Neonectria Research Articles

Postharvest foliar nitrogen applications increase <i>Neonectria ditissima</i> leaf scar infection in apple trees

Postharvest foliar nitrogen (urea) is often applied to apple leaves immediately after picking for bud fertilising and/or during leaf fall for Venturia inaequalis control During 20132016 ethylene diamine tetraacetic acid copper (EDTACu to enhance leaf abscission) urea calcium nitrate and BudWiser foliar treatments were applied alone or in combination to determine their effects on leaf scar infection by Neonectria ditissima in Braeburn (201314) Scifresh and Royal Gala (201516) orchards In 201314 leaf scar infection increased sixfold when 5 urea was added to EDTACu and sprayed at the onset of leaf fall In 201516 up to a ninefold increase in leaf scar infections was observed The timing of application was more important than the amount or form of nitrogen used As a result of this research the use of ureabased foliar nitrogen fertilisers for V inaequalis before leaf fall are not recommended and growers should consider all factors affecting Neonectria ditissima infections before applying nitrogen immediately after harvest

Freezing and melting conditions affect the viability of <i>Neonectria ditissima</i> conidia

Different freezing and melting conditions of conidial suspensions of Neonectria ditissima were examined to determine optimal longterm storage conditions Four concentrations of glycerol two freezing temperatures and three melting methods were compared using two isolates RS305p with singlecelled conidia and RS324p with multicelled conidia After 10 months conidia of RS305p had significantly higher germination rates than those of RS324p Glycerol added to conidial suspensions before freezing reduced the germination rate significantly Suspensions frozen at 80C had significantly higher germination rates than those at 20C Defrosting in a 20C water bath resulted in significantly higher germination rates than defrosting in ice water However freezing for 10 months at 80C without glycerol reduced the conidial germination rate of RS324p from 65 before freezing to 8 In contrast the conidial germination rate of RS305p frozen in the same conditions increased from 15 to 74 More research is needed to determine optimal storage conditions

Hot water disinfection treatment to eliminate <i>Neonectria ditissima</i> latent infections in apple scion wood

The European canker pathogen Neonectria ditissima can be transmitted by apple scion wood into newly developing trees following grafting or budding resulting in disease development and progression An in vitro hot water treatment showed that both conidia and mycelium of N ditissima can be killed when placed into water at 50C for 8805; 5 min However diseased scion wood required 8805; 15 min disinfection at the same temperature to eliminate all internal pathogens including N ditissima At this temperature and time duration no mycelium growth was observed after 2 weeks incubation of cut pieces of the disinfected tissues on apple sap amended water agar Although the treatment was 100 effective at eliminating some identified and nonspecific pathogens visual assessment of both the scion and rootstock viability and vigour six months after the hot water treatment showed that 98 of the rootstocks and scions failed to grow and develop

Are shelter belts potential inoculum sources for <i>Neonectria ditissima</i> apple tree infections

The susceptibility of plants around apple orchards to Neonectria ditissima infections in the Tasman region was determined during summer 2013/14 Shelter belt and other neighbouring plants (in the absence of shelter trees) surrounding 20 apple orchards (approximately 51 km shelter length) were identified and compared with known European canker hosts Onethird of all neighbouring plants identified were either species known to be European canker hosts or shared a genus with a known host Nine nonpomaceous plant species were selected for inoculation studies Two rasp wounds were created (July 2014) and one was inoculated with N ditissima conidia the other with mycelium Symptoms were recorded and the pathogen reisolated In February 2015 all symptomless inoculation sites were harvested to determine potential latent infections Neonectria ditissima was reisolated from 38 of inoculations including from symptomless inoculation sites The fungus could be reisolated from all species inoculated

