Studies on reproductive characteristics of an interspecific chimera between Brassica juncea and Brassica oleracea

Periclinal chimera plants of red cabbage and tuber mustard were studied for investigating reproductive processes. In the shoot apical meristem of chimera TCC (L1-L2-L3, L1 being the outermost layer of shoot apical meristem, L2 the middle layer, L3 the innermost layer; T = tuber mustard, C = red cabbage), the outermost layer was derived from tuber mustard, while the middle and the innermost layers were from red cabbage. In the present study, displacement of the L1 cell layer was found to result in infertile plants. The viability of TCC’s pollen from the L2 layer became significantly lower than that of red cabbage, and the self-pollinated embryo aborted at an early stage. Anatomical observation of ovules showed that the cellularized endosperm developed partially and degraded prematurely at the globular-embryo stage. Ovule culture was carried out to rescue the selfed embryos of TCC, and the results showed that ovules at 16 days after pollination could be rescued on Murashige and Skoog (MS) medium supplied with 3% sucrose, 0.2% active carbon, 400 mg/l glutamine, and casein hydrolysate. Morphological, chromosomal, and molecular identifications consistently showed that the selfed progeny of TCC was red cabbage. These investigations indicated that the heterologous L1 cell layer greatly influenced the reproductive characteristics of the plants, although it did not participate directly in gametogenesis and embryo ontogenesis.