Inducing Genetic Variability of Black Pepper (Piper Nigrum L.) by Irradiation

Genetic variability of black pepper germplasm in Indonesia is low. To broaden genetic variability, newly growth shoot tips from in vitro culture of black pepper var. LDL were y irradiated with doses 0, 0.3 0.6, 0.9, 1.2 and 1.5 krad. The treatments were designed in a complete block with five replications. The irradiaed plantlets were grown on MS medium. Response of the variety is described by recording an increase in leaves, shoots and node, numbers, plantlet height, and morphological abnormality in the irst vegetative mutation generation (MVI) and the second vegetative mutation generation (MV2). Ater 6 weeks, the plantlets were sub cultured and the leaves of MV2 were used for RAPD analysis. Six random primers were used for the study, i.e. OPC-01 (TTCGAGC- CAG), OPC-02 (GTGAGGCGTC), OPC-04 (CCGCATCTAC), OPC-05 (GATGACCGCC), OPC-06 (GAACGGACTC) and Abi 117.17 (GCTC- GTCAAC). The results showed that the lowest averages value on the increase of leaves, shoots, nodes and plantlets height al MVI are resulted at dose 1.5 krad, whereas dose 0.3 krad increases averages value on shoots and plantlet height. The highest percentage of abnormal leaves is resulted at dose 1.2 krad. Ater subculture, the MV2 plantlets showed higher averages value for almost all parameters observed than the untreated plantlets. The number of score able bands varied from 2-5 bands with molecular weight 0.4-12 kb. Thirty three bands were detected from the six primers, with OPC-01, OPC-04 and OPC-06 showed polymorphisms with 8 (24%) polymorphic bands. In OPC-01 one band with DNA size 1 -1.5 kb was absence rom the treated plants at dose 0.9-1.5 krad, while with OPC- 04, one band size 1 5 kb present only at 1.2 krad and with OPC-06 one band size 12 kb absence from 0.6 and 0.9 krad, and 3-5 bands size 1.5, 1.8 and bands with size 3-12 kb disappeared at dose 1.2 and 1.5 krad. The appearance and disappearance of bands may be related to the genetic changes due to y irradiation, and further exploration may be needed to ind how much genetic variation induced by irradiation in ield and the relationships with the changes in plant characters