ABSTRACT
The study was conducted to characterise bean common mosaic virus strain Blackeye (BCMV-BICM) and determine the likelihood of seed transmission in cowpea breeding lines. F6 cowpea lines obtained from crosses between 'Ife-Brown' and 'IT-95 K-193-12' were planted at five locations in Southwest Nigeria for multilocational evaluation. Virus symptoms were observed on leaves of the breeding lines planted in Ibadan at eight weeks after planting. Enzyme-linked immunosorbent assay (ELISA) was used to determine the presence of six viruses: BCMV-BICM, cowpea aphid-borne mosaic virus, cucumber mosaic virus, cowpea mottle virus, southern bean mosaic virus and cowpea mild mottle virus. Seed transmission tests were carried out to determine virus transmission by seeds while growth and yield components of the cowpea lines were obtained. Reverse transcription polymerase chain reaction, sequencing and phylogenetic analyses were also used to characterise the BCMV-BICM isolates. The observed symptoms, leaf curling and mosaics, were typical of BCMV-BICM infection and ELISA results confirmed the presence of only BCMV-BICM. Line 'L-22-B' had the highest yield of 1653.9 kgha-1 followed by 'L-43-A' (1072 kgha-1). A non-significant relationship existed between the virus and germination parameters and similarly, the relationship between virus titres and yield parameters was not significant. Sequence analysis of the virus coat protein (CP) gene revealed the presence of three isolates with 96.87-97.47% nucleotide and 98.2-98.65% amino acid similarities and a 99.10-99.55% match with BCMV-BICM CP genes in GenBank. The deduced CP gene sequences showed unique changes at specific sites, while phylogenetic inferences revealed at least two separate origins for the isolates. Seed transmission is evident in all the cowpea breeding lines and 'L-22-B' and 'L-43-A' showed significant tolerance to BCMV-BICM. Thus, it is recommended that seeds from infected fields should not be used for further planting to prevent the introduction of viruses into new areas where their effect could be devastating in susceptible lines. Supplementary Information: The online version contains supplementary material available at 10.1007/s13337-023-00812-3.
ABSTRACT
Viral diseases constitute obstacles to pepper production in the world. In Nigeria, pepper plants are primarily affected by pepper veinal mottle virus (PVMV), Cucumber mosaic virus (CMV), Pepper leaf curl Virus (TLCV), Tobacco mosaic virus (TMV), Pepper mottle virus (PMV) and a host of other viruses. The experiment was carried out with a diagnostic survey on the experimental field of the National Horticultural Research Institute, Ibadan, Nigeria and on pepper farms in six local government areas within Ibadan Oyo State, Nigeria, forty samples were collected from each of the farms. Diseased samples were obtained from the field and taken to the laboratory for indexing. In ELISA test some of the samples from the pepper farms showed positive reaction to single infection with PVMV (36.79%), CMV (22.14%) while some others showed positive reaction to mixed infection of the two viruses (10%) but some also negative reaction to PVMV and CMV antisera (31.07).
