Pythiogeton zizaniae, a new species causing basal stalk rot of water bamboo in Taiwan

A new species, Pythiogeton zizaniae, was isolated from diseased water bamboo (Zizania latifolia) in central Taiwan. The organism formed a colony with scanty mycelia and mycelial aggregates on rye-water bamboo medium. Special treatments were required for production of sporangia which were terminal, noncaducous and mostly ovoid. Chlamydospores were absent. The fungus was homothallic. Oogonia produced on V-8 water bamboo medium in water were mostly globose to subglobose and each was attached with a club-shaped, monoclinous antheridium by the base of the oogonium stalk. Oospores were plerotic and globose to subglobose. Py. zizaniae caused death of water bamboo suckers but did not infect seedlings of corn, rice, wheat, sorghum, cucumber, tomato, soybean or water spinach. It also did not affect cucumber and tomato fruit, carrot roots or potato tubers

(63(4):267-273)Mating Type Distribution of Phytophthora palmivora from Papaya in Taiwan

自1977 年至2011 年於13 縣市39 地區之106 處木瓜果園，採集罹病果實及根、莖、葉組織，共計分離到278 株疫病菌。經鑑定所有菌株均為Phytophthora palmivora (Butler) Butler，其中屬於A1 配對型的菌株有262 株，A2 配對型的僅有16 菌株。如果以果園來區分，106 個果園中，僅有2 處果園完全出現A2 菌株，有101 處果園完全出現A1 菌株，有3 處果園同時出現A1 與A2 菌株，但A1 菌株為優勢，A2 菌株在各果園僅有1 株。如果將木瓜菌株分離的年代區隔成3 個不同時段，包括1977–1980 (早年)、1988–2000 (中年) 及2001–2011 (近年)，則1980 年以前分離的13 個菌株均為A2 配對型；1988–2000 年分離的164 個菌株中161個菌株均為A1 配對型，僅有3 菌株為A2 配對型；2000 年以後 (2001–2011) 分離的101 個菌株均為A1 配對型。資料顯示，A1 菌株為目前台灣木瓜園內的絕對優勢種。 From 1977 to 2011, a total of 278 Phytophthora isolates were obtained from papaya diseased tissues, including fruit, roots, and young seedlings, which were collected from 106 papaya orchards located at 39 sites (districts, townships or cities) of 13 counties/cities. All isolates were identified as Phytophthora palmivora (Butler) Butler, of which 262 isolates were A1 mating type and only 16 isolates were A2 mating type. Isolates from 101 of 106 orchards were all of the A1 mating type, while isolates from 2 orchards were all A2 mating type. Isolates from the other three orchards contained both A1 and A2 mating types, but A1 was dominant. Only one A2 was found in each of the 3 orchards. All 13 isolates obtained before 1980 were A2 mating type. Of the 164 isolates obtained during the periods from 1988 to 2000, 161 were A1 mating type and only 3 were A2 mating type. The 101 isolates obtained after 2000 (2001-2011) were all A1 mating type. These results indicate that A1 mating type of P. palmivora is currently the dominant Phytophthora pathogen in papaya orchards in Taiwan

重新評審在台灣番茄上發現 Phytophthora infestans A2

In June 2008, Deahl et al. reported the first detection of two isolates of the A2 mating type of Phytophthora infestans on tomato from two locations in Taiwan based on the tests performed at USDA, Beltsville, using A1 and A2 mating types of P. infestans as testers. However, the third and fourth authors of the paper showed that these two isolates (Pi 214 and Pi 566) behaved as A1 mating type when paired with AI and A2 testers of P nicotianae (= P. parasitica) at Asian Vegetable Research and Development Center, Shanhua, Taiwan. This information was not included in the report. These two isolates along with two other isolates of P infestans (Pi 215 and Pi 564) isolated from the same locations on the same dates were re-tested independently in three laboratories using A1 and A2 mating types of P infestans, P nicotianae and P capsici as testers. All four isolates displayed oospore formation when paired with A2 but not A1 mating type regardless of species used as the testers, indicating that all of them are of the A1 mating type. New isolation of P infestans from diseased tomato plants from the same locations also showed the presence of only the A1 mating type. These results refute the claim by Deahl et al. of the discovery of the A2 mating type of P infestans from Taiwan

