Bait method to detect Pythium species that grow at high temperatures in hydroponic solutions

Abstract

Pythium helicoides, P. aphanidermatum and P. myriotylum are important pathogens that cause root rot of several crops in hydroponic culture and in ebb-and-flow irrigation systems. These species belong to a group of Pythium species that can grow at temperatures higher than 40°C. We developed a method for baiting these high-temperature Pythium species and evaluated its practicality to monitor their presence in nutrient solutions. Seeds of cucumber, tomato, radish, hemp, perilla and millet and leaves of bent grass and rose were tested as baits in hydroponic systems. Hemp, perilla and radish seeds and bent grass and rose leaves were more effective than the other baits for Pythium zoospores, and bent grass leaves were the most effective. In a sensitivity test, bent grass leaf traps (BLTs) detected three Pythium species after only a 1 day exposure to suspensions of 40 zoospores per liter of water, and the frequency of detection increased with zoospore density and with baiting period. A temperature of 38°C was optimum for the selective reisolation of the high-temperature Pythium species from the BLTs. The BLT was also tested with inoculated and noninoculated miniature roses that shared a recirculating nutrient solution. The pathogen was detected in the nutrient solution 23 days before the disease spread to the noninoculated roses. In addition, P. helicoides was detected 30 days before the disease was evident in a commercial greenhouse. The baiting method described here will be useful for monitoring high-temperature Pythium species in recirculating hydroponic culture systems.

Detection of Fungal Pathogens in the Environment

“…The use of baits has been shown to be an effective approach for monitoring high-temperature Pythium spp. in recirculating hydorponic culture systems (Watanabe et al 2008).…”

Development of loop-mediated isothermal amplification assay for the detection of Pythium myriotylum

“…; Watanabe et al . , ). However, it is difficult, laborious and time‐consuming to detect Pythium species based on morphological characteristics, partly because these characteristics vary under different culture conditions and involve intraspecific phenotypic variation (Pettitt et al .…”

“…Rapid and reliable detection is essential for an effective control of these diseases. Traditionally, detection and identification of Pythium species have been achieved by plating methods, bait methods or a combination of both (Pettitt et al 2002;Watanabe et al 2007Watanabe et al , 2008. However, it is difficult, laborious and time-consuming to detect Pythium species based on morphological characteristics, partly because these characteristics vary under different culture conditions and involve intraspecific phenotypic variation (Pettitt et al 2002).…”

Characterization of species associated with Pythium soft rot of ginger and evaluation of Pythium Oligandrum as a biocontrol

“…Likewise, Watanabe et al (2008) concluded that seeds of hemp, perilla, and radish and leaves of bentgrass and rose were highly effective in attracting zoospores of P. helicoides, P. myriotylum and P. aphanidermatum and consequently these were employed to "catch" those species from hydroponic solutions. Other successful methods have included the use of rhododendron leaf discs and Douglas-fir needle segments in obtaining Pythium spp.…”

“…from forest soils (Weiland, 2011) and soybean leaf discs from soybean fields (Jiang et al, 2012). Thanks to the effectiveness of various methods, baiting is believed to be a useful tool for monitoring Pythium populations and forecasting disease occurrence under field conditions (Sánchez et al, 2000;Stanghellini and Kronland, 1985;Watanabe et al, 2008).…”