Induction and selection of mandarin mutants with fruits containing low number of seeds.

Abstract The Brazilian citrus industry has a worldwide presence for production and export of sweet orange juice, but it has little contribution to the production of fruits for the fresh fruit market. One requirement of this market is the production of seedless fruits. The Fremont IAC 543 mandarin produces fruits with good commercial qualities, large numbers of seeds (10-12), and plants with resistance to Alternaria brown spot (ABS), an important disease present in several countries. The objective of this work was to induce and select mutants of Fremont IAC 543 mandarin with seedless fruits or fruits with a low number of seeds, using gamma-ray induced mutagenesis. In vivo buds were irradiated with doses of 20 and 30 Gy of gamma-rays. After irradiation and grafting of 2000 in vivo buds with each mutagenic dose, 4000 plants were produced and planted in an experimental field. During development of these plants, they were pruned several times allowing only the development of M1V4 branches or more advanced ones (without new grafting). A total of 32 branches were selected during the harvesting period because they produced seedless fruits and nine mutant clones were selected after another vegetative multiplication. Fruit and juice qualities, including seed number of the fruits, were evaluated in a further experiment including six mutants and a control. The results obtained showed that all mutants produced fruits with a lower number of seeds (between 3.7 and 9.1 seeds per fruit) in relation to the control (22.0 seeds per fruit), but without the existence of other alterations (fruit metric and chemical characteristics of the juice). All selected mutants (nine) are participating in advanced agronomic evaluation experiments, with a greater number of replicates and several local checks, in order to evaluate commercial yield, presence of chimeras, disease resistance and organoleptic quality of the fruits.