Regeneration of soybean via embryogenic suspension culture

Abstract

In an attempt to establish an alternative plant regeneration system for soybean [Glycine max (L.) Merrill] cultivars used in Brazilian breeding programs, ten genotypes were tested for their embryogenic potential. Cotyledons were removed as explants from immature seeds harvested from field-grown plants. After 45 days on induction medium, the number of responding cotyledons and the number of somatic embryos per immature cotyledon were evaluated. The percentage of explants that produced somatic embryos varied from 1 to 70% among cultivars. The average number of somatic embryos produced per cotyledon pair ranged from 0.01 to 10.3 with a mean of 3.4. Suspension cultures were initiated with three Agrobacterium tumefaciens susceptible cultivars. Suspensions were successfully developed from Bragg and IAS5 cultivars. The packed cell volume, in one-month growth, increased 8.1 fold for Bragg and 3.5 fold for IAS5 and the fresh weight increased 6.6 and 2.8 fold, respectively. The cultivars differed for the analysed parameters. All tissue from each cultivar was transferred to the maturation medium and subsequently to the germination medium. The germination frequency was 45.7 and 54.9% for Bragg and IAS5, respectively. Plants were gradually exposed to ambient humidity over one week and then planted in soil. All plants yielded seeds in the greenhouse.

Strategies for Improvement of Soybean Regeneration via Somatic Embryogenesis and Genetic Transformation

“…That study only assessed somatic embryo induction stage. Other studies also reported the high capacity of IAS-5 to produce somatic embryos (Santos et al, 1997;Di Mauro et al, 2000;Droste et al, 2001). More recently, Droste et al (2010) identified Brazilian soybean genotypes with potential to respond to in vitro culture stimuli for somatic embryo induction, embryo proliferation and plant regeneration.…”

“…Subsequently, several papers have reported the development of somatic embryos from cotyledons of immature embryos. But until today the measured frequencies at which these embryos convert into plants are significantly lower than that expected (Parrott et al, 1988;Meurer et al, 2001;Droste et al, 2001Droste et al, , 2010. Therefore, efforts have been directed towards developing and refining protocols for initiation, proliferation, and histodifferentiation/maturation of soybean somatic embryogenesis.…”

“…In soybean, considerable variation in embryogenic capacity was found to exist between individual genotypes (Komatsuda et al, 1991;Bailey et al, 1993a, b;Santos et al, 1997;Droste et al, 2001;Meurer et al, 2001;Tomlin et al, 2002;Hiraga et al, 2007;Yang et al, 2009;Droste et al, 2010) as will be discussed below (Genotype-dependent response and screening of highly responsive cultivars section).…”

“…Studies with soybean plants indicated that germination/conversion capacity is also greatly influenced by genotype (Komatsuda & Ohyama, 1988;Bailey et al, 1993;Santos et al, 1997;Droste et al, 2001Droste et al, , 2010.…”

“…Several studies have revealed the differences among soybean genotypes in their capacity to respond to the different steps of somatic embryogenesis (Bailey et al, 1993;Santos et al, 1997;Simmonds & Donaldson, 2000;Droste et al, 2001;Meurer et al, 2001;Tomlin et al, 2002;Hiraga et al, 2007;Yang et al, 2009;Droste et al, 2010). The efficiencies were shown to be different among cultivars at each SE phase: induction, proliferation, histodifferentiation/maturation, germination and conversion (Bailey et al, 1993;Santos et al, 1997).…”