Development of tomatillo (Physalis ixocarpa Brot.) autotetraploids and their chromosome and phenotypic characterization

Abstract

The tomatillo, Physalis ixocarpa Brot. (2n = 2x = 24), is an important crop in Mexico, and it is becoming appreciated in other countries. Polyploidy induction is expected to increase its breeding potential. The objective of this work was to develop and characterize tomatillo autotetraploids through colchicine-based induction. Young seedlings of the Rendidora cultivar were treated for 24 h with colchicine in concentrations ranging from 0.04% to 0.20%, and ploidy levels were tested by cytological and flow cytometry techniques. Autotetraploidy was induced with colchicine concentrations of 0.12% and 0.16%, with success rates of 67% and 65%, respectively. Presence of univalents, bivalents and multivalents was observed in prophase I and metaphase I. The basic genome size was not altered in the third generation progeny from treated plants. Autotetraploid plants were fertile and productive, but their pollen development was lower than their diploid counterpart. The polyploid plants showed higher values for life cycle length, plant height, fruit weight and equatorial diameter, fruits per plant, and soluble solid concentration. This is the first report of an autopolyploid cultivated tomatillo. Its genome duplication is readily induced with production of fertile plants, and may be valuable to introduce genetic plasticity in this crop.