Blackgram (Vigna mungo L. Hepper) or urd is an impor- tant grain legume, reported to have originated in India (Dhuri et al. 1986). In India, the protein requirement of the vegetari- an population and those who cannot afford meat is met through legumes. Vigna mungo is also used as nutritive fod- der for cattle or as a green manure. India is the largest pro- ducer accounting for more than two-thirds of the world’s total production of blackgram (Jeswani and Baldev 1990). The crop is also widely grown in other Asian countries, Africa, and Australia. In India, the total area under blackgram cultivation is 3.01 million ha with a production of 1.2 metric tons but the yield per hectare is stagnant though there is an increase in land under cultivation. The production constraints are susceptibili- ty to yellow mosaic virus (VMYMCV) (Sahoo et al. 2002), fungal pathogens (powdery mildew, Cercospora leaf spot), bruchids (Sahoo et al. 2002), and pod borer (Rao and Chand 2006; Sarma and Borah 2004; Satyanarayana et al. 1990). Blackgram has been found to be recalcitrant to in vitro regeneration (Sahoo et al. 2002) and efficiency of the multi- ple shoot formation and regeneration has been found to be dependent on various parameters, viz. explant size, age, type and genotype, and media composition (Saini and Jaiwal 2002). Moreover, the above protocols are restricted to a few cultivars and none of these systems were found to be suitable for routine genetic transformation of blackgram. The most critical events affecting cotyledonary node- based, Agrobacterium-mediated transformation are induction of shoots from the wounded site and the high frequency of multiple shoots per explant. Genetic transformation of black- gram has been reported using cotyledonary nodes (Bhomkar et al. 2008; Saini et al. 2003) and shoots tips (Saini and Bidyut Kumar Sarmah ( ) E-mail:bidyutsarmah@yahoo.co.in Tel: +91-376-234-0095 The Korean Society of Crop Science J. Crop Sci. Biotech. 2012 (December) 15 (4) : 311 ~ 318 RESEARCH ARTICLE DOI No. 10.1007/s12892-011-0122-3 Effect of Thidiazuron (TDZ) on In vitro Regeneration of Blackgram (Vigna mungo L.) Embryonic Axes Sumita Acharjee 1 , Pratap Jyoti Handique 2 , Bidyut Kumar Sarmah 1 * 1 Department of Agricultural Biotechnology, Assam Agricultural University, Jorhat 785013 Assam, India 2 Department of Biotechnology, Guahati University, Guwahati, Assam, India Received: December 27, 2011 / Revised: May 8, 2012 / Accepted: September 3, 2012 Ⓒ Korean Society of Crop Science and Springer 2012 Abstract Regeneration has been achieved in blackgram (Vigna mungo) using thidiazuron (TDZ) in the culture medium. The explanted cotyledon with wounded embryonic axes produced the highest number (9.75-10.45) of healthy, elongated shoots when cultured on shoot bud regeneration medium (SRI) composed of 2 μM BAP, 2 μM KIN, 2 μM TDZ, and 0.5 μM NAA followed by multiple shoot regeneration (SRII) medium containing 2 μM BAP, 2 μM KIN, and multiple shoot elongation (SE) medium (0.5 μM of BAP + 0.5 μM of KIN). The presence of TDZ in combination with BAP and NAA in the SRI medium for one sub-culture cycle (10 - 14 days) significantly increases formation of multiple shoot buds per explant. Independent, healthy shoots obtained were selected for both in vitro rooting and grafting. Establishment of plantlets in the soil was highest (80 - 100%) in the case of in vitro rooted compared to grafted shoots (40%). The protocol appears to be competent to Agrobacterium-meditated transformation with ‘gus’ as a reporter gene. PCR analysis of the T0 and T1 progenies showed the presence and transmission of the transgene. We document here the regen- eration and transformation of blackgram using cotyledons with wounded embryonic axes and the protocol appears to be suitable for genetic transformation of blackgram. Key words : Agrobacterium, blackgram, embryonic axes, TDZ, Vigna mungo Introduction 311