often and to a lesser extent with a few responsive indica varieties. Comparative response of 23 popular high yielding varieties for callus induction and regeneration was evaluated on appropriate MS medium. Regeneration was tested at 30-40d and 60-70d on MS medium supplemented with 2.5 mg/L BAP, 1.0 mg/L K, 0.5 mgfL NAA with addition of 1.0 g/L proline and 500 mg/L casein hydrolysate (enzymatic). Critical evaluation of in vitro response in terms of frequency of callus induction, calli initiating green regions or shoots, calli giving shoots as well as roots, rhizogenic calli and number of plants regenerated per unit culture was carried out by replicated experiment.

Comparative study of tissue culture response of indica varieties with Tapei 309 (T 309), ajaponica type revealed distinct differences in the pattern of callus formation. A number of calli originated along the entire length of coleoptile in T 309, whereas there was distinct proliferation of only the scutellar tissue leading to a compact callus in all the indica genotypes. The calli from T 309 proliferated rapidly upon subculture and continued to yield friable callus. The calli of indica varieties were slow and compact with different degree of friability. Apart from the variation in quantitative response, the varieties also differed in the lag period for callus induction.

On transfer to regeneration medium green regions appeared, some of which only gave rise to shoots. The development of green regions as well as shoots was simultaneous and sustained over 3-4 passages in T 309. However, it was in sequence but overlapping and lasted upto two passages in indica varieties studied. Variation in number of regenerants per unit culture was high with vibhava and Seshu yielding highest and at par with T309. Regenerants were more or less synchronous in indica varieties. Owing to rapid callus proliferation, T 309 yielded larger callus mass in a given time resulting in more number of green plants. Further, T 309 sustained the regeneration capacity over longer period followed by Vibhava and Seshu whereas Salivahana, Rasi, Pusa Basmati- 1, Nagarjuna, Vikas and Jaya though initially showed good regeneration potential did not sustain it over time.

Based on Duncan’s multiple range test (DMRT) the varieties are ranked in descending order of their percent response indicated by significant differences among them for important parameters related to tissue culture (Table 1). The principal component analysis indicated that primary axis was differentiated mainly by plants per unit culture and parameters contributing to genetic variation are in the order of i) regenerants per unit culture ii) culture giving rise to shoots and iii) appearance of green regions on callus mass. Further, it was possible to group the genotypes following three methods of clustering viz., Non hierarchial eucledian cluster analysis, D2 analysis and Joint score method. The distribution of genotypes into clusters by the three methods is given in Table 2. Interestingly two indica varieties Vibhava and Seshu fell in the same cluster along the japonica variety T 309 by all the methods. Since T 309 is successfully and frequently transformed by many laboratories the indica varieties, Vibhava and Seshu behaving close to T 309 were selected for transformation. Based on the information by clustering of the genotypes the two indica varieties are being used for biolistic or Agrobacterium mediated genetic transformation.