ARS | Publication request: A New Cytotype of Lesquerella Pallida

Submitted to: Association For The Advancement Of Industrial Crops Conference
Publication Acceptance Date: August 15, 2004
Publication Date: September 19, 2004
Citation: Ames, D., Ray, D.T., Dierig, D.A., Tomasi, P. 2004. A New Cytotype Of Lesquerella Pallida. Association For The Advancement Of Industrial Crops Conference. P. 19

Technical Abstract: The fatty acid seed oil profile of many Lesquerella species makes them ideal candidates for use in an assortment of industrial applications. Efforts to introgress higher lesquerolic acid content from L. pallida into L. fendleri have resulted in hybrids with improved oil profiles but low levels of fertility. This study was initiated to study the chromosome numbers and pairing in the parent species and interspecific hybrids. Meiotic chromosome pairing in L. pallida, L. fendleri and the interspecific hybrid L. pallida x L. fendleri was visualized microscopically by staining immature anthers with aceto-carmine and isolating meiocytes. Diakinesis or metaphase I chromosome configurations were examined and scored to determine chromosome number and pairing. The interspecific hybrids of L. pallida x L. fendleri were found to be sterile, and to enhance fertility the chromosome number was doubled using colchicine. The doubled interspecific hybrids were all found to have 24 chromosomes (2n = 24, n = 12). This implied that the chromosome number of the L. pallida and L. fendleri parent plants were 2n = 12 (n = 6). L. fendleri was found to be 2n = 12 (n = 6, with 6 bivalents, 6 II). However, 19 L. pallida plants were analyzed, and all had 2n = 34 (n=17, with 17 II), rather than n=6, as was expected and has been previously reported. The n = 17 L. pallida is a never before described cytotype, and is undoubtedly a polyploid (triploid), with aneuploidy (6 + 6 + 6 ' 1 = 17) of an n = 6 L. pallida population. As natural L. pallida populations are small and isolated, polyploidy and aneuploidy would not necessarily be uncommon, especially around the periphery of the species. It appears that the n = 17 L. pallida plants were not used in making the interspecific hybrids with L. fendleri, although the n = 6 L. pallida has yet to be found. The hybrids do show differing amounts of fertility, and this may be due to differing amounts of chromosome pairing. The most common pairing during meiosis in the hybrids was 11 II + 2 I (11 bivalents + 2 univalents), followed by 10 II + 4 I and 12 II; with anaphase bridges detected at a high frequency in particular plants. Although the data are scant, it appears that there may be a positive correlation between chromosome pairing and fertility (plants with predominately 12 II having the highest fertility, and the fertility decreasing with increased numbers of univalents).