Passionflower viruses: incidence in the Northwest region of São Paulo State; damage caused by the <i>Passion fruit woodines virus</i> (PWV) and sintomatology caused by <i>Cucumber mosaic virus</i> (CMV)

Author(s)

Ricardo Gioria

• Document type: Master's Dissertation
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2000-01-21
• Advisor: Jorge Alberto Marques Rezende

Abstract

A survey was carried out for evaluating the relative incidence of &lt;i&gt;Passion fruit woodiness virus&lt;/i&gt; (PVW), Cucumber mosaic virus (CMV) and a Rhabdovirus like-particles causing vein clearing symptoms in passionflower plantings in the Northwest region of the State of São Paulo, Brazil. Forty-five orchards, totaling approximately 75,000 plants, were visited and 991 randomly chosen plants were visually inspected for characteristic symptoms induced by these viruses. Samples from 310 plants were collected and analyzed by PTA-ELISA using antisera against &lt;i&gt;Passion fruit woodiness virus&lt;/i&gt;(PWV) and &lt;i&gt;Cucumber mosaic virus&lt;/i&gt; (CMV). Ten samples with vein clearing symptoms were examined on thin section in the electron microscope, to confirm the association with Rhabdovirus like particles. PWV and CMV were the most frequently found viruses, with incidences of 71,8% and 40,7%, respectively. lncidence of vein clearing apparently associated with a possible Rhabdovirus was 5,8%. Although CMV was the second virus in incidence, its importance is apparently small, because the virus has limited distribution in the passionflower stems. Biological and serological (PTA-ELISA and Westem-blot) assays showed that CMV was apparently restricted to symptomatic parts of the stems from infected plants in the field. Further studies for better understanding of this phenomenon are underway. Studies were also done to evaluate the effect of PWV infection on plant development in the greenhouse and yield losses under screenhouse in the field. In the greenhouse, plants mechanically inoculated with four isolates of PWV showed 50% reduction in leaf area and fresh and dry weight of upper part and root system, independently of the virus isolate. Passionflower plants grown under screenhouse were mechanically inoculated with PWV at 2, 4 and 6 months after transplanting. Healthy control plants were naturally infected by PWV 7 to 8 months after transplanting, due to accidental entrance of aphids into the greenhouse. Leaf area indexes (LAI) for plants inoculated at different age were stabilized at 4,4, 3,8, 5,6 and 10,0, respectively, 12 months after transplanting. Fruits harvested during 5 months indicated that plants infected at 2, 4, 6 and between 7 and 8 months after transplanting showed average yields of 2,4, 3,4, 6,9 and 12,9 kg, respectively. The number of woody fruits was drastically reduced on later infected plants. These results are indicative that systematic elimination of diseased plants during the first 6 to 8 months after transplanting can be an option to minimize the damage caused by PWV in passionflower orchards, while more permanent control measures are not developed. (AU)