Leaf Marks in Medicago, With Special Reference to Their Inheritance in Medicago truncatula

Abstract

Leaf marks in the genus Medicago are described and the anatomical basis and genetic control of marks and flecks in M. truncatula analysed. The purple pigment in flecks or marks is confined to the epidermal cells. Yellow marks are due to reduced chlorophyll in palisade cells, and white marks to reduced chlorophyll, as well as larger air spaces between palisade cells and detached upper epidermis. White and yellow marks are controlled by a gene in which seven alleles were identified which determine colour and position, white being dominant to yellow, and, in order of decreasing dominance, upper, central, and basal positions along the midrib. Another gene, independent of the one controlling yellow or white marks, controls both the production of a central purple mark and the purple borders around marks. A comparison is made between the genetic control of marks in M. truncatula and those reported for other Medicago and Trifolium species.