Seed pod shattering in the genus Lotus and its overcoming

Abstract

Birdsfoot trefoil (Lotus corniculatus L.) is a perennial species that is known for its outstanding characters as a crucial component of meadow and pasture vegetation and a highly successful fodder crop. However, its cultivation has been limited by the inability to control pod shattering. The anatomic and physiological bases of pod shattering are known and are considered to be controlled by more than one gene. This paper reviews the known causes of pod shattering and potential ways of overcoming pod indehiscence in L. corniculatus. Genetic transformation is possible in the genus Lotus; however, the useful genes determining the seed pod indehiscent character have not been identified yet. The only way of introducing pod indehiscence characters into L. corniculatus is by interspecific hybridization within the genus Lotus; embryo rescue and protoplast cultures are promising. To determine useful genotypes for crosses, investigations of pre-and post-fertilization barriers are necessary. To that end, we present here a convenient procedure for a whole-mount clearing treatment of immature seeds that leaves the cell walls of tissues intact. This is a useful technique for the study of post-fertilization barriers in Lotus.

Generation and Characterization of Interspecific Hybrids of Lotus uliginosus × Lotus corniculatus

“…After crossing L. corniculatus × L. uliginosus (4 x ), only one globular stage embryo (day 7) was observed by Řepková and Hofbauer (2009) in 30 pollinated flowers analyzed. However, we were able to isolate many embryos at the heart stage or at later stages with greater success in plant acclimation.…”

“…Pre‐ and postfertilization crossability barriers may affect interspecific hybridization in Lotus . Řepková and Hofbauer (2009) described prefertilization barriers constraining the ability of pollen grains to germinate on the stigma and the pollen tubes to grow through the style. Postfertilization barriers include defects in the endosperm during embryo development (Sharma et al, 1996; Galati et al, 2006) as was observed in our experiments.…”

“…Hybrid detection was accomplished using two different approaches: genome size analysis and molecular markers. Both tools are powerful and faster for identification of large numbers of hybrids compared with isozyme or chromosome analyses (Řepková and Hofbauer, 2009). Information from the model species L. corniculatus var.…”

“…Three F 1 plants produced more than 1000 seeds after being pollinated with each other. Řepková and Hofbauer (2009) and Isobe et al (2001) recommend backcrossing F 1 plants with one parental species to increase fertility in hybrid plants.…”

“…Natural interspecific hybridization is restricted in the genus Lotus due to pre‐ and postzygotic barriers (Řepková and Hofbauer, 2009). Therefore, embryo rescue could provide a feasible strategy to obtain interspecific hybrids (De Lautour et al, 1978; Sharma et al, 1996).…”