Geometric morphometry of Phytophthora plurivora sporangia

Abstract

Eigenshape analysis and Relative Warp Analysis were employed in the study of the shape of highly variable sporangia of Phytophthora plurivora, a widespread oomycetous pathogen isolated from woody species, in several South-East European countries: Bulgaria, Greece, Serbia and Romania. The aim of the study was to estimate whether shape variables permitted the quantitative assessment of sporangial shape variability in P. plurivora and also, the discrimination between species based solely on sporangial shape, P. cactorum being selected for comparisons. Both Eigenshape and Relative Warp Analyses showed that the most variable sporangial areas were apical and basal regions. More than half of the shape variation was accounted for the first 2 ES axes (66.75%) and first two RW axes (61.74%). ESA performed better in terms of species shape (P. plurivora and P. cactorum) separation. Canonical Variate Analysis/MANOVA and Discriminant Analysis indicated the clear discrimination between species and between isolates of P. plurivora. Mean or consensus shape performed as the best shape descriptor of sporangia. High dimensional variation considered in terms of centroid size corroborated with shape variation spanning from symmetrical consensus shape to conspicuously asymmetric shapes.

Keywords

• phytophthora plurivora, phytophthora cactorum, geometric morphometry, eigenshape analysis, relative warp analysis, canonical variate analysis, discriminant analysis, discrepancy index