Selecting plant species to rehabilitate Phytophthora cinnamomi infested forest

Abstract

For most Western Australian plant species, no information is available on the effect of Phytophthora cinnamomi on seedling emergence, early survival, and early plant growth. Such information is required when selecting species for rehabilitating Eucalyptus marginata (jarrah) forest areas affected by Phytophthora dieback. This study evaluates the response of several native species to P. cinnamomi to identify those resistant to the pathogen at the early stages of plant development. Firstly, the effect of P. cinnamomi on seedling emergence and early survival was evaluated for 50 native species. Then, 24 species were selected and tested for their resistance to P. cinnamomi when more mature. They were infested at 5–7 months old and disease impact assessed after two months. Of 38 species that emerged in sufficient numbers for statistical analysis, P. cinnamomi did not affect either emergence or survival of 9 species, emergence or survival was decreased in 14 species, and both emergence and survival were significantly decreased in 15 species. Of the species tested at 5–7 months old, two were resistant, six were moderately resistant, ten were susceptible, three were highly susceptible, and three were tolerant hosts of P. cinnamomi. These results indicate that field resistance recorded from mature plants may be due to asymptomatic infection or resistance may not be present in seedlings. Therefore, data from mature plants may not be appropriate when selecting species for seed-based restoration.