ABSTRACT

Transgenic sorghum plants resistant to stem borer, were evaluated for the expression of bar and Cry IB genes through Basta spray tests, PCR and southern analysis. Objective of the current study is to devise Basta spray tests in young plants i.e., before 21d and prior to insect bioassays and, correlate them with PCR, Southern blots and insect bio-assays using transgenic progeny plants carrying CryIB gene. Sensitivity tests were conducted to optimize the Basta spray tests with four genotypes at five developmental stages (15d, 25d, 35d, 45d and 60d). Sensitivity to GA was genotype as well as  age dependent. Therefore, based on the stage of the plant growth and genotype, concentration of GA is to be monitored for effective use of Basta spray tests in the evaluation of transgenic plants. Thus 0.006% w/v GA was used to evaluate the transgenic (T1) progeny at 15d, 25d and 0.01%w/v GA was used at 35d. Likewise an increased concentration of GA i.e., 0.04% at 45d and 60d was used for screening transgenic plants. Transgenic plant progeny in genotype CS3541 of event 23-1, were used for evaluation with Basta spray at five plant growth stages, PCR and insect bioassays under natural infestation. A strong correlation between PCR and dead hearts was observed. Correlation between PCR  and, Basta spray tests at 15d and 25d was significant. Basta spray test results at 60d were in total agreement with the PCR analysis results and insect bioassays viz., dead hearts. Results of Basta spray at 15d and 25d at 0.006% cannot be recommended to authentically distinguish transgenic and non-transgenic plants. Since sorghum is one of the most difficult plant species to manipulate through tissue culture and transformation, In planta method of transformation that excludes all tissue culture works proves to be a promising technology for producing more transgenic plants in future.