(62(1):57-70)Phytophthora Diseases of Cedrela sinensis and Zanthoxylum ailanthoides

2006 年起發現多處地區的香椿 (Cedrela sinensis) 與食茱萸 (紅刺蔥) (Zanthoxylum ailanthoides) 苗木發生嚴重枯萎腐敗現象。香椿的罹病部位包括莖基部與根系；莖基部染病後，基部隘縮，繼而全株枯萎死亡，而在環境潮濕時，罹病部位長出白色霉狀物；根部染病時，根系壞疽且稀少，嚴重時地上部矮化黃葉，甚而全株死亡。食茱萸則全株可被感染，包括根、莖及葉片，被感染葉片初現淡褐色水浸狀圓形斑點，病斑面積迅速擴大轉為暗褐色，並提早落葉；莖部被感染時，新稍與主莖初現褐色病斑，而後擴大環繞莖部，造成頂芽與罹病處以上部位枯死；莖基部與根系的病徵則與香椿受害情形相似。罹病組織經分離，從香椿上獲得兩種疫病菌，分別為Phytophthora nicotianae (P. parasitica) 與Phytophthora palmivora，而食茱萸上分離到的疫病菌則全為P. nicotianae。將分離到的疫病菌游走子懸浮液各自噴霧接種於兩種作物一年生幼苗上，2–3 d 後均會造成新稍褐變枯萎、葉片出現褐斑後掉落；接種莖基部時，10–14 d 則可造成組織隘縮與植株死亡；接種根部時，約20–30 d 則可造成植株死亡；均與田間出現之病徵一致，並且自接種後發病的組織上均可回分到相同的疫病菌，證實香椿與食茱萸的莖、葉及根系腐敗係由疫病菌引起。兩種疫病菌均為典型 (typical type)疫病菌，P. nicotianae 的菌絲生長溫度為8–36℃，最適溫為28℃；孢囊球形或橢圓形，具顯著乳突 (papilla)及不脫落性；P. palmivora 的菌絲生長溫度為12–35℃，最適溫亦為28℃；孢囊橢圓形、檸檬形或卵圓形，具顯著乳突及脫落性，孢囊柄 (pedicels) 極短，在5 μm 以下。兩種疫病菌均可形成厚膜孢子 (chlamydospores)。其中香椿分離的P. nicotianae 為2 株A1 配對型 (mating type)，而P. palmivora 為3 株A2 配對型；而食茱萸分離的P. nicotianae 包括7 株A1 與4 株A2 配對型。利用分子序列特性，包括核糖體內轉錄區間 (ITS) DNA 序列與β 微管蛋白 (β-tubulin) 部分基因序列分析，序列比對結果亦佐證傳統形態分類的正確性。本研究結果係疫病菌為害香椿與食茱萸的首度報導。 Serious Phytophthora diseases of Cedrela sinensis and Zanthoxylum ailanthoides were found in the fields in Taiwan during the investigation of diseases of medicinal herb plants from 2006 to 2012. Diseased plants of C. sinensis showed symptoms of browning on basal stems which were shrunken within a few days, and the plants were droopy. Severely infected plants were leaf yellowing, stunted and killed due to root rotting. Diseased plants of Z. ailanthoides showed symptoms of water-soaked lesions on leaves, buds and stems, which enlarged in size and turned dark brown quickly. Eventually, the infected leaves turned yellow and fell prematurely, and the buds and stems rotted and collapsed. Diseased plants also showed symptoms of basal stem rot and root rot. Two species of Phytophthora, including P. nicotianae (P. parasitica) (2 A1 isolates) and P. palmivora (3 A2 isolates) were isolated from C. sinensis and one species of Phytophthora (P. nicotianae, 7 A1 and 4 A2 isolates) was isolated from Z. ailanthoides. Results of pathogenicity tests by artificial inoculations showed that both P. nicotianae and P. palmivora were the pathogens of C. sinensis and P. nicotianae was the pathogen of Z. ailanthoides, with disease symptoms identical to the diseased plants observed in the fields. Each Phytophthora isolate was re-isolated from the infected tissues of the inoculated plants. All the isolates of Phytophthora obtained from C. sinensis and Z. ailanthoides belonged to the typical types of P. nicotianae or P. palmivora. The range of temperature for mycelial growth of P. nicotianae isolates were 8–36℃ with optimal temperature at 28℃, while the range for P. palmivora was 12–35℃ with optimal temperature at 28℃. Sporangia of P. nicotianae isolates were spherical or sub-spherical, unsymmetrical, with semi-spherical papilla, and non-deciduous, whereas sporangia of P. palmivora were spherical, ovoid or elliptical, symmetrical, with semispherical papilla, and deciduous with very short pedicels (< 5 μm). Both Phytophthora species produced chlamydospores on agar media. DNA sequences of the internal transcribed spacers (ITS1-5.8S rDNA-ITS2) region and the partial β-tubulin gene also support the morphological classification of P. nicotianae and P. palmivora. This is the first record of Phytophthora diseases of C. sinensis caused by P. nicotianae and P. palmivora and Z. ailanthoides caused by P. nicotianae in Taiwan and in the world

