Inheritance of seedlessness and the molecular characterization of the INO gene in Annonaceae

Herança da ausência de sementes e a caracterização molecular do gene INO em Annonaceae

Abstract

The inheritance of the seedless fruit characteristic of Annona squamosa has not yet been explained. Molecular techniques may aid breeding programs, mainly in the assisted selection of the target gene. The INO gene may be related to seed development in these fruits. The objective of the present paper was to investigate the inheritance of seedlessness in the 'Brazilian seedless' sugar apple and INO gene conservation in Annona squamosa and Annona cherimola x Annona squamosa genotypes by assessing their homology with the INO database genes. The F₁ generation was obtained by crossing the mutant 'Brazilian seedless' (male genitor) (P₁) with the wild-type A. squamosa with seeds (M₁ and M₂, female genitors). The INO gene was studied in mutant and wild-type A. squamosa (P₁, M₁, M₂ and M₃) and in the Gefner atemoya (A. cherimola x A. squamosa) (M₄) cultivar. The DNA was extracted from young leaves, and four sets of specific primers flanking the INO gene were amplified. The seedless characteristic was identified as stenospermatic in the fruits of parental P₁, suggesting monogenic inheritance with complete dominance. High sequence similarity of the INO gene amplifications in the sugar apple accessions (M₁, M₂, M₃) and the atemoya cultivar Gefner (M₄) reinforces the hypothesis of their conservation.

Keywords:
Annona cherimola x Annona squamosa; Annona squamosa; genetic improvement