Protoplast fusion for production of hybrid plants between Citrus and its related genera

Abstract

Electrofusions between embryogenic callus protoplasts from Citrus species and mesophyll protoplasts from other Aurantioideae representatives, including Clauseneae, Triphasiinae, Balsamocitrinae, and Citrinae, were performed to estimate the range within which fusion could produce embryos. Production and regeneration of hybrids between Citrus and allied species depended on the taxonomical distance of the parents; the closer the mesophyll parent were taxonomically to Citrus, the greater the potential of forming viable hybrid plants. The most successful fusions were obtained between Citrus and other Citrinae species. Most of these combinations produced embryos that generated normal plantlets with good rooting ability. Embryoids from fusions with Balasamocitrinae species initiated numerous adventitious buds, but they were incapable of rooting. When these shoots were grafted onto existing stocks, some produced deformed leaves. In fusions between Citrus and Clausenae species, most of the regenerated shoots were weak and abnormal, but a few normal plantlets were rescued. In fusions with Triphasiinae species, the embryos which survived failed to develop shoots. Thus, from fusions involving Triphasiinae species, which considered closer to Citrus than are Clausenae species, we were unable to regenerate any somatic hybrids.