日 植 病 報 64: 303-306 (1998) 短 報 Ann. Phytopathol. Soc. Jpn. 64: 303-306 (1998) Phytopathological Note Root Rots of Black Pepper Caused by Pythium splendens in the Dominican Republic Akira MATSUDA*, Juan de Dios MOYA FRANCO**, Jose Luis GONZALEZ** and Tsuneo WATANABE***,•õ Key words: black pepper, the Dominican Republic, pathogenicity, Pythium deliense, P. splendens. Foot rot of black pepper (Piper nigrum L.) caused by potted soil/plate culture). Phytophthora capsici Leonian occurs yearly on black Healthy seedlings were transplanted to artificially pepper plantations in the Dominican Republic. To under- infested soil (six young seedlings or four mature seed- stand the microbiological conditions in the plantations lings/pot) one week after preparation. Inoculation ex- important for disease control, fungal flora associated periments using 18 young or 12 mature seedlings in each with roots and fruits were analyzed in a preliminary treatment were repeated at least twice under green- study8). house conditions at 23-33•Ž. Two stages of seedlings Twelve isolates of four Pythium species were col- were used -67-day-old seedlings with two leaves, and lected, and using methods by previous workers4,5), were 143-day-old mature seedlings with four to six leaves. identified as P. deliense Meurs, P. intermedium de Bary, Disease was assessed 5, 7, 12 and 20 days after trans- and P. splendens Braun. One species was not identified. planting, checking disease incidence for young seedlings The three identified species are pathogens of various and counting the number of collapsed plants. At 20 days plants such as kidney beans against P. deliense6), P. after transplanting, surviving seedlings were removed intermedium against cucumber7) and melon against P. entirely from the soil, and were separated into three splendens9). Because they have been isolated occasion- categories by the amount of rot. The first had serious ally from collapsed black pepper vines during this study, damage involved more than half of the roots. The sec- pathogenicity of the representative isolates of each ond had light damage with healthy taproots and slight species was then tested on black pepper seedlings. damage on lateral roots. The third had healthy roots. Isolates were collected from four locations including For mature seedlings, disease occurrence was checked the Exhibition Farms of CENDETECA (Centro Nacion- during the inoculation experiment. At 44 days after al de Desarrollo Tecnologico de Cacao) in the Domini- transplanting, seedlings were removed entirely from the can Republic. They are three isolates of P. splendens soil for assessing growth of seedlings and degree of [isolate SP7, K4(=ATCC200560), PyLM], and one iso- rotting. On the basis of the degree of rotting for the late each of P. deliense [K6(=ATCC200559)], P. inter- taproots, a disease index with the following five cate- medium [K5(=ATCC200569)] and Pythium sp. (SP5); gories was established: 0, healthy; 1, less than one third four isolates of Mortierella spp. (SP6, K8, K9, K10) and of the total taproot area rotted; 2, one- to two-thirds of two Phytophthora isolates [Phy. capsici (A16) and a total taproot rotted; 3, more than two-thirds of total Phytophthora sp. (HPS2)]. The last two genera served as taproot rotted. For slender lateral roots, five categories controls. were set with the following indices: 0, healthy; 1, less The morphology, identification and pathogenicity of than one-third rotted in the total lateral root area; 2, both Phytophthora and Pythium spp. were described by one- to two-thirds rotted; 3, one-half or two-thirds Matsuda et al. in 19943)and Watanabe et al. in 19968). rotted; 5, more than two-thirds rotted. Based on these Potted soils were artificially infested by mixing data, rotting degree indexes were estimated by the minced 5-day-old cultures grown on carrot juice agar following equation: (decoction of 200g of fresh carrot roots, glucose 20g, agar 20g, distilled water 11) with potted soils (500g * Previous JICA specialist , Japan International Cooperation Agency (JICA), Nishi-ohshima 1-26-6, Hitachinaka 312-0041, Japan 前 国 際 協 力 事 業 団 長 期 派 遣 専 門 家 ** Centro Nacional de Desarrollo Tecnologico de Cacao (CENDETCA) , San Francisco de Macoris, the Dominican Republic *** Previous JICA specialist , Japan International Cooperation Agency (JICA), Minami-nakazuma 180-5, Tsukuba 305-0065, Japan 前 国 際 協 力 事 業 団 短 期 派 遣 専 門 家 † Present address: Bioconsortia Program Laboratory , National Institute of Bioscience and Human Technology, Agency of Industrial Science and Technology, 1-1 Higashi, Tsukuba 305-8566, Japan 現 在:通 産 省 工 業 技 術 院 生 命 工 学 工 業 技 術 研 究 所 複 合 生 物 系 プ ロ ジ ェ ク ト研 究 室 304 日本植物病理学会報 第64巻 第4号 平成10年8月 Rotting degree index rotted. Seedlings attacked by P. splendens