Infection and colonization of triticale by Puccinia graminis f. sp. tritici

Histological investigations elucidate infection structure development and the subsequent colonization process of rust pathogens in their cereal hosts. No comprehensive information exists for the infection process of the wheat stem rust fungus, Puccinia graminis f. sp. tritici (Pgt), on triticale, an amphiploid species carrying both the wheat and rye genomes. The adult plant stem rust response of the triticale cultivars ‘Kiewiet’, ‘Coorong’ and ‘Satu’ and the bread wheat control, Line 37–07, was determined under controlled conditions using Pgt pathotypes UVPgt56, UVPgt60 and UVPgt62. Flag leaf sheaths were sampled 24 and 48 h post-inoculation (hpi) for scanning electron microscopy (SEM), 120 hpi for fluorescence microscopy, and 16 days post-inoculation for a fungal biomass assay. Although slight differences were observed between the epidermal morphology of triticale and wheat stem sheaths, SEM results indicated that this did not influence early infection by Pgt. Fluorescence microscopy revealed that colony size was affected by both host genotype and pathotype. Colony size strongly corresponded with fungal biomass accumulation, except in ‘Kiewiet’, where fungal growth was not restricted to the same degree as in other incompatible interactions. This study shows that methods commonly used for studying histopathology of Pgt in wheat are equally applicable to triticale.

组织学研究阐明了锈菌在谷类宿主中的侵染结构发育及后续定殖过程。目前尚无关于小麦茎锈菌（*Puccinia graminis* f. sp. *tritici*，Pgt）在小黑麦——一种同时携带小麦与黑麦基因组的异源多倍体物种——上的侵染过程的全面研究数据。本研究在可控环境下，利用Pgt生理小种UVPgt56、UVPgt60与UVPgt62，测定了小黑麦品种'Kiewiet'、'Coorong'、'Satu'以及面包小麦对照品系37–07的成株茎锈病抗性反应。分别于接种后24小时、48小时（hpi）采集旗叶鞘用于扫描电子显微镜（SEM）观察，于接种后120小时（hpi）采集用于荧光显微镜观察，并于接种后16天采集样本用于真菌生物量测定。尽管观测到小黑麦与小麦茎鞘的表皮形态存在细微差异，但扫描电镜结果显示，该差异并未影响Pgt的早期侵染。荧光显微镜观测结果表明，菌落大小同时受宿主基因型与生理小种影响。菌落大小与真菌生物量积累高度相关，但'Kiewiet'是例外——其真菌生长的受抑制程度并未与其他不亲和互作体系保持一致。本研究证实，以往用于小麦中Pgt组织病理学研究的常规方法，同样适用于小黑麦相关研究。