See more from this Session: Cover Crop and Weed Management Considerations in Organic Management Systems
Tuesday, November 2, 2010: 3:15 PM
Hyatt Regency Long Beach, Shoreline B, First Floor
A trial was conducted to determine the most effective nutritional regimes & Spore concentration in order for intensifying conidiation, germination and consequently disease incitement of F. oxysporum isolates. Sufficient media culture defined after enumerating the highest conidia and germinated conidia, consequently Semi-defined media (SDM) & Richard Solution (RS) were adjusted to pH 6.8 and C: N ratio of 15:1 containing 0 & 5% of glycerol. Darkness relative to day light and Ultra Violet increased spore production and germination as well as germ-tube length. 20°C was preferable to Sporulation whereas conidial germination increased at 15°C. Results obtained from conidial germination in Semi-Defined Medium (SDM) & Richard Solution (RS) demonstrated that Although in the short run adding glycerol to liquid media of RS and SD had no significant effect on sporulation of both isolates, in the long run it was effective on increasing desiccation tolerance in poor RS and even caused germ-tube elongation in spores which were cultured in RS with 5% (v / v) of glycerol content. No significant difference was seen between 6, 11, 16, and 20-day old cultures. However, the superiority of the 6-day old culture was remarkable in maintaining conidia germinability after 35 days of desiccation tolerance (at 20ºC, in the dark and 15% RH). Conidia harvested from 6-day old SD was suspended in Tween 20, coconut oil, and glycerol separately (0, 0.5, 1 and 2%). Germination rate and desiccation tolerance of the given spores were shown to be magnified in Tween1% v/v, coconut oil 0.5% v/v, and glycerol 2%. Spores grown in SDM & RS with and without glycerol were prepared in 4 concentrations 5×106, 107, 5×107,108 spore ml-1. Mentioned suspensions were used to inoculate tomato seedlings which had been planted two weeks beforehand in the 2 Kg pots (containing 0.6 g of sterilized Egyptian broomrape seeds). 108 spore ml-1 caused a significant increase in the Mean Dry Weight (MDW) of tomato seedlings. In addition, isolate 502 significantly decreased MDW of broomrape seedlings relative to other concentrations and the control treatment. Concentration of 108 spore ml-1 in both isolates caused a significant decrease of mean capsule number in broomrape relative to the non treated control.
Keywords: Mycoherbicide, Orobanche aegyptiaca, culture age, glycerol, desiccation tolerance, spore concentrations