PLOIDY LEVEL ANALYSIS OF SEEDLINGS FROM EMBRYOS EXTRACTED FROM SEEDS RARELY PRODUCED BY TRIPLOID MANDARIN HYBRIDS

Triploidy is a promising way for the creation of new tangerine seedless fruit hybrids. Citrus triploid hybrids are generally sterile, although they can sometimes produce fruit with very few seeds. Hence the interest in analyzing, by flow cytometry, the level of ploidy of embryos from these seeds and testing two culture media in vitro for their germination in vitro. The seeds were extracted from the ripe fruit of the triploid mandarin and the seeds derived embryos were cultured in vitro on a Murashige and Tucker medium (1969) according to two compositions M1 = MT + 1 mg / l gibberellic acid and M2 = MT + 0.25 g / l adenine sulfate. The triploid seedlings were identified by flow cytometry at the INRA Kenitra laboratory level. The In vitro germination rate of embryos is 86% and 78% respectively for M1 and M2 media. Whereas, according to the mandarin hybrids, it is 86% and 79% respectively for HT11 and HT44. Furthermore, analysis by flow cytometry of the leaves of young seedlings showed that the triploidy rate is 94% for the HT11 hybrid and 38% for the HT44 hybrid. The preliminary results of this study clearly explain that sterile triploid hybrids can spontaneously give diploid or triploid seeds. Likewise, the degree of sterility varies according to the triploid hybrids which differ in the ability to produce seeds.

The diploid and triploid seedlings obtained will be analyzed by molecular markers in a later study in order to determine their genetic origins (zygotic or nucellar).