Effects Of Rain-shelter Cultivation On Volatile Compounds Formation Of Peach Fruit

In order to protect plants from negative environmental influences, rain shelter cultivation has become important for horticulture crop production. However, the effects of this cultivation on flavor-associated volatiles were not well understood. In present study,’Hujingmilu’ and ’Yulu’(Prnus persica L. Batsch) peach fruit were grown under rain shelter and open field as the control. Changes in fruit volatile compounds during maturation and postharvest cold storage were determined and subjected to multivariate data analysis tools. The main results are as follows:1. Environmental parameters under rain shelter and open field cultivation were firstly evaluated and compared. No significant difference was found for temperatures in the canopy. Blue-violet light (430-450nm) and red (640～660nm) that are necessary for leaf photosynthesis was reduced by10%～20%because of the PE film used for rain shelter overhead coverage, In the tree root area (20～60cm soil depth), values of soil water content were reduced by13～32%by rain shelter.2. E-nose generated DFA model could effectively separate peach fruit from two different cultivation systems. Rain-shelter cultivated Yulu peach fruit that harvested on August4and August7were mainly distributed on the DF2positive axis, while the fruit from the open field were located on the negative axis, indicating changes in volatile profiles caused by rain-shelter cultivation. Eleven classes of volatiles were identified in peach fruit by SPME-GC-MS, including C6compounds, aldehydes, alcohols, esters, lactones, terpenes, terpenoids, phenylpropanoids and others. PLS-DA model was performed to evaluate differences in volatile profile between rain-shelter and open field fruit. And18compounds with VIP value higher than1were identified that changed significantly in contents and play important role in seprating peach fruit from two different cultivation systmes, including (Z)-3-hexyl alcohol,(E)-2-hexyl alcohol and other "green flavor" volatiles, and lower levels of "fruity" volatiles like (Z)-3-hexenyl acetate, y-undecanolactone and δ-decalactone. Compared to rain-shelter fruit, the open field produced higher color saturation (C*) and hue angle (h°) values, indicating differences in maturation process between the rain-shelter cultivation and the open field cultivation.3. Peach fruit from rain-shelter system developed chilling injury after21d of cold storage, appearing severe flesh browning and hard texture, while the cold induced disorders were delayed until28d of storage for peach fruit from open filed. E-nose DFA and SQC models clearly seprated chilling injury fruit from the health samples. PLS-DA analysis showed indicated that significant differences in volatile contents between rain-shelter and open field fruit during cold storage. Gerenrally, lower levels of lactones, esters, furans and norisoprenoids was found for rain-shelter peach fruit throughout cold storage period, γ-decalactone and δ-decalactone are peach fruit character aroma volatiles, whose contents were62%and43%of that produced by open field fruit, respectively. Difference in production of lactones in response to cold storage could be due to a difference in development of chilling injury between rain shelter and control fruits.In summary, chemical compounds affected by rain shelter cultivation method were identified throughout peach fruit maturation and postharvest storage. Changes in volatile compounds are probably due to delayed maturation process after rain shelter treatment, although the effects of microclimate parameters and detailed molecular mechanism will require further study.