MUTANT SELECTION AND INDUCTION IN PERA SW EET ORANGE USING GAMMA-RAYS

The objective of the present research was to evaluate the methodology to select mutants of interest in the 'Pera' sweet orange (Citrus sinen sis L. Osb.), using bud gamma irradiation with 4,0 kR. The cutting bac k method was appplied to the V1M1 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 V3M1 generation. Selection was made in the quadrants (North, South, East an d West) of the surviving plants, and 127 were selected. These plants d iffered from the controls in relation to agronomic characteristics suc h as canopy height, seed number in the fruits, yield, fruit shape, lea ve morphology, etc. The higher frequency of morphological changes obse rved in the leaves and fruits leads to conclude that the fifth and six th buds along the V1M1 branch should be used when the present methodol ogy is applied. The system of dividing the selecting plants into quadr ants proved to be efficient because, despite the cutting back method u sed, the plants still showed chimerism. The selected clones are under evaluation in field condition in order to confirm the nature and the g enetic stability of changes.