Francl L, Shaner G, Bergstrom G, Gilbert J, Pedersen W, Dill-Macky R, Sweets L, Corwin B, Jin Y, Gallenberg D, Wiersma J
North Dakota State University, Fargo.
Purdue University, West Lafayette, IN.
Plant Dis. 1999 Jul;83(7):662-666. doi: 10.1094/PDIS.1999.83.7.662.
The inoculum level of Gibberella zeae on wheat spikes was measured during 1995 and 1996 in nine locations of Canada and the United States prone to Fusarium head blight of wheat. Spikes were exposed after exsertion and until kernel milk or soft dough stage in fields with wheat or corn residue as a source of inoculum; other spikes were exposed in a location remote from any obvious inoculum source; and in 1995 only, control plants remained in a greenhouse. After 24 h, spikes were excised and vigorously shaken in water to remove inoculum. Propagules were enumerated on selective medium and identified as G. zeae from subcultures. Significantly more inoculum was detected from fields in epidemic areas than from remote sites in an epidemic and from fields in nonepidemic areas. The median inoculum level was 20 CFU of G. zeae per spike per day in fields experiencing an epidemic, 4 CFU in locations remote from epidemic fields, 2 CFU in nonepidemic fields, and 1 CFU in locations remote from a source of inoculum in non-epidemic areas. In an epidemic region, inoculum levels near corn stubble reached up to 587 CFU of G. zeae per spike per day, and the median inoculum level of 126 CFU was significantly higher than the median of 13 CFU found near wheat residue. Inoculum was not detected or occurred sporadically during extended dry periods. While inoculum increased during rainy periods, timing of increased levels was variable. Fusarium head blight epidemics were associated with multiple inoculation episodes and coincident wet periods.
1995年至1996年期间，在加拿大和美国九个易发生小麦赤霉病的地点，对小麦穗上的玉米赤霉病菌接种量进行了测定。在有小麦或玉米残茬作为接种源的田块中，穗在抽出后暴露，直至籽粒灌浆期或软面团期；其他穗在远离任何明显接种源的地点暴露；仅在1995年，对照植株留在温室中。24小时后，剪下穗并在水中剧烈摇晃以去除接种物。在选择性培养基上对繁殖体进行计数，并从继代培养物中鉴定为玉米赤霉病菌。与流行地区的偏远地点以及非流行地区的田块相比，流行地区田块中检测到的接种物明显更多。在发生疫情的田块中，玉米赤霉病菌的接种量中位数为每穗每天20 CFU，在远离流行田块的地点为4 CFU，在非流行田块为2 CFU，在非流行地区远离接种源的地点为1 CFU。在一个流行地区，靠近玉米茬的接种量高达每穗每天587 CFU玉米赤霉病菌，中位数126 CFU明显高于在小麦残茬附近发现的中位数13 CFU。在长时间干旱期间未检测到接种物或偶尔出现接种物。虽然接种物在雨季增加，但增加水平的时间各不相同。小麦赤霉病流行与多次接种事件和同时出现的潮湿期有关。
