RFLP STUDIES OF GENETIC-RELATIONSHIPS AMONG INBRED LINES OF THE CULTIVATED SUNFLOWER, HELIANTHUS-ANNUUS L - EVIDENCE FOR DISTINCT RESTORER AND MAINTAINER GERMPLASM POOLS

One-hundred-and-eighty-one nuclear DNA probes were used to examine res triction-fragment length polymorphism in inbred lines of the cultivate d sunflower (Helianthus annuus L.). The probes were from six libraries : two genomic libraries - one made with PstI and the other with HindII I, and four cDNA libraries - from etiolated plantlets, green leaves, o varies, petals and anthers. Total DNA from 17 inbred lines representin g an overview of the genetic stocks of sunflower, including restorer a nd maintainer lines of the classical cytoplasmic male sterility, was d igested with four different restriction enzymes and probed in 331 prob e-enzyme combinations. Of 181 clones analysed, 73 probes were found to be polymorphic. Genetic distances between inbreds were calculated fro m the resultant proportion of shared bands and submitted to principal component analysis and the UPGMA 'tree-making' method. The RFLP analys is allowed a clear differentiation between restorer and maintainer lin es of the cytoplasmic male sterility, together with a grouping of some of the genotypes from the same origin. The analysis of the accuracy o f distance estimation as a function of the number of probe-enzyme comb inations used, indicates that 40-50 combinations ensure a confidence l evel of near 95%. Considering the inbreds as representatives of the ra nge of cultivated inbreds, estimates of gene diversity, as well as est imates of average gene diversity between and within the sets of restor er and maintainer lines, were calculated. Estimation of gene diversity showed that the available genetic variability in cultivated sunflower , based on allelic frequencies, is lower than that of other plants (H= 0.20). Moreover, we show that the proportion of genetic variability du e to the difference between maintainer and restorer lines (D-m) is abo ut 2%.