Department of Botany and Zoology, Stellenbosch University, Stellenbosch, South Africa.
Planta. 2012 Dec;236(6):1677-85. doi: 10.1007/s00425-012-1727-6. Epub 2012 Aug 3.
The vast majority of flowering plants rely solely on insects for pollination. A number of pathogens have evolved mechanisms to exploit these close associations and use pollinators as vectors of infective propagules. Factors that affect pollinator movements and successful pollination may in turn also influence successful transmission of fungal spores. Here we investigate the effect of host density and the frequency of diseased Oxalis lanata individuals infected by the anther-smut fungus, Thecaphora capensis, on the likelihood of receiving pollen and fungal spores. Specifically, we determined the numbers of spores and pollen grains deposited on stigmatic surfaces of selected flowers under natural and standardized conditions where host density and disease frequency varied. The effect of host flower density and diseased flower frequency on pollen and spore transfer was variable under natural conditions and these factors interacted significantly. However, an increase in host density and disease frequency significantly influenced pollen and spore deposits under standardized conditions. The effect of host density was, however, not linear and an optimal flower density for pollen and fungal spore transmission was found. Similar to other systems of vector-borne disease, the transmission of anther-smut of Oxalis lanata is more frequency-dependent than density-dependent. This study represents a first step towards understanding the disease transmission process of T. capensis on Oxalis and lays the foundation for future comparative studies between this and other systems to develop and test general hypotheses of disease dynamics in vector-borne disease transmission systems.
绝大多数开花植物仅依靠昆虫来进行授粉。许多病原体已经进化出利用这些密切联系的机制，并利用传粉媒介作为感染性繁殖体的载体。影响传粉者运动和成功授粉的因素反过来也可能影响真菌孢子的成功传播。在这里，我们研究了宿主密度和受花药黑粉菌感染的 Oxalis lanata 个体的频率对接收花粉和真菌孢子的可能性的影响。具体来说，我们在自然条件和标准化条件下确定了选择花朵的柱头表面上沉积的孢子和花粉粒的数量，其中宿主密度和疾病频率有所不同。在自然条件下，宿主花密度和患病花频率对花粉和孢子转移的影响是可变的，并且这些因素相互作用非常显著。但是，在标准化条件下，宿主密度和疾病频率的增加会显著影响花粉和孢子的沉积。然而，宿主密度的影响并非线性的，并且发现了花粉和真菌孢子传输的最佳花密度。与其他载体传播疾病的系统类似，Oxalis lanata 的花药黑粉病的传播更依赖于频率，而不是密度。这项研究代表了理解 Oxalis 上 T. capensis 疾病传播过程的第一步，并为未来在该系统与其他系统之间进行比较研究奠定了基础，以开发和测试载体传播疾病系统中疾病动态的一般假设。
