PLOIDY ANALYSIS OF CITRUS SEEDLINGS FROM In vivo GERMINATION OF IMMATURE EMBRYOS

Morocco is among the major Citrus exporting countries. However, the majority of varieties is self-incompatible and requires homogeneous planting to avoid cross-pollination, which favors the formation of fruits with many seeds. Therefore, the use of triploidy is a promising way for genetic improvement in Citrus fruits. Rescue of immature embryos in vitro is the most recommended universal method for producing triploid hybrids. The present study evaluates in vivo germination of immature embryos from undeveloped seeds. Thus, seeds were extracted from ripe fruits of Citrus varieties of different species and were classified according to their morphologies (small, flat and normal). Then they were sown in pots containing peat and placed in a greenhouse. The germination rate in vivo of immature embryos is variable depending on the variety, shape and size of the undeveloped seeds. It fluctuated from 2% in the mandarin Anana for the flat shape to 95% in clementine Sidi Aissa for the small size. Similarly, depending on the species, this rate varied for the small size from 40% in Citrus paradisi to 81% in Citrus clementina, followed by Citrus reticulata (74%) and lemon (70%). Depending on the size of the seed, this rate varied from 14% (flat) to 63% (small). On the other hand, Janvier-1 clementine and Eureka lemon were characterized by good growth with an average seedling height of 6 cm. The triploidy and tetraploidy rate were 24% and 2%, respectively. Triploids are found exclusively in seedlings from germination of small seeds. Thus, in vivo sowing of immature embryos seems an interesting and possible route, even if its efficiency varies according to the Citrus varieties. Another molecular study will be started to determine the genetic origin of the seedlings from the polyembryonic mother variety.