Bud Rot Caused by Phytophthora palmivora: A Destructive Emerging Disease of Oil Palm.

Oomycetes from the genus Phytophthora are among the most important plant pathogens in agriculture. Epidemics caused by P. infestans precipitated the great Irish famine and had a major impact on society and human history. In the tropics, P. palmivora is a pathogen of many plant species including cacao (Theobroma cacao), citrus (Citrus sp.), durian (Durio zibethines), jackfruit (Artrocarpus heterophyllus), rubber (Hevea brasiliensis), and several palm species including coconut (Cocos nucifera), and the African oil palm (Elaeis guineensis) as determined recently. The first localized epidemics of bud rot in oil palm in Colombia were reported in 1964. However, recent epidemics of bud rot have destroyed more than 70,000 ha of oil palm in the Western and Central oil palm growing regions of Colombia. The agricultural, social, and economic implications of these outbreaks have been significant in Colombia. Identification of the pathogen after 100 years of investigating the disease in the world enabled further understanding of infection, expression of a range of symptoms, and epidemiology of the disease. This review examines the identification of P. palmivora as the cause of bud rot in Colombia, its epidemiology, and discusses the importance of P. palmivora as a major threat to oil palm plantings globally.

Fungal Planet description sheets: 371-399.

Novel species of fungi described in the present study include the following from Australia: Neoseptorioides eucalypti gen. & sp. nov. from Eucalyptus radiata leaves, Phytophthora gondwanensis from soil, Diaporthe tulliensis from rotted stem ends of Theobroma cacao fruit, Diaporthe vawdreyi from fruit rot of Psidium guajava, Magnaporthiopsis agrostidis from rotted roots of Agrostis stolonifera and Semifissispora natalis from Eucalyptus leaf litter. Furthermore, Neopestalotiopsis egyptiaca is described from Mangifera indica leaves (Egypt), Roussoella mexicana from Coffea arabica leaves (Mexico), Calonectria monticola from soil (Thailand), Hygrocybe jackmanii from littoral sand dunes (Canada), Lindgomyces madisonensis from submerged decorticated wood (USA), Neofabraea brasiliensis from Malus domestica (Brazil), Geastrum diosiae from litter (Argentina), Ganoderma wiiroense on angiosperms (Ghana), Arthrinium gutiae from the gut of a grasshopper (India), Pyrenochaeta telephoni from the screen of a mobile phone (India) and Xenoleptographium phialoconidium gen. & sp. nov. on exposed xylem tissues of Gmelina arborea (Indonesia). Several novelties are introduced from Spain, namely Psathyrella complutensis on loamy soil, Chlorophyllum lusitanicum on nitrified grasslands (incl. Chlorophyllum arizonicum comb. nov.), Aspergillus citocrescens from cave sediment and Lotinia verna gen. & sp. nov. from muddy soil. Novel foliicolous taxa from South Africa include Phyllosticta carissicola from Carissa macrocarpa, Pseudopyricularia hagahagae from Cyperaceae and Zeloasperisporium searsiae from Searsia chirindensis. Furthermore, Neophaeococcomyces is introduced as a novel genus, with two new combinations, N. aloes and N. catenatus. Several foliicolous novelties are recorded from La Réunion, France, namely Ochroconis pandanicola from Pandanus utilis, Neosulcatispora agaves gen. & sp. nov. from Agave vera-cruz, Pilidium eucalyptorum from Eucalyptus robusta, Strelitziana syzygii from Syzygium jambos (incl. Strelitzianaceae fam. nov.) and Pseudobeltrania ocoteae from Ocotea obtusata (Beltraniaceae emend.). Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Fungal Planet description sheets: 107-127.

