Assessment of Hybrid Identification in Mango Progenies Using SSR Markers
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Abstract
Nam Dokmai Si Thong is a mango cultivar known for its desirable flavor and high economic value in Thailand. However, the breeding of true hybrids is challenging because mango is polyembryonic, meaning that seedlings arising from maternal nucellar tissue can resemble true hybrids morphologically. Molecular markers can therefore improve selection accuracy and shorten the breeding process. This study used 13 simple sequence repeat (SSR) markers to examine 21 progenies derived from crosses between Nam Dokmai Si Thong (female parent) and three male parents: R2E2, Yu Wen, and Ngachang Daeng. A total of 24 alleles were detected, with 1–3 alleles per locus. The mean observed heterozygosity, expected heterozygosity and polymorphic information content (PIC) were 0.245, 0.226, and 0.183, respectively. A parentage exclusion test based on loci at which the male parents carried paternal-specific alleles revealed that two-thirds of the progenies (14 lines; 66.7%) lacked paternal alleles and were identical to Nam Dokmai Si Thong at all scored loci, consistent with a nucellar origin. Line 10 lacked paternal alleles but differed from the female parent at one locus, whereas six lines carried non-maternal alleles. The markers also revealed discrepancies in the recorded crosses that would be difficult to detect based on plant morphology alone. Line 8 had a genotype consistent with a cross between Nam Dokmai Si Thong and R2E2 rather than the recorded cross involving Yu Wen. Lines 11, 12, and 23 shared an identical genotype and carried paternal alleles that did not match any of the three designated male parents, suggesting possible pollination by another tree. Lines 13 and 14 differed from the female parent at one locus. The results of unweighted pair group method with arithmetic mean (UPGMA) clustering (cophenetic correlation coefficient, r = 0.91), principal coordinate analysis (PCoA), and STRUCTURE analysis at K = 2 were consistent with the parentage exclusion results. The SSR marker set clearly distinguished the female parent from the male parents, but could not differentiate among the three male parents. These findings demonstrate that early screening of mango seedlings using SSR markers can help eliminate non-hybrid plants at an early stage and verify the accuracy of cross records, thereby supporting more efficient and reliable mango breeding programs.
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References
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