水稻恶苗病苗性状变化及对产量的影响

CHANGE IN TRAIT OF BAKANAE DISEASE INFECTED LEGGY RICE SEEDLINGS AND ITS INFLUENCE ON RICE YIELD

水稻恶苗病徒长苗有 3个显病高峰 :稻苗 3叶期、拔节初期、破口初期 ;徒长苗又有明显的症状隐蔽现象。症状隐蔽始于秧龄 13d时 ,高峰发生于水稻分蘖盛期 :武育粳 5号与寒优10 2 7分蘖盛期的症状隐蔽率分别达 92 .6% ,89.7%。部分症状隐蔽病苗又会重新转化为徒长苗 ,其转化高峰发生于水稻拔节初期、破口初期。未出现症状隐蔽的徒长苗及移栽 15 d后出现症状隐蔽的徒长苗均在水稻抽穗前陆续死去 ,部分栽后 15 d内进入症状隐蔽状态的徒长苗可以成穗。适时施肥 ,尤其是增施有机肥料 ,能明显提高病苗成穗率 。

Bakanae disease infected leggy rice seedlings in our experiment in 1998 showed three symptom display peaks in total at three leaf seedling stage, early jointing stage and early earing stage. The leggy rice seedlings showed also an obvious phenomenon of symptom hiding. The symptom hiding began at the 13 days age of seedlings and attained to a peak at full tillering stage when the symptom hiding rates of Wuyujing No.5 and Hanyou 1027 seedlings were 92.6% and 89.7% respectively. A part of hidden symptom seedlings might retransform into leggy seedlings, the transformation peaks occurred at early jointing stage and early earing stage. The leggy seedlings which did not show symptom hiding and which showed symptom hiding 15 days after transplant died all successively before early earing. A part of leggy seedlings which entered into symptom hiding state within 15 days could form ears. Opportunely applying fertilizer, especially applying supplementary organic fertilizer, will increase obviously the ear formation rate of diseased plants and decrease the yield loss.