Abstract
Seventeen Agrobacterium tumefaciens strains were used to study the effects of co-cultivation time and temperature on the transformation efficiency of these strains in callus suspension cultures and freshly excised callus pieces of Brassica oleracea L. Amongst these seven strains, AM1, EI1, E12, E13, M12, MI3 and M14 were used to check the effects of co-cultivation time and temperature on the transformation efficiency of these strains in explants (leaf discs, stem cuttings and root cuttings) of five different species (Capsicum annuum L., Lycopersicon esculentum lvlill., Medicago falcata L., Raphanus sativus L. and Spinacea oleracea L.). T-DNA transfer and expression was demonstrated by auxin independent growth of calluses/explants. Results of these experiments revealed that time and temperature play an important role in the oncogenicity, virulence and transformation efficiency of the A. tumefaciens strains. Generally co-cultivation for a longer period (10 minutes) and at higher temperature (37°C) yielded no transformation response. Albeit the co-cultivated calluses/explants were shifted to 24°C for T-DNA transfer and expression, but co-cultivation at higher temperature caused irreversible damage. Although varied and individual responses were observed with different strains but in general co-cultivation for 3 minutes at 28°C exhibited best transformation response for majority of strains in callus suspensions, callus pieces and explants. Transformation responses were better in callus suspensions and callus co-cultivations relative to explant co-cultivations. Co-cultivation of callus and callus suspension at 24°C for 3 minutes also exhibited transformation response but to a. lesser extent. The AM1, E12 and E13 showed better and efficient transformation response when co-cultivated for 3 minutes time interval at 28°C with callus, callus suspension and explants. These strains also showed various morphogenetic responses in callus and callus suspension co-cultivations which were not observed with other strains.
S.H. AMER QAZI , SHAHIDA HASNAIN . (1997) IMPACT OF AGROBACTERIUM TUMEFACIENS CO-CULTIVATION TIME AND TEMPERATURE ON T-DNA TRANSFER AND EXPRESSION IN PLANT CELLS , Punjab University Journal of Zoology, Volume 12, Issue 1.
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