Root and Foot Rot of Loquat in Taiwan Caused by Phytophthora

Loquat trees growing in central Taiwan were inflicted with a disease causing wilting and death of plants due to severe foot and root rot. The vascular tissues of all infected plants turned brown. Typical as well as atypical isolates of Phytophthora parasitica were isolated from the diseased basal stem and root tissues but not from the discolored vascular tissues. Symptoms observed in the field were reproduced when roots and stems of loquat seedlings were inoculated with zoospores of atypical isolates of P. parasitica; whereas only fibrous root rot resulted from inoculation with typical isolates of P. parasitica. Atypical isolates could be differentiated from the typical isolates of P. parasitica by several characteristics, including colony appearance, partial caducous sporangia, size of oospore, growth at 36°C, mycelial soluble protein patterns, and pathogenicity.