Abstract:

The purpose of this study is to analyze the relationship of the occurrence of grape fruit cracking with the cell wall metabolism substances and apoptosis under different concentrations of plant growth regulators in ‘Black Monukka’ grape production, explore the main physiological reasons for the difference of fruit cracking characteristics, and find the most suitable plant growth regulator spraying concentration for ‘Black Monukka’ grape. The easy-to-crack variety ‘Black Monukka’ was used as the test material, different concentrations of plant growth regulators were sprayed 10-15 days after flowering, and the fruit cracking rate was induced by soaking in water for 24 hours after the berries were picked at the mature stage. The water-soluble pectin, protopectin, hemicellulose, and PG, PEP, CE and PL enzyme activities were determined by enzyme-linked immunoassay, and the apoptosis rate was observed and counted by TUNEL staining. The results showed that there were significant differences among different treatments after the berries were soaked in water for 24 h. The fruit cracking rate under the treatment of 100 mg/L gibberellins plus 5 mg/L forchlorfenuron was 56%, which was the lowest and significantly lower than that under other treatments, and the apoptosis rate was relatively low. Protopectin and hemicellulose were very significantly and negatively correlated with the fruit cracking rate, and the PEP enzyme activity had a significantly negative correlation with the fruit cracking rate. Water-soluble pectin/protopectin had very significantly positive correlations with the fruit cracking rate. The results of this study indicate that proper spraying of gibberellin and forchlorfenuron can improve the activities of PEP and CE, increase the contents of hemicellulose and protopectin, and reduce the rate of apoptosis and alleviate the occurrence of fruit cracking.

Key words: grape, fruit cracking, cell wall metabolism, apoptosis, plant growth regulators