Markell S G, Francl L J
Department of Plant Pathology, University of Arkansas, Fayetteville 72701.
Department of Plant Pathology, The Pennsylvania State University, University Park 16802.
Plant Dis. 2003 Jul;87(7):814-820. doi: 10.1094/PDIS.2003.87.7.814.
The objectives of this study were to examine the relative abundance of Gibberella zeae ascospores and conidia and other Fusarium species on wheat spikes in a field environment, to relate inoculum counts of G. zeae to airborne spore counts, and to evaluate an inoculum bioassay technique. The inoculum levels of Fusarium species and airborne spores of G. zeae were measured in North Dakota during the 1999, 2000, and 2001 growing seasons. Spores were collected from wheat spikes in a 24-h potted-plant bioassay in a fallowed field and in a spring wheat plot bioassay. Inoculum levels of Fusarium species were assessed by placing a solution recovered from bioassays on selective medium; meanwhile, ascospores and conidia of G. zeae were enumerated microscopically. A Burkard cyclonic sampler measured airborne spore levels in the fallowed field. Wheat spikes were inoculated with known concentrations of conidia or ascospores, and rinsate was put on selective medium at different intervals to compare recovery rates. Known concentrations of both spore types were also applied directly to selective medium to compare with recovery of spore types from inoculated spikes. Fusarium graminearum was the most prevalent Fusarium species on wheat spikes, although F. moniliforme and F. poae counts were highest on some days. Approximately twice as many ascospores were recovered in both the 24-h potted-plant field bioassay and the cyclonic sampler as were conidia. Significantly more colonies were recovered from wheat spikes after conidial inoculation than after ascospore inoculation at an identical concentration regardless of time of rinsate collection. Colony numbers did not differ significantly following application of ascospores and conidia to selective medium. Results confirm the predominance of G. zeae inoculum in North America but indicate conidia play an important role in the primary disease cycle.
本研究的目的是检测田间环境下小麦穗上玉米赤霉的子囊孢子和分生孢子以及其他镰刀菌属物种的相对丰度，将玉米赤霉的接种体数量与空气中的孢子数量相关联，并评估一种接种体生物测定技术。在1999年、2000年和2001年生长季节期间，在北达科他州对镰刀菌属物种的接种体水平和玉米赤霉的空气传播孢子进行了测量。在休耕地的24小时盆栽生物测定和春小麦小区生物测定中，从小麦穗上收集孢子。通过将从生物测定中回收的溶液置于选择性培养基上来评估镰刀菌属物种的接种体水平；同时，通过显微镜对玉米赤霉的子囊孢子和分生孢子进行计数。使用伯卡德气旋采样器测量休耕地中的空气传播孢子水平。用已知浓度的分生孢子或子囊孢子接种小麦穗，并在不同时间间隔将冲洗液置于选择性培养基上以比较回收率。还将已知浓度的两种孢子类型直接应用于选择性培养基，以与从接种穗中回收的孢子类型进行比较。禾谷镰刀菌是小麦穗上最常见的镰刀菌属物种，尽管在某些日子里串珠镰刀菌和燕麦镰刀菌的数量最高。在24小时盆栽田间生物测定和气旋采样器中回收的子囊孢子数量大约是分生孢子的两倍。在相同浓度下，无论冲洗液收集时间如何，分生孢子接种后从小麦穗中回收的菌落明显多于子囊孢子接种后。将子囊孢子和分生孢子应用于选择性培养基后，菌落数量没有显著差异。结果证实了玉米赤霉接种体在北美的优势地位，但表明分生孢子在初次病害循环中起重要作用。
