Physiological and transcriptomic analysis of abnormal young berry abscission in different grapevine cultivars grown in arid regions

Introduction Abnormal early berry drop is a major factor affecting grape yield, and differences in the physiological and transcriptional responses to berry drop among different cultivars have not yet been clarified. Methods While each grape cultivar exhibits unique physiological traits associated with berry drop, there is a notable scarcity of research addressing the physiological, biochemical, or molecular causes of young berry drop across various cultivars. This study employs statistical methods, alongside data on physiological and biochemical properties and transcriptomic sequencing, to evaluate the behaviour and dynamics of early berry drop in several grape cultivars in the field. The objective is to analyze the physiological traits of these cultivars and identify genes that are differentially expressed in relation to young berry drop. Results Of the four grape cultivars considered here, the maximum rate of young berry drop took place between 9 and 12 days following full bloom, with differences among cultivars. The activities of PG and Cx in the abscission stalks were significantly higher than those in normal stalks or berry tissues. Hormone profiling analysis confirmed that the accumulation of ABA in berry tissues is cultivar-specific, and there are differences at the tissue level. The ABA concentration in the detached stalks remains relatively high. Finally, transcriptome profiling analysis found differentially expressed genes related to abscission, which were mainly enriched in plant hormone signal transduction, pentose and glucuronic acid interconversion, phenylpropanoid biosynthesis pathways, amino sugar and nucleotide sugar metabolism. Discussion This study provides the causes of early grape berry abscission at physiological and molecular levels. The candidate genes and signaling pathways discussed herein, there exists significant potential for theoretical advancement regarding the regulation of berry retention and loss in viticulture.