Differential development of plastids during microspore embryogenesis in barley

Abstract

Summary. In order to understand and limit albino plantlet formation during pollen embryogenesis in barley (Hordeum vulgate L. cv. Igri), plastid feature was followed during pollen embryogenesis under two anther culture conditions and compared to plastid development in the zygotic embryo. The first condition was characterized by cold pretreatment and maltose in the induction medium. Both embryos and caUi were then obtained. During pollen embryo development, up to 30% of plastids had abnormal features. Disruptions mainly affected the plastid size, the feature of plastid envelopes, thylakoid and granum organization, as well as starch accumulation. In pollen calli, superficial cells had meristematic features. Up to 50% of plastids exhibited the above mentioned abnormalities. Internal cells were highly vacuolated with amyloplast-like plastids; envelopes had normal features but no internal membrane was detected. Pollen embryo-derived plantlets had a green-to-albino ratio (G/A) being equal to 1.0, whereas calli-derived embryos only formed albino plantlets. The second condition was characterized by mannitol pretreatment and the presence of both maltose and mannitol in the induction medium. No callus was formed but most of microsporederived structures developed haploid embryos and then the green piantlets (200 plantlets per 100 responding anthers, G/A = 9.4). In this case, plastid development in zygotic and pollen embryos were similar and almost no albino plantlets were formed.

Direct embryogenesis and green plant regeneration from isolated microspores of hexaploid triticale (� Triticosecale Wittmack) cv. Bogo

“…It is possible that direct embryogenesis (without callus phase) of triticale enhances the probability of green plant regeneration. Caredda et al (1999) demonstrated that during direct embryo development up to 30% of the plastids exhibited abnormalities, while among callus-derived embryos up to 50% of the plastids were abnormal, and all regenerants were albino. Harwood et al (1995) reported that of the barley cv.…”

Albinism in barley androgenesis

“…The research of Caredda and co-workers (1999, 2000, 2004) made a significant contribution to the understanding of plastid physiology in microspores prior to the switch to sporophytic development, at various times during androgenesis itself and in the regenerated plants. Their research focused on two barley cultivars, winter cv.…”

“…Based on Caredda et al (1999, 2000, 2004), with modifications. Arrows indicate the trend relative to the previous column…”

“…Research to elucidate the mechanism of albinism has focused on three areas: cytology, plastid genomics and the nuclear genome-focused studies. Cytological studies aim to identify structural changes in plastids at different stages of androgenesis that prevent chloroplast formation (Caredda et al 1999, 2000, 2004). Genome studies focus on the identification of differences in the genomes of green and albino plant plastids (Hofinger et al 2000).…”

Advances in Haploid Production in Higher Plants

“…High frequency of albino plant formation in anther and microspore cultures is a general phenomenon in most cereals like wheat (Andersen et al 1987), barley (Knudsen et al 1989, rice , rye (Immonen 1999), oat and in several grasses like ryegrass (Olesen et al 1988) and timothe (Abdullah et al 1994). These white plants contain plastids arrested in development towards functional chloroplasts (Caredda et al 1999Sun et al 1974) and therefore cannot grow without the sugar containing media of in vitro cultures (Sun et al 1974). …”