A Trade-Off Between Sporangia Size and Number Exists in the Potato Late Blight Pathogen Phytophthora infestans, and Is Not Altered by Biotic and Abiotic Factors.

Nicolas Mariette,Romain Mabon,Roselyne Corbière,Annabelle Androdias,Didier Andrivon,Alexander Kröner,Bruno Marquer,Josselin Montarry

doi:10.3389/fpls.2018.01841

Abstract

The negative relationship between offspring size and number is a classic example of trade-off between life-history traits, reported many times in animal and plant species. Here, we wanted to ascertain whether such a trade-off occurred in the oomycete Phytophthora infestans, and whether it was impacted by biotic and abiotic factors. We thus conducted three infection experiments under controlled conditions and measured the number and the size of sporangia (asexual propagules) produced on potato by different P. infestans isolates. In all experiments, we observed a negative relationship between sporangia size and number, demonstrating the existence of a trade-off. Moreover, although the potato host cultivar, temperature and host of origin (tomato or potato) all affected sporangia number, sporangia size or both, none of these biotic and abiotic factors did change the trade-off. Therefore, the trade-off between sporangia size and number could maintain the polyphenism for these traits in P. infestans populations, and favors the coexistence of distinct reproductive strategies within this species. Our results emphasize the relevance to focus on the relationship between offspring size and number in other fungal plant pathogens, as well as to study the impact of offspring size on fitness-linked traits (virulence and disease lesion development) in these organisms.

Highlights

The widely accepted trade-off concept states that an organism cannot simultaneously maximize all traits involved in fitness, owing to dilemmas in resource allocation (Law, 1979)
In experiment 1, potato cultivar had a significant effect on Sporangia size (SS) of P. infestans isolates (ANOVA, F2,352 = 3.58, P = 0.029), with bigger sporangia produced on Bintje than on Robijn as revealed by Tukey post hoc tests (Table 2)
A significant effect of potato cultivar on sporangia number (SN) was detected (ANOVA, F2,352 = 158.48, P < 0.001), with the highest number of sporangia produced on Bintje, on Robijn, when the lowest number of sporangia was observed on Möwe (Table 2)

Summary

Introduction

The widely accepted trade-off concept states that an organism cannot simultaneously maximize all traits involved in fitness, owing to dilemmas in resource allocation (Law, 1979). According to this theory, any beneficial change in one trait will unavoidably have a detrimental effect on another trait (Anderson and May, 1982; Stearns, 1989). The trade-off concept has a prominent importance in evolutionary biology, as it can explain how the adaptation of populations to new environments can be constrained and how life-history strategies can evolve (Rausher, 1984; Roff, 1992). Tradeoffs between fitness components are of central importance in plant pathogens, as they could limit their evolutionary potential (Lannou, 2012; Laine and Barres, 2013) and may be exploited to engineer durable control strategies (Quenouille et al, 2013; Brown, 2015).

Objectives

Methods

Results

Conclusion