Effects Of Low Temperature Storage On Lotus Roots Texture And Transcri Tome Analysis

Texture of fruits and vegetables has an important influence on their mechanical damage resistance,storage quality and shelf life during post-harvest transportation.Fruits and vegetables in different harvest periods and post-harvest storage periods will be reduced in texture and nutrients due to tissue dehydration,metabolism and microbial effects.The research on the quality difference of fruits and vegetables under different harvest periods can better grasp the harvest time of fruits and vegetables and improve the economic value.At present,low temperature storage is one of the most commonly used ways of fruits and vegetables after harvest,which can effectively reduce the respiration rate,the loss of water and nutrients,and maintain the quality and texture changes of fruits and vegetables.Lotus root is a characteristic vegetable in Hubei Province,however,at present,there are few researches on the quality difference of lotus root in different harvest periods and the texture change during low temperature storage after harvest,and the molecular mechanism of the effect of low temperature storage on lotus root texture is still unclear.In this paper,the changes of color,sensory,texture and fatty acids of lotus root("Elian No.5")under different harvesting periods and post-harvest storage were analyzed.the quality difference between harvest periods H1-H5(September of that year to January of the following year)and the effect of low-temperature storage(4℃)on lotus root texture were studied,and RNA-Seq technology was used to dig out genes related to lotus root hardness,which provided the basis for molecular mechanism research of lotus root hardness change after harvest,and also provided reference basis for lotus root harvest,storage and preservation after harvest.The main research results are as follows:(1)Quality and texture differences of lotus roots("Elian No.5")in different harvest periods:before harvest period H3(November),there was no significant change in color difference and sensory evaluation of " Elaine No.5" lotus roots.During H3 to H4(December),the color difference and sensory evaluation decreased significantly,and the total fatty acid content is gradually decreasing.Meanwhile,the texture(hardness,chewing and tissue elasticity)changes of lotus roots were consistent with sensory quality,during the harvesting period,the hardness decreased significantly between H3 and H4,and the hardness reduction rate reached 30%.Therefore,based on sensory and texture evaluation of lotus roots,November and before is a better harvest period for lotus roots.(2)Effect of low-temperature storage on lotus root("Elian No.5")quality and texture:when stored at low temperature(4℃)for 3 weeks,lotus root brightness decreased by 10,3%,yellow accumulation increased by 16.5%,sensory quality decreased by 18.6%,water loss rate decreased by 0.90%,hardness decreased by 15.4%,fatty acid content showed a decreasing trend,and microorganisms developed in lotus root joints and skin became sticky during 2-3 weeks of storage.After 3 weeks of storage,low-temperature storage alone could not delay the quality decline better.The brightness of lotus root decreased by 4.3%,yellow accumulation increased by 3.1%,water loss rate was 0.58%,sensory score decreased by 16.3%,and hardness of lotus root decreased by 16.7%during low temperature storage(15 days),which were significantly lower than the changes of various indexes during normal temperature storage.And on the 3rd day of storage,the hardness of lotus roots at both temperatures decreased significantly.After storage for 3 days,compared with the control(20℃),low temperature(4℃)significantly delayed the hardness of lotus root.(3)RNA-Seq-based gene mining for lotus root("Elian No.5")hardness 1:lotus root hardness decreased significantly after 3 days of storage.Transcriptome analysis was carried out on lotus root samples stored for 3 days,and the related genes causing hardness decrease in the early storage period were mainly:α-L-arabinofuranosidase gene(LOC104587424),xylanase gene(LOC104587300,LOC104589127,LOC104591922 etc.),Beta-galactosidase gene(LOC104600726),pectate lyase gene(LOC104591566),pectinase gene(LOC104598897,LOC104604877,LOC104606204 and LOC104607428),polygalacturonase gene(LOC104599720)and polygalacturonase inhibitor gene(LOC104603468,LOC104603470,LOC104603472 and LOC104609468).(4)RNA-Seq-based lotus root("Elian No.5")hardness related gene mining 2:lotus root hardness decreased significantly at low temperature(4℃)after 3 days storage compared with the control(20℃),and further transcriptome analysis was performed on lotus root samples at different storage temperatures for 3-12 days.The main genes related to low temperature significantly delaying lotus root hardness decline in the late storage period were preliminarily screened out as follows:a-arabinosidase gene(LOC104593587),xylanase gene(LOC10460533,LOC104612365,LOC104587300 etc.),β-galactosidase gene(LOC104589083 and LOC104588175),pectate lyase gene(LOC104593013 and LOC104604548),pectinase gene(LOC104598592,LOC104598897,LOC104599290 etc.),polygalacturonase gene(LOC104607173,LOC104611520,LOC104597760 and LOC104593217),polygalacturonase inhibitor gene(LOC104593217,LOC104597507,LOC104598708 etc.),pectin esterase gene(LOC104598168,LOC104609251,LOC104587941 etc.),endoglucanase gene(LOC104600374 and LOC104603995).