In vivo micrografting to eliminate passiflora latent virus from infected passion fruit plants

Abstract

An in vivo micrografting method was developed to obtain Passiflora latent virus (PLV)-free passion fruit from infected plants. The scion length required to eliminate PLV was ≤2mm. The method required no aseptic handling and the procedure was relatively simple, and resulted in more than 10 micrografts in one hour. Moreover, no special equipment or procedures were necessary, allowing it to be conducted at an individual farm level. Rapid growth of the scion after grafting was also observed due to the use of fully established seedlings as rootstock. Leaf samples for analysis of PLV infection could therefore be obtained about two months after grafting with fruit harvest possible about four months later. In vivo micrografting was conducted with a scion length of 0.5-1 mm from September to November to determine the optimal air temperature conditions. The graft success rate increased from 18% to 58% with a decrease in the average air temperature from September (28.6°C) to November (23.3°C), although there was no significant difference in PLV-free rates between months (73% to 80%). Accordingly, in vivo micrografting of passion fruit is not recommended under high air temperature conditions. The effect of scion shoot storage conditions was also examined, revealing that in vivo micrografting using shoots stored for one day could be performed without difficulty, whereas the rate of graft success and PLV-free rate were close to those obtained using shoots selected less than 30 min before. These findings suggest that with this method, virus-free plants can be obtained using PLV-infected shoots selected in the field one day earlier. In conclusion, our in vivo micrografting technique is useful to eliminate PLV from infected plants; it is simple and leads to rapid growth of the scion after grafting.