In Vitro Induction of Autotetraploids in the Subtropical Fruit Tree Cherimoya (Annona cherimola Mill.)

Polyploidization is a powerful tool in plant breeding that can induce desirable morphological and physiological modifications. This study aimed to establish an efficient in vitro protocol for inducing autotetraploid plants in cherimoya (Annona cherimola Mill. cv. Fino de Jete) using colchicine. Hypocotyl explants from seedlings germinated in vitro were treated with different colchicine concentrations (0.01–0.2%) for 24 and 48 h, and the effects on shoot regeneration and ploidy level were evaluated by flow cytometry and chromosome counting. Regeneration and survival rates decreased with increasing colchicine concentration and exposure time. The most effective treatment for autotetraploid induction was 0.1% colchicine for 24 h, yielding a 10.5% polyploidization rate with 5.8% autotetraploids. Tetraploid shoots were successfully rooted (80%) and acclimatized (100%) under greenhouse conditions. Autotetraploid plants exhibited significantly larger and more rounded leaves, higher chlorophyll contents and an increased Chl a/Chl b ratio compared with diploids, indicating enhanced photosynthetic efficiency. The induction of stable autotetraploid lines in A. cherimola provides a reliable approach for generating novel genotypes with improved physiological traits and potential tolerance to abiotic stress. These results offer valuable material for future breeding programs aimed at developing new cherimoya rootstocks and cultivars with enhanced vigor and adaptability.