Inheritance of a Mutation Influencing Chlorophyll Content and Composition in Cowpea

Chlorophyll‐deficient mutants are useful for studying the functional significance of photosystem components and the influence of chlorophyll composition on productivity. Individual mutants can exhibit changes in several characteristics, such as the contents of chlorophylls a and b, and the chlorophyll a:b ratio. It is not known which of these characteristics provides the least ambiguous classification of the mutant phenotype. Inheritance of a chlorophyll‐deficient mutation in cowpea [Vigna unguiculata (L.) Walp.] was studied by crossing the mutant to its presumed parent ‘California Blackeye No. 3’, and a genotype specifically chosen for its dark green foliage. Chlorophyll a and b content and chlorophyll a:b ratios in leaves of progeny were measured. Chlorophyll a:b ratio provided more distinct classification of progeny than chlorophyll content. Segregation of the F1, F2, and backcross generations for chlorophyll a:b ratio was consistent with the hypothesis that the mutation involves a single recessive nuclear gene.