Effects Of Pre-harvest GA₃ Spray On Agronomic Traits And Post-harvest Quality Of Mango Fruit

Gibberellin?GA₃?has been widely used in agricultural production.Preharvest spraying GA₃ can significantly improve the fruit yield and storage quality,delay the aging rate of fruit,and have the advantages of no poison,easy degradation and no residue.It i is one of the main regulation of Hainan 'Guifei' mango production.Since 2011,Hainan 'Guifei' mango fruit peel appeared the stay-green phenomenon,and the fruit quality decreased.After investigated the effects of several plant growth regulators on mango.We found that preharvest spraying the high concentration GA₃ induced mango peel appeared stay-green phenomenon.This study use 'Guifei' mango as the experimental material,spraying GA₃ 3 times after flowering with different mass concentrations?50 mg/L,100 mg/L and 250 mg/L?.Researching the effects of preharvest spraying GA₃ on yield,quality,storability of mango fruit,stay-green phenomenon of mango fruit peel,and clarify the physiological mechanism of stay-green phenomenon.In order to provide a scientific basis for the rational use of GA₃ in the production of mango.The main results are as follows:1.The influence of preharvest spraying GA₃ on the yield of'Guifei' mango Preharvest spraying 50 mg/L and 100 mg/L GA₃ increased single fruit weight and set fruit rate of no-empryo fruits,so it significantly increased the yield.Preharvest spraying 250 mg/L GA₃ significantly increased single fruit weight of no-empryo fruits,but decreased set fruit rate,which has a little effect on production per plant.With the increaseing GA₃ concentration,the fruit shape index increased,and the effect on fruit elongation became more significant.2.The influence of preharvest spraying GA₃ on the quality of 'Guifei' mango For fruit at the full ripe stage,the TSS of fruit treated with 50 mg/L was slightly higher than that of CK,and the difference was not significant.Besides,the TSS of fruit treated with 100 mg/L and 250 mg/L GA₃ were significantly lower than that of CK.The titratable acid content of fruit with the 3 GA₃ treatments was higher than that of CK,and the titratable acid content of fruit?0.143%?treated with 250 mg/L GA₃ was 18.85%higher than CK?0.120%?,thus the difference was significant?p<0.05?.The content of Vc in 3 GA₃ treatments was significantly lower than that in CK,and the content of Vc decreased with the increase of GA₃ concentration.So preharvest spraying GA₃ caused the decline of fruit edible quality.3.The influence of preharvest spraying GA₃ on the postharvest ripening and softening of 'Guifei' mango Compared with CK,hardness of fruit treated with GA₃ decreased slower during storage.However,the hardness was all lower than CK at the full ripe period.GA₃ treatment could delay the decrease of pectin content and inhibit the increase of soluble pectin content during the storage of mango.There was a little difference between different concentrations of GA₃ treatment,but the difference was not significant.The peak of ethylene release treated with preharvest GA₃ was delayed for 2 days,and the ethylene release rate decreased gradually with the increase of GA₃ concentration,and the peak of ethylene release treated with 250 mg/L GA₃ was 51%lower than that of CK.The incidence of postharvest fruit increased with the increase of 3 GA₃ treatments,which aggravated the occurrence of postharvest diseases.4.The influence of preharvest spraying GA₃ on the peel pigment and postharvest coloration of 'Guifei' mango At the physiological maturity stage?when harvesting?,with the increase of GA₃ concentration,carotenoid content in pericarp of mango decreased gradually,and anthocyanin content increased,chlorophyll content changed little,so fruit with spraying of GA₃ looks more bright.At the ripe stage?edible state?,with the increase of GA₃ concentration,the carotenoid content had little difference in all the treatments,but the anthocyanin and chlorophyll content increased gradually.Three GA₃ treatments were compared with CK,and there were significant differences in chlorophyll content?p<0.01?.The chlorophyll content in pericarp with 250 mg/L GA₃ treatment?22.72 ?g/g?is 136.37%higher than that of CK?9.61?g/g?.Besides,stagnant green phenomenon occurred in part of the fruit appearance.5.The influence of preharvest spraying GA₃ on the chlorophyll degradation gene of'Guifei' mango Through real-time quantitative analysis of genes related to the degradation of chlorophyll.The results show that,during the fruit ripening process,250 mg/L GA₃ treated fruit compared with the control group,the expression of Chlase?Chlorophyllase??PPH?Pheophytinase??PAO?Pheophorbide a Oxygenase??RCCR?Red Chlorophyll Catabolite Reductase?gene was decreased,especially in the storage period,decreased more significantly delayed the degradation of chlorophyll.The inhibition of PAO was the most obviously at the later stage of storage,and the process of pheophorbide a?green substance?to its red degradation product was inhibited,which eventually led to the phenomenon of stay-green.This study from the physiological and molecular aspects preliminarily explained Effects of pre-harvest GA₃ spraying on yield,quality,storability and stay-green of Mango Fruit.This study enriched and developed the related theory of chlorophyll degradation in fruits,provide a scientific theoretical basis for the GA₃ induced postharvest stay-green and quality decline of 'Guifei' mango,And provide tech-nical support for 'Guifei' mango production.