The nature of quantitative variation in a large set of early maturing sunflower test crosses

Changes in environmental conditions and the EU policy have put more emphasi s on growing alternative crops in the set aside farmlands of western Europe , and sunflowers are increasingly being grown as a minor crop in the UK, Ho wever, long-term success of sunflowers as a commercial crop depends largely on the availability of early maturing, high yielding, disease resistant va rieties. The present study was conducted to investigate the nature of genet ic variation among the available breeding stocks that may have to be exploi ted to produce such cultivars. Analysis of 182 test crosses, produced by cr ossing 13 male sterile (CMS) lines with 14 restorer (SB) lines, has reveale d that genetic variability exists for many important traits, including matu rity, vigour and seed yield. Genetic differences were also detected within the male sterile and restorer groups of lines even though they were classed as early maturing. All types of gene effects, additive, dominance and epis tasis, contributed to variation among the test crosses and dominance was la rgely unidirectional and partial. CMS and SE lines also showed some allelic complementation and the CMS exerted a modest degree of maternal control fo r flowering time. The test crosses were generally more vigorous and high yi elding compared to their inbred parents. But they also matured significantl y late, indicating that all crosses will not be suitable as potential hybri ds for the UK conditions. Genotypic correlations indicated that faster grow th, early flowering, high seed number and seed weight can be combined more readily in the F-1 crosses.