First Notice of Phytophthora Root and Stem Base Rot of Sciadopitys Verticillata in Polish Ornamental Nurseries

Abstract

Severe root and stem base rot was noticed for the first time on Sciadopitys verticillata in 3 hardy ornamental nursery stocks. Phytophthora citrophthora was isolated from about 4/5 of the analysed plants. In the laboratory trials this species caused stem and root rot. On stem parts and needles inoculated by isolates from the host plant and Pinus sylvestris, necrosis was observed to have spread at a similar rate. The needles, however, were colonized significantly quicker than the stem parts. Sciadopitys verticillata (Thunb.) Siebold. & Zucc., known as Japanese umbrella pine, is a slow-growing ornamental tree found in Polish nurseries over the last 10 years. Small plants grow to about 30 cm under cov- er, and later they are put in outside container nurseries. Lambe and Wills (1983) did not notice disease symptoms on plants in the landscape whereas in containers hav- ing excessive moisture, the trees are highly susceptible to root rot incited by Phytophhtora cinnamomi Rands. Af- fected plants showed wilting and an off-green color, with needles turning yellow. The reason for such changes were the rotting of the fibrous roots and the discoloration in the wood at the stem base. The first time yellowing of the needles was noticed on small S. verticillata growing in plastic tunnels and older plants as tall as 50-70 cm was in 2008-2010. This observa- tion took place in two hardy ornamental nursery stocks in the south-east part of Poland and in one nursery in the north of Poland. The purpose of this study was to evaluate a causal agent of dieback of S. verticillata, and its pathogenicity to a host plant. Nurseries were surveyed from July to September at one month intervals. On plants as tall as 10-25 cm nee- dles changed color from green to light green and finally to brown (Fig. 1). On the base of the plants, up to 5-10 cm of brown or dark brown discoloration of wood was observed. Most of the roots were dark brown and dead. On older trees growing at outside container nurseries, yellowing and browning of needles was noticed, usually on one part of the plants (Fig. 2). Base rot even extended 15 cm up the stem. Plants showing disease symptoms were placed in plastic bags together with substratum, and transported to the laboratory. The procedure of Or- likowski and Szkuta (2001) was used for isolating micro- organisms from diseased plant tissues. Over the span of 3 years, 50 diseased plants were analysed. Rhododen- dron leaf baits and the procedure described by Themann and Werres (1998) was used for the detection of Phytoph- thora spp. from the substratum. Obtained isolates were grouped by growth pattern and their morphology. Repre- sentative cultures were identified to species on the base of morphology features and confirmed by molecular meth-