Abstract

Phytophthora capsici causes root and crown rot of protected pepper (Capsicum annuum L.) crops in the Basque Country (northern Spain), a humid temperate climate area. The objective was to determine the effect of winter biofumigation and plastic cover (biodisinfestation) with Sinapis alba L. (cultivar 'Ludique') fresh green manure on the survival of introduced P. capsici inoculum (oospores) in a greenhouse soil. After autumn-winter Brassica cover crop soil incorporation in February, oospores remained at 15 and 30 cm depth for four weeks´ time exposure in two consecutive years, 2009 and 2010. Oospores viability was estimated with a plasmolysis method and infectivity with a potted pepper bioassay. Viability was significantly higher in biodisinfestated oospores than in the non-treated control in both years (81% and 21% relative increase in 2009 and 2010, respectively) and significantly higher at 30 cm depth than at 15 cm in 2009 (24% relative increase). Conversely, biodisinfestation significantly delayed disease incidence progression until the first half of infectivity bioassays in both years compared to the non-treated soils (83% and 75% relative decrease of dead plants in 2009 and 2010 respectively). The low soil temperatures could explain the low oospore survival reduction and suggest that the suppressiveness expressed in the infectivity bioassay was related with an increase of microbial activity in the biodisinfestation treatment. We conclude that winter biodisinfestation with fresh Brassica green manure is a promising management strategy for Phytophthora root rot control of protected peppers crops in regions of humid temperate climate such us northern Spain.

Highlights

  • Phytophthora capsici is one of the main soil-borne pathogens that causes root and crown rot of protected pepper (Capsicum annuum L.) crops worldwide (Ristaino & Johnston, 1999) and in the Basque Country (Riga et al, 2000; Larregla et al, 2015), an area characterized by a humid temperate climate

  • Soil temperature remained below certain levels (40-53°C) that are considered critical to the survival of P. capsici oospores (Etxeberria et al, 2011b)

  • An absence of thermal inactivation was observed in this greenhouse experiment, located in the humid temperate Atlantic agroclimatic conditions of northern Spain

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Summary

Introduction

Phytophthora capsici is one of the main soil-borne pathogens that causes root and crown rot of protected pepper (Capsicum annuum L.) crops worldwide (Ristaino & Johnston, 1999) and in the Basque Country (northern Spain) (Riga et al, 2000; Larregla et al, 2015), an area characterized by a humid temperate climate. This pathogen species produces survival spores (oospores) that are capable to persist in the soil and act as the main initial inoculum that causes primar­y infec­ tions in the crop cycle (Erwin & Ribeiro, 1996). Regarding the cycling temperature regimes, 4 h-40oC regime killed 100% of oospores after 28 days, while the 5 h-35oC regime after 70 days killed only 75% (Etxeberria et al, 2011b)

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