CA STORAGE OF KIWIFRUIT AT DIFFERENT O₂ AND CO₂ LEVELS: INFLUENCE ON BOTRYTIS CINEREA, PHIALOPHORA SPECIES ROTS AND FRUIT MATURITY

The main problems encountered in Italy in the storage of kiwifruit are the rots caused by Botrytis cinerea and Phialophora species (the first occurring after 2–3 months’ storage and the second normally after 4–5), and softening of the flesh (in fruit stored for over 3 months in normal refrigeration) below 2 kg firmness.
Our trials, performed over a number of years, have attempted to identify: alternative fungicides to Vinclozolin for post-harvest treatments; CA conditions which do not increase the incidence of Botrytis and Phialophora rots; and the optimum time for bringing O₂ and CO₂ levels in CA to their long-term storage values (CA delay). Regarding alternative fungicides, only KBR (Bayer) was as effective as Vinclozolin towards Botrytis rot.
BC1000 (Chemie Res.
Man.
FL) was less effective but of interest.
All fungicides failed to control Phialophora rot.
Regarding CA conditions (Table 1), the incidence of Phialophora rot (and to a lesser degree Botrytis rot) was significantly reduced in CA by combining low levels of O₂ with low levels of CO₂ (both 1.3–1.5% O₂; 1.3–1.5% CO₂, and 1–1.2% O₂; 1–1.2% CO₂) compared to conventional CA (1.8-2% O₂; 4.5–4.8% CO₂), and there was a slight decrease in flesh firmness.
Regarding CA delay (Table 2) it appears that a delay of 30 days from harvest before applying CA conditions allows the incidence of Botrytis rot to be held at the same levels as for regular storage, without reducing the positive effects of CA on flesh firmness.
In conclusion, it seems that the benefits of conventional CA can be retained while reducing the incidence of Phialophora rot through decreasing the CO₂ level in CA storage from 4.5–4.8% to 1.3- 1.5%; and that a reduced incidence of Botrytis rot can be achieved by not changing the O₂ and CO₂ levels from air values to the final CA values until 30 days after harvesting.

Table 1. Influence of CO₂ and O₂ levels and curing on storability (160 d at -0.5 to -0.8°C)

1994 & 1995 Trials

Immediate cooling

48 hours curing

Rots

Firmness

Rots %

Firmness

	Botrytis	Phialo.	kg	Botrytis	Phialo.	kg
Regular Storage	11.4 B	3.9 b	0.6 b	2.9 b	2.3 b	0.7 b
CA at 1.9% O2; 4.7% CO2	36.3 a	12.8 a	2.6 a	7.8 a	15.0 a	2.6 a
CA at 1.4% O2; 1.4% CO2	31.1 a	0.4 b	2.2 a	6.8 a	2.1 b	2.2 a

Fisher PLSP P <0.05 for column

Harvest: Firmness 5.8 kg; SSC 8.1%

Table 2 – Influence of CA delay on storability (immediate cooling after harvest; assessed after 190 days at -0.5 to -0.8°C;

1995 & 1996 Trials

Days delay until imposing CA conditions

	Regular storage	7 days	15 days	22 days	30 days
Botrytis cinerea (%)	4.2 c	14 a	12.4 a	8.8 b	5.7 bc
Firmness (kg)	0.7 b	2 a	2.3 a	2 a	2.1 a
SSC (%)	15.3	14.9	14.8	15.3	15.4

*CA at O2 1.8-2%; CO2 4.5-4.8%

Harvest: Firmness 5.9 kg; SSC 7.7%

Research suppórted pro parte by Department of Agriculture, Emilia Romagna Region

International Postharvest Science Conference Postharvest 96

G. Tonini, L. Alessandri, F. Bassi, R. Proni

https://doi.org/10.17660/ActaHortic.1998.464.111