Novel species of microfungi described in the present study include the following from Australia: Phytophthora amnicola from still water, Gnomoniopsis smithogilvyi from Castanea sp., Pseudoplagiostoma corymbiae from Corymbia sp., Diaporthe eucalyptorum from Eucalyptus sp., Sporisorium andrewmitchellii from Enneapogon aff. lindleyanus, Myrmecridium banksiae from Banksia, and Pilidiella wangiensis from Eucalyptus sp. Several species are also described from South Africa, namely: Gondwanamyces wingfieldii from Protea caffra, Montagnula aloes from Aloe sp., Diaporthe canthii from Canthium inerne, Phyllosticta ericarum from Erica gracilis, Coleophoma proteae from Protea caffra, Toxicocladosporium strelitziae from Strelitzia reginae, and Devriesia agapanthi from Agapanthus africanus. Other species include Phytophthora asparagi from Asparagus officinalis (USA), and Diaporthe passiflorae from Passiflora edulis (South America). Furthermore, novel genera of coelomycetes include Chrysocrypta corymbiae from Corymbia sp. (Australia), Trinosporium guianense, isolated as a contaminant (French Guiana), and Xenosonderhenia syzygii, from Syzygium cordatum (South Africa). Pseudopenidiella piceae from Picea abies (Czech Republic), and Phaeocercospora colophospermi from Colophospermum mopane (South Africa) represent novel genera of hyphomycetes. Morphological and culture characteristics along with ITS DNA barcodes are provided for all taxa.

Residential characteristics predict changes in Der p 1, Fel d 1 and ergosterol but not fungi over time.

BACKGROUND: Allergen and fungal exposures are important risk factors for asthma. We conducted a longitudinal analysis of allergen levels in Melbourne homes between 1996 and 1998 to examine the effects of changing residential characteristics on allergen and fungal levels. We also examined the changes in levels of indoor allergens. METHODS: The subjects were participants in the European Community Respiratory Health Survey (ECRHS) in Melbourne. In 1996, 485 subjects participated in a follow-up study, which involved both home and laboratory visits. Dust and air samples were collected from participants' bedrooms and a validated residential questionnaire was administered. In 1998, 360 participants underwent further follow-up. House dust mite (Der p 1) and cat allergens (Fel d 1) and ergosterol were measured in dust. RESULTS: We observed moderate within home correlations between 1996 and 1998 in floor Der p 1 (intraclass correlation ICC=0.48), bed Der p 1 (ICC=0.61), Fel d 1 (kappa=0.53) and ergosterol (ICC=0.28) levels. We found that the floor Der p 1 levels decreased from 1996 to 1998 in the homes of participants who moved to an attached home, moved their bedrooms to the first floor, removed fitted carpet or central heating. Replacing or vacuuming the mattress more than twice per year reduced levels of Der p 1 in the bed. Ergosterol levels were reduced by removing visible mould and fitted carpet. CONCLUSIONS: These findings provide evidence to support current advice with regard to allergen avoidance in patients with dust mite and fungal allergies.

Influence of building construction work on Aspergillus infection in a hospital setting.

BACKGROUND AND OBJECTIVE: Aspergillus fumigatus is a major pathogen causing nosocomial infections. Hospital outbreaks of invasive aspergillosis have been associated with the renovation and construction of buildings. Building construction work for fire safety upgrading was undertaken during a 16-week period in 2001 at Box Hill Hospital. This study was designed to examine the effect of construction on invasive aspergillosis when using standard and additional protective measures. METHODS: Baseline air sampling was conducted in 18 areas. The validity of the air sampling was assessed by comparing the ability of two air samplers to detect Aspergillus conidia. Surveillance of nosocomial Aspergillus infection was conducted by reviewing the records of patients with a sputum culture positive for Aspergillus and those prescribed amphotericin or itraconazole for the period of construction activity and the same period the previous year. RESULTS: Aspergillus was isolated infrequently and there was no statistically significant difference in the levels of viable pathogenic fungi between areas w here construction work was undertaken and areas where it wasnot undertaken. A moderate agreement was observed between the two air samplers (kappa = 0.4; P < .05). There was no difference in the incidence of invasive aspergillosis between 2000 and 2001 (incidence density ratio, 1.2; 95% confidence interval, 0.3 to 4.1). CONCLUSION: The influence of construction work performed with protective measures needs to be examined in an environment with higher levels of airborne fungi to confirm the findings of this study.