were severely =[(no. of healthy roots with index 0)•~0+(no. of stunted and had discolored roots (Plate I-1-3). From lightly diseased roots with index 1)•~1+(no. of these diseased seedlings, the applied fungi were reisolat- intermediately diseased root rot with index 2)•~2+ ed. Therefore, P. splendens was definitely pathogenic (no. of severely diseased root rot with index 3)•~3+ and probably associated with root rot decline of black (no. of seriously diseased root rot with index 5)•~5]/ pepper in the Dominican Republic. However, P. deliense (total no. roots surveyed)•~5. was only weakly pathogenic. Holliday and Mowat in 19632) isolated P. splendens Three isolates of P. splendens were pathogenic to from rotted lateral roots of young black pepper seed- black pepper seedlings, but varied in their pathogenicity. lings with damping-off in Malaysia. However, because Especially in the 2-leaf stage, three isolates of P. splen- the fungus was not isolated from the thick taproots and dens and two of the Phytophthora spp. were equally was not pathogenic to nearly 50-day-old mature seed- pathogenic. Isolate K-6 of P. deliense was more patho- lings, they did not believe P. splendens was the causal genic to young seedlings than to mature seedlings agent of foot rot. Instead, they named Phytophthora (Tables 1 and 2, Plate I). palmivora (Butler) Butler as its cause. On the other hand, One isolate of P. intermedium and four of Mortierella Pythium vexans de Bary was reported as causal agent of spp. were not pathogenic although lateral roots partially foot rot in India1). A black pepper disease caused by P. Table 1. Collapse of two-leaf black pepper seedlings at various times after transplanting into soils artificially infested with Pythium species, Mortierella or Phytophthora speciesa) and noninfested soil and rotting of lateral roots of surviving seedlings 20 days after transplanting a) Pythium deliense (=P. del), P. intermedium (=P. int), P. splendens (=P. spl), unidentified Pythium sp. (=Py. sp.), Mortierella (=Mort.) spp., Phytophthora catsici (=Phy. c) and unidentified Phytophthora sp. (=Phy. sp.) were tested. Table 2. Stem and root lengths of black pepper seedlingsa), number of their roots and collapse of seedlings in soils artificially infested with Pythium species or Mortierellab) and in noninfested soil and root rot of surviving seedlings a) Seedlings had four to six leaves by 44 days after transplanting when assayed. b) Pythium deliense (=P. del), P. intermedium (=P. int), P. splendens (=P. spl), unidentified Pythium sp. (=Py. sp.) and Mortierella (=Mort.) spp. were tested. Ann. Phytopathol. Soc. Jpn. 64 (4). August, 1998 305 splendens in the field however, has never been described. 6. Watanabe, T. (1981). Detection of Pythium deliense in Nor has P. vexans ever been isolated in the Dominican the Ryukyu Islands and its ecological implication. Ann. Republic. Pythium splendens isolated occasionally from Phytopathol. Soc. Jpn. 47: 562-565. the roots of declining saplings and discolored roots of 7. Watanabe, T. (1983). Formation and deciduousness of mature vines, and was pathogenic to seedlings. Thus, we sporangia of Pythium intermedium. Trans. Mycol. Soc. Japan 24: 25-33. propose the name of root rot for the root disease of 8. Watanabe, T., Moya, J.D., Gonzalez, J.L. and Matsuda, black pepper accompanied by the yellowing and wilting A. (1996). Fungi associated with roots and fruits of symptoms caused by P. splendens, thus differentiating it black peppers in the Dominican Republic. Mycoscience from the foot rot caused by Phytophthora spp. 37: 471-475. 9. Watanabe, T., Onogi, S., Uematsu, S. and Tsuchiya, Y. The first and fourth authors wish to thank Japan Interna- (1983). New wilt disease of melon with root rots caused tional Cooperation Agency (JICA), Tokyo, Japan for the by Pythium splendens. Ann. Phytopathol. Soc. Jpn. 49: financial support for their dispatch to the Dominican Repub- 127 (Abstr. in Japanese). lic as long and short-term experts, respectively. 和 文 摘 要 Literature cited 松 田 明 ・Juan de Dios MoYA FRANCO・Jose Luis GON- 1. Chattopadhyay, S.B. (1967). Diseases of Plants Yield- ZALEZ・ 渡 邊 恒 雄:ド ミニ ヵ共 和 国 で のPythium splendensの コ ing Drugs, Dyes, and Spices, Indian Council of Agricul- シ ョ ウ実 生 苗 へ の病 原 性 ture Research, New Delhi, pp. 48-72. 2. Holliday, P. and Mowat, W.P. (1963). Foot rot of Piper ド ミニ カ 共 和 国 で の コ シ ョ ウ幼 樹 の 黄 化 ま た は 枯 死 株 お よ び nigrum L. (Phytophthora palmivora). Phytopathol. Pap. 生 産 樹 の 根 部 か ら 分 離 し た4種 のPythium属 菌 お よ びMor-1 6: 1-62. tierella spp.を2葉 期 ま た は4～6葉 期 の コ シ ョ ウ 実 生 苗 へ 接 種 3. Matsuda, A., Hamada, M. and Gonzalez, J.L. (1994). し病 原 性 を検 討 し た 。 供 試 菌 で 人 為 的 に 汚 染 し た 病 土 に健 全 な Outbreak and control of foot rot on black peppers in 実 生 苗 を 移 植 し20～44日 ま で の 発 病 程 度 を 調 べ た 結 果,P.