Studies of pollen grain germination, pollen tube growth, micropylar penetration and seed set in intraspecific and intergeneric crosses within three Cruciferae species

Abstract

Pollen grain germination, pollen tube growth and micropylar penetration were investigated in intraspecific and intergeneric crosses involving Brassica napus L. ssp. oleifera (Metzg.) Sinsk. (oil-seed rape or fodder rape), xBrassicoraphanus Sageret (Raparadish) and diploid (2x) and tetraploid (4x) accessions of Sinapis alba L. (white mustard). For the reciprocal intergeneric crosses between B. napus and xBrassicoraphanus no effective barriers to pollen tube growth on stigmata or in styles were observed. The resulting low frequency of hybrid plants was mainly associated with a low rate of ovules with micropylar penetration per siliqua or with embryo abortion. Hybrid plants could be obtained without use of embryo rescue. In reciprocal crosses between B. napus and S. alba 2x or 4x incongruity barriers were observed on the stigma, in the style, and in the ovary resulting in a low frequency of ovules with micropylar penetration per siliqua. Open flower-pollination compared to bud-pollination generally was the more favourable procedure for pollen grain germination and pollen tube growth in crosses involving S. alba, but for micropylar penetration and seed set no differences were observed. Crosses between S. alba 2x ( 9 ) and B. napus (~) were found to result in a higher frequency of ovules with micropylar penetration as compared to reciprocal crosses or crosses with S. alba 4x. All reciprocal crosses between B. napus and S. alba 2x or 4x were unsuccessful when no embryo rescue was applied. Embryo rescue shortly after pollination, i.e. 2 to 5 days, however, resulted in hybrid seeds and plants, but only when applied to crosses between S. alba 2x ( 9 ) and B. napus ((;). The possible effects of the genome constitution, taxonomic distance and the parthenogenetic and parthenogenesis inducing ability of the parental genotypes on the observed malfunctions at the pre-and/or post-zygotic stage of the pollen grain-pistil interactions are discussed.

Interspecific Crossing Barriers in Sesame (Sesamum indicum L.)

“…In the present study, the percentage of pollen germination in all the crosses was significantly lower than the selfing of corresponding female parent at same time interval after pollination. This is similar to the results obtained by Lelivelt (1993) in intergeneric crosses between B. napus and S. alba (2x) and by Ramesh et al, (2003) in interspecific crosses of sesame. This shows that for pollen germination on stigma, proper recognition substances are necessary which might be lacking to promote pollen germination in interspecific crosses.…”

“…However, reports of Lelivelt (1993) and Ramesh et al, (2003) indicated nonsignificant differences between control and interspecific crosses in B. napus x S. alba and S. occidentale x S. indicum, respectively.…”

Changes in DNA-methylation during zygotic embryogenesis in interspecific hybrids of beans (Phaseolus ssp.)

“…The maternal parent seemed to play an important part in the degree of incompatibility, especially in the crosses using P. coccineus as the female parent. The maternal link to cross-compatibility has also been reported in the other interspecific crossing (Lelivelt 1993). More recently, Garcia et al (2005), FitzGerald et al (2008), and Hoe Huh et al (2008 have all supported the hypothesis that the maternal genome plays the predominant role in controlling early seed development.…”

Trigenomic Bridges forBrassicaImprovement

“…Matromorphy (production of progeny that are genetically identical to the female parent) is a common phenomenon in interspecific crosses (Ayotte et al, 1988;Lelivelt, 1993). Matromorphs are thought to develop following micropylar penetration by the pollen tube and deposition of the male gamete in the embryo sac, followed by a parthenogenetic outgrowth of the unreduced egg cell without fertilization and subsequent elimination of the male gamete (Noguchi, 1928).…”