Hydrogen peroxide yields during the incompatible interaction of tobacco suspension cells inoculated with Phytophthora nicotianae.

Rates of H(2)O(2) production by tobacco suspension cells inoculated with zoospores from compatible or incompatible races of the pathogen Phytophthora nicotianae were followed by direct measurement of oxygen evolution from culture supernatants following catalase addition. Rates of HO(2)(*)/O(2)(-) production were compared by following the formation of the formazan of sodium, 3'-[1-[phenylamino-carbonyl]-3,4-tetrazolium]-bis(4-methoxy-6-nitro) benzene-sulfonic acid hydrate. In the incompatible interaction only, both reactive oxygen species (ROS) were produced by the cultured host cells in a minor burst between 0 and 2 h and then in a major burst between 8 and 12 h after inoculation. Absolute levels of H(2)O(2) could not be accurately measured due to its metabolism by host cells, but results are consistent with the majority of H(2)O(2) being formed via dismutation of HO(2)(*)/O(2)(-). The effects of inhibitors of endogenous Cu/Zn superoxide dismutase (diethyldithiocarbamate) and catalase (3-amino-1,2,4-triazole and salicylic acid) were also examined. Yields of ROS in the presence of the inhibitors diphenylene iodonium, allopurinol, and salicylhydroxamic acid suggest that ROS were generated in incompatible host responses by more than one mechanism.

Suppression of Phytophthora cinnamomi in Potting Mixes Amended with Uncomposted and Composted Animal Manures.

ABSTRACT We examined the effects of fresh and composted animal manures on the development of root rot, dieback, and plant death caused by Phytophthora cinnamomi. Fresh chicken manure, or chicken manure composted for 5 weeks before incorporation into the potting mix (25%, vol/vol), significantly reduced pathogen survival and the development of symptoms on Lupinus albus seedlings. Chicken manure composted for 2 weeks was less suppressive. Cow, sheep, and horse manure, whether fresh or composted, did not consistently suppress populations of P. cinnamomi or disease symptoms at the rates used (25%, vol/vol). All composts increased organic matter content, total biological activity, and populations of actinomycetes, fluorescent pseudomonads, and fungi. Only chicken manure stimulated endospore-forming bacteria, a factor that was strongly associated with seedling survival. Fallowing the potting mix for an additional 8 weeks after the first harvest increased the survival of lupin seedlings in a second bioassay, with survival rates in chicken manure compost-amended potting mix exceeding 90%. These data suggest that the ability of composted manure to stimulate sustained biological activity, in particular the activity of endospore-forming bacteria, is the key factor in reducing disease symptoms caused by P. cinnamomi. Supporting these results, the survival of rooted cuttings of Thryptomene calycina was significantly higher in sand-peat potting mix following amendment with commercially available chicken manure (15% vol/vol). However, this protection was reduced if the potting mix was steam pasteurized before amendment, indicating that suppression was due to endogenous as well as introduced microbes. Chicken manure compost incorporated at 5% (vol/vol) or more was strongly phytotoxic to young Banksia spinulosa plants and is not suitable as an amendment for phosphorus-sensitive plants.

The 5S ribosomal RNA gene is linked to large and small subunit ribosomal RNA genes in the oomycetes, Phytophthora vignae, P. cinnamomi, P. megasperma f.sp. glycinea and Saprolegnia ferax.

Southern hybridization and polymerase chain reaction data indicate that the 5S ribosomal RNA gene is linked to the ribosomal RNA gene repeat unit in the oomycetes, Phytophthora vignae, P. cinnamomi, P. megasperma f.sp. glycinea and Saprolegnia ferax, and is apparently transcribed in the same direction as the large and small subunit ribosomal RNA genes. The polymerase chain reaction has been used to amplify all components of the entire ribosomal RNA gene repeat unit for each of these oomycetes. The total size of all amplified products is identical to the size of the ribosomal RNA gene repeat unit, as determined by Southern analysis.