稻紋枯病菌菌核脫落之數量及其發芽試驗

Abstract

1. 本報告係調查稻紋枯病第一次發生有關之越冬菌核，脫落於田間之數量及比較田間採集之自然菌核與室內人工培養菌核之發芽力。 2. 菌核於割稻時，大部份脫落於田間，被害程度在28.5%之稻田，約每公頃有 200 萬個之菌核脫落，為次期作之第一次傳染源，越冬於土壤之菌核可能由於整地，中耕，除草等作業浮游於水面後附著葉鞘而感染。 3. 一般培養菌核之發芽力比自然菌核強，培養菌核於 1 天內即能達 100%之發芽率，自然菌核則需3天以上。 4. 水質與菌核之發芽，似無顯著差異，但對菌絲生長以雨水最優，水田水次之。自然菌核於苗床土壤上經三天未見發芽。 5. 不同碳素源及氮素原與菌核發芽之關係，自然菌核之發芽在不同碳素原中均比蒸餾水之對照處理為佳，但氮素原中 NH4HPO4。及 NaNo3 卻比對照差。 6. 藥劑稀釋溶液對菌核發芽之抑制作用，有機汞劑強於有機砷劑， Granosan 1.5ppm即能抑制自然菌核之發芽，培養菌核需達 6 ppm 才具抑制效果。 7.浮游於水面之菌核，其發芽力比附著菌核差。所以發病與菌核之附著，菌核附著與發芽均有密切關係。 1. The present paper deals with an estimation of the number of scierotia spontaneously dropped on the paddy field and difference in germination rate between natural and artificially cultured sclerotia in relation to water quality, nutrients and fungicidal chemicals. 2. In 28.5% diseased paddy field, approximately two millions of sclerotia per hectare were estimated to be dropped on the soil surface. The dropped sclerotia may serve as the primary inocula in the successive crop-season adhering on leaf- sheath through irrigation water. 3. In general, the germinability of cultured sclerotia was stronger than that of natural ones. The rate of germination in cultured ones reached to 100% within one day, while that of natural ones needed more than three days. 4. No distinct difference in effect of sclerotial germination for different kinds of water was found. However, rainwater was found to give more effect the growth of mycelia than the paddy field water. No germination of scierotia was observed within three days after the drop of sclerotia on the surface of paddy soil. 5. It was found that various carbon sotrces gave good effect to scierotia germination as compared to distilled water, while NH4HPO4 and NaNe3 solutions of nitrogen source gave bad effect. 6. The diluted fungicidal solution of organomercurials were found to give stronger inhibitory effect to sclerotia germination than organoarsenicals. Granosan which belong to the former could inhibit the germination of natural scierotia at 1.5 ppm concentration, however it needed 6 ppm concentration for artificially cultured ones. 7. As stated before the germinability of sclerotia. adhered on leaf-sheath was stronger than those of floating on water surface. From this fact it is known that there are close relation among outbreak of the disease and germination and adhere of sclerotia.