Obtaining seedless cultivars of tangerine for the fresh-fruit market using mutation induction techniques

Abstract

The Brazilian citriculture holds a worldwide outstanding position on the production and exportation of citrus juice, but it is not remarkable on the fresh fruit market. Amongst citrus plants, the tangerines and their hybrids make the most important group of fresh fruits. An important requirement of the fresh fruit marked is the commercialization of seedless fruits. Thus, to actively take part on this market, it is necessary to change the varietal profile of the tangerines cultivated in Brazil, which bear an average of 20 to 30 seeds per fruit. Traditional breeding methods are difficult to implement on citrus plants. Researches on inducted mutagenesis have been carried out in many countries, including in Brazil, resulting in commercial mutants of seedless tangerines, oranges and lemons. The objective of the present work is to obtain mutant populations of the tangerines Thomas IAC 519 and Fremont IAC 543, developed from propagation material exposed to gamma ray irradiation, using three methods. 1) In vivo mutation induction through irradiation of cuttings (buds), followed by grafting. 2) Two methods of in vitro mutation induction, using tissue culture, as follows: a) Obtaining regenerated plants from irradiated internode segments, b) Obtaining regenerated plants from irradiated epicotyl segments. These new plant populations will then be evaluated, in search of mutants that bear seedless fruits or other characteristics, such as: dwarf plants, changes of fruit maturation time and resistance to pests and diseases. This present project can be consider as a continuation of another one, funded by FAPESP, named Selection of new varieties of tangerine for São Paulo State (02/01121-1). On that project, the varieties Thomas IAC 519 and Fremont IAC 543 were selected, for bearing fruits with good characteristics and to showed more tolerance to alternaria black spot, an important citrus disease that affect tangerines in different areas of São Paulo State. (AU)