Abstract
Knowledge of population dynamics of mating types is important for better understanding pathogen’s evolutionary potential and sustainable management of natural and chemical resources such as host resistances and fungicides. In this study, 2250 Phytophthora infestans isolates sampled from 61 fields across China were assayed for spatiotemporal dynamics of mating type frequency. Self-fertile isolates dominated in ~50% of populations and all but one cropping region with an average frequency of 0.64 while no A2 isolates were detected. Analyses of 140 genotypes consisting of 82 self-fertile and 58 A1 isolates indicated that on average self-fertile isolates grew faster, demonstrated higher aggressiveness and were more tolerant to fungicides than A1 isolates; Furthermore, pattern of association between virulence complexity (defined as the number of differential cultivars on which an isolate can induce disease) and frequency was different in the two mating types. In A1 isolates, virulence complexity was negatively correlated (r = −0.515, p = 0.043) with frequency but this correlation was positive (r = 0.532, p = 0.037) in self-fertile isolates. Our results indicate a quick increase of self-fertile isolates possibly attributable to their higher fitness relative to A1 mating type counterpart in the field populations of P. infestans in China.
Highlights
Processes such as aggressiveness, mycelium growth and maintenance of cell wall integrity[8,9,10]
The mating type of P. infestans isolates collected from 15 provinces in China (Table 1) was determined in vitro by pairing individual isolates with reference testers on rye B media
Substantial research has been conducted to quantify the spatiotemporal distribution of mating types in P. infestans with the ultimate goals of understanding the evolutionary potential and trajectory of the pathogen[15,24,25,26] and to Mating type Self-fertile A1 Difference T-values P-values azoxystrobin iprovalicarb
Summary
Processes such as aggressiveness, mycelium growth and maintenance of cell wall integrity[8,9,10]. The occurrence and severity of potato late blight in China has intensified, possibly associated with the emergence of new physiological races able to overcome the main commercial cultivars currently in use, and the invasion of a novel mating type[15] that has increased the evolutionary potential of the pathogen. Self-fertile isolates have existed at low frequency in nature for a long time[20] but recent surveys indicate that they have emerged as a primary mating type in some parts of the world[19,21,22,23]. The objectives of this study were to redress this omission by: 1) studying the spatial distribution of mating types in P. infestans populations in China; and 2) determining the mechanisms driving changes in mating type frequency by comparing their life history traits– aggressiveness, in vitro growth rate and tolerance to some commercial fungicides
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