ABSTRACT

Experiments were carried out between 2009 and 2013 in the Biotechnology laboratory, Department of Plant Science, Ahmadu Bello University Samaru, Zaria with the aim of developing tissue culture regeneration, cryopreservation and slow growth protocols for conservation of groundnut. Embryonic axes obtained from seeds of Four (4) groundnut varieties; (SAMNUT 10, SAMNUT 21, SAMNUT 22 and SAMNUT 23) were used in the study. In the regeneration experiment, results showed that maximum shoot multiplication was obtained from Murashige and Skoog (MS) medium supplemented with 15 mg/L BAP. Among the groundnut varieties evaluated SAMNUT 23 and SAMNUT 22 recorded the maximum shoot height (4.7 and 4.8cm, respectively). For in vitro rooting, MS media supplemented with 1 mg/L NAA produced the highest root-induction frequency (82%). While the hormone free medium recorded the longest roots (7.4cm). A Significant genotypic effect was also observed, with SAMNUT 22 having the highest root-induction frequency (60%). In the cryopreservation study, the desiccation technique gave the highest survival of 97% - 100% and shoot formation of between 92% and 97% of cryopreserved embryonic axes at an average moisture content of 17% after 4 - 5 hr desiccation. Among the varieties evaluated, SAMNUT 23 and SAMNUT 22 recorded the highest survival of 65% and shoot formation of 57-60% respectively. The results of the vitrification technique showed that the highest survival (70%) and shoot formation (65%) were obtained from embryonic axes treated for 2 hr in PVS2. SAMNUT 22 and 23 gave the highest survival of 74% and 76% and shoot formation of 72% and 73% after cryopreservation. A significant interaction was observ etween the varieties and dehydration time in PVS2 on survival and shoot formation. Highest shoot formation was observed in SAMNUT 10, SAMNUT 21 and SAMNUT 23 after 2 hr dehydration in PVS2. In the case of SAMNUT 22 this was achieved after 3hr dehydration in PVS2. In the encapsulation-dehydration, the highest survival of 73% and shoot formation of63% of encapsulated cryopreserved embryonic axes of groundnut was obtained after 6hr air dehydration to moisture content of 20%. Among the varieties evaluated SAMNUT 23 recorded the highest survival of 67% and shoot formation of 61% respectively. In the encapsulation-vitrification technique, maximum survival rate of cryopreserved encapsulated embryonic axes was 48% obtained after 1hr dehydration in PVS2. Among the varieties evaluated SAMNUT 22 and SAMNUT 23 produced the highest survival rates of 44% and 42% respectively. A Slow growth experiment was conducted with four conservation media (MS medium+30g/L sucrose, MS medium+20 g/L sucrose +10 g/L mannitol, MS medium+15 g/L sucrose +15 g/L mannitol and MS medium+10 g/L sucrose +20 g/L mannitol) and for four conservation periods (3, 6, 9 and 12 months). Results revealed that the highest survival rate (34%) and lowest shoot height (3.03cm) were obtained on MS medium supplemented with 10g/L sucrose and 20 g/L mannitol. Among the varieties evaluated SAMNUT 23 recorded the highest survival (33%). With regard to the effect of different conservation periods, the highest survival (74%) was obtained from cultures conserved for 3 months. This study indicates that MS medium supplemented with 15mg/L BAP and MS medium supplemented with 1mg/L NAA is suitable for shoot multiplication and in vitro rooting of the groundnut varieties respectively. The techniques of desiccation, vitrification and encapsulation could be used for the cryopreservation of embryonic axes of groundnut. Also, MS medium supplemented with 10g/L sucrose and 20g/L mannitol could be used for the medium term conservation of groundnut with subculturing intervals of three (3) to six (6) months.