A Component of Disease Resistance in Mango is due to Amistar (Azoxystrobin) Residue
M.K. Hassan, D.E. Irving ,L.M. Coates, E.K. Dann ,P.J. Hofman and A.W. Cooke
Program and Abstract. Australasian Postharvest Horticulture Conference. Royal Lakeside Novote., Rotorua, New Zealand. 27-30 September 2005. July 5-10, 2005. Page 29
2005
บทคัดย่อ
A Component of Disease Resistance in Mango is due to Amistar (Azoxystrobin) Residue
Amistar is a systemic fungicide registered for field application to control anthracnose disease on mango. Amistar (azoxystrobin) is a synthetic analogue of a naturally occurring fungal metabolite (strobilurin) found in wild mushroom (Strobilurus tenacellus). The present study aimed to determine whether there was variation in resistance to postharvest anthracnose disease in several cultivars of Australian mango. Mango fruits were harvested at commercial maturity from the Gin Gin, Bundaberg and Gatton areas of Queensland where commercial Amistar spray programmes were in place. The harvested fruits were surface-sterilised with ethanol and then inoculated with Colletotrichum gloeosporioides(9.5 x 105 spores/ml). Disease incidence and severity (artificial and natural) were measured daily during storage at 22°C. The varieties Calypso, Honey Cold, Kensington Pride, Celebration and Brooks were resistant, Kent and R2E2 were susceptible, and Nam Doc Mai was highly susceptible to postharvest anthracnose disease. Fruit peal was subjected to homogenisation and extraction with organic solvents, and extracts run on TLC plates. Upon subsequent bioassay using C. gloeosporioides as a test fungus, inhibition zones were observed at different RF positions. However, the strongest inhibition zone was found at RF 0.2 in all the resistant varieties. Initially, it was assumed that this was a constitutive antifungal compound that conferred resistance, but azoxystrobin alone also produced an inhibition zone on the TLC plate at the same RF position. This provides strong evidence that (he inhibition zone was due to residues of azoxystrobin and that this compound, and not constitutive antifungal compound(s), was responsible for conferring resistance.