Genetic Diversity in Tomato Genotypes (Solanum lycopersicum) Based on Salinity Responsive Candidate Gene Using Simple Sequence Repeats Umar Ja’afar 1,* , A.A. Aliero 2 , K. Shehu 1 , L. Abubakar 3 1 Department of Biology, Federal University, Birnin Kebbi, Nigeria 2 Department of Biological Sciences, Usmanu Danfodiyo University, Sokoto, Nigeria 3 Department of Crop Science, Usmanu Danfodiyo University, Sokoto, Nigeria realumar2001@gmail.com Keywords: Tomato, candidate gene, salt responsive gene, DNA, dendrogram. Abstract. Salinity inhibition of plant growth is the result of osmotic and ionic effect and different plant species have developed different mechanisms to cope with those effects. With the discovery of molecular markers and marker assisted selection technology, it is possible to develop markers that identify salt tolerance. The genetic diversity of tomato genotypes were analyzed using SSRs polymorphic markers and Unweighted Pair Group Method with Arithmetic Mean. Leaves of the twenty tomato genotypes (landraces/accessions in Nigeria) were used to isolate their DNA using Bioland Plant Genomic DNA protocols. Primers were designed from 15 different salt responsive candidate genes, using Vector NTI and the sequence of the genes were obtained from ncbi genomic web site. All 15 primers sets generated shows clear distinct polymorphic profiles as evident from the 6% agarose gel profile. Dendrogram generated shows three groups, none of the panel intermixed in a subgroup. The genetic distance information reported in this study might be used by breeders when planning future crosses among tomato genotypes. From the result obtained UC82B recorded the highest vegetative and yield parameters, therefore, adoption of this genotype could be help to increase the tomato production in Sokoto agro-climatic area. Introduction Tomato (Solanum lycopersicum L.), belong to the Solanaceae family which is one of the most important vegetables being widely grown in both fields and under protected cultivation. Most tomato cultivars are sensitive to moderate levels of salinity [1]. Indeed, all plant development stages, includingseed germination, vegetative growth and reproduction, show salinity sensitivity, that leads to poor harvests and reduced economic yield [2]. Tomato is considered as a vegetable model and has thus been subjected to molecular investigation resulting in abundant genomic information (http://solgenomics.net/). In addition to its worldwide agricultural and economic importance as a crop, tomato is a pre-eminent model system for genetic studies in plants. The use of molecular markers in breeding by means of marker assisted selection (MAS) could improve performance under extreme environments [3]. Tomato (Solanum lycopersicum L.), a major horticultural crop consumed all over the world, suffers heavy losses due to salinity. USP (universal stress protein) family proteins, first identified in prokaryotes, appear to play an active role in abiotic stress response, but their function remains largely unknown in plants [4]. A USP gene (SpUSP), cloned from wild tomato (S. pennellii) and functionally characterized in cultivated tomato exhibited increased expression under dehydration stress, salinity, oxidative stress and phyto-hormone ABA treatment. With the discovery of molecular markers and marker assisted selection technology, research has entered in to a new era and has made it possible to develop new and more informative PCR-based markers, including simple sequence repeats (SSRs), and to further facilitate the use of markers in tomato breeding. Genomic microsatellite markers are an elite group of markers, but there is possible uncertainty of linkage with the important genes. In contrast, there are better possibilities of linkage detection with important genes if SSRs are developed from candidate genes [5]. International Letters of Natural Sciences Submitted: 2018-08-16 ISSN: 2300-9675, Vol. 72, pp 37-46 Revised: 2018-10-06 doi:10.18052/www.scipress.com/ILNS.72.37 Accepted: 2018-10-24 © 2018 SciPress Ltd., Switzerland Online: 2018-11-07 SciPress applies the CC-BY 4.0 license to works we publish: https://creativecommons.org/licenses/by/4.0/