Conditions for Development of Powdery Mildew of Tomato Caused by Oidium neolycopersici

Abstract

Oidium neolycopersici causes severe powdery mildew on all aerial parts of tomato, excluding the fruit. The objective of the present work was to examine factors that influence the development of O. neolycopersici on tomato and to identify potential methods for managing tomato powdery mildew. Under controlled conditions, the highest rates of conidial germination were observed at 25 degrees C, 99% relative humidity (RH) and minimal light, and the lowest on leaves adjacent to fruits. Optimal conditions for appressoria formation were 25 degrees C, RH ranging from 33 to 99%, and 1,750 lux light intensity. More conidia were formed at 20 degrees C, 70 to 85% RH, and 5,150 lux light intensity than at 16 and 26 degrees C, 99% RH, and 480 to 1,750 lux, respectively. Conidia survived and remained capable of germination for over four months when initially incubated at lower temperatures and higher RH, as compared with their fast decline under more extreme summer shade conditions. In growth chamber experiments, disease did not develop at 28 degrees C. Within the range of 70 to 99% RH, disease was less severe under the higher RH than the drier conditions. Disease was also less severe at lower light intensities. Data collected in three commercial-like greenhouse experiments involving various climate regimes were used to draw correlations regarding the effects of temperature and RH on the development of epidemics. Severity of powdery mildew was positively correlated with the duration of the range 15 to 25 degrees C, 1 to 4 weeks before disease evaluation (BDE), RH levels of 60 to 90% at 2 to 4 weeks BDE, and RH of 50 to 60% during the week BDE. Conversely, disease was negatively correlated with the duration of temperatures in the low and high ranges (5 to 15 degrees C and 35 to 40 degrees C) at 1 to 4 weeks BDE, with the duration of RH levels of 40% and below at 1 to 4 weeks BDE, and with 50 to 60% RH during the third week BDE. High (90 to 100%) RH was also negatively correlated with disease severity. These results suggest that the combination of high temperatures and low RH may help reduce O. neolycopersici powdery mildew severity in greenhouse tomatoes.

Resistance mechanisms of wild tomato germplasm to infection of Oidium neolycopersici

“…Jacob et al (2008) found that the highest rates of conidial germination were observed at a minimum light intensity, optimal conditions for appressoria formation were at 1750 lx, and the greatest number of conidia was produced at the highest light intensity, 5150 lx. similar results were confirmed by Kashimoto et al (2003a), who found, that optimal light conditions for development of a Japanese isolate of O. neolycopersici were 3,500 lx (~62.2 μmol.m −2 .s −1 ), while in their experiments this intensity was the maximal tested, and under lower light intensity the rate of pathogen development was limited.…”

“…All pictures taken 9 days after inoculation (Prokopová et al 2010) powdery mildews is significantly affected by host genotype and by combinations of environmental variables, including temperature, relative humidity and light. The basic conditions important for development of O. neolycopersici have also been studied (Fletcher et al 1988;Hannig 1996;Whipps and Budge 2000;Jacob et al 2008;Mieslerová and Lebeda 2010).…”

“…The most suitable temperature for germination, development and conidia formation is considered to lie in the range 20-25°C (Fletcher et al 1988;Jacob et al 2008). In a detailed study by Mieslerová and Lebeda (2010) it was found that conidia germinated across the whole range of the tested temperatures (10-35°C); however, at the extremes germination was strongly limited.…”

“…Pathogen development was also markedly influenced by light conditions (Jacob et al 2008;Mieslerová and Lebeda 2010). Jacob et al (2008) found that the highest rates of conidial germination were observed at a minimum light intensity, optimal conditions for appressoria formation were at 1750 lx, and the greatest number of conidia was produced at the highest light intensity, 5150 lx.…”

The Analysis of Plant’s Organic Volatiles Compounds with Electronic Nose and Pattern Recognition Techniques

“…Effective control of powdery mildew can be achieved by applying fungicides at early stages of the disease development. (Jacob et al, 2008;Jones et al, 2001) spider Mite…”