Genetic and Chlorophyll Studies of a Yellow-Green Mutant in Muskmelon

Chlorophyll-deficient individuals have been reported in most species of plants studied intensively by genetic methods. The majority of these chlorotic types have been shown to be the expression of a single gene mutation. However, there is a large group of types that exhibit maternal inheritance, and transmission of the deficiency to their offspring is conditioned by the cytoplasm. Until rather recently most workers have been content to report the hereditary nature of the individual deficiencies and their end results without attempting to analyze the physiological effects upon the plant. The chief hindrance to analytical and quantitative studies of the pigments has been the laborious, complicated, and time-consuming methods for their extraction, chemical separation, and identification. Comparatively rapid and simple techniques are now available for the extraction of chlorophyll from plant tissues and the quantitative determination of the chlorophyll components a and b. Highkin (6) working with barley analyzed eight apparently chlorophyll-deficient types (called chlorinas) of known genetic constitution. One mutant was entirely lacking in chlorophyll b. Another had a higher total chlorophyll content than normal green plants. Two were found to be similar to normal green plants in total chlorophyll content and in the ratio of chlorophyll a to chlorophyll b. This indicates that a deficiency of pigments other than chlorophyll may determine the chlorotic appearance of some of these plants. Three others were evidently chlorotic because of low chlorophyll content, and one extremely chlorotic type was completely lacking in chlorophyll. Various types of chlorophyll-deficient plants are of fairly common occurrence in inbred lines and segregating progenies of muskmelons, Cucumis melo L. The writer has studied the genetics of several of these deficiencies. The present report discusses the mode of inheritance and the physiological effects of the gene controlling one of them.