Journal de pathologie végétale et de microbiologie

Abstrait

Evaluation of Low Temperature Induced Mutants of Cucumber green mottle mosaic virus for Cross-protection in Cucurbits

Asad Ali, Musharaf Ahmad, Hisashi Nishigawa and Tomohide Natsuaki

Cucumber green mottle mosaic virus has been reported as the most prevalent and dominant virus infecting cucurbit crops in KPK, Pakistan. Inoculated plants of C. sativus were treated at low temperature to generate and select mild strain of CGMMV for cross protection. Among 200 inoculated plants during mild strain selection, only two were showing no symptoms and were also strongly positive in serological assay as well as in electron microscopy. These two isolates, designated as Pk-47 and Pk-81, were selected for subsequent experiments on cross-protection.

In greenhouse experiments, the control plants started developing symptoms just 5 days after inoculation and were exhibiting severe symptoms in 10-12 days post challenge inoculation. Plants inoculated with Pk-47 isolate initially developed very mild symptoms that disappeared in one week post inoculation period. In cross-protection test, with the two selected isolates, symptoms developed in plants that were challenge-inoculated 5 or 7 days post protection-inoculation. Those plants that were given challenge-inoculation 10 days after the protection-inoculation did develop some mild symptoms, but later on they showed recovery. In all other treatments (challenge-inoculation done after 15, 20 and 25 days post protection-inoculation) both the Pk-47 and Pk-81 mild isolates were exhibiting convincing protection abilities to control the severe strain of CGMMV-Pk. The effectiveness of the cross-protection was evaluated at three different temperatures (17-22°C, 22-27°C and 27-32°C), and it was observed that it worked equally well under all the experimental conditions. Among the two isolates, protection abilities of Pk-81 seemed to be more promising comparing to Pk-47. All the plants remained symptom-less, for almost two months, after the challenge inoculation. The experimental results revealed that protection inoculation at least 15 days prior to challenge inoculation will serve better.