利用中和後之亞磷酸防治荔枝果實露疫病

Field studies were conducted to evaluate the effect of neutralized phosphorous asid solution (NPA) on the control of fruit downy blight of lychee (Litchi chinensis) caused by Peronophythora litchi during 1999-2003. Trees of lychee, variety ‘Black Leaf’, were sprayed with NPA at 1000 mg/L, 2 or 3 times at 7-day intervals, at the fruit maturing stage and then inoculated with sporangial suspension of P. litchi at 200-500 spores/mL. Matured fruits were harvested and percentage of downy blight fruit was recorded. Results of the 3-year field trials showed that lychee trees sprayed with NPA significantly (P<0.01) reduced the incidence of fruit downy blight (0.5-11.8%), compared to untreated controls (26.1-46.6%). The treatment of NPA also was as effective as the treatment of mancozeb 80WP (dilution 500 times), a commercial synthetic chemical registered for the control of lychee fruit downy blight in Taiwan. Meanwhile, three applications of NPA in the fields not noly significantly (P<0.01) reduced the incidence of postharvest Peronophythora fruit rot of lychee (0-16%), compared to the untreated control (12.2-96.6%), but also delayed the development of postharvest fruit downy blight by 2-4 days. However, treatment of freshly harvested lychee plants at fruit development or maturing stage in the fields to induce resistance of lychee fruits against P. litchi and thereby, reduce downy blinght of lychee fruits in the field and at postharvest stage. 近年來，農試所研發一種簡單的方法配製亞磷酸中和液(NPA)，將等重量之氫氧化鉀加入亞磷酸水溶液中和後使用。於 1999 -2003 在田間施用NPA，以評估其對荔枝果實露疫病的防治效。在黑葉近成熟期，每隔7天噴布濃度1000 mg/L之 NPA一次，共2-3次，相隔7天之後，再接種露疫病菌孢囊懸浮液（濃度為200 -500 spores/mL）。結果顯示，NPA在田間防治荔枝果實露疫病之效非常好，果實發率可從26.1 -46.6% 下降為0.5 -11.8%。同時， NPA防治果實露疫病的效與噴施三次 80%鋅錳乃浦可濕性粉劑（稀釋 500 倍）的效果一樣好，無顯著性差異。此外人工接種之結果顯示，在田間施用相同濃度的NPA 2-3次，同樣可以顯著降低採收後果實露疫病之發率，從12.2-96.6% 下降至 0-16% ；還可以延緩果實露疫病徵之出現達 2-4日。然而，以相同濃度之NPA處理採收後的果實再接種露疫菌，則無法顯著降低果實之發病率，此項結果顯示NPA必須施用於田間才有防治荔枝果實露疫病之功效

