First Report of Phytophthora capsici Causing Wilting and Crown and Root Rot on Eggplant (Solanum melongena) in Southeastern Spain

In spring 2017, diseased eggplant plants (Solanum melongena L.) were observed in greenhouses in the Almería province, where eggplant is a significant crop (around 2,500 ha). The first symptoms developed 40 days after transplanting, on less than 10% of the total plants. Affected plants showed wilting and dark brown cankers on crown and roots. A Phytophthora sp. was consistently isolated from the roots of plants on potato dextrose agar (PDA) and corn meal agar amended with pimaricin, ampicillin, and rifampicin (P₅ARP). Four nutrient-agar single-hyphal purified isolates were identified morphologically (Erwin and Ribeiro 1996). All isolates produced abundant sporangia on lima bean agar, many displaying umbellate sporangiophores. Sporangia (length, 40.3 to 65.87 μm, mean 51.46 μm; breadth, 20.81 to 36.85 μm, mean 28.52 μm) were papillate and caducous (pedicel length, 9.15 to 83.0 μm, mean 39.27 μm) and varied in shape, mostly limoniform. The isolates were crossed with Phytophthora capsici strains of known mating types. All isolates produced amphigynous antheridia and were mating type A1. Most of the oospores (19.49 to 29.27 μm, mean 24.17 μm in diameter) were plerotic. Isolates grew well at 35°C, and chlamydospores were not observed. Molecular identification was performed by sequencing amplicons of the internal transcribed spacer region (ITS) rDNA using universal primers ITS5 and ITS4 (White et al. 1990). The segments for all four isolates were identical, and in a GenBank BLAST analysis had 99.86% identity with the sequence of a P. capsici from the database Phytophthora-ID.org (Grünwald et al. 2011) (GenBank accession AB217670.1). The sequence of isolate MI5922 was deposited in GenBank as accession MG976795. Pathogenicity of all four isolates was confirmed by inoculating eggplant plants in two separate experiments. The first experiment was performed in the summer of 2017 in a semicontrolled environment greenhouse (15 to [27] to 40°C), and the second was carried out in a growth chamber (14 h/day of light, >12,000 lux, 23 to 33°C). Both experiments were randomly distributed in four blocks. There were four replicates per isolate. Experimental units consisted of two 1-liter pots containing vermiculite, each pot containing two plants, cultivar Alegria (i.e., four plants per experimental unit). Plants were inoculated per isolate at the 4 to 6 true leaf stage by drenching pots with 50 ml of a mycelial suspension, obtained by growing isolates on PDA in 9-cm Petri dishes until they fully covered the surface and then blending and homogenizing mycelium in 200 ml of sterile distilled water. Noninoculated plants (arranged as experimental units in the four blocks) served as controls. Plants were maintained for 42 days postinoculation. Symptoms first developed on at least one plant of each isolate 7 days after inoculation, in both tests. After 42 days, all the isolates produced plants showing brown roots and wilting. The percentage of symptomatic and dead (in brackets) plants per isolate at the end of the test ranged from 12.5% (12.5%) to 50% (37.5%) and 75% (68.75%) to 87.5% (87.5%), for the first and second tests, respectively. Control plants remained asymptomatic. P. capsici was reisolated from all symptomatic plants, whereas the pathogen was not obtained from control plants. To our knowledge, this is the first report of P. capsici causing disease on S. melongena in Spain. This disease has been previously reported in Italy, Venezuela, Japan, Taiwan, the United States, and Argentina (Erwin and Ribeiro 1996). Eggplants infected with P. capsici pose a threat to greenhouse crop production in Almería because eggplant is used as a rotation crop along hosts of P. capsici (de Cara et al. 2017).