- 作者: 孫守恭
- 作者服務機構: 國立中興大學
- 中文摘要:
徒長病在秧田中最普遍,但多數病株在插秧時即行死亡。插秧後在本田中重新被感染
者,約一個月後始現徒長病徵,再3-4週後,病株節處有白色菌絲及少量小型分生胞子
。插秧後5-6週,病株下部莖上出現灰白色菌絲,同時小型分生胞子增多,病株開始萎
黃,上部逐漸死亡,莖基部菌絲變黑灰色至藍黑色,上部菌絲增多,此時大型分生胞子出
現(同時亦有小分生胞子),莖基部有黑色小點生出,此乃子囊穀,收穫前十日左右,子
囊胞子成熟,開始放射。但少數早期罹病株,子囊胞子於水稻孕穗期即行釋放。
以Hirst氏胞子採集器安裝於稻田中收集子囊胞子,得知子囊胞子於午夜後開始放射
,日出後停止“但如落雨,雨後即行放射“由田間採集稻種,置於PCNB培養基上,100彫
出現徒長病菌(Fu}arium moniliforme)之菌落。以無菌水洗稻種,將水洗物滴於PCNB
培養基上,亦有許多徒長病菌之菌落。鏡檢亦證明水洗物中有子囊胞子,故稻種上有徒長
病菌附著。
稻株地上部如葉片,葉腋及莖是否可被Fusarium moniliforme侵入引起病害,乃頗饒
興趣而尚未明瞭之問題。經多次接種試驗,得知除根尖、發芽之種子及莖基部外,其餘各
部均不能被侵入惑染。
當徒長病發生期中,分生胞子及子囊胞子常常被雨水?至土中,病株及殘莖亦時被耕
入田土中,故稻田土中有Fusarium moniliforme存在,其存活期間約為3-4個月。試
驗證明,如每克土中有5個胞子,即可引起徒長病,病原濃度增加,病害亦隨之增多。如
增至每克土中胞子為4.8 x 10,則發病率達至80%左右。臺灣兩期稻作相隔1-2個月,
故土中之徒長病菌存活數量,足可侵入稻苗引起病害。
由以上研究結果,吾人可知稻種帶有子囊胞子及分生胞子,引起秧田徒長病。健株移
至田間,田中之存活菌侵入稻苗引起徒長病。本菌為異絲生殖,在臺灣(卜)(一)菌系
同時存在,故在病株上形成子囊胞子,具有完整之生活史。
i - 英文摘要: Bakanae disease is very common in rice seedling beds, but most diseasedseedlings die during transplanting. Infection takes place again in fieldfrom soil. Infected plants show bakanae symptoms about one month aftertransplanting. 3-4 weeks later after bakanae symptoms showing up, thereappears mycelium mass on stem nodes of lower portion of stem. 35-45 daysafter bakanae symptom, the lower portion of the stem is covered withmycelium and microconidia. 55-65 days later, there appears macroconidiaand the lower part of the stem becomes dark to dark-blue in color. Black,spherical bodies, the perithecia, begin to form among mycelium matrix on thesurface of the stem. Most perithecia mature about 7-10 days before harvest-ing, but for some earlier diseased plants, perithecia matured during theheading stage of rice plants. Ascospores discharge after midnight. If there is rainfall, spores liberateafter rain. Since ascospores are air-borne, seeds are easily contaminatedwith them. Experiments showed that only seeds, roots, and stem base could be infe-cted, the above-ground parts of the rice plants were resistant to infection.Diseased plants and stubs are usually abandoned in paddy field, conidia andperithecia or spores are eventually washed off into soil by rain, so paddysoil is the reservoir of the fungal propagules. Experiment showed that 5spores per gram of soil is capable to cause infection. Although the fungussurvives not long in soil, it is active enough to cause infection to the nextcrops under the environmontal conditions in Taiwan.
- 中文關鍵字: --
- 英文關鍵字: --