First Report of Phytophthora nicotianae Causing Foliar Blight on Zamioculcas zamiifolia in Florida

Zamioculcas zamiifolia, commonly known as the 'ZZ' plant, is a member of the Araceae, indigenous to South Africa. Zamioculcas zamiifolia is different from most other foliage plants, being a stemless, herbaceous, forest plant that develops short sprouts from a thick underground tuberlike rhizome that stores water. Due to this rhizome, the plant can survive without water for longer periods than most common foliage plants. The combination of dark green, attractive foliage and the ability to thrive under low-light conditions has made the ZZ plant very popular for indoor use. During July 2015, a local nursery submitted samples of Z. zamiifolia to the Florida Extension Plant Diagnostic Clinic in Homestead, FL. Affected foliage appeared water soaked and black. Phytophthora was initially confirmed by serological testing with a commercially available ImmunoStrip test (Agdia, Elkhart, IN). After closer examination, the pathogen was identified as Phytophthora nicotianae by spherical to sharply papillate and noncaducous sporangia with short pedicels. The sporangia averaged 40 x 29 [mu]m with ranges of 11 to 60 [mu]m long and 20 to 45 [mu]m wide (n= 20) (Erwin and Ribeiro 1996). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1 and ITS4 and the PCR product was sequenced. The resulting 850-bp sequence was deposited in GenBank (Accession No. KT455619). A BLAST search in GenBank exhibited 99% nucleotide identity with an isolate of P. nicotianae(HG007960) collected on Buxus spp. in Italy. To further support identification, phylogenetic analysis by the Maximum Likelihood method (Tamura-Nei model) was performed (MEGA 6.06). Our isolate grouped with other P. nicotianae isolates with high support (100% bootstrap values, 1000 replicates). To confirm pathogenicity, Z. zamiifolia plants were inoculated with a suspension of zoospores (1 x 10 super(6) spores/ml) of the isolate of P. nicotianae that was sequenced. Inoculum or autoclaved water was sprayed over the foliage until runoff. Three plants per treatment were sprayed and the experiment was repeated. Inoculated plants were covered with plastic bags to maintain humidity and placed in a shade house where temperature ranged from 25 to 32[degrees]C. After 72 h some leaves from inoculated plants became water soaked and turned brown to black matching initial symptoms. Phytophthora nicotianae was reisolated from symptomatic leaf tissue. No symptoms developed on the control plants. A bas