FRUIT ROT OF DATE CAUSED BY FUSARIUM EQUISETI
A ALAVI and A SONBOLKAR
Plant Pests and Diseases Research Institute, PC Box 1457, Tehran-19395, IRAN
Background and objectives
Date is considered among the main agricultural produce of Iran. The acreage under date palm plantations here in Iran amounts to 200,000 ha, out of which the sum of 850,000 tonnes of date is produced per annum. A great proportion of the product is consumed domestically (ca.600,000 tonnes) whereas the rest is exported to some 52 different countries. In recent years some cases of date abscission have been reported off and on, to which, due to the importance of the subject, prime priority has been given. No fungal or bacterial agent has so far been reported to our available knowledge. The present investigation was based on the research done on the fruit (Mazafati cv.) harvested from Barn and Diiroft province.
Materials and methods
(i) Sampling of diseased date fruits was carried out for three consecutive years during the months of August and September. Dates were washed thoroughly in sterile distilled water. The resulting suspension was added on to an agar substrate and spread evenly to be used for studying the date micaflora. (ii) Unripe fruits of date were surface-sterilized and were either thoroughly sprayed with a spore suspension (106ml) of the suspected fungus or exposed to mycelial growth on PDA inserted through a wound. (iii) Infected tissues were cultured on PDA and the fungus grown on the medium was single-spored. (iv)The isolated fungus was studied for optimal growth temperature, colony colour and feature, followed by measurements of different fungal organs. lndentification was performed using the key provided by Nelson et al .
A culture filtrate of a thick spore suspension of the fungus was prepared axenically and was used in two different ways:- incorporated into the wells of PDA plates enriched with Bacillus megaterium, or filter paper discs dipped into the CF and plated on agar medium merged with B. megaterium. The metabolite of the fungus was united with date cells produced from both the fruit and the crown of pat plants, employing a solution of cellulase, macerozyme, rhozyme, morpholino ethane suifonic acid and BSA.
Study of the mycoflora of date on PDA showed the presence of the following: Penicillium sp., Alternaria sp., Cladosporium sp., Aspergillus sp., Rhizopus sp., and predominant to all was Fusarium sp. The last one was carefully isolated and proved to be creative of the same symptoms on the inoculated dates as were observed in date palm plantations. The fungal substrate had a moist, sticky surface on PDA. The aerial mycelia were white to beige as a mass. Conidiophores were monophialid, radiated, or unradiated. Macroconidia were formed by the time conidiophores started to grow. They had thick walls, with a deep dorsal curve and a slight ventral one, while giving the terminal cell a foot-shape formation. They were septate and the number of the cell walls varied from 3 to 5 with the average size of 31x5.5 mm. Oval or comma shaped microconidia were scarcely formed. Chlamydospores started to grow on PDA after 72 h, existing both in single and chain forms, with the average diameter of 8.75 mm. The fungus was identified as Fusarium equiseti (Corda) Sacc. The fungal extract proved suppressive against B. megaterium by creating inhibitory zones around the wells and discs. The said toxin was likewise destructive to the date cells resulting the rupture of protoplast membrane.
1. Djerbi M, 1993. Diseases of the Date Palm. FA0 publications. 119pp.
2. Nelson PE, Toussoun TA, Marasas, WFO, 1983. Fusarium Species, An Illustrated Manual for Identification, The Pennsylvania State University.