Development of the Embryo of Medicago Sativa L. After Normal Fertilization and After Pollination by Other Species of Medicago

Abstract

The embryonic development of diploid and tetraploid Medicago sativa from the formation of the zygote to mature seed is described and illustrated. The embryo reaches the global stage at 7 to 8 days; the heart stage at 11 to 13 days; and the torpedo stage at 14 to 16 days after pollination. Full size is attained at about 25 days but food reserves apparently continue to be stored and maturity may not be reached until about the 35th day.Pollination of M. sativa stigmas with pollen from highly incompatible species failed to produce mature embryos. Crosses involving M. lupulina produced no sign of embryo development. However, when M. arborea, M. blancheana, M. marina, M. platycarpos, M. rigidula, M. ruthenica, or M. scutellata was used as a pollen parent the early stages of embryonic growth were initiated.

The Hybridization Barrier between Herbaceous Medicago sativa and Woody M. arborea Is Weakened by Selection of Seed Parents

“…The unsuccessful attempts to hybridize alfalfa and M. arborea have not been reported until now, except for a report in 1963 [ 5 ]. Our failed attempts prior to 1998 and 1998–2002, herein reported, used male sterile alfalfa seed parents that were unrelated to ones that have since produced hybrids.…”

“…Historically, the hybridization barrier between M. sativa and M. arborea (both autotetraploids, 2n = 4x = 32) was thought to be complete. Fredrickson and Bolton in 1963 reported M. arborea pollen growth into the ovarian cavity of alfalfa, but no hybrids were obtained [ 5 ]. In Wisconsin, USA, direct crosses of alfalfa and M. arborea in 1970 and 1985 produced no hybrids, and results were not reported.…”

Morphological stages and storage protein accumulation in developing alfalfa (Medicago sativa L.) seeds

“…Earlier studies on Medicago have described, in microscopic detail, embryonic development up to the heart stage (Fridriksson and Bolton, 1963;Sangduen et al, 1983a,b) and into the stage of embryo elongation (Fridriksson and Bolton, 1963). As well, fresh and dry weight accumulation have been studied during growth, food reserve deposition and ripening stages of alfalfa seed development (Fridriksson and Bolton, 1963;Kowithayakorn and Hill, 1982). Despite these studies, a timetable of seed development, which would enable uniform staging of developing alfalfa seeds, is not available.…”

Les cultures in vitro chez les légumineuses à grosses graines

“…L'échec du dévelop-pement complet des embryons dans des croisements est souvent attribué à un développement retardé de l'albumen (Fridriksson et Bolton, 1963 ;Gritton et Wierzbicka, 1975 Fellenberg (1978Fellenberg ( , 1982 et Naylor (1984) (Pelletier et al, 1983) ou le tabac (Belliard et Pelletier, 1978 (Keller et Melchers, 1973) soit, plus couramment, l'utilisation de polyéthylène glycol (Kao et Michayluk, 1974 (Teoule, 1983) (Lin et al, 1987).…”