(60(2):149-156)利用亞磷酸中和水溶液防治果樹苗木疫病

A greenhouse study was conducted to determine effects of neutralized phosphorous acid solution (NPA) on control of Phytophthora diseases of kumquat (Fortunella margarita) grafted on Rangpur lemon (Citrus limon), loquat (Eriobotryajaponica cv. ‘Mogi’) and avocado (Persea americana cv. ‘Tainan’). The NPA solution was prered by dissolving phosphorous acid in water and then adding equal weight of potassium hydroxide to the solution. For kumcpat, 1-year-old seedlings were sprayed with NPA solution (1000 mg/L), 50 mL/seedling, for 2 or 3 times at weekly interval and then sprayed with zoospore suspensions of Phytophthora citrophthora, 10 mL/seedling, at 7 days afler last NPA spray. After inoculation for 14 days, each seedling was recorded for disease incidence on leaves. In another experiment, 5-year-old kumquat plants grafled on Rangpur lemon were sprayed with NPA (1000 mg/L), 500 mL/plant, for 3 times at weekly interval and incculated with the pathogen, 200 mL/plant, at 7 days after last NPA spray. For loquat, 6-month-old seedlings were treated with NPA (2000 mg/L) by soil drenching or with NPA (1000 mg/L) by spraying for 3 times at 30-thy interval. The seedlings were then incculated with Phytophthora nicotianae by placing one gram of pathogen-colonized wheat-oat grains on the wounded area of basal stems. For avocadoes, 6-month-old seedlings were inoculated with Phytophthora cinnamomi by drenching with 100 mL of chlamydospore suspension on each plant and then treated with NPA (1000 or 2000 mg/L) by soil drenching for 3 times at 3-month interval. Results showed that spraying kumquat seedlings with NPA at 1000 mg/L (a.i.) for 2-3 times significantly reduced seedling blight (44.8% infected leaves). Similarly, NPA sprayed three times on 5-year-old kumquat plants was also effective in reducing incidence of Phytophthora fruit rot leaf blight and twig blight. Application of NPA at 2000 mg/L by soil drenching or at 1000 mg/L by spraying completely controlled basal stem rot of loquat caused by P. nicotianae, whereas more than 60% of seedlings were killed in the controls. The avocado seedlings treated with NPA by soil drenching and inoculated with the pathogen were all survived during the test period, whereas 50-60% seedlings were killed in the pathogen-inoculated control. Avocado seedlings treated with NPA were taller and heavier than the pathogen-inoculated control, but they were shorter and lighter than the non-inoculated control. This study reveals that NPA is a chemical with potential for practical use in the management of Phytophthora diseases of kumquat, loquat and avocado. 本研究評估簡便調製之亞磷酸中和水溶液（neutralized phosphorous acid solution, NPA）對三種果樹幼苗疫病之防治效果。一年生的長實金柑（Fortunella margarita)／廣東檸檬（Citrus limon）嫁接苗每株噴布50 mL NPA （濃度1000mg / L ) ，每星期施用一次，2-3次後，再接種Phytophthoa citrophthora的游走子懸浮液，接種14天後疫病幾乎不會發生；而對照處理則有44.8％與50.8％的葉片染病，並且伴隨枝條流膠與枝枯。而五年生的結果金柑苗每株噴布500 mL 相同濃度的NPA 三次，可以完全保護果實、葉片及枝條不被病菌戚染；而接種病菌的對照處理的發病率分別為80%，59％及20%，發病之枝條同樣伴隨流膠與枝枯。六個月大的茂木枇杷（Eriobotrya japonica cv. ‘Mogi’）實生苗之土壤表面每株灌注50 mL NPA ( 2000 mg/L ）或噴布10 mL NPA (1000 mg / L) 三次，每次間隔30天，之後莖基部接種疫病菌P. nicotianae之麥粒菌種，90 天後均無幼苗死亡；而對照處理則有60％與65％的死亡率。六個月大的台南種酪梨（Persea Americana cv. ‘Tainan’）在接種P. cinnamomi。朋厚膜抱子懸浮液後，每盆土壤灌注100 mL NPA (1000 mg/L 或2000 mg/L）三次，每次間隔90天，NPA的處理在試驗期間均無植株死亡，而接菌對照處理有50％與60％死亡率，NPA處理組的平均株重比接菌對照處理顯著為重，但比不接菌對照處理顯著為差