Effect of temperature on spore viability of <i>Neonectria ditissima</i>

The fungus Neonectria ditissima causes European canker on apple and pear trees in temperate regions The thermal death point of ascospores and conidia of this pathogen is unknown In this study ascospores and conidia were exposed to six temperatures between 20C and 50C for seven time intervals between 5 min and 24 h The viability of the spore suspensions was determined by germination on slides and growth on potato dextrose agar Temperatures up to 30C did not reduce spore viability Exposure to 35C for 24 h reduced conidial and ascospore germination by 92 and 85 respectively At 40C and 45C spore viability was reduced after 5 min declining rapidly with increasing exposure times No spores germinated after 5 min at 50C This study suggests that 15 min dips in 45C water may kill surface spore contamination of budwood prior to grafting Budwoodbased validation studies are now recommended

Modelling fungal spore dispersal using <i>Neonectria ditissima</i>

Neonectria ditissima is the causal organism of European canker in apple Conidia are formed in sporodochia in canker lesions and released during rain The splash pattern of conidia was monitored in four directions from a central inoculum source held at approximately 17 m height using vertical and horizontal rain traps trap plants and petroleumjellycoated glass slides during simulated rain events Nonlinear models were fitted to the conidia count data to estimate the proportion of inoculum exceeding any distance from the inoculum source When fitted to horizontal rain trap data the model suggested that half of all spores splashed beyond 042 m from the inoculum source and 4 travelled over 2 m Conidia were observed at a greater distance from the inoculum source using rain traps than glass slides In a separate set of experiments water was dropped in single droplets from various heights onto either a sealed surface or bare soil and watersensitive paper was used to estimate droplet sizes and dispersal (height and distance) Water droplets were found to splash up to 120 cm outwards and 60 cm upwards Smaller droplets travelled further than larger droplets

Black-foot disease of grapevine: an update on taxonomy, epidemiology and management strategies

Black-foot is one of the most destructive grapevine trunk diseases in nurseries and young vineyards, causing necrotic root lesions, wood necrosis of the rootstock base, and a gradual decline and death of grapevines. Causal agents of the disease are included into the genera Campylocarpon, “ Cylindrocarpon ”, Cylindrocladiella and Ilyonectria . Recent taxonomical studies of Neonectria and related genera with “ Cylindrocarpon ”-like anamorphs based on morphological and phylogenetic studies, divided Neonectria into five genera. Thus, the current taxonomical po sition and classification of the causal agents of black-foot disease, mainly “ Cylindrocarpon ”/ Ilyonectria , comprises one of the main topics of this review. The review also provides an update on geographical distribution, epidemiol ogy and management strategies of the disease.

Antibacterial activity of the endophytic fungi from a traditional Chinese herb Paris polyphylla var. chinensis

A total of 29 endophytic fungal isolates were separated from the healthy rhizomes of Paris polyphylla var. chinensis (Trilliaceae), which is a traditional medicinal herb mainly distributed in central China. Eight distinct isolates (that is, Papochf01-Papochf08) were selected for further taxonomical identification by morphological traits and internal transcribed spacer (ITS) rRNA gene sequence analysis. The results based on morphological characters revealed six genera namely Bionectria (Papochf04), Fusarium(Papochf05), Leptodontidium (Papochf07), Neonectria (Papochf02), Setophoma(Papochf08) and Trichocladium (Papochf01). Isolates Papochf01, Papochf02, Papochf03, Papochf06 and Papochf08 have not been previously reported as the endophytic fungi. The filtrate and mycelia n-butanol extracts obtained from the isolates Papochf05 and Papochf08 exhibited strong inhibition on all the test bacteria including Agrobacterium tumefaciens, Bacillus subtilis, Escherichia coli, Pseudomonas lachrymans,Staphylococcus aureus, Staphylococcus haemolyticus, Salmonella typhimurium, andXanthomonas vesicatoria. This finding shows that endophytic fungi from P. polyphylla var.chinensis could be an alternative source for producing antimicrobial agents. Key words: Paris polyphylla var. chinensis, endophytic fungi, n-butanol extract, TLC-bioautography assay, antibacterial activity

