Mutant selection and induction in 'Pera' sweet orange using gamma-rays

Abstract

The objective of the present research was to evaluate the methodology to select mutants of interest: in the 'Pera' sweet orange (Citrus sinensis L. Osb.), using bud gamma irradiation with 4,0 kR. The cutting back method was applied to the V 1 M 1 branchs originated after irradiation, and the six first buds from these: branches were used to obtain V2M1 generation. Buds from these V2M1 branchs were grafted to get the V3M 1 generation. Selection was made in the quadrarits (North, South, East and West) of the surviving plants, and 127 were selected. These plants difficred from the controls in relation to agronornic characteristics such as canopy height, seed number in the fruits, yield, fruit shape, leave rnorphology, etc. The higher frequency of morpliological changes observed in the leaves and fruits leads to conclude that the fifth and sixth litids along the V 1 M 1 branch should be used when the present methodology is applied. The system of dividing the selecting plarits into quadrarits proved to be efficient because, despite the culting back method used, the plarits still showed chimerism. The selected clones are under evaluation in field condition in order to confirm the nature and the genetic stability of changes.