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Ninety nine yeast isolates were isolated from surface of mango fruits and were tested in vivo in preliminary study for biocontrol potential of Lasiodiplodia rot of mango fruits. According to primary screening, nine isolates were selected to continue the secondary screening using different concentrations of the washed yeast cells in water suspension to study their biocontrol efficacy at 16±1°C. It was found that using washed cells of yeast isolate Mg 147 (Candida multisgemmis) at 1x10 9 , 5x10 8 and 2x10 8 CFU/ml produced complete protection for 14 days to wounds of mango fruit inoculated with spore suspension of the fungus Lasiodiplodia theobromae 1x10 5 conidia/ml. Meantime, no lesion developed on the mango fruit treated with the isolates Mg 39 (Pichia guilliermondii strain A) at the highest tested colony forming unit (CFU) levels, i.e. 1x10 9 and 5x10 8 CFU/ml. Supernatant of the yeast cultures, tested in secondary screening, did not prevent spore germination of L. theobromae or decay of wounded mango fruit but had inhibitory effect. However, 1-Methylcyclopropene (1-MCP) treatment significantly reduced the infected area mm 2 on mango fruit inoculated with L. theobromae (1x10 5 conidia/ml) during the 14 days of storage at 16±1°C and improved efficacy of isolates Mg147 and Mg39. When applied as combined treatments between 1-MCP and biocontrol agents, no lesion developed on the fruit treated with the isolate Mg 147 at 1x 10 8 CFU/ml or higher. Meanwhile, no lesion developed on the fruit treated with the isolate Mg 39 at 2x 10 8 CFU/ml or higher while, the percentages of rot reduction were ranged between 94.1%-81.3% for concentrations 1x10 8 and 6.6x10 7 CFU/ml respectively.

Ninety nine yeast isolates were isolated from surface of apple, grape, orange and tomato fruits. The isolates were tested in vivo in preliminary study for biocontrol potential against green mould of navel orange fruit. According to primary screening, twenty two isolates were selected to continue the secondary screening (phase one) using different concentrations of the washed yeast cells in water suspension to evaluate their biocontrol efficacy at 21±1°C. Among twelve yeast isolates were passed to the secondary screening (phase two) at 7±1°C, washed cells of yeast isolates CT 503, CT 507, CT 508, CT 512 and CT 550 at 1x10 9 , 2x10 8 and 1x10 8 CFU/ml produced complete protection for 21 days to wounded navel orange fruits inoculated with spore suspension of Penicillium degitatum (1x10 4 conidia /ml). Meantime, no lesions developed on the navel orange fruits treated with the yeast isolates CT 503, CT 507 (Debaryomyces hansenii var. hansenii strain C) and CT 512 (Endomycopsella vivi) at 6.6x10 7 CFU/ml, while the percentage of rot reduction of the isolate CT 550 (Candida edax) was 99.81%. Culture filtrate of twenty two different yeast isolates used in secondary screening (phase one) did not prevent decay of wounded navel orange fruits but had an inhibitory effect on rot development. The relative abili-ties of the promising yeast isolates (CT 503, CT 507, CT 512 and CT 550) to induce disease resistance against P. digitatum on navel orange fruits were studied. Inoculation of promising yeast isolates significantly triggered induction of resistance in navel orange fruits. The lesion diameters of green mould 66 hours later after inoculation by spore suspension of P. digitatum in a neighbouring wound that was made approximately 6 mm away from the initial wound which inoculated with the isolates CT 512, CT 550, CT 507 and CT 503 were reduced by 25.5%, 20.5%, 16.7% and 14.1%, respectively. In this respect, there were no significant differences among the three different isolates CT 503, CT 507 and CT 550.