Occurrence of a Reovirus Infecting Maize in India.

During the 1998-99 season, maize plants showing viruslike symptoms were observed at two locations in the Andhra Pradesh state in Southern India. Several hybrids were evaluated at Hyderabad in a replicated yield trial and most were affected, with disease incidence ranging from 4.4 to 61.8% of the plants among plots. Hybrid 4642 (Proagro 3-way hybrid, late maturity) and the pre-commercial hybrid YLY102 were the most susceptible, whereas the popular hybrid 4640 was among the least susceptible entries. In seed production fields near Eluru, incidence ranged from 10 to 15% among plots, with the female parent of hybrid 4210 (Proagro 3-way hybrid, early maturity) being especially affected. Symptoms observed in hybrids varied, presumably, according to the infection time and included severe plant dwarfing, dark-green leaves, enations on the lower leaf surface, and small malformed ears with few or no kernels. Symptomatic and asymptomatic field plants (root and leaf tissues) were tested by ds-RNA polyacrylamide gel electrophoresis and by double-antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) with antiserum to Mal de río cuarto virus (MRCV), a Reoviridae-Fijivirus member. MRCV and Maize rough dwarf virus (MRDV) were selected as controls because the symptoms were similar to those caused by these maize viruses (1,2). ds-RNA gels from symptomatic plants showed 10 bands with banding patterns different from those of MRCV or MRDV. DAS-ELISA indicated a distant relationship to MRCV. These results provide evidence of a reovirus infection to maize hybrids in India and suggest that a virus belonging to the family Reoviridae, genus Fijivirus is causing this new disease. The high disease incidence and the severity of symptoms should alert breeders and pathologists in southern Asia about potential yield losses. References: (1) G. Boccardo and R. G. Milne. 1984. Descriptions of Plant Viruses 294. Inst. Hortic. Res., Wellesbourne. (2) C. Marzachi et al. J. Plant Dis. Prot. 106:431-436, 1999.