<i>Neonectria fuckeliana</i> infection of <i>Pinus radiata</i> nursery stock

Nectria flute canker is a disease of Pinus radiata stems caused by Neonectria fuckeliana The fungus is not known in the North Island leading to concern that it may be transported north via asymptomatically colonised nursery stock Wounded P radiata seedlings and cuttings were exposed to natural inoculum from an adjacent infected forest and half were artificially inoculated No disease symptoms were recorded throughout the trial Neonectria fuckeliana was reisolated from 24 and 7 of inoculated seedlings and cuttings respectively 3 months after inoculation and at 12 months from 35 of the remaining inoculated seedlings only Neonectria fuckeliana was not isolated from uninoculated seedlings or cuttings exposed to natural inoculum These results indicate that nursery plants have little capability of retaining N fuckeliana within the tissue even when directly inoculated Nursery stock is therefore unlikely to be a pathway for transport of the fungus

Survival of <i>Neonectria fuckeliana</i> in woody material

In southern New Zealand Neonectria fuckeliana is associated with a stem flute canker of Pinus radiata which can result in severe stem malformation and growth loss This research consisting of three distinct experiments aimed to determine pathogen survival in processed and unprocessed wood and woody debris In the first experiment the survival of the pathogen in living trees was examined by sampling trees infected with N fuckeliana in 6 different years In the second experiment the survival of the pathogen in woody debris was examined using 36 infected logs in a range of sizeclasses The logs were left on the forest floor in shaded and unshaded conditions and sampled for N fuckeliana after 4 and 9 months The third experiment examined the survival of the pathogen in processed wood Boards cut from infected trees were tested in six standard timber drying treatments Boards were sampled before and after drying to determine the presence of living N fuckeliana Neonectria fuckeliana was successfully isolated from trees at all infection times tested The fungus was also successfully isolated from 81 of logs after 9 months on the forest floor There was no significant difference between shaded and unshaded treatments Neonectria fuckeliana was not found in any boards following kilndrying but was successfully isolated from 69 of infected boards subjected to the two standard airdrying treatments for 9 weeks

Potential Use of Chitosan in the Control of Grapevine Trunk Diseases.

Summary. Due to its fungistatic or fungicidal potential, chitosan, a high molecular-weight polymer that is non-toxic and biodegradable, has become an alternative to conventional fungicides. In addition, chitosan is reported to elicit defense mechanisms in plant tissues. In this study, we explored the in vitro fungicidal effect of chitosan on some of the most important grapevine wood fungi, such as Botryosphaeria sp. (dieback and cane blight), Phomopsis sp. (Phomopsis cane and leaf spot), Eutypa lata (eutypa dieback), Neonectria liriodendri (black foot disease), Phaeomoniella chlamydospora (Petri disease and esca) and Fomitiporia sp. (esca). Inhibition of mycelial growth was evaluated at five concentrations 50, 25, 5, 2.5 and 0.5 mg a.i. l -1 of chitosan. Chitosan was effective in reducing mycelial growth of all the fungi. The lowest EC50 values were obtained with Pa. chlamydospora, Fomitiporia sp. and Botryosphaeria sp., and the highest with Neon. liriodendri. All these were inferior to the maximum recommended field rate (8.33 mg a.i. l -1 ) with exception of the value obtained with Neon. liriodendri. Greenhouse experiments were carried out to evaluate the efficacy of foliar sprays of chitosan on potted grapevine plants (cultivar Castelao) growing in a substrate artificially infested with Pa. chlamydospora or Neon. liriodendri. The effect of chitosan against Neon. liriodendri was similar to that achieved with some selected fungicides (carbendazim+flusilazole, cyprodinil+fludioxonil and tebuconazole). Chitosan significantly improved plant growth (plant height and number of roots) and decreased disease incidence compared with untreated plants. As regards Pa. chlamydospora, chitosan only reduced the disease incidence caused by this fungus.