EFFECTS OF SUCROSE AND METHYLGLYOXAL BIS-(GUANYLHYDRAZONE) ON CONTROLLING GRAPE SOMATIC EMBRYOGENESIS

The effects of sucrose and methylglyoxal bis-(guanylhydrazone) (MGBG) on grape (Vitis vinifera L. cv. Thompson Seedless) somatic embryogenes is was examined by subculturing somatic embryos and embryogenic cells monthly to embryo maintenance medium (MMS) containing 60, 90, 120, 150 , or 180 g/l sucrose; or 0, 0.1, 1, or 10 mM MGBG for three months. Th e growth and development of grape embryogenic cultures was inhibited b y incubating them on MMS with 150 or 180 g/l sucrose compared to 60, 9 0, or 120 g/l. Culture dry weight was significantly greater for embryo genic cells grown on MMS with 90 or 120 g/l sucrose compared with thos e reared on standard MMS (60 g/l sucrose), indicating that embryogenic cells grew better on MMS with 90 or 120 g/l sucrose and were less hyd rated. The number of cotyledonary-stage somatic embryos that resembled zygotic embryos was improved 10.8- to 21.3-fold by incubating grape e mbryogenic cells on MMS with 90 or 120 g/l sucrose, respectively. Germ ination-and plant development of grape somatic embryos was improved fo llowing incubation on MMS with 150 g/l sucrose before transfer to germ ination medium with benzyladenine. However, fewer embryos were produce d on this medium compared to all other sucrose levels, suggesting that maintaining embryogenic cultures on MMS with 120 g/l sucrose followed by one transfer onto MMS with 150 g/l sucrose may improve embryo deve lopment and plant regeneration. MGBG at 1 to 10 mh I inhibited the gro wth and development of grape embryogenic cultures. Exposure of embryog enic cells to 10 mM MGBG inhibited their growth and development throug h the course of the experiment and caused their death by the third mon th of culture. In contrast, a 3-month exposure was required to inhibit embryo growth in the presence of 1 mM MGBG. Addition of MGBG to MMS d id not improve embryo quality or plant development.