Soil-Borne Fungal Diseases of Citrus in Taiwan

本省柑橘之重要土壤傳播性真菌病害包括疫病、幼苗猝倒病與細根腐敗病、流膠病、及木材腐敗病等，其中以疫病最具破壞性。危害本省柑橘之主要疫病菌共有五種，依次為Phytophthorn porositicQ , P. polmivoro , P. citrophthoro , P. citricolo 及P. cinnomomi。病菌主要危害柑橘之幼苗、根系、樹幹基部、及果實。初次感染源主要來自污染之栽培介質與灌溉用水，連續降雨與土壤濕度過高為誘發病害猖獗之重要因子。目前可行之防治策略為使用抗病或耐病品種之健康種子育苗以供為砧木，使用無病原菌栽培介質與灌溉水，苗期宜有防雨設施，注意田間排水，及藥劑防治。幼苗猝倒病與細根腐敗病由Pythium spp., Rhizoctonio Solon¡（或R. soloni like), Phytophthoro spp. 及Fusarium spp.所引起，注意育苗用栽培介質之衛生與種子消毒即可預防本病害。引起樹幹流膠之病原菌除疫病菌外，大部分為弱病原菌，分離到的有Rhizoctonio sp., Fusorium sp., Diplodio sp ., 及Phomopsis sp.等，一般在樹勢衰弱時，才會由樹皮傷口侵入感染，引起之流膠病徵與疫病菌引起者不盡相同，注意施肥、施藥、水患、及保持樹勢健旺，可預防本病害。木材腐敗病大部分由靈芝或樹舌引起，危害較少。 Phytophthora diseases, seedling damping off and fibrous root rot, gummosis, and wood rot are the important soil-borne diseases of citrus in Taiwan. Based on the frequency of isolation and pathogenicity to citrus, Phytophthora species were the most destructive fungal pathogens, and a total of 5 species including P. parasitica, P. palmivora, P. citrophthora, P. citricola, and P. cinnamomi were detected to be distributed wildly in citrus orchards. These fungi could attack seedlings, root systems, wound bark of stems, and fruit of citrus. The contaminated cultural media and irrigation water were the main sources carrying the primary inoculum, and heavy rainfall and moist soil environment were the two key factors inducing serious Phytophthora diseases. Integrated use of 1. healthy seeds, 2. resistant or tolerant root stocks, 3. disinfected cultural media or vergin soil, and pathogen free water for irrigation, 4. greenhouse or plastic sheet covering to protect young seedlings from rainfall, and 5. protective chemicals, could provide a satisfactory effect for decreasing citrus diseases caused by Phytophthora. Seedling damping off was mainly caused by Pythium spp., Rhizoctonia solani (or R. solani like), Phytophthora spp., and Fusarium spp. Sterilized or disinfected cultural mixtures and using healthy seeds cound improve seedling problems caused by these fungi. Rhizoctonia sp., Fusarium sp., Diplodia sp. and Phomopsis sp. have been isolated from the diseased barks of citrus stems with gummosis. All of the four fungi were weak pathogens which attacked weak citrus trees, and caused gummosis symptoms different from those induced by Phytophthora. Control of gummosis could be achived by enhanceing citrus trees growing stronger by avoding flooding fields and application of inadiquate ferterlizers and chemicals. Wood decay and root rot of citrus, which were occassionaly found in citrus orchard, were mainly caused by Ganoderma and Phellinus spp

