闽西北桃小叶症病因诊断与区域性骤发诱因

2003—2005年闽西北桃产区大范围骤发"桃小叶症",典型症状为春梢展叶期叶片不能正常伸展,病叶狭小细长,呈丛生莲座状、花萎无果,各主栽品种均同时受害。经研究该病嫁接不传染,且经2年20个重复的发病果园病株叶片分析,含B≤9.71mg/kg,远低于适宜值下限20mg/kg,结合生殖障碍等形态症状与施B矫治疗效,诊断"桃小叶症"为重度缺B症。再则,根据萌芽期2月至翌年4月发病期各时段雨量与次年发病率的滑动相关分析还表明,中亚热带季风红壤缺B≤0.45mg/kg地区,桃生长季2月中旬—9月上旬的严重干旱是引发翌年桃小叶症区域性骤发的诱因,而非发病季当年春季的降水不足;同时由同类土壤的模拟干旱试验还表明,高温、干旱并不导致同类土壤热水溶性B明显下降,干旱对桃B吸收障碍另有原因。还就桃小叶症矫治提出相应措施。

Diagnosis of small leaf symptom of peach in Northwestern Fujian province and factors inducing the regional outbreak of this symptom

The small leaf symptom of peach was regional outbroken in north western part of Fujian province between 2003-2005. The typical symptom of diseased plants have small leaves, rosette leaves, atrophic flowers and no fruit. All the peach cultivals suffered from this disease. By means of graft transmission and nutritional diagnosis, the results showed that small leaf disease of peach can not infect by graft transmission; leaf nutritional diagnosis showed that B in diseased plants was ≤9.71 mg/kg, far below the limit of diagnosis of standard 20 mg/kg (significant at P≤0.0001). Considering the reproductive barrier symptom in diseased plants and curative effect of B, it has been proved to be a physiological disorder caused by severe B deficiency. The results of slide correlation between different period precipitation (from February to April in next year) and incidence of disease showed that extreme drought in peach growing seasons was the reason inducing the outbreak in the red soil region with subtropical monsoon climate where the B content in the soil was low (B ≤0.45 mg/kg); the reason caused the incidence of this disease was also due to not enough of rainfall in spring the same year. The results of the simulate drought examination showed that high temperature and drought did not knock down the validity of B in the same type of soil, this indicated that some unknown factors affect B absorbability in drought season. Based on the research the remedy measures of the disease are put forward.