Assessment of molecular markers associated with photosensitivity in cowpea [Vigna unguiculata (L.) Walp.] recombinant inbred lines

The length of daylight is an environmental factor that affects the productivity of many plant species, such as some cowpea varieties that only flower during periods of short days. This work aimed to identify the putative molecular markers associated with the sensitivity to day-length variation in cowpea. This study was conducted on the varieties Bambey 21 (non-photosensitive) and Ndout (photosensitive short-day), as well as their 77 recombinant line (RIL) from the 9th generation. These plants were grown during the long days to determine their photosensitivity. Bulked segregant analysis (BSA) was used on these genotypes, with 105 simple sequence repeat (SSR) primers used to discriminate between the parents. Subsequently, 22 cowpea cultivars with different photosensitivities were screened for putative markers. Amplified deoxyribonucleic acid (DNA) fragments associated with photosensitivity were sequenced and aligned with those of the non-photosensitive cultivar and the National Center for Biotechnology Information (NCBI) database. Among the 10 SSR markers related to photosensitivity according to the BSA, only SSR-6258 and SSR-6323 were specific for the Ndout variety and RIL that were photosensitive. SSR-6258 produced a band (330 bp) located on chromosome 4 only in photosensitive varieties. This sequence is 72% identical to the non-photosensitive one, with 20 SNPs (single-nucleotide polymorphisms). This DNA fragment has 86.14% similarity with CLV2, which is involved in the flowering process. As for the SSR-6323 marker, its sequence is identical to a portion of the 28-like ubiquitin-conjugated enzyme E2 gene of V. unguiculata, involved in collaboration with the COP1 gene encoding the E3 enzyme, in the control of photoperiodic flowering. These markers identified in this study could help cowpea breeders in marker-assisted selection (MAS) from the seedling stage to determine photosensitive genotypes. Key words: Photosensitivity, Vigna unguiculata, bulked segregant analysis, simple sequence repeat.