Foliar and root applications of the rare sugar tagatose control powdery mildew in soilless grown cucumbers

Paola E Corneo,Mauro Jermini,Stefano Nadalini,Oscar Giovannini,Andrea Nesler,Michele Perazzolli,Ilaria Pertot

doi:10.1016/j.cropro.2021.105753

Paola E Corneo, Mauro Jermini + Show 5 more

Open Access

https://doi.org/10.1016/j.cropro.2021.105753

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Abstract

Powdery mildew is a constant threat to cucumber production in soilless systems requiring the intensive use of chemical fungicides to limit yield losses. However, the toxicity risks for the growers and the food safety issues linked to fungicide residues represent a major concern for crops with a frequent and extended harvest period, like cucumber, and create an urgent need of eco-friendly alternatives. The objective of this study was to assess the effectiveness of foliar and root applications of the rare sugar tagatose, against naturally occurring powdery mildew (Podosphaera xanthii and Golovinomyces cichoracearum) on cucumber plants grown in a soilless system under commercial-like greenhouse conditions. Foliar and root applications of tagatose reduced powdery mildew severity and incidence under conditions of low severity in untreated plants, but tagatose and the chemical standard strategy lost their effect in the control of powdery mildew when the disease severity was increasing steadily. The combination of sulphur with foliar applications of tagatose effectively reduced powdery mildew under high severity conditions. Overall, under high disease pressure, foliar and root applications of tagatose were more effective than the standard chemical treatment reducing powdery mildew disease incidence and severity. Foliar application of tagatose directly inhibited P. xanthii conidial germination. After root application, tagatose was translocated to the leaves guaranteeing a systemic protection with no accumulation in cucumber fruits. Root applications of tagatose represent a novel strategy for cucumber protection against powdery mildew and reduce fungicide applications.

Highlights

In response to the continuous drop in fertile soil and water avail ability, vegetable production has increased its reliance on soilless agri culture techniques based on hydroponic solution (Sambo et al, 2019)
Conidial germination was lower in 0.8% formulation of tagatose (F_TAG), 2.4% F_TAG- and 0.8% TAG-treated leaf discs compared to Control leaf discs (CTRL) leaf discs after foliar application, while it was comparable in CTRL and 0.16% F_TAG-treated leaf discs (Fig. 1)
Conidial germination was lower in 0.16% F_TAG, 0.8% F_TAG- and 0.8% TAG-treated plants compared to CTRL plants after two and four root applications (Fig. 2a) and it was comparable among the different tagatose treatments

Summary

Introduction

In response to the continuous drop in fertile soil and water avail ability, vegetable production has increased its reliance on soilless agri culture techniques based on hydroponic solution (Sambo et al, 2019). The presence of the two species can vary depending on the geographic area considered; in France, Netherlands and Great Britain, only mixed infections of P. xanthii and G. cichoracearum were recorded, while at several locations in Italy, Germany and Slovenia only P. xanthii was recorded and there were no locations with an exclusive occurrence of G. cichoracearum, but only as a mixed infection with P. xanthii. Both powdery mildews were instead found in Austria and Switzerland as a unique or mixture species (Krístkovaet al., 2009). The reason of the different distribution can be attributed to the different climatic conditions (Trecate et al, 2019)

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