Hassan M.A., Chindo P.S., Marley P.S., Alegbejo M.D. (2010) and sawdust (SD), for the management of root knot nematodes, Meloidogyne spp., on tomato. Organic wastes were applied at the rate of 15, 30 and 45 metric tons per hectare. Furadan (3G) was applied at the rate of 16, 32 and 64 kg/ha and non-amended plots served as control. The experiment was laid out in randomized complete block design (RCBD). Four weeks old tomato seedlings (cv. Roma VF) susceptible to root knot nematodes were transplanted at a number of eight seedlings per plot of 2 m × 1 m with 45 cm spacing between stands. Fertiliser application, weeding, irrigation and other practices were done as recommended. The results showed that RD treatment gave the significantly (P = 0.05) highest reduction in the nematode population compared to nonamended treatment. It resulted in a significant (P = 0.05) increase in the yield of tomato by 17-100% for RD, 13-84% for SD and 21-63% for RH.

Investigations on the mode of transmission of rice yellow mottle virus (RYMV) revealed that it is located in the rice husks. It is therefore, not transmitted through rice seeds. The virus was transmitted through leaf debris, empty rice spikelets, intertwining roots, leaf contact, rice stubble, contaminated hands and from closely spaced plants. Chrysomelid beetles, Chnootriba similis Thurnberg (Coccinelidae) and some long homed grasshoppers transmitted RYMV. The virus is not transmitted by nematodes. Oryza sativa L., O. glaberrima, and O. barthii are systemic hosts while O. longistaminata and a few weed species are local lesion hosts. The virus was readily detected by visual assessment based on the standard evaluation system (SES) and a serological test utilising enzyme linked immunosorbent assay (ELISA) and agar gel diffusion.

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Bacterial spot (BS) is an important disease of tomato in Nigeria (2). Although a xanthomonad was isolated from tomato in Nigeria and characterized using phenotypic and pathogenicity tests, the bacterium was not characterized genetically to confirm the species. To determine the species associated with BS, leaves were collected in fields in northwestern Nigeria from tomato plants showing typical BS symptoms, which consisted of dark, irregular-shaped brown leaf spots that coalesced, resulting in a blighted appearance. Isolations from individual lesions were made on nutrient agar (NA). Yellow, mucoid colonies typical of Xanthomonas were isolated from 14 lesions and all were determined to be amylolytic (3). To determine the races of these strains, bacterial suspensions of the tomato strains, derived from 24-h cultures grown on NA at 28°C, were adjusted to 108 CFU/ml and infiltrated into leaves of tomato and pepper differential genotypes (5). The tomato strains elicited hypersensitive reactions (HRs) on the four pepper differential lines and an HR on the tomato genotype FL 216, which contains the R gene Xv3, but elicited susceptible reactions on the tomato genotypes Hawaii 7998 and Bonny Best. These reactions are typical of X. perforans tomato race 3 strains (5). Multilocus sequence analysis (MLSA) of six housekeeping genes (fusA, lacF, gyrB, gltA, gapA, and lepA) was used to further analyze four representative strains (1) (GenBank Accession Nos. KJ938581 to KJ938584, KJ938588 to KJ938591, KJ938595 to KJ938598, KJ938602 to KJ938605, KJ938629 to KJ938632, and KJ938636 to KJ938639, respectively). A partial sequence of hrpB2 was also made since the four Xanthomonas species associated with BS can be differentiated based on sequence divergence of this gene (3) (KJ938609 to KJ938621 and KJ938628). The housekeeping gene sequences were aligned along with other Xanthomonas sequences imported from the National Center for Biotechnology Information (NCBI) database ( www.ncbi.nlm.nih.gov ) using the MUSCLE tool from MEGA software, 5.2.2. Maximum likelihood phylogenetic trees constructed for the six housekeeping gene sequences individually and in concatenation revealed that the strains grouped most closely with the X. euvesicatoria reference strain 85-10 but more distantly to X. perforans. The hrpB2 sequence, which is highly conserved for each Xanthomonas species pathogenic on tomato (4), was sequenced from the tomato strains. These sequences were identical to the hrpB2 sequence from X. perforans strains but different from X. euvesicatoria. Although BS is common in Nigeria, to our knowledge, this represents a unique group of X. euvesicatoria strains from tomato that are identical to X. perforans based on pathogenic reactions on tomato and pepper and hrpB2 sequence identity but are more closely related to X. euvesicatoria based on the six housekeeping gene sequences. References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (2) E. U. Opara and F. J. Odibo. J. Mol. Genet. 1:35, 2009. (3) J. B. Jones et al. Syst. Appl. Microbiol. 27:755, 2004. (4) A. Obradovic et al. Eur. J. Plant Pathol. 88:736, 2004. (5) R. E. Stall et al. Annu. Rev. Phytopathol. 47:265, 2009.

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