D. bryoniae is an Ascomycota fungus. In spring, asexual fruiting bodies called pycnidia and sexual fruiting bodies called perithecia are formed from last year’s infected plant debris. Pycnidia are flask-shaped structures that house asexual conidia which are readily released from pycnidia through the ostiole when enough moisture is present.[1] Perithecia are also flask-shaped, but they are sexual fruiting bodies which give rise to bitunicate asci that contain 8 ascospores. Ascospores are readily dispersed and spread by wind after rain or during evening dew periods.[2]
Temperature and moisture are the most important factors for germination and development of the pathogen on the plant, with moisture being most important of all.[1] Free moisture must be present on susceptible leaves for at least one hour in order for germination of spores to occur.[6] The pathogen can enter a healthy host in a variety of ways. With enough moisture, conidia directly penetrate through the cuticle and infect healthy cucurbits.[2] Wounds to the plant, especially those left by feeding insects such as the striped cucumber beetle or aphids, are important passageways for the pathogen to enter in older hosts.[6] Other diseases, like Powdery Mildew, can also weaken a host enough to provide easy entry for D. bryoniae. After spore germination, symptoms can appear as soon as 7 days later.[4]
D. bryoniae survives on or in seeds, surrounding weeds, or organic debris from previously infected cucurbits.[4] Without a host, the pathogen is able to overwinter and survive for over a year as chlamydospores, hardened masses of hyphae that act as survival structures during dry or otherwise adverse conditions.[1] The pathogen is transferred from infected hosts to healthy plants via ascospores carried in the wind and by conidia that are released from pycnidia by water splash and in gummy exude. Conidia are hyaline and aseptate if produced by the anamorph, and either septate or aseptate (more common) if produced by the teleomorph form of the pathogen.[4]
The host must remain wet for growth and spread of the disease. Once the primary infection takes place, as long as it remains wet, the pathogen will spread to the stem where cankers form and ooze a gummy substance full of conidia.[2] Conidia spread from the gummy ooze to another host is considered the secondary asexual cycle.
D. bryoniae is an Ascomycota fungus. In spring, asexual fruiting bodies called pycnidia and sexual fruiting bodies called perithecia are formed from last year’s infected plant debris. Pycnidia are flask-shaped structures that house asexual conidia which are readily released from pycnidia through the ostiole when enough moisture is present.[1] Perithecia are also flask-shaped, but they are sexual fruiting bodies which give rise to bitunicate asci that contain 8 ascospores. Ascospores are readily dispersed and spread by wind after rain or during evening dew periods.[2]Temperature and moisture are the most important factors for germination and development of the pathogen on the plant, with moisture being most important of all.[1] Free moisture must be present on susceptible leaves for at least one hour in order for germination of spores to occur.[6] The pathogen can enter a healthy host in a variety of ways. With enough moisture, conidia directly penetrate through the cuticle and infect healthy cucurbits.[2] Wounds to the plant, especially those left by feeding insects such as the striped cucumber beetle or aphids, are important passageways for the pathogen to enter in older hosts.[6] Other diseases, like Powdery Mildew, can also weaken a host enough to provide easy entry for D. bryoniae. After spore germination, symptoms can appear as soon as 7 days later.[4]D. bryoniae survives on or in seeds, surrounding weeds, or organic debris from previously infected cucurbits.[4] Without a host, the pathogen is able to overwinter and survive for over a year as chlamydospores, hardened masses of hyphae that act as survival structures during dry or otherwise adverse conditions.[1] The pathogen is transferred from infected hosts to healthy plants via ascospores carried in the wind and by conidia that are released from pycnidia by water splash and in gummy exude. Conidia are hyaline and aseptate if produced by the anamorph, and either septate or aseptate (more common) if produced by the teleomorph form of the pathogen.[4]The host must remain wet for growth and spread of the disease. Once the primary infection takes place, as long as it remains wet, the pathogen will spread to the stem where cankers form and ooze a gummy substance full of conidia.[2] Conidia spread from the gummy ooze to another host is considered the secondary asexual cycle.
การแปล กรุณารอสักครู่..