Generation of Virus Free Potato Plantlets through Meristem Culture and Their Field Evaluation

Different aspects of micropropagation through meristem culture for the production of virus indexed source plants, in vitro tuberization and field evaluation of the in vitro regenerated plants were studied on four commercial cultivars of potato (Solanum tuberosum L.) viz., Diamant, Cardinal, Shilbilati and Lalpakri. The investigation was conducted at Rajshahi, Bangladesh from December 2010 to March 2012 to produce virus-free potato plantlets through meristem culture, shoot multiplications with root induction as well as their acclimatization and evaluation of morphological characters and tuber yield under field condition. Shoot tips of 25 - 30 day old field-grown plants of above mentioned four cultivars were used for meristem isolation. After isolation, meristems of these varieties of potato were cultured on “M” shaped filter paper bridge in Murashige and Skoog (MS) liquid medium. Four different treatments of media formulations viz. 0.1 mg/L KIN + 0.1 mg/L GA3, 0.1 mg/L KIN + 0.5 mg/L GA3, 0.5 mg/L KIN + 0.1 mg/L GA3 and 0.5 mg/L KIN + 0.5 mg/L GA3 were used as plant growth regulators. From these formulations MS + 0.1 mg/L KIN + 0.5 mg/L GA3 was found to be the best for the primary establishment of meristem culture. The primarily established meristems were subcultured on to MS semisolid basal medium supplemented with four different treatment combinations of hormones viz. 0.5 mg/L BA + 1.0 mg/L IBA;0.1 mg/L KIN + 0.1 mg/L GA3;0.5 mg/L BA + 0.5 mg/L GA3 and 0.5 mg/L KIN + 0.5 mg/L GA3 were used to identify the suitable media compositions for shoot proliferation. Results showed that out of these four media treatments the formulation 0.5 mg/L BA + 0.5 mg/L GA3 was found to be the best suitable for shoot generation. Among the four cultivars of potato higher frequency of shoot proliferation (number of shoots/explant and longest shoot length) was observed in Diamant, though the highest shoot formation (76%) was recorded in Cardinal. Virus free in vitro grown potato plantlets were obtained through DAS-ELISA test and used substantially for micro-propagation. After gradual acclimatization of rooted plantlets of four potato cultivars, they were transferred into the field for cultivation and established successfully. It was observed from the field study of in vitro meristem-derived plantlets that there were no virus-affected plants. The virus-free exotic varieties were much superior in all vegetative attributes and yield compared to those of indigenous varieties with producing potato plants of normal height. In contrast, the indigenous varieties took a longer time to tuber initiation and maturity, lower plant height and number of leaves per plant, a higher number of tubers but a lower amount of tuber weight per plant, and poorer tuber grade than the exotic varieties. However, the variety Cardinal exposed the best performances in the context of survival percentage of plantlets (90%), days to tuber initiation (DTI), a number of leaves per plant (NL), tuber weight per plant (343.40%) and the percentage of rich tuber grade.

Biotechnological Potential of Endophytic Bacteria to Improve the Micropropagated Seedling of Variety RB92579 Sugarcane(Saccharum officinarum L.)

Endophytic bacteria may influence agricultural production in several ways, including promoting plant growth. Two experiments were conducted in order to evaluate the combination of endophytic bacteria from the Brazilian Northeast region aims at the commercial introduction of the inoculation of these bacteria in micropropagated sugarcane plants using a temporary immersion bioreactor. One experiment was done in tubes with sterile commercial substrate, and the other was done in pots with soil;both were installed in a greenhouse. A mixed inoculation was performed in six inoculated endophytic diazotrophic bacteria in micropropagated sugarcane plants, variety RB92579. In the experiment with soil, the mixed inoculation significantly increased the shoot dry matter of plants without the addition of nitrogen fertilizer. However, the accumulation of total-N in the tissues showed no significant differences between treatments with and without nitrogen fertilization. The evaluation of micropropagated seedlings showed no increases in the parameters tested. The results showed that the response of inoculation in temporary immersion bioreactor micropropagation is possible, and that the application of homologous strains may have contributed to a better response by the interaction of endophytic bacteria with sugarcane RB92579. Further studies should be conducted to improve the methodology, which indicates a great potential to optimize this process on a commercial scale.