Inheritance of Male Sterility in Lesquerella fendleri

ADDITIONAL INDEX WORDS. cytoplasmic effects, epistasis, self incompatibility, hybrid seed production, Brassicaceae ABSTRACT. Lesquerella fendleri (Gray) Wats. (lesquerella, Brassicaceae), native to the southwestern United States, is a potentially useful industrial oilseed crop. The seed oil contains hydroxy fatty acids, similar to castor ( Ricinus communis L.) seed oil. The unique properties of the oil, along with coproducts, allow additional applications that would not compete with castor oil. Plants with vestigial anthers (male-sterile) were discovered in a greenhouse-grown, nonselected population in 1993. The inheritance of the trait was investigated through four crop seasons. Crosses were made among male-sterile and male-fertile plants from an open pollinated population, thus, they were heterozygous for many traits. Statistical analysis indicated that male sterility is expressed as a result of two nonlinked nuclear genes with epistatic relations and different cytoplasms, which cause partial or total fertility restoration. These ratios fit a 13:3 epistatic ratio , indicating that male sterility is controlled by homozygous recessive alleles at one locus in combination with at least one dominant allele at the second locus, i.e., ms1ms1 Ms2_. Some cross results were skewed in favor of fertile phenotypes presumably due to cytoplasmic effects causing partial fertility restoration. Male-sterile lines could be used for hybrid development and this information will be helpful in implementing a strategy for hybrid development. Hybrid plants and higher yields will enhance the potential for commercialization of this new alternative crop. that are functional. Flowers occur indeterminately on inflores- cences. Following anthesis, seeds develop in siliques attached along the axis of the infructescence. A silique resulting from pollination of a single flower may contain up to 32 seeds. Seed yield from lesquerella is determined by the number of siliques, the number of seeds per silique, and the individual seed weight. A sporophytic multiple allelic incompatibility system occurs in some Lesquerella S. Wats. sp. (Sampson, 1958). We have observed that L. fendleri has a similar system of self-incompat- ibility (unpublished). This system insures a high degree of het- erozygosity and a high percentage of outcrossing. Self-incompat- ibility also prevents production of an F 2 generation. Under field conditions, bees, flies, and other insects pollinate flowers that occur from February until June in most low desert elevations. Male sterility has not been reported previously in any Lesquerella sp. Many related Brassica L. sp. exhibit both nuclear and cytoplasmic control of male sterility including Brassica campestris L. (Ohkawa and Shiga, 1981), mustard greens (B. juncea (L.) Czerniak), (Rawat and Anand, 1979), and oilseed rape (B. napus L.) (Yang and Fu, 1990). Cytoplasmic male sterility in many Brassica sp. is the result of specific nuclear and mitochon- drial interactions (Delourme and Budar, 1999). Both nuclear and cytoplasmic male sterility have been re- ported for oilseed rape. Two genes at two loci, designated Ms1 and Ms2, interact so that male sterility occurs when plants are either homozygous or heterozygous for the dominant allele at one locus and homozygous for the recessive allele at the other, indicating dominance epistasis at the Ms2 locus over the Ms1 locus (Li et al., 1988). In another study by Thompson (1972), a dominant cytoplasmic gene was found to restore fertility. Several male-sterile cytoplasmic restorers have been discovered in oil- seed rape as a potential pollination control system for production of commercial quantities of hybrid seed.