**3.2. Effect of production systems on SSC, TA and firmness**

SSC, TA and firmness dramatically affect strawberry fruit quality. The production systems had a significant effect on the SSC, TA and firmness of the strawberry fruits and the SSC increased, while TA and firmness decreased all through the harvest season (**Table 3**). PMRC significantly increased the SSC, TA and firmness of the strawberry fruits at all harvests compared to PM and MRS (**Table 3**). Meanwhile PM significantly enhanced SSC and TA of strawberry fruit but had no effect of firmness of strawberry fruit compared to MRS (**Table 3**). Strawberry planted under PMRC produce higher-quality fruits than those without row covers, possibly because the microclimate under the covers was modified and the soil temperature was elevated which maybe result in better root establishment and advanced growth stages [20].


LSD0.05: least significant difference at the 0.05 level.

The individual phenolic compounds of berries were analysed by HPLC, using a Varian (Varian Inc., Palo Alto, CA, USA) HPLC system. A photodiode array detector (Model 335) and a quaternary pump (Model 240) were equipped in the HPLC system. Samples were injected at 40°C, and the separation was performed with a reverse phase 4.6-mm Polaris C18-A column coupled with a 4.6-mm MetaGuard Polaris C18-A guard column (Varian Inc., Palo Alto, CA, USA). The mobile phase was acidified water containing 2.5 g/100g formic acid (A) and acidified methanol containing 2.5 g/100 g formic acid (B). The flow rate was 1.0 ml/min, with a gradient profile consisting of B with the following proportions (v/v) of A: 0–15 min, 15–30% B; 15–20 min, 30% B; 20–25 min, 30–80% B; 25–42 min, 80% B; 42–42.5 min, 80–100% B; 42.5–50.25 min, 100% B; and 50.25–51.25 min, 0% B. The detector was simultaneously monitoring the different groups of phenolics at 254, 280, 320, 350 and 510 nm. Equilibration time between samples was 15 min. Data were collected and analysed by Varian Workstation Star version 6.41. Total phenolic compounds were divided into six groups and quantified as described in our previous work [30].

Statistical analysis was performed using SAS software [31]. Data were analysed using GLM procedure, and the least significant difference (LSD) test was used for mean separation at 5% level when it was significant. The arcsine transformation was used for rank data before data analysis, and the results were presented as a rank for simplicity when the outcomes of transformed and non-transformed data were the same. The data from 2009 to 2010 were pooled together after

Yield is an important characteristic that farmers considered a lot in strawberry production. Compared to the MRS, PMRC accelerated strawberry fruit production by 8 and 10 days in 2009 and 2010, respectively, followed by PM when fruits were harvested 4 and 5 days before MRS in 2009 and 2010, respectively, similar to those observed by Jin et al. [32]. Soria et al. [33] also reported that based on two consecutive cropping seasons data, plastic tunnels improved early marketable yield, total marketable yield and first-class fruits of strawberry. The increased yield and fruit size might be due to the increase in soil temperature for PM and PMRC. The early ripening of the fruits under PM and PMRC systems will probably generate a better income due to off-season production. Total yields of PM and PMRC were significantly lower than that of MRS, but the yield per plant of PMRC was significantly higher than PM and MRS (**Table 2**). Fruits harvested from PMRC and PM were significantly larger than those harvested from MRS (**Table 2**). This might be because of less competition between the plants

analysing each year separately and testing the homogeneity of the experimental error.

since all the runners were removed under PM and PMRC but kept under MRS [24].

SSC, TA and firmness dramatically affect strawberry fruit quality. The production systems had a significant effect on the SSC, TA and firmness of the strawberry fruits and the SSC increased, while TA and firmness decreased all through the harvest season (**Table 3**). PMRC significantly

**3.2. Effect of production systems on SSC, TA and firmness**

**2.11. Statistical methods**

**3. Results and discussion**

**3.1. Effect of production systems on yield**

202 Phenolic Compounds - Natural Sources, Importance and Applications

Different lower-case letters in the same column indicate statistically significant differences between different treatments (*p* < 0.05).

