Transmission of chlorophyll deficiencies in Medicago sativa: Evidence for biparental inheritance of plastids

Developmental patterns and transmission of two chlorophyll deficiencies were studied in tetraploid Medicago sativa L (alfalfa). Both chlorophyll deficiencies originally appeared as sectors within otherwise normal (green) tissue. One of the deficiencies arose in tissue culture and had yellow-light green sectors in normal leaves and stems. The other variant was discovered in a breeding population and exhibited albino sectoring in shoot tissues. Neither chlorophyll deficiency was sap-or graft-transmitted, indicating that virus infection was not responsible for the irregularities in coloration. Developmental patterns in sectored plants were characteristic of the sorting-out of normal and abnormal plastids. Significant reciprocal differences in rates of transmission were observed for both traits in crosses of chlorophyll-deficient and normal plants. Transmission of both chlorophyll deficiencies was higher through the pollen than through the egg. All developmental and genetic evidence strongly suggests that both chlorophyll deficiencies represent plastid mutations, and that plastids are inherited biparentally in M. sativa.