Global epigenetic and metabolic changes accompany the alterations in fruit size and shape of Cucurbita pepo L. intra-species grafting

Abstract

To further understand the impact of grafting on fruit characteristics and to comprehend the mechanisms involved in graft-induced changes we studied homo- and hetero- grafted Cucurbita pepo cultivars (cv.) that vary in fruit size and shape. C. pepo cv. ‘Munchkin’ (small fruit) and cv. ‘Big Moose’ (large fruit) as well as cv. ‘Round green’ (round fruit) and cv. ‘Princess’ (elongated fruit) were homografted and reciprocally heterografted. The results show significant changes in fruit size when ‘Big Moose’ was grafted onto ‘Munchkin’ rootstocks in comparison to homo-grafted controls. Moderate changes in fruit shape were observed when grafting of cv. ‘Round green’ and cv. ‘Princess’ were performed. This is the first report of such phenotypic changes after intra-species/inter-cultivar grafting in Cucurbitaceae. Additionally, we found significant changes in i) secondary metabolite profile, ii) global DNA methylation pattern and iii) miRNA expression patterns in grafted scions and iv) DNA methylation on graft-induced phenotypic changes in grafted plants. Our results contribute to further understanding graft-induced effects on fruit morphology in intra-species grafting. Furthermore, our results pave the way for understanding the role of phenolic metabolites and epigenetic molecular mechanisms on the phenotypic changes recorded.