Temperature effects on the germination of sporangia and zoospores and colony establishment of Phytophthora kernoviae

• Published in: Phytopathology Vol. 105; no. 9S
• Main Authors: Shelley, B, Widmer, T L, Luster, D G, Smith, O P, Falkenstein, K
• Format: Journal Article
• Language: English
• Published: 01-09-2015
• Subjects: Magnolia; Phytophthora; Rhododendron ponticum
• ISSN: 0031-949X

Phytophthora kernoviae, first reported in 2003 has the ability to infect and cause foliar necrosis on Rhododendron ponticum and other woody ornamentals. However, little is known about the specific conditions necessary for this species to infect host plants. Temperature plays a significant role in the life cycle of all Phytophthora spp. and preliminary studies showed it is important to the infection process of P. kernoviae. This study was designed to understand what factors in the infection process are controlled by temperature. Sporangia and zoospores from six P. kernoviae isolates were exposed to different temperatures ranging from 20 to 25[degrees]C. A study on infection of plant tissue showed that after 1 wk, foliar necrosis of detached R. ponticum and Magnolia stellata leaves only appeared between 20 and 23[degrees]C. Colony development studies originating from sporangia and zoospores show that germination is about equal across all temperatures, but the establishment of new colonies is significantly diminished above 23[degrees]C. However, a less noticeable difference in colony establishment originating from mycelia plugs is observed at these temperatures. In summary, germination of sporangia and zoospores for P. kernoviae occurs at all temperatures, but the establishment of new colonies from asexual propagules appears to depend on temperature conditions not exceeding 23[degrees]C. This also appears to impact disease development on host tissue at these higher temperatures.