. virens caused 80% inhibition of mycelial growth of the test fungus. The three selected antagonists when tested in planta in the glasshouse completely suppressed production of wilt symptoms on 12‐month‐old shisham plants. Further work is needed to ascertain the potential of these isolates to be used as biocontrol agents to manage shisham wilt under field conditions.     

Forest fire risk assessment in parts of Northeast India using geospatial tools

Forest fire is a major cause of changes in forest structure and function. Among various floristic regions, the northeast region of India suffers maximum from the fires due to age-old practice of shifting culti- vation and spread of fires from jhum fields. For proper mitigation and management, an early warning of forest fires through risk modeling is required. The study results demonstrate the potential use of remote sens- ing and Geographic Information System (GIS) in identifying forest fire prone areas in Manipur, southeastern part of Northeast India. Land use land cover (LULC), vegetation type, Digital elevation model (DEM), slope, aspect and proximity to roads and settlements, factors that influ- ence the behavior of fire, were used to model the forest fire risk zones. Each class of the layers was given weight according to their fire inducing capability and their sensitivity to fire. Weighted sum modeling and ISODATA clustering was used to classify the fire zones. To validate the results, Along Track Scanning Radiometer (ATSR), the historical fire hotspots data was used to check the occurrence points and modeled forest fire locations. The forest risk zone map has 55 63% of agreement with ATSR dataset.