Cause of Death: Phytophthora or Flood? Effects of Waterlogging on Phytophthora medicaginis and Resistance of Chickpea (Cicer arietinum)

Nicole Dron,Steven Simpfendorfer,Georgina Pengilley,Kristy Hobson,Tim Sutton

doi:10.3390/agronomy12010089

Abstract

Chickpea production in Australia is constrained by both waterlogging and the root disease Phytophthora root rot (PRR). Soil saturation is an important pre-condition for significant disease development for many soil-borne Phytophthora spp. In wet years, water can pool in low lying areas within a field, resulting in waterlogging, which, in the presence of PRR, can result in a significant yield loss for Australian chickpea varieties. In these circumstances, the specific cause of death is often difficult to discern, as the damage is rapid and the spread of PRR can be explosive in nature. The present study describes the impact of soil waterlogging on oxygen availability and the ability of P. medicaginis to infect chickpea plants. Late waterlogging in combination with PRR reduced the total plant biomass by an average of 94%; however, waterlogging alone accounted for 88% of this loss across three reference genotypes. Additional experiments found that under hypoxic conditions associated with waterlogging, P. medicaganis did not proliferate as determined by zoospore counts and DNA detection using qPCR. Consequently, minimizing waterlogging damage through breeding and agronomic practices should be a key priority for integrated disease management, as waterlogging alone results in plant stunting, yield loss and a reduced resistance to PRR.

Highlights

Chickpea (Cicer arietinum) was first domesticated 10,000 to 12,000 years ago in the arid to semi-arid Middle-East and has since been integrated into many cropping systems internationally [1,2]
Phytophthora root rot (PRR) caused by the soil-borne oomycete Phytophthora medicaginis is endemic to this region, and yield losses of over 70% can occur during seasons when above average rainfall is experienced [8]
This study investigated the effects of waterlogging on P. medicaginis infection of chickpea, both of which are common occurrences in the northern grain region of Australia

Summary

Introduction

Chickpea (Cicer arietinum) was first domesticated 10,000 to 12,000 years ago in the arid to semi-arid Middle-East and has since been integrated into many cropping systems internationally [1,2]. The sustainable production of plant protein is dependent on plants’ resilience to abiotic and biotic stress, and the frequency of severe weather events including flooding and drought is expected to increase, posing a threat to global food production into the future [6,7]. Phytophthora root rot (PRR) caused by the soil-borne oomycete Phytophthora medicaginis is endemic to this region, and yield losses of over 70% can occur during seasons when above average rainfall is experienced [8]. Phytophthora spp. are obligate aerobes, and during periods of soil saturation in many circumstances it is difficult to decipher whether the crop damage is from PRR, waterlogging or a combination of both [10,11]. Evidence from other pathosystems indicates that there is a possibility that PRR management could be improved though minimizing the impact of waterlogging, as waterlogging contributes to disease development and yield loss in chickpea [14], as previously reported in soybean (Glycine max) [15]

Methods

Results

Discussion

Conclusion