RESUMEN
Aims@#Dendrobiums are majorly affected by Fusarium proliferatum and F. oxysporum. The aim of this research was to utilise the mycotoxin, fusaric acid (FA) on Dendrobium hybrid to produce cultivars that are resistant towards these fungi. @*Methodology and results@#FA of concentrations 0.05, 0.10, 0.15 and 0.20 mM were transferred to sterilised half-strength Murashige and Skoog (MS) medium and inoculated with four weeks old thin cell layer (TCL) of protocorm-like bodies (PLBs) for eight weeks. It was deduced that PLBs treated with 0.10 mM of FA resulted in highest survival and shoot regeneration rate but the survival and regeneration rate began to decline as the concentrations of FA were increased. Histology and scanning electron microscopy (SEM) observation showed prominent cell damage and stomatal closure in PLBs treated with FA. Direct amplification of minisatellite DNA (DAMD) markers showed polymorphism in the FA treated PLBs compared to the control PLBs. In the leaf bridge bioassay, plantlets treated with 0.05 mM of FA showed most resistance towards both fungal species. @*Conclusion, significance and impact of study@#Therefore, this research is a preliminary screening study where the optimum concentration of FA was selected based on the reaction of treated TCL of PLBs towards these mutagens.
RESUMEN
Shoot tips and in vitro grown proliferating buds of banana cv. Rasthali (Silk, AAB) were treated with various concentrations and durations of chemical mutagens viz., EMS, NaN3 and DES. LD50 for shoot tips based on 50% reduction in fresh weight was determined as 2% for 3 h, 0.02% for 5 h and 0.15%for 5 h, while for proliferating buds, they were 0.6% for 30 min, 0.01% for 2 h and 0.06% for 2 h for the mutagens EMS, NaN3 and DES, respectively. Subsequently, the mutated explants were screened in vitro against fusarium wilt using selection agents like fusaric acid and culture filtrate. LD50 for in vitro selection agents calculated based on 50% survival of explants was 0.050 mM and 7% for fusaric acid and culture filtrate, respectively and beyond which a rapid decline in growth was observed. This was followed by pot screening which led to the identification of three putative resistant mutants with an internal disease score of 1 (corm completely clean, no vascular discolouration). The putative mutants identified in the present study have also been mass multiplied in vitro.