ANALYSIS OF MITOCHONDRIAL-DNA, CHLOROPLAST DNA, AND DOUBLE-STRANDED-RNA IN FERTILE AND CYTOPLASMIC MALE-STERILE SUNFLOWER (HELIANTHUS-ANNUUS)

The extent of variation in the mitochondrial DNAs (mtDNAs), chloroplast DNAs (ctDNAs), and double-stranded RNAs (dsRNAs) of sunflower lines carrying fertile and male-sterility conferring cytoplasms was examined. To minimize nuclear gene effects, efforts were concentrated on two chromosomally isogenic lines, CM400 (fertile) and cmsCM400 (male sterile), which differ only in their cytogenes. A circular 1.45 kilobases (kb) plasmid DNA was found in the mitochondria of the four fertile lines examined, but was absent in the male-sterile line. Restriction enzyme analysis of mtDNAs of the fertile and male-sterile cytoplasms with BamHI, EcoRI, and HindIII revealed no fragment mobility differences between them other than those which could be ascribed to the 1.45-kb circle. Similar restriction analysis of ctDNA showed no differences between fertile and male-sterile cytoplasms. Both CM400 and cmsCM400 contain dsRNA molecules. The number and sizes of these dsRNAs varied from preparation to preparation in both lines. Species of 3.3 and 1.5 kb, which wree the only dsRNAs common to all preparations from CM400, were also the only species common to all preparations from cmsCM400. Thus, no consistent differences between the fertile and male-sterile cytoplasms were seen in these molecules. The specific association of the 1.45-kb plasmid with fertile cytoplasm together with the absence of variation in ctDNA and dsRNA, suggests the involvement of mtDNA in sunflower cytoplasmic male sterility.