**Table 2.** Total yield, yield per plant and average fruit weight of strawberry selection 'SJ8976-1' grown under three production systems.


LSD0.05: least significant difference at the 0.05 level.

Different lower-case letters in the same column indicate statistically significant differences between different treatments (*p* < 0.05).

**Table 3.** Early-, mid- and late-harvest soluble solids content (SSC), titratable acidity (TA) and firmness of strawberry selection 'SJ8976-1' grown under three production systems.

### **3.3. Effect of production systems on shelf life**

Photographs of disease development and fruit juice leakage of strawberry selection 'SJ8976-1' used for shelf life, juice leakage and presences of grey mould classification are presented in **Figure 1**. 'SJ8976-1' has a special longer shelf life (about 9 days) after storage at room temperature than the commercial strawberry varieties. Production systems significantly affected strawberry

**Figure 1.** Photographs of disease development and fruit juice leakage of strawberry selection 'SJ8976-1' used for shelf life, juice leakage and presences of grey mould classification.

shelf life, including fruit weight loss, juice leakage, glossiness and presences of grey mould during storage (**Figure 2**). Fruit weight loss, juice leakage and presences of grey mould after storage were lower, and fruit glossiness was higher for those fruits harvested from PMRC than those from the MRS. Significant lower fruit weight loss was observed for PMRC and PM compared to the MRS, and the results were more pronounced after day 7 (**Figure 2A**). It was interesting to note that PMRC had significant lower juice leakage than the MRS, but the differences between PMRC and PM and PM and MRS were not significant until day 11 (**Figure 2B**). The fruits from PMRC kept their glossiness longer during storage at room temperature than MRS and PM. The remarkable difference among different production systems was obtained at 7 days after harvest (**Figure 2C**). Similar finding was reported in Finland that plastic production systems promoted better shelf life [11]. No significant differences were observed between the production systems on the first 5 days of harvest for presences of grey mould, but significantly less grey mould were observed on fruits harvested from PMRC than those harvested from MRS and PM from day 7 to the end of the test when all fruits were ranked as non-marketable (**Figure 2D**). Lower grey mould incidence on fruit harvested from PMRC might be due to the higher TPC and TAC content of the fruits as suggested previous [25, 34] or the protection that fruits received from the row cover against pathogen and rainfall as suggested by Freeman and Gnayem [16].

shelf life, including fruit weight loss, juice leakage, glossiness and presences of grey mould during storage (**Figure 2**). Fruit weight loss, juice leakage and presences of grey mould after storage were lower, and fruit glossiness was higher for those fruits harvested from PMRC than those from the MRS. Significant lower fruit weight loss was observed for PMRC and PM compared to the MRS, and the results were more pronounced after day 7 (**Figure 2A**). It was interesting to note that PMRC had significant lower juice leakage than the MRS, but the differences between PMRC and PM and PM and MRS were not significant until day 11 (**Figure 2B**). The fruits from PMRC kept their glossiness longer during storage at room temperature than MRS and PM. The remarkable difference among different production systems was obtained at 7 days after harvest (**Figure 2C**). Similar finding was reported in Finland that plastic production systems promoted better shelf life [11]. No significant differences were observed between the production systems on the first 5 days of harvest for presences of grey mould, but significantly less grey mould

**Figure 1.** Photographs of disease development and fruit juice leakage of strawberry selection 'SJ8976-1' used for shelf

life, juice leakage and presences of grey mould classification.

204 Phenolic Compounds - Natural Sources, Importance and Applications

**Figure 2.** Early-, mid- and late-harvest fruit weight loss (A), fruit juice leakage (B), fruit glossiness (C) and incidence of grey mould (D) on strawberry selection 'SJ8976-1' during 11 days of storage at room temperature (23°C) grown under three production systems. Means with the same letter within the same day were not significantly different at 0.05 level. ◆, Matted row system; ■, plastic mulch; and ▲, plastic mulch with row covers.
