Abstract

Gamma irradiation of buds is a technique that has been successfully used in citrus breeding programs that seek to produce seedless or low seeded selections of known cultivars. In 2007, the Pontificia Universidad Católica de Chile CITRUS lab with FONDEF funds started a new breeding program of mandarins and lemons using this technique. The gamma irradiated and grafted buds were grown in commercial nurseries and then transplanted in 2009 to a field trial with 4500 hybrid mandarins, 1200 clementines and 2500 lemons, in Pomaire, Chile (33°39’S, 71°10’W). First evaluations of fruit seed content were made between 2010 and 2011. Early productions were achieved by the use of high density planting, minimal pruning managements, fertirrigation and enhancement of cross pollination using 10 to 12 hives/ha. After 2 harvest seasons, most phenotypical variations have been observed in lemons, obtaining 164 seedless selections, 4 thornless selections and a different fruit shape and compact selection interesting for ornamental purposes. In the case of mandarins, 14 individuals have been found as seedless selections and an individual shows narrow leaves, kumquat type fruit with low seed production. Techniques used in this program allow shortening in 5 years the time spent obtaining new citrus varieties. The stability of mutations detected is being evaluated and new commercial field trials will be established with the selected materials