Correlation between polyovules and number of pistil lobes (stigmatic rays) in sugar beet (Beta vulgaris L.)

The polyovules phenomenon in sugar beet has the same importance for breeding as multigermity, because only mono-ovulic monogerm plants can be used for mechanized cultivation. The polyovules trait was investigated in two Japanese lines, mono-ovulic line NK-219-O and polyovulic line NK-183-cms. Plants of the former had three pistil lobes (stigmatic rays) in each flower, a single ovule per ovary, a single seed in the mature fruit and a single seedling germinated in subsequent tests. Plants of the latter had 5-6 pistil lobes in each flower, 2-3 ovules per ovary, double-seeds and double-seedlings. The correlations between a Pistil Lobes Index (PLI) and the number of ovules per ovary, percentage of double-seeds in an X-ray test, and percentage of double-seedlings in germination tests were 0.885, 0.838, and 0.749, respectively indicating close associations. These results are important both in sugar beet breeding for indirect selection to eliminate the undesirable polyovules trait and for botanical investigations of the relationship among different parts of the gynoecium.