Effect of Agrobacterium Infection Time, Co-Cultivation and Cell Density on in vitro Response in Hypocotyl of Eggplant (Solanum melongena L.)

Abstract

The present study purports to assess the effect of Agrobacterium infection time, co-cultivation and cell density on in vitro response in hypocotyl explants of eggplant (brinjal) cv. Manjarigota. Agrobacterium(OD₆₀₀ 0.3-0.5) infection for 10-15 minutes (24.44±2.34%) was found to be optimum, while, higher or lower infection-time resulted in reduced callus initiation, shoot regeneration and explant survival. Explants with no (only Agrobacterium infection) or short (1 day) co-cultivation, showed reduced callus-initiation response and turned yellow, with no regeneration. Callus-initiation response increased from Day 1 (96.66±03.33%), and reached a maximum on Day 2 and Day 3 (100±00.00%). It decreased on further increase in co-cultivation time. Explants co-cultivated for three days showed highest regeneration response (30.00±02.96%) which thereafter reduced with further increase in co-cultivation time. Explants infected with Agrobacterium culture at 0.05 OD₆₀₀ showed hardly any regeneration, and turned yellow and necrotic on the selection medium. Highest regeneration response (28.33±02.33%) was obtained in explants infected with 0.1 OD₆₀₀ culture, and this gradually reduced as celldensity increased (upto 1.0 OD₆₀₀), becoming zero in explants treated with cultures at 1.5 OD₆₀₀ or above. Agrobacterium overgrowth was noticed on explants infected with cultures of 0.5 OD₆₀₀ and above. Exposure of hypocotyl explants to higher cell-density, longer infection-time and prolonged co-cultivation regime resulted in severe necrosis of explants; time taken for development of Agrobacterium overgrowth was less with increase in the level of these factors. Regenerated shoots were healthy, green, elongated and showed root induction on culture medium containing Kanamycin.