CONTROL OF POSTHARVEST PEAR DISEASES USING NATURAL SAPROPHYTIC YEAST COLONISTS AND THEIR COMBINATION WITH A LOW-DOSAGE OF THIABENDAZOLE

Thirty-one morphologically different strains of yeasts and yeast-like fungi, isolated from the surface of pear fruits, were evaluated for bi ocontrol potential of blue mold on d'Anjou pear fruits. Seven yeast st rains (Cryptococcus albidus strain HRB2, C. infirmo-miniatus strain YY 6, C. laurentii strain HRA5, Rhodotorula aurantiaca strain YCL5, and R . glutinis strains HRA3, HRA4 and HRB6) reduced incidence of blue mold on pears. C. laurentii HRA5 and R. glutinis HRB6 were most effective for reduction of incidence and severity of blue mold. C. laurentii HRA 5 and R. glutinis HRB6 combined with a low dose of thiabendazole (TBZ) (15 mu g ml(-1)) gave significantly better disease control at 5, 10 a nd 20 degrees C than either TBZ or the yeast alone and was comparable to disease control achieved using a commercially-recommended high dose of TBZ (525 mu g ml(-1)). C. infirmo-miniatus strain YY6 was most eff ective for the control of Mucor rot of pears. C. laurentii HRA5, C. in firmo-miniatus YY6, and R. glutinis HRB6 reduced incidence and severit y of gray mold of pears and were more effective when combined with a l ow dose of TBZ. Side rot of Bose pears was completely controlled by C. laurentii HRA5, C. infirmo-miniatus YY6 and R. glutinis HRB6, whereas TBZ was ineffective. Bull's-eye rot of pears was completely controlle d by all yeasts when they were combined with a low dose of TBZ. Popula tions of C. laurentii HRA5, C. infirmo-miniatus YY6 and R. glutinis HR B6 in pear wounds increased approximately 1.3 log units within 10 days at -1 degrees C and 1.7 log units in 2 days at 5, 10 and 20 degrees C . Addition of cell-free supernatants of yeast cultures to wounds did n ot suppress decay, and substances inhibitory to fungal germination wer e not detected on culture plates.