Cryptic Species Diversity and Phylogenetic Relationship in the Rust Genus Chrysomyxa from China.

Clement K. M. Tsui,Rui Wang,Chongjuan You

doi:10.3390/jof8010083

Abstract

Chrysomyxa rusts are fungal pathogens widely distributed in the Northern hemisphere, causing spruce needle and cone rust diseases, and they are responsible for significant economic losses in China. Taxonomic delimitation and precise species identification are difficult within this genus because some characters often overlap in several species. Adequate species delimitation, enhanced by the use of DNA-based methodologies, will help to establish well-supported species boundaries and enable the identification of cryptic species. Here, we explore the cryptic species diversity in the rust genus Chrysomyxa from China. Species delimitation analyses are conducted using a distance-based method (ABGD) and three tree-based methods (GMYC, bPTP, and mPTP) based on combined LSU and ITS sequences of over 60 specimens. Although there is some incongruence among species delimitation methods, two new species and three putative cryptic species are identified. The key to 20 Chrysomyxa species distributed in China is presented. These results suggest that a significant level of undiscovered cryptic diversity is likely to be found in Chrysomyxa from China. Future studies should consider multiple analytical methods when dealing with multi-locus datasets.

Highlights

IntroductionRust fungi (Pucciniomycotina, Pucciniales) are some of the most important plant pathogens that cause devastating diseases of agricultural crops and forests
Academic Editor: Philippe SilarRust fungi (Pucciniomycotina, Pucciniales) are some of the most important plant pathogens that cause devastating diseases of agricultural crops and forests
The results showed that the index of substitution saturation (Iss) was less than the critical index of substitution saturation assuming a symmetrical topology

Summary

Introduction

Rust fungi (Pucciniomycotina, Pucciniales) are some of the most important plant pathogens that cause devastating diseases of agricultural crops and forests. Rust fungi have complex and variable life cycles that include up to five different spore stages (spermatia, aeciospores, urediniospores, teliospores, and basidiospores) on a single host or two unrelated hosts [4]. Rust taxonomy has traditionally been based on a combination of host specificities and morphological traits of certain spore stages, which are potentially plastic [5,6,7]. Several studies have uncovered a great number of rust species complexes and cryptic species. Similar patterns of cryptic speciation have been in the rust species Endoraecium digitatum and Dasyspora gregaria [9,10,11]

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Conclusion