Transmission of a New Cowpea Aphid Borne Mosaic Virus Isolatein Passion Fruits

Abstract

Passion fruitwoodiness is an important potyviral disease affecting passionfruits in the world. The causative agent for this disease in Kenya isCowpeaaphid borne mosaic virus. However, this disease manifestation in some fieldsat the present is different in regards to disease severity and symptomatologyfrom the commonly known variant.Thenewly identified isolate was namedCABMVvirus isolate1, while thecommonlyknownonewas named virusisolate 2.Currently, information onCABMVisolate 1 is scarce relative tothat ofCABMVisolate 2,which has been studied widely. This study wascarried out to determine whether virus isolate 1 is transmitted by seed andselect aphid species.The select aphid species are pest of crops grown near oralongside passion fruits in mostKenyan farms.For seed transmission test,mature seeds were isolated from fruits harvested from infected passion fruitsplants maintained in a greenhouse. Thereafter, the seeds were planted in anursery bed which was screened against aphids. The resultantseedlings hadno symptoms associated with virus isolate 1. Furthermore, using reversetranscription–polymerase chain reaction, seed transmission rate of 0% wasobserved, showing that this isolate 1 is not transmitted by seed.Aphidtransmission test was carried out in passion fruit plants using aphids fromfarmers’ fields in Njoro. Four aphid species which areAcyrthosiphon pisum,Aphis fabae, Schizaphis graminumandMyzus persicaewere selected for thestudy.The aphids were allowed30 minutes virus acquisition period on virusisolate 1 infected passion fruits plants. Thereafter, the aphids were left tofeed on healthy test plant for inoculation to take place. Symptomsdevelopment on healthy plants signified successful transmission by theaphids. Aphid transmission test results indicated thatMyzus persicae,Acyrthosiphon pisum,andAphis fabaesuccessfully transmitted the virus.