Mango (Mangifera indica L.) (2n = 40) is an important perennial fruit tree in tropical and subtropical regions. The lack of information on genetic diversity at the molecular level hinders efforts in mango genetic improvement and molecular marker-assisted breeding. In this study, a genome-wide screening was conducted to develop simple sequence repeat (SSR) markers using the Alphonso reference genome. A total of 187 SSR primer pairs were designed based on SSR loci with consisting of tri- to hexa-nucleotide motifs, and 34 highly polymorphic primer pairs were selected to analyze the diversity of 231 germplasm resources. These primers amplified 219 alleles (Na) across 231 accessions, averaging of 6.441 alleles for per marker. The polymorphic information content (PIC) values ranged from 0.509 to 0.757 with a mean of 0.620. Genetic diversity varied among populations, with Southeast Asia showing the highest diversity, and Australia the lowest. Population structure analysis, divided the accessions into two groups, Group I (India) and Group II (Southeast Asia), containing 104 and 127 accessions, respectively, consistent with results from phylogenetic analysis and principal component analysis (PCA). Sixteen SSR primer pairs capable of distinguishing all tested accessions, were selected as core primers for constructing fingerprints of 229 mango accessions. These findings offer valuable resources for enhancing the utilization of mango germplasm in breeding programs.

Mango (Mangifera indica L.) belongs to the genus Mangifera and family Anacardiaceae, and is an important tropical fruits. Artificial cross breeding (hand pollination) is an important method for breeding new mango cultivars. It is easy to produce false hybrids in the process of artificial pollination breeding. Therefore, it is necessary to establish rapid and accurate molecular detection methods to identify the authenticity of hybrids. Mango ‘Jinhuang’ and ‘Renong No.1′ and 65 individual plants of their F₁ hybrids were used as experimental materials, eight SSRs (simple sequence repeats) primer pairs with polymorphism in parents were used to identify the F₁ hybrids by capillary electrophoresis. The results showed that PCR product size (bp) for eight primers ranged from 108 bp (ES55) to 176 bp (ES63) in 65 samples. A total of 62 true hybrids were identified from 65 hybrid progenies, and the true hybrid rate was 95.38%. A total of 18 alleles were amplified by eight SSRs, seven SSR loci showed binary segregations, whereas only one SSR locus ES83 showing ab:ac:bb:bc segregation fitted to the expected segregation ratio of 1:1:1:1. The value of expected heterozygosity (He), ranged from 0.34 to 0.62, whereas the value of observed heterozygosity ranged from 0.44 to 0.81. Chi-square test showed that eight SSR loci were in accordance with Mendel’s segregation law. The results of cluster analysis showed that the parents and 62 true hybrids could be classified into two categories at 0.58: the first category contained 27 offspring, clustered with ‘Jinhuang’ and showed a maternal genetic tendency. The second category contained 35 offspring, clustered with ‘Renong No.1′ and showed a partial paternal genetic tendency. DNA fingerprint of hybrids from ‘Jinhuang’ × ‘Renong No.1′ cross were constructed using eight SSR primers for variety protection.

This study investigated the optimal strategies for improving sugar biosynthesis in mango fruits. Randomized block design was used for experimental treatments. The mango cultivar “Renong-1” was sprayed with five green plant growth regulators, including solutions of SBP (sucrose-based polymers, a new highly efficient and eco-friendly plant growth regulator), SPM (sucrose + potassium dihydrogen phosphate + microelement fertilizer), TPM (taurine + potassium dihydrogen phosphate + microelement fertilize), PFA (potassium fulvic acid), and SOP (seaweed oligosaccharide peptide) at different fruit development stages. Indicators, such as soluble solid content, soluble sugar and starch contents, and activities of 11 enzymes associated with sugar metabolism in physiologically mature and in full ripening fruits were evaluated. The results showed that SBP solution diluted 100-fold exerted the strongest effect on the soluble sugar content and sweetness value of “Renong-1” mango fruits. Based on the linear regression analysis, a significant negative correlation was observed between the activity of acid invertase and the perceived sweetness of physiologically mature fruits, while the activities of other enzymes were significantly negatively correlated with the perceived sweetness of full ripening fruits. According to multiple regression (by lars function in R) and other comprehensive analysis, A1B3 (spraying SBP solution one time in the young fruit stage) was selected as the optimal treatment combination for enhancing “Renong-1” mango perceived sweetness, followed by A1B2 (spraying SBP solution for the first time in the young fruit stage and the second time at medium maturity) as the alternative treatment combination.

MADS-box genes play a crucial role in fruit ripening, yet limited research has been conducted on mango. Based on the conserved domains of this gene family, 84 MADS-box genes were identified in the mango genome, including 22 type I and 62 type II MADS-box genes. Gene duplication analysis revealed that both tandem duplication and segmental replication significantly contributed to the expansion of MADS-box genes in the mango genome, with purifying selection playing a vital role in the segmental duplication events within the MiMADS gene family. Cis-acting element analysis demonstrated that most MiMADS genes were hormonally regulated and participated in the growth, development, and stress resistance of mango fruit. Moreover, through expression pattern analysis and phylogenetic tree construction, we identified six MiMADS genes belonging to the SEP1 subfamily and two belonging to the AG subfamily as potential candidates involved in mango ripening regulation. Notably, Mi08g17750 and Mi04g18430 from the SEP1 subfamily were identified as key regulators inhibiting mango fruit maturation; their interaction network was also analyzed. These findings provide a foundation for further investigation into the regulatory mechanisms underlying mango ripening.

Sugar content critically determines mango fruit quality and varies significantly among varieties. Preliminary studies indicate that fructokinases (MiFRKs) MiFRK1 and MiFRK2 likely regulate intervarietal sugar variation. We characterized these MiFRKs using heterologous expression in tomato. Both isoforms phosphorylate fructose, promoting downstream catabolism, with R-MiFRK2 (from low-sugar ‘Renong No. 1’) exhibiting higher activity than T-MiFRK2 (high-sugar ‘Tainong No. 1’) and MiFRK1. Transcriptomic and metabolic analyses reveal that MiFRK overexpression inhibits sugar accumulation by altering the expression of key metabolic genes, including sucrose degradation enzymes (invertases), starch breakdown genes (β-amylases), and glycolytic genes (enolases). Intriguingly, MiFRK1 and MiFRK2 exhibit distinct regulatory effects on these pathways, suggesting functional specialization between the two isoforms. These findings provide novel insights into the molecular mechanisms through which MiFRKs govern sugar metabolism in mango, highlighting their potential as key targets for metabolic engineering to enhance fruit quality.

MADS-box genes play a crucial role in fruit ripening, yet limited research has been conducted on mango. Based on the conserved domains of this gene family, 84 MADS-box genes were identified in the mango genome, including 22 type I and 62 type II MADS-box genes. Gene duplication analysis revealed that both tandem duplication and segmental replication significantly contributed to the expansion of MADS-box genes in the mango genome, with purifying selection playing a vital role in the segmental duplication events within the MiMADS gene family. Cis-acting element analysis demonstrated that most MiMADS genes were hormonally regulated and participated in the growth, development, and stress resistance of mango fruit. Moreover, through expression pattern analysis and phylogenetic tree construction, we identified six MiMADS genes belonging to the SEP1 subfamily and two belonging to the AG subfamily as potential candidates involved in mango ripening regulation. Notably, Mi08g17750 and Mi04g18430 from the SEP1 subfamily were identified as key regulators inhibiting mango fruit maturation; their interaction network was also analyzed. These findings provide a foundation for further investigation into the regulatory mechanisms underlying mango ripening.