沙打旺种带真菌——环境、致病力及防治

Seed-borne Fungi of Astragalus adsurgens——Environment, Pathogenicity and Control

对来自江苏、内蒙古、河南和河北等四省（区）的沙打旺（ＡｓｔｒａｇａｌｕｓａｄｓｕｒｇｅｎｓＰａｌ．）种子进行了健康检验；测定了细交链孢〔Ａｌｔｅｒｎａｒｉａａｌｔｅｒｎａｔａ（Ｆｒ．）Ｋｅｉｓ１．〕和多主枝孢〔Ｃｌａｄｏｓｐｏｒｉｕｍｈｅｒｂａｒｕｍ（Ｐｅｒｓ）Ｌｉｎｋ．〕对沙打旺种子和幼苗的致病力；评价了甲基托布津浸种和菲醌拌种防治沙打旺种带真菌的效果。结果表明，种子产地９～１１月的湿润度（Ｋ）与种子带菌率显著正相关，ｒ２＝０．９８７（Ｐ＜０．０１），二者的关系可用ｙ＝－１７．０＋２７．３ｘ表示；种子带菌率和混杂于种子间的植株残体带菌率分别与种子发芽率呈显著负相关，ｒ２分别为０．９８７（Ｐ＜０．０１）和０．９３１（Ｐ＜０．０５）。人工侵染试验与相关分析的结果表明，细交链孢是沙打旺种子和幼苗的主要病原菌，接种处理的种子发芽率为４１．８％，苗腐率为１５．８％，而未接种对照组的相应数值是７８．８％和０．０；多主枝孢对种子发芽无显著影响，但可引致４．５％的幼苗腐烂（Ｐ＜０．０５），该菌是沙打旺种子和幼苗的较重要的病原真菌。甲基托布津浸种和菲醌拌种均可显著降低种子带菌率，与对照相比，总带菌率降低６２．３％～７８．７?

Milkvetch (Astragalus adsurgens Pall.) seeds produced in the provinces of Jiangsu, Henan, Hebei and Inner Mongolia Autonomous Region were tested for seed-borne fungi. Pathogencity tests were carried out in laboratory to study the role of Alternaria alternata (Fr.) Keissl. and Cladosporium herbarum (Pers.) Link. in seed germination and seedling growth of milkvetch. Effects of thiophanate-methyl and phenanthraquinone seed treatments on seed-borne fungi and seed germination were evaluated. The results showed that percentage of number of seeds yielding fungi was correlated positively with Ren and Hu’s moisture index (K) calculated from local accumulated temperature and rainfall during the period of September to November, and could be expressed as Y=-17.0+27.3X, r 2=0.987 (P<0.01). Seed germination was correlated negatively with percentages of number of seeds yielding fungi and of plant debris yielding fungi, r 2=0.987 (P<0.01) and 0.931 (P< 0.05), respectively. Pathogenicity tests showed that A. alternata is an important pathogen of milkvetch seed and seedling. Percentages of germination and seedling rot of inoculated seeds were 41.8% and 15.8%, while the corresponding numbers from uninoculated control were 78.8% and 0.0, respectively. Cl. herbarum did not affect seed germination, but it caused 4.5% seedling rot (P<0.05), so it should be considered as a pathogen of milkvetch seed and seedling. Soaking seeds in suspension containing 0.3% active ingredient of thiophanate-methyl or dusting seeds with phenanthraquinone at 3 g a.i. per kg seeds were both effective in reducing seed infection. Compared with untreated control, the treatments reduced the percentage of total number of seed infection or contamination by 62.3% to 78.7%, A. alternata by 46.1% to 61.5% and Cl. herbarum by 38.1% to 100%, respectively.