Effects of the combined application of 2 ppm MCP 1 O2 on ripening of apple fruits
Asif, Mehar, Prabodh Trivedi, Theophanes Solomos
Program and Abstract. 9th Controlled Atmosphere Research Conference (CA2005). Michigan State University, East Lansing, Michigan, USA. July 5-10, 2005. page11
2005
บทคัดย่อ
For the past two years we have been studying the effects of the combined application of 2 ppmMCP + 1% O2 on apple fruit ripening at 1°C and 7 °C. Last year, in fruits stored at 7 °C the onset of the C2H4 climacteric occurred 10, 55 and 95 d, for the controls, 1% O2 and 2 ppm, respectively, whereas in fruits treated with MCP and kept under 1% O2 the onset of the C2H4 climacteric did not occur for 200 d, the duration of the experiment. Even now (March 2005), there is still no rise in C2H4 evolution in fruits kept at 7°C under the combined treatment of MCP and O2. The retardation of the climacteric rise was attended by a complete suppression of the ACS1 and ERS1 genes that are critically dependent on the rate of C2H4 evolution, The promoters of both genes contain C2H4-responsive elements. Thus once ACS1 is induced, it can sustain the auto-catalytic increase in C2H4 evolution. The dependence of mRNA accumulation in both genes on C2H4 was also demonstrated by treating climacteric fruits with 1.5% O2, 2 ppm MCP, and 2 ppm MCP + low O2. The degree of decrease in C2H4 evolution differed with the treatments, being stronger in the last treatment. This was reflected in the amounts of the accumulated transcripts. At present the developmental changes that precede the induction of ACS1are unknown. A rise in C2H4 may be involved since treatment of early maturity fruits with 25 ppm C2H4 for 48 hours induces ACS1 within 18 d, whereas in controls it took about 30 d. At 1°Cthe climacteric rise in C2H4 evolution was also retarded by the combined treatment for 250 d. However, when the fruits were transferred after 250 d, to 18°C, ripening occurred normally, as could be judged by the rise in C2H4 evolution, softening and induction of the expression of C2H4-dependent genes, e.g., polygalacturonase. The data thus show that apples treated with MCP + 1% O2 can be successfully stored at relatively high temperatures.