Taxonomy and Nomenclature in Citrus

Abstract

MANY HORTICULTURISTS are inclined to question the utility of knowledge concerning the botanical classification of the plants with which their studies or work are concerned, and for those engaged in certain fields of horticultural research this attitude may have some justification. On the other hand, such knowledge is almost indispensable to the breeder and finds important applications in certain other fields. An illustration is afforded by the problem of rootstock-scion relations in general and graft compatibility and virus reactions in particular. In both of these cases, knowledge of natural relationships, as reflected in botanical classification, provides a basis for both understanding and predicting rootstock-scion relations and virus reactions. Indeed the tristeza virus rootstock-scion reactions so extensively reported by virologists and horticulturists in recent years have provided information of great value concerning the degree of natural relationship between the rootstocks employed. Likewise the colorimetric identification tests developed a few decades ago and considerably extended and refined in recent years have contributed useful information in this connection. An example is afforded by the rough lemon, which commonly has been grouped with the true lemons and assigned to Citrus limon. Its reactions to the tristeza virus and colorimetric tests cast extreme doubt on the validity of this classification and suggest that the rough lemon may deserve species standing, a belief long held by some botanists and horticulturists. Indeed these reactions actually indicate possible relationship to the Rangpur lime, likewise a conclusion reached by several botanists.