Phytopathology. 2005 Jul;95(7):751-8. doi: 10.1094/PHYTO-95-0751.
ABSTRACT The early infection and colonization processes of Colletotrichum acutatum on leaves and petals of two almond cultivars with different susceptibility to anthracnose (i.e., cvs. Carmel and Nonpareil) were examined using digital image analysis of light micrographs and histological techniques. Inoculated tissue surfaces were evaluated at selected times after inoculation and incubation at 20 degrees C. Depth maps and line profiles of the digital image analysis allowed rapid depth quantification of fungal colonization in numerous tissue samples. The results showed that the early development of C. acutatum on petals was different from that on leaf tissue. On petals, conidia germinated more rapidly, germ tubes were longer, and fewer appressoria developed than on leaves. On both tissues, penetration by the pathogen occurred from appressoria and host colonization was first subcuticular and then intracellular. On petals, colonizing hyphae were first observed 24 h after inoculation and incubation at 20 degrees C, whereas on leaves they were seen 48 to 72 h after inoculation. Intercellular hyphae were formed before host cells became necrotic and macroscopic lesions developed on petals >/=48 h and on leaves >/=96 h after inoculation. Histological studies complemented data obtained by digital image analysis and showed that the fungus produced infection vesicles and broad hyphae below the cuticle and in epidermal cells. In both tissues, during the first 24 to 48 h after penetration fungal colonization was biotrophic based on the presence of healthy host cells adjacent to fungal hyphae. Later, during intercellular growth, the host-pathogen interaction became necrotrophic with collapsed host cells. Quantitative differences in appressorium formation and host colonization were found between the two almond cultivars studied. Thus, on the less susceptible cv. Nonpareil fewer appressoria developed and host colonization was reduced compared with that on cv. Carmel.
摘要 使用数字图像分析和组织学技术，研究了不同炭疽病易感性的两个巴旦杏品种（即 Carmel 和 Nonpareil）叶片和花瓣上炭疽菌（Colletotrichum acutatum）的早期感染和定殖过程。在 20°C 接种和孵育后，选择时间评估接种组织表面。数字图像分析的深度图和线轮廓允许快速定量分析大量组织样本中的真菌定殖深度。结果表明，炭疽菌在花瓣上的早期发育与叶片组织上的不同。在花瓣上，孢子萌发更快，芽管更长，产生的附着胞较少。在两种组织上，病原体都是通过附着胞穿透，定殖最初是在表皮下，然后是细胞内。在花瓣上，接种后 20°C 孵育 24 小时后首次观察到定殖菌丝，而在叶片上则在接种后 48 至 72 小时后观察到。在花瓣上，接种后 >/=48 小时和叶片上 >/=96 小时，细胞间菌丝形成前，宿主细胞发生坏死并出现宏观病变。组织学研究补充了数字图像分析获得的数据，并表明真菌在表皮下和表皮细胞中产生感染泡和宽菌丝。在两种组织中，在穿透后 24 至 48 小时内，由于与真菌菌丝相邻的健康宿主细胞的存在，真菌定殖是生物营养的。随后，在细胞间生长过程中，随着宿主细胞的坍塌，宿主-病原体相互作用变成了坏死营养型。在研究的两个巴旦杏品种之间发现了附着胞形成和宿主定殖的定量差异。因此，在较不易感的 Nonpareil 品种上，与 Carmel 品种相比，附着胞的形成较少，宿主的定殖也减少。
