彩色海芋種薯細菌性軟腐病之研究

Abstract

自彩色海芋栽培田中採集軟腐罹病組織，共計分離得到37株Erwinia 屬軟腐細菌菌株， 經生理生化之鑑定結果得悉此37株菌株皆為Erwinia carotovora subsp. carotovora。測 試彩色海芋種球傷口對細菌性軟腐 病發生之影響，結果顯示種薯在人為製造傷口後較無傷 口之種薯其軟腐 病發生率明顯增加。而金黃種彩色海芋抽花後，立刻自傷口處接種軟腐細 菌，其軟腐病發生率可達100％；抽花傷口經36小時之癒合時間後接種， 其軟腐病發生率 可降至16.7％。檢測不同來源之彩色海芋種薯，發現 Erwinia軟腐細菌之帶菌率在23.3％至 84.0％間。偵測儲藏後之彩色海芋 種薯表皮之帶菌量，具軟腐癒合組織之種薯表皮帶菌量 可介於104 ~ 106 cfu/g dry material間。於溫室試驗中，栽種具軟腐癒合組織之種薯 、 軟腐癒合組織已切除之種薯及無病徵之彩色海芋種薯，其細菌性軟腐 病之發生率分別為 86.7％、33.3％及6.7％。於NA平板上測試化學藥 劑對彩色海芋軟腐細菌之抑制能力，結果 得知銅合浦、銅鋅錳乃浦、氧 化亞銅、嘉賜銅、銅快得寧及三元硫酸銅等藥劑可抑制所 有菌株之生 長；鏈四環黴素、鏈黴素與多保鏈黴素亦可抑制大部份菌株之生長；而鋅 錳乃浦、亞納銅及克枯爛等藥劑則無法抑制任何菌株之生長。以化學藥劑 配合溫度處理以軟腐細菌懸浮液浸菌之海芋種薯，得知以藥劑配合溫度處 理可明顯降低種薯上之Erwinia屬軟腐細菌 族群，然藥劑處理之效果種薯 間常有差異，且受處理溫度影響；在45℃溫度下藥劑處理後之種薯上之 Erwinia屬軟腐細菌明顯較處理溫度為26℃時低，當種薯以Erwinia屬軟腐 細菌浸菌之濃度為108 cfu/ml時，在所測試之11種藥劑中銅鋅錳乃浦在45 ℃下處理種薯之效果最佳，可將種薯上之Erwinia屬軟腐細菌降低至無法 偵測到。而以45℃之熱酸性硫酸鋅、多保鏈黴 素、銅合浦、氧化亞銅、 銅快得寧等藥劑處理種薯40分鐘則部份種薯Erwinia屬軟腐細菌之 帶菌量 仍為104 ~ 105 cfu/g dry periderm；而當種薯Erwinia屬軟腐細菌浸菌 濃度為106 cfu/ml時，以45℃之銅鋅錳乃浦與多保鏈黴素處理種薯則大 部份種薯亦偵測不到Erwinia 屬軟腐細菌，且此些處理後之種薯其細菌 性軟腐病之發生率亦可明顯降低。偵測市售之栽培介質，並未發現 Erwinia屬軟腐細菌之存在；而於軟腐細菌之殘存試驗結果顯示低溫有助 於 Erwinia軟腐細菌在介質中之存活。於12℃時Erwinia屬軟腐細菌在發 泡煉石、南海蛭石、 珍珠石、深層火山岩、TKS-1 Instant及水苔等介 質中殘存可超過180天，而於南海蛭石與 珍珠石中更可達289天以上；而 於30℃時，軟腐細菌於各介質中之殘存則不超過50天。利用 抗生素抗性 突變菌株測試軟腐細菌於彩色海芋葉片上的殘存，結果顯示高溼環境有利 於 Erwinia屬軟腐細菌在葉片上殘存。於彩色海芋生長期間施用1％之 硝酸鈣溶液可提高植株 各部位鈣元素之含量。

