AN ABSTRACT OF THE THESIS OF

Muhammad Bashir for the degree of Doctor of Philosophy in

Plant Pathologypresented onSeptember 17, 1992

Title: Serological and Biological Characterization of

Seed-borne Isolates of Blackeye Mosaic and

Cowpea -borne Mosaic Potyviruses in Vigna

unguiculata (L.)

Abstract approved: Redacted for Privacy Richar0. Hamp

Five were detected in cowpea plant samples

from Pakistan:blackeye cowpea mosaic(B1CMV), cowpea aphid-borne mosaic (CABMV), cowpea mottle (CPMoV),

cowpea severe mosaic virus (CSMV), and southern bean mosaic

virus (SBMV). Neither (CMV)nor

cowpea mosaic virus (CPMV) were detected in these samples. Only CABMV was found to be seed-transmitted in four of

seven seed lots at rates of 0 to 7 percent. Although all

viruses occurring in cowpea in Pakistan were not identified, the present study has probably determined the

principal seed-borne viruses of cowpea.

Fourteen of 158 U.S. Vigna unguiculata Plant Introduction accessions tested for seed-borne potyviruses were found to be infected with B1CMV (6.9%)and CABMV (13.3%) potyviruses, and seven with CMV (2.0%) cucumovirus. Forty-three isolates of B1CMV and 55 of CABMV were derived from Vigna unguiculata accessions, pre- introductions and commercial cowpea plantings. Viral identities were determined by DAS-ELISA serology and verified by electron microscopy and host reactions.

The highest seed-transmission rates of 48.5% and 55% were produced by B1CMV isolate PI-2581 and CABMV isolate RN-27C respectively. Aphid transmissibility of these viruses byAphis craccivora Koch, using three per inoculated plant,ranged from 24% to 55% among B1CMV isolates and 18% to 57% among isolates of CABMV.

Antiserum produced against a typical CABMV isolate

RN-7C, yielded CABMV-specific immunoglobulin G, when used in DAS-ELISA.

Twenty-one seed-borne isolates each of B1CMV and CABMV were compared for pathogenicity on 51 cowpea genotypes, and found to vary markedly in both pathogenicity and virulence. Based on differential reactions of these genotypes, 21 distinct variants of B1CMV and 25 of CABMV were identified. Two genotypes, TVU 401 and TVU 1582, were immune to all isolates of CABMV. Two other genotypes, TVU 2657 and TVU 3433, were immune to all isolates of B1CMV except those naturally seed-transmitted in the cowpea cultivar 'Pusa Phalguni' (). Serological and Biological Characterization ofSeed-borne

Isolates of Blackeye Cowpea Mosaic and CowpeaAphid-borne

Mosaic Potyviruses in Vigna unguiculata (L.)Walp.

by

Muhammad Bashir

A THESIS

Submitted to

Oregon State University

in partial fulfillment of the requirement for the degree of Doctor of Philosophy

Completed September 17, 1992 Commencement June, 1993 APPROVED:

Redacted for Privacy Professor of Botany and Plant Phology in charge of major

Redacted for Privacy Head of Department of Botany and PlantPat ology

Redacted for Privacy Dean of Graduat chool

Date thesis is presented September 17, 1992 Typed by M. Bashir for Muhammad Bashir ACKNOWLEDGEMENTS

In the name of Allah, the most beneficent, the most

merciful:

It is my great privilege to thank Dr. R.O. Hampton, my major professor,for hisinvaluable technical advice,

assistance, patience and friendship in planning my thesis

research, andfor providing excellentlaboratory and

greenhouse facilities.

I am also grateful to the faculty members Dr. J. R.

Baggett, Dr. W. G. Dougherty, Dr. G. W. Krantz, and

Dr. C. C. Mundt, who served on my committee, and for their

valuablesuggestions