An Intergeneric Hybrid of Microcitrus Papuanaand Citrus Medica

Abstract

The first reported hybrid between Microcitrus papuanaH. F. Winters, Brown River finger lime, and Citrus medica.L., citron, is recorded and some of the prominent attributes of this new intergeneric hybrid are described. The hybrid was made for the purpose of creating a genetic bridge for gene exchange between species and genera in the orange subfamily Aurantioideae of the family Rutaceae. Important barriers to gene exchange are ovule and pollen sterility in the F ₁generation and the widespread occurrence of apomixis in the Aurantioideae. Attributes of this hybrid most relevant to citrus breeding are small stature, remontant flowering and fruiting, ease of rooting from cuttings, very short reproductive cycle, zygotic reproduction, sufficient degree of fertility to function in further breeding, and tenderness to cold. The hybrid appears to have a significant potential for improving citrus rootstocks in the areas of size control and ease of propagation. The attribute of a very short reproductive cycle, inherited from Μ. papuana,may have a potential for obtaining precocious bearing in seedling progenies, and thus reduce the juvenility component of the long time period between origination and completion of validation testing.