Epidemiology, Biology and Detection of Phaeoacremonium spp. And Phaeomoniella Chlamydospora Vine Decline (Black Measles or Esca and Petri Disease (syn: Young Vine Decline) in California

Phaeoacremonium inflatipes, P. aleophilum, and Phaeomoniella chlamydospora are three pathogenic fungi That cause Petri disease young vine decline and measles of grapevines. These grapevine diseases can cause significant economic losses due to vineyard replanting and yield loss. These fungi have been documented in vineyards for at least 100 years, and have been identified in vineyards in every grape growing region in the world. Large losses due to replanting have been seen especially in northern California vineyards. This may be due to the huge planting boom with new hybrid rootstocks in the last 10 years. Currently, it is known that these fungi are present in propagation material coming from mother plant material in nurseries. However, vines also apparently become infected during the propagation procedure. A detection method using nested-PCR is currently being developed to provide a rapid and sensitive test to determine the presence of these fungi in grapevine material throughout the propagation process. Field experiments are being conducted to explore the epidemiology and biology of the young vine decline and measles organisms. It is speculated that P. inflatipes and P. aleophilum are capable of producing aerial fruiting structures in infected vineyards, as the teleomorph has been recently been produced in vitro. In addition, it is known that P. chlamydospora produces pycnidia, microsclerotia, and chlamydosporas. However, the mode of dissemination of these fungi is unclear. Spore traps were placed in select vineyards throughout California in areas where measles and vine decline are known to occur. Initial results showed that the 3 pathogens were aerially dispersed, as loads of spores have been trapped in many areas. This study will elucidate how the fungi spread and under what condition the spores are being released to re-infect plants.For years, symptom expression of esca in vineyards less than 10 years of age was rare. However, recently we have observed esca symptoms in vineyards only 1-3 years of age. Phaeomoniella chlamydospora has recently been identified as the primary cause of esca in California vineyards. However, Phaeoacremonium spp. Also seems to paly a role in disease occurrence and symptom expression. Weather conditions seem to be roughly correlated with occurrence of esca in that the years with higher than normal rainfall and higher summer temperatures we would see more severe symptoms of the disease. Vineyard observations, spore trapping data and some speculation seemed to indicate that symptom expression occurs in a year when new infections took place. Vineyard surveys over the past two years however, point to the possibility that symptom expression may not occur until the following year after infection. Correlations between symptom expression, rainfall and temperature data will be presented. Philaophora spp. Has been isolated from symptomatic grapevine wood including spurs, cordons and trunk from 8 different grapevine production regions in California. Greenhouse experiments have demonstrated that this fungus is an effective pathogen of grape seedlings. One-month-old seedlings (Vitis vinifera var. ?Carignane?) as well as rooted cuttings were inoculated by root dipping them into Phialophora sp. Conidia suspensions. Seedlings were grown out in greenhouses and then isolated for the presence of the fungus. Positive isolations were made from high number of the inoculated seedlings. Symptoms included a significant reduction in the number of roots, vascular discoloration and overall stunting of plant height. Previous studies have shown the Pa. Chlamydospora has the ability to produce pycnidia in culture. However, these structures were not yet documented in California vineyards. Pycnidia were observed primarily on 2-4 year-old pruning wounds and beneath bark, particularly where injury resulted in exposed vascular tissue. These pycnidia were similar to those that were artificially produced in culture. Spores from pycnidia were plated onto agar plates and shown to be viable. Pathogenicity tests of pycnidiospores from artificially and naturally produced pycnidia were compared. ITS and Beta-tubulin regions from pycnidiospores were compared to that of known isolates of the Pa. Chlamydospora and showed the pycnidiospores to be those Pa. Chlamydospora.Experiments will also be discussed on the newly described teleomorph of Phaeoacremonium spp. This teleomorph is a pyrenomycete in the genus Togninia. From preliminary paring studies, it appears as though this fungus is heterothallic in its mating. Molecular data comparing perithecia and progeny of this teleomorph to known Phaeoacremonium spp., indicate that his teleomorph is that of Phaeoacremonium spp. This teleomorph has not yet been seen in naturally infected vineyards, but we speculate it is present and playing an important role in this disease cycle.