Monoecy and gynomonoecy in Spinacia oleracea L.: Morphological and genetic analyses

Two cosexual spinach lines, 03-336 and 03-258, were examined to investigate their sex expression. We found that line 03-336 consisted of plants bearing both pistillate and staminate flowers on the same individual (strictly monoecious type), while line 03-258 consisted of plants with both pistillate and hermaphroditic flowers on the same individual (gynomonoecious type). Interestingly, the two lines exhibited distinct patterns of inheritance when crossed with the pistillate plants derived from a dioecious line. The strictly monoecious character was considered to be conditioned by the known allele Xm, whereas the gynomonoecious character appeared to be governed by a novel monoecious allele or modifying gene(s) that may affect the sex expression.