CHARACTERIZING THE INTERFERENCE BETWEEN 2 COMOVIRUSES IN COWPEA

In certain cultivars of cowpea [Vigna unguiculata (L.) Walp.] that are operationally immune to cowpea mosaic virus strain SB (CPMV), coinocu lation of CPMV,vith cowpea severe mosaic virus strain DG (CPSMV) reduc es severity and delays expression of symptoms normally induced by CPSM V alone. In cultivars susceptible to both viruses, coinoculation delay s development of symptoms in response to CPSMV. Using monoclonal antib odies for serological assays and virus-specific RNA probes for hybridi zation, it is demonstrated that the presence of CPMV in the inoculum y ields a concomitant delay in the synthesis of CPSMV coat protein and r eplication of CPSMV RNA and restricts the transport of CPSMV out of in fection centres. Only bottom component of CPMV containing RNA1 is requ ired to offer protection against CPSMV. Destroying the integrity of CP MV RNA eliminates its protective capability. In cowpea cultivars that are operationally immune to CPMV, the presence of CPSMV in the inoculu m is unable to compensate for events of CPMV replication that are inhi bited. The lack of complementation suggests a high degree of specifici ty in the replication of these two comoviruses.