利用亞磷酸簡便調配技術、合適濃度及施用方法防治作物疫病

A simple method for application of phosphorous acid to control Phytophthora diseases was developed. The proposed method involves measuring equal weight of phosphorous acid and potassium hydroxide and dissolving phosphorous acid in water before adding potassium hydroxide. The pH of the neutralized phosphorous acid solution (NPA) is 6.2-6.7. The NPA concentration at 5000 mg/L was effective in controlling tomato seedling blight caused by Phytophthora capsici when using soil drench method. For suppression of lily leaf and blossom blight caused by Phytophthora parasitica, foliar application is much more effective than soil drench. However, NPA concentrations exceeding 2000 mg/L were phytotoxic to young plant tissues. The best results were achieved by applying NPA at the rate of 1000 mg/L for 3 times at one week intervals. Applying NPA to mother lily plants also effectively protected bulblets from infection by P. parasitica during storage periods. 研發一種簡便調製中和亞磷酸水溶液的技術，可用來防治作物疫病，該方法將亞磷酸(H3PO3)與氫氧化鉀(KOH)以1:1 (w/w)等重稱量後，先將亞磷酸溶解於水中後，再將氫氧化鉀加入溶解，該中和後的亞磷酸水溶液(neutralized phosphorous acid solution，簡稱NPA)的酸鹼值為pH6.2~6.7。防治由Phytophthora capsici引起的番茄幼苗根莖部疫病時，以較高濃度的NPA（如5000 mg/L）灌注根圈土壤的防治效果較佳。而防治由P. parasitica引起的白合地上部花器與葉片疫病時，以葉面噴部的效果較土壤灌注為佳。但NPA施用於地上部時，濃度超過2000 mg/L時易造成花器與幼嫩組織藥害。試驗中最佳的組合施用方法為，NPA的施用濃度為1000 mg/L，每隔7天施用一次，連續三次，防治白合疫病的效果最佳。此外，NPA施用於百合母株及其根圈土壤，亦能保護貯藏期的小種球，降低被疫病菌感染的機率

Phytophthora Diseases of Citrus in Taiwan

自1976年7月至1980年5月，自本省15縣229柑橘園內採集土壤及罹病之果實、葉片及莖部組織。利用葉片誘釣法及配合選擇性培養基分離，疫病菌可自14縣108果園中分得。依疫病菌之分離頻率及重要性，依次如下；A1及A2型的phthora parasitica及P. palmivora分佈於中南部柑橘園中，P. parasitica引起根腐病及鋸腐病，而P. palmivora引起根腐病及褐腐病；A1型的P. citrophthora及P. cinnamomi與同絲性之P. citricola存在於中部以北地區，主要為害根系。以上5種疫病菌均對甜橙有病原性。而P. heave, P. insolita及P. humicola僅自土壤中分得，對甜橙無病原性。在檢定之79種柑橘品種系中，甜橙類對P. parasitica及P. palmivor抵抗力最弱；椪柑、桶柑、檸檬及葡萄柚次之；酸橘、枳橙及廣東檸檬中感；部份柚類中等；酸橙、根殼及紅柚為中抗；金柑類及烏柑刺則具強烈之抗性。 From July 1976 to May 1980 soils and diseased fruit, leaves and stems were collected from 229 citrus orchards in all 15 counties on the island of Taiwan, and assayed for the presence of Phytophthora by baiting with discs of citrus leaves and plating on selective medium. Phytophthora species were isolated from 108 citrus orchard in 14 counties. Based on the frequency of isolation and pathogenicity to citrus, both of A1 and A2 mating types of P. parasitica and P. palmivora were isolated from the central and southern area. P. parasitica was the main pathogen causing foot rot, and root rot, while P. palmivora causing fruit brown rot and root rot. A1 but not A2 types of P. citrophthora and P. cinnamorni, and P. citricola (Homothallism) were mainly distributed on the central and northern regions, causing citrus root rot. All of the 5 species were pathogenic to sweet orange. P. heave, P. insolita and P. humicola infrequently isolated from soils were non-pathogenic to sweet orange. One to two months old citrus seedling were planted in artifical inoculated-diseased soils for testing of resistance to P. parasitica and P. palmivora. Of 79 citrus and related tested varieties, sweet orange (9 varieties) were most susceptible; ponkan, tankan, lemons and grape fruit were next; sunki, troyer and rangpur lime were susceptible; some of pummelo were morderate; sour orange, trifoliate orange and red pummelo were morderately resistant; while Severinia and Kumquat were high resistant