A total of 37 strains of soft-rot Erwinia were isolated from the diseased plant tissues collected from colored calla lily grown fields. Based on the physiological and biochemical tests, they were all identified as Erwinia carotovora subsp. carotovora. The incidence of rhizome rot of colored calla lily caused by E. corotovora subsp. carotovora was greater in the rhizomes artificially wounded than those not artificially wounded. The soft rot incidenceof colored calla lily cultivar Best Gold inoculated with E. carotovora subsp. carotovora through the wounds just after flowers being plucked was 100 %, while the incidence of rotting decreased to 16.7 % when the inoculation was made 36 hours later. Rhizomes of colored calla lily obtained from various sources were detected for the soft-rot Erwinia, the results showed that 23.3 % ~ 84 % of rhizomes were contaminated with soft-rot Erwinia. The number of soft-rot Erwinia on rhizomes of colored calla lily after storage was detected on modofiedCVP selective medium. The results showed that soft-rot Erwinia on rhizomes with cured rotted lesions could reach to 104 ~ 106 cfu/g dry periderm. In green housetest, the soft rot incidence of colored calla lily grown from rhizomes with cured rotted lesions, rhizomes which rotted lesions were excised and symptomlessrhizomes was 86.7 %, 33.3 % and 6.7 %, respectively. Sensitivity of the 37 strains of E. carotovora subsp. carotovora. to commercial formulated agroche- micals was tested on nutrient agar plates. It was found that all the Erwinia carotovora subsp. carotovora strains tested were sensitive to basic copper sulfate + cufram Z (500X), copper oxychloride + manzeb + zinzeb (500X), cuprous oxide (500X), kasugamycin + copper oxychloride (1000X), oxine-copper + copper hydroxide (500X) and tribasic copper sulfate (500X). And with the exception of 1 ~ 3 strains, most strains tested were also sensitive to streptomycin + tetracycline (1000X), streptomycin sulfate (100 and 200 ppm) and thiophanate-methyl + streptomycin (1000X), while all the strains tested were resistant to mancozeb (400X), nonyphenol copper sulfonate (500X) and tecloftalam (1000X). Treatment of rhizomes with agrochemicals was able to reduce the population of E. carotovora subsp. carotovora on the rhzomes artificially infested. Chemical treatment of rhizomes at 45℃ were much better than that at 26℃ to reduce the population of E. carotovora subsp. carotovora onthe rhizomes. However, the effectiveness of chemical treatment varied among the rhizomes treated. Copper oxychloride + manzeb + zinzeb (500X) appeared to be the most effective among 11 agrochemicals tested to reduce the population of E. carotovora subsp. carotovora on the infested rhizomes. When the infested concentration of E. carotovora subsp. carotovora was at 108 cfu/ml, the number of E. carotovora subsp. carotovora on the infested rhizomes after treated with copper oxychloride + manzeb + zinzeb (500X) at 45℃ for 40 minutes could reduce to an undetected level. When the infested concentration of E. carotovora subsp. carotovora was at 106 cfu/ ml, the number of E. carotovora subsp. carotovora on most of the infested rhizomes after treated with both copper oxychloride + manzeb + zinzeb (500X) and thiophanate-methyl + streptomycin (1000X) could also reduce to an undetected level. In addition, soft rot incidence of both copper oxychloride + manzeb + zinzeb (500X) and thiophanate-methyl + streptomycin (1000X) treated rhizomes was much lower than that of untreated rhizomes. Among 11 commercial growing media examined, no soft-rot Erwinia was detected after enrichment in these media. Survival of E. carotovora subsp. carotovora in these growing media was studied, it was found that E. carotovora subsp. carotovora could survive much better in these media at low temperature (12℃) than at high temperature (30℃). E. carotovora subsp. carotovora was able to survive for over 180 days in vermiculite, perlite, Hydrocorn, TKS-1 Instant, volcano rock and sphagnum moss at 12℃, whereas they could only survive less than 50 days at 30℃. High humidity (RH 100 %) was favorable for E. carotovora subsp. carotovora to survive on the leaves of colored calla lily. In addition, application of 1 % of calcium nitrate solution to colored calla lily during the growing season could increase the calcium content of various parts of plants.