Study On The Induction Of Disease Resistance Of Postharvest Winter Jujube By CO Combined With DPI Treatment

Black spot caused by Alternaria alternata is a major disease in the storage of postharvest winter jujube.In this paper,winter jujube was used as the test material,which was fumigated with 10?mol/L CO for 2 h,then immersed in 20?mol/L DPI solution for 5min,air-dried,and finally inoculated with A.alternata.By analyzing the physiological and biochemical defense responses and the expression of defense genes during the infection of winter jujube fruit pathogens,the differences between CO treatment group and CO+DPI treatment were compared to explore the effect of H₂O₂ on the disease resistance induction process of jujube fruits.The effects of CO fumigation treatment on the disease resistance and storage quality of postharvest winter jujube were studied.The results showed that:1.In vitro,0.1–10?mol/L hemin?CO donor?had no significant effect on mycelium growth and spore germination of A.alternata;On winter jujube,10?mol/L CO fumigation treatment could effectively inhibit the extension of lesion diameter and reduce the rate of winter rot,indicating that the inhibition of CO treatment on the infection of winter jujube pathogens was induced by self-resistance of winter jujube instead of direct act on pathogenic bacteria.2.After the winter jujube was fumigated by 10?mol/L CO,the metabolic pathway of phenylpropanol was enhanced.The activities of PAL,C4H,4CL,and CHS were enhanced,and the accumulation of polyphenols,flavonoids and lignin was increased.3.After fumigating 10?mol/L CO,the active oxygen metabolism pathway was enhanced,which promoted the increase of the O₂^·-production rate and the accumulation of H₂O₂ content,Increased activity of NOX,SOD and POD,increased levels of ASA and GSH,The activities of APX and CAT were inhibited.CO enhanced the resistance of winter jujube fruits by regulating the metabolism of active oxygen.4.In the jujube after fumigation of 10?mol/L exogenous CO,The activity of enzymes related to the disease process such as GLU,CHT,PPO and POD was significantly enhanced.5.Compared with CO treatment group,CO+DPI treatment group added DPI,and the phenylpropanoid metabolism,the enhancement of reactive oxygen metabolism pathway and the increase of pathogenesis-related enzyme activity induced by CO treatment were all inhibited.DPI blocked the synthesis of H₂O₂ and the signal transmission of H₂O₂ as a messenger between plant cells,weakened the disease resistance of the fruit,and reduced the quality of the fruit after harvest.6.10?mol/LCO fumigation treatment significantly increased the expression of SOD,POD,PPO,PAL,CHT,GLU and other defense-related genes and related enzyme activities,inhibited the expression of CAT gene and related enzyme activities.Compared with the CO treatment group,the CO+DPI treatment group significantly attenuated or even inhibited the effect of CO treatment on the above defense-related genes and enzyme activities,It further explained that H₂O₂ as a signal molecule indirectly participates in the disease resistance of CO-induced jujube fruits.7.10?mol/LCO fumigation treatment delayed the weight loss rate,hardness and titratable acid content of winter jujube,significantly reduced the reddening rate,inhibited the accumulation of malondialdehyde content,improved DPPH·clearing capacity,maintained the quality of winter jujube after harvest.The effect of CO+DPI treatment on weight loss rate,hardness,titratable acid and reddening rate was not much different from CO treatment,but CO+DPI treatment reduced the effect of CO treatment on malondialdehyde.