**3.2 Susceptibility of soybean to** *Agrobacterium*

Soybean genotype susceptibility for tumor induction was studied by Pedersen et al., 1983 and Owens & Cress in 1984 on infection with *Agrobacterium*. According to their reports, crown gall formation is dependent upon soybean genotype and *Agrobacterium* strain used as well as on environmental conditions. Physiological age of soybean cotyledons also exert great influence on tumor initiation and tumor morphology. Owens and Smigocki (1988) indicated that transformed soybean cells could be recovered by co-infecting with supervirulent strain and addition of phenolic compounds (Acetosyringone or Syringaldehyde) in inoculation medium increase transformation efficiency. It is also possible to produce tumorigenic genotype by crossing non-tumorigenic with highly tumorigenic genotype in soybean so conventional crossing may help to transform non-susceptible genotypes. Luo et al. (1994) observed production of transformed calli from mature seed cotyledons working on transformation friendly genotype "Peking" with *Agrobacterium* strain A281 harboring pZA-7 (UidA + nptII). They mentioned that production of transformed calli is a simple tool to test constructs designed for soybean transformation. Genotype of *Agrobacterium* (nopaline, agropine, octopine) also plays an important role in infection and T-DNA inheritance (Mauro et al., 1995). Acetosyringone may facilitate tumor formation significantly but not for all *Agrobacterium* strains. However, strain/genotype difference was observed significant while older plant parts showed less susceptibility to tumor formation. Transformation event occurs in number of cells but poor selection and non-regenerable callus formation attribute to poor recovery of transformed plants (Donaldson & Simmond, 2000). A new *Agrobacterium tumefaciens* strain KAT23 isolated from peach root also found effective to induce callus at soybean tissues (Yukawa et al., 2007). This nopaline type strain can transform T-DNA of Ti plasmid and of binary vector efficiently to many legumes including soybean.
