an economically viable crop requires improvement of many traits, such as rubber yield and plant vigor. Male sterility is characterized by a lack of functional pollen and has been identified in over 600 species including many agriculturally important
, hybrid vigor can improve the yield, resistance, and quality of pepper. Cytoplasmic male sterility facilitates the production of hybrid seed. A major concern of hybrid seed production is prevention of self-pollination that can produce seeds that are not
. Self-sterility is a common reproductive phenomenon in plants. It describes the reduction in seed set following selfing relative to that following outcrossing and is widely distributed among flowering plants ( Mahy and Jacquemart, 1999 ). Self-sterility
Hybrid-onion ( Allium cepa ) seed is produced using sources of CMS. The first source of onion CMS was described by Jones and Clarke (1943 ), and male sterility is conditioned by the interaction of the male-sterile (S) cytoplasm with the
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.
The inheritance of male sterility was studied in germplasm of common bean (Phaseolus vulgaris L.) obtained from the Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia. The source was selected for plants with high pollen abortion rates (mean = 91%) and for failure to set any seed or pods by self-pollination when grown in screened greenhouses. These male-sterile plants were crossed with the snap bean ‘Sprite’, and the resulting F1 progenies were all male-sterile under greenhouse conditions. The F1 plants were backcrossed to ‘Sprite’ and the BC1 progenies did not segregate for male-fertile plants under field conditions. Four more backcrosses to ‘Sprite’ have produced progenies that were uniformly male-sterile. It was concluded that the CIAT source of male sterility is inherited through the maternal parent and is cytoplasmic. Nineteen commercial cultivars of snap beans and dry beans were crossed onto BC3 plants, and none of these genotypes restored the pollen fertility in F1 progeny.
Eggplant ( Solanum melongena ) is an important vegetable globally. With rising labor costs, it is estimated that the utilization of eggplant with male sterility will play a greater role in their cultivation. Hybrid seed production using male
Genetic male sterility was found in the Bell type pepper variety ‘All Big’. Breeding experiments suggest that the character is controlled by a single recessive gene in Bell type pepper varieties. This new source of male sterility appears to be superior to sources formerly reported by being highly stable and already present with a Bell type genetic background, and by the absence of undesirable pleiotropic effects. The usefulness of the character for hybrid seed production is discussed.
Autotetraploid watermelons were produced by treating the growing points of diploid seedlings with aqueous colchicine solution or by soaking diploid seeds in colchicine solution. The soaking method was more effective.
Diploid pollen was apparently more viable than tetra-ploid pollen. Examination of germinating tetraploid pollen revealed that while over two-thirds germinated normally a small percentage sent forth 2, 3 or 4 normalsized pollen tubes or a single bifurcated tube. Germinating diploid pollen always put forth only one unbranched pollen tube. Tetraploid plants did not set fruit when pollinated with pollen from tetraploids; however, they did set fruit when pollinated with pollen from diploids.
Cytological observations were made of pollen mother cells of both diploid and tetraploid plants. Meiosis in diploids was regular; however, irregularities were observed in tetraploids. Examination of some pollen mother cells of tetraploids at the quartette stage revealed micro sporocytes in addition to the 4 microspores. The abnormal quartette formations and lower pollen viability of tetraploids were believed associated with irregularities observed at meiosis. Preliminary investigations of megaspore formation revealed no apparent differences between the diploid and tetraploid megaspores. Although meiotic irregularities were found, a sufficient amount of apparently viable pollen was observed. A physiological basis for the self-sterility is suggested.
Several cytoplasmic-genic male-sterile (partially fertile) cultivars were developed in pepper. Three cultivars demonstrated different levels of male sterility; male sterility stability of ‘Bikura’ was reliable for hybrid seed production.