Molecular Characterization of Tomato (Solanum lycopersicum L.) Accessions under Drought Stress

Exploring the genetic diversity among plant accessions is important for conserving and managing plant genetic resources. In the current study, a collection of forty-six tomato accessions from Jordan were evaluated based on their performance and their morpho-physiological, in addition to molecularly characterizing to detect genetic diversity. Tomato accessions seedlings were exposed to drought stress with 70% field capacity and 40% field capacity under field conditions in Jordan. Drought stress had significantly negatively influenced the dry root weight, fresh root weight, root growth rate, fresh shoot weight, dry shoot weight, and shoot growth rate. Moreover, proline content showed a highly significant increase of 304.2% in response to drought stress. The analysis of twenty morphological characters revealed a wide range of variations among tomato accessions. Accessions were screened with fourteen SSR primers; six primers were informative to explain the genetic diversity. Based on resolving power, primers LEct004 and LEat018 were most significant with all 46 accessions. Interestingly, polymorphic information content (PIC) values ranged from 0.00 (Asr2 marker) to 0.499 (LEct004), which confirms that the SSR markers are highly informative. Our findings provide new insights into using informative molecular markers to elucidate such wide genetic variation discovered in our collections from Afraa and Abeel (the southern part of Jordan). Interestingly, the SSR markers were associated with genes, e.g., LEat018 with ACTIN_RELATED PROTEIN gene, the LEct004 with the HOMEOBOX PROTEIN TRANSCRIPTION FACTORS gene, and Asr2 with ABA/WDS. Moreover, the AUXIN RESPONSE FACTOR8 gene was associated with the LEta014 SSR marker and the LEta020 with the THIOREDOXIN FAMILY TRP26 gene. Therefore, the genetic diversity analysis and functional annotations of the genes associated with SSR information obtained in this study provide valuable information about the most suitable genotype that can be implemented in plant breeding programs and future molecular analysis. Furthermore, evaluating the performance of the collection under different water regimes is essential to produce new tomato varieties coping with drought stress conditions.