Khan J, Rio L E Del, Nelson R, Rivera-Varas V, Secor G A, Khan M F R
Department of Plant Pathology, North Dakota State University, Fargo 58105.
North Dakota State University and University of Minnesota.
Plant Dis. 2008 May;92(5):741-745. doi: 10.1094/PDIS-92-5-0741.
Cercospora beticola survives as stromata in infected crop residue. Spores produced on these survival structures serve as primary inoculum during the next cropping season. This study was conducted to determine how long C. beticola can survive at different soil depths, the mechanism of inoculum dispersal, and the primary infection site in sugar beet. Longevity of C. beticola was studied over a 3-year period under field conditions at Fargo, ND. C. beticola-infected leaves were placed at depths of 0, 10, and 20 cm and retrieved after 10, 22, and 34 months. Survival of C. beticola inoculum declined with time and soil depth. Inoculum left on the soil surface, 0 cm in depth, survived the longest (22 months) compared with that buried at 10 cm (10 months) and 20 cm (10 months). C. beticola dispersal from the primary source of inoculum was studied in the field for three growing seasons. Sugar beet plants were surrounded with plastic cages with and without ground cover, or exposed with and without ground cover. Significantly higher disease severity was observed on exposed plants than caged plants with or without ground cover, suggesting that wind was the major dispersal factor for C. beticola inoculum. The primary infection site by C. beticola was determined in a greenhouse study. Leaves, roots, and stems of healthy sugar beet plants were inoculated with C. beticola. Cercospora leaf spot symptoms were observed only on plants that were leaf inoculated, suggesting that the leaf was the primary infection site for C. beticola.
甜菜尾孢菌以菌核的形式在受感染的作物残体中存活。在这些存活结构上产生的孢子在下一个种植季节作为初侵染接种体。本研究旨在确定甜菜尾孢菌在不同土壤深度下能存活多长时间、接种体传播机制以及甜菜的主要感染部位。在北达科他州法戈的田间条件下，对甜菜尾孢菌的存活期进行了为期3年的研究。将感染了甜菜尾孢菌的叶片放置在0、10和20厘米的深度，在10、22和34个月后取回。甜菜尾孢菌接种体的存活率随时间和土壤深度而下降。留在土壤表面（0厘米深度）的接种体存活时间最长（22个月），而埋在10厘米（10个月）和20厘米（10个月）深度的接种体存活时间较短。在田间三个生长季节研究了甜菜尾孢菌从初侵染接种体源的传播情况。甜菜植株被放置在有或没有地面覆盖物的塑料笼中，或者暴露在有或没有地面覆盖物的环境中。观察到暴露植株上的病情严重程度明显高于有或没有地面覆盖物的笼中植株，这表明风是甜菜尾孢菌接种体的主要传播因素。在温室研究中确定了甜菜尾孢菌的主要感染部位。用甜菜尾孢菌接种健康甜菜植株的叶片、根和茎。仅在接种叶片的植株上观察到尾孢叶斑症状，这表明叶片是甜菜尾孢菌的主要感染部位。
