Murillo-Williams A, Munkvold G P
Centro para Investigaciones en Granos y Semillas, Universidad de Costa Rica, San José, Costa Rica.
Seed Science Center and Department of Plant Pathology, Iowa State University, Ames, IA 50011.
Plant Dis. 2008 Dec;92(12):1695-1700. doi: 10.1094/PDIS-92-12-1695.
Fusarium verticillioides causes seedling decay, stalk rot, ear rot, and mycotoxin contamination (primarily fumonisins) in maize. Systemic infection of maize plants by F. verticillioides can lead to kernel infection, but the frequency of this phenomenon has varied widely among experiments. Variation in the incidence of systemic infection has been attributed to environmental factors. In order to better understand the influence of environment, we investigated the effect of temperature on systemic development of F. verticillioides during vegetative and reproductive stages of plant development. Maize seeds were inoculated with a green fluorescent protein-expressing strain of F. verticillioides, and grown in growth chambers under three different temperature regimes. In the vegetative-stage and reproductive-stage experiments, plants were evaluated at tasseling (VT stage), and at physiological maturity (R6 stage), respectively. Independently of the temperature treatment, F. verticillioides was reisolated from nearly 100% of belowground plant tissues. Frequency of reisolation of the inoculated strain declined acropetally in aboveground internodes at all temperature regimes. At VT, the high-temperature treatment had the highest systemic development of F. verticillioides in aboveground tissues. At R6, incidence of systemic infection was greater at both the high- and low-temperature regimes than at the average-temperature regime. F. verticillioides was isolated from higher internodes in plants at R6, compared to stage VT. The seed-inoculated strain was recovered from kernels of mature plants, although incidence of kernel infection did not differ significantly among treatments. During the vegetative growth stages, temperature had a significant effect on systemic development of F. verticillioides in stalks. At R6, the fungus reached higher internodes in the high-temperature treatment, but temperature did not have an effect on the incidence of kernels (either symptomatic or asymptomatic) or ear peduncles infected with the inoculated strain. These results support the role of high temperatures in promoting systemic infection of maize by F. verticillioides, but plant-to-seed transmission may be limited by other environmental factors that interact with temperature during the reproductive stages.
轮枝镰孢菌可引发玉米的幼苗腐烂、茎腐病、穗腐病以及霉菌毒素污染（主要是伏马毒素）。轮枝镰孢菌对玉米植株的系统感染会导致籽粒感染，但在不同实验中，这种现象出现的频率差异很大。系统感染发生率的变化被归因于环境因素。为了更好地理解环境的影响，我们研究了温度对轮枝镰孢菌在植物营养生长和生殖生长阶段系统发育的作用。用表达绿色荧光蛋白的轮枝镰孢菌菌株接种玉米种子，并在三种不同温度条件下的生长室中培养。在营养生长阶段和生殖生长阶段的实验中，分别在抽雄期（VT期）和生理成熟期（R6期）对植株进行评估。无论温度处理如何，在近100%的地下植物组织中都能重新分离出轮枝镰孢菌。在所有温度条件下，接种菌株在地上节间的重新分离频率从下向上递减。在VT期，高温处理使轮枝镰孢菌在地上组织中的系统发育程度最高。在R6期，高温和低温条件下的系统感染发生率均高于平均温度条件下的。与VT期相比，在R6期的植株中，轮枝镰孢菌可从更高的节间分离得到。虽然各处理间籽粒感染发生率无显著差异，但在成熟植株的籽粒中可重新分离出接种菌株。在营养生长阶段，温度对轮枝镰孢菌在茎中的系统发育有显著影响。在R6期，高温处理下真菌可到达更高的节间，但温度对接种菌株感染的籽粒（有症状或无症状）或穗柄的发生率没有影响。这些结果支持高温在促进轮枝镰孢菌对玉米的系统感染中所起的作用，但在生殖阶段，植株到种子的传播可能受到与温度相互作用的其他环境因素的限制。
