Historical Differentiation and Recent Hybridization in Natural Populations of the Nematode-Trapping Fungus Arthrobotrys oligospora in China.

Duanyong Zhou,Jianping Xu,Haixia Li,Jianyong Dong,Da Wang,Juan Gu,Ke-Qin Zhang,Ying Zhang

doi:10.3390/microorganisms9091919

Abstract

Maintaining the effects of nematode-trapping fungi (NTF) agents in order to control plant-parasitic nematodes (PPNs) in different ecological environments has been a major challenge in biological control applications. To achieve such an objective, it is important to understand how populations of the biocontrol agent NTF are geographically and ecologically structured. A previous study reported evidence for ecological adaptation in the model NTF species Arthrobotrys oligospora. However, their large-scale geographic structure, patterns of gene flow, their potential phenotypic diversification, and host specialization remain largely unknown. In this study, we developed a new panel of 20 polymorphic short tandem repeat (STR) markers and analyzed 239 isolates of A. oligospora from 19 geographic populations in China. In addition, DNA sequences at six nuclear gene loci and strain mating types (MAT) were obtained for these strains. Our analyses suggest historical divergence within the A. oligospora population in China. The genetically differentiated populations also showed phenotypic differences that may be related to their ecological adaptations. Interestingly, our analyses identified evidence for recent dispersion and hybridization among the historically subdivided geographic populations in nature. Together, our results indicate a changing population structure of A. oligospora in China and that care must be taken in selecting the appropriate strains as biocontrol agents that can effectively reproduce in agriculture soil while maintaining their nematode-trapping ability.

Highlights

Plant-parasitic nematodes (PPNs), especially the root-knot nematodes in the genusMeloidogyne, are widespread pests that cause crop yield losses worth more than US $157 billion worldwide each year [1]
The 20 short tandem repeat (STR) markers we developed for A. oligospora were found to have a moderate to high level of polymorphism, with 13 having high polymorphism, six having medium polymorphism, and only one having a low polymorphism information content (PIC) value (Table 2)
Our results indicated some morphological differentiation among the clades within A. oligospora strains from China

Summary

Introduction

Plant-parasitic nematodes (PPNs), especially the root-knot nematodes in the genusMeloidogyne, are widespread pests that cause crop yield losses worth more than US $157 billion worldwide each year [1]. Plant-parasitic nematodes (PPNs), especially the root-knot nematodes in the genus. The control of Meloidogyne spp. has heavily relied on chemical nematicides. Currently available chemical nematicides are being phased out, and an increasing number of biocontrol agents are being introduced to help control PPNs [3]. About 700 fungal species are known to be capable of attacking living nematodes (juveniles, adults, and eggs). These fungi are taxonomically diverse but traditionally divided into five groups based on the mechanisms by which they attack nematodes: Microorganisms 2021, 9, 1919.

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Results

Conclusion