Molecular profiling of Heliconia genotypes using SRAP and ISSR markers
The use of SRAP and ISSR markers effectively demonstrated genetic diversity among the 28 Heliconia genotypes. Morphological analysis further corroborated these findings, underscoring the utility of both molecular and phenotypic data in assessing genetic variation.
SRAP marker analysis
Nine SRAP primer combinations were selected for their reproducibility and clarity in amplification, yielding a total of 38 alleles across the 28 Heliconia genotypes (Table 4; Fig. 1). The number of alleles per primer combination ranged from 2 to 7, with an average of 4.22 alleles per primer. Of the 38 alleles, 37 were polymorphic, resulting in a polymorphism rate of approximately 98%, highlighting the high efficacy of SRAP markers in capturing genetic variability. This level of polymorphism exceeds previously reported values, such as the 88% observed in Magnolia wufengensis (Chen et al., 2014), indicating that SRAP markers are highly informative for Heliconia species. The amplified fragment sizes ranged between 100 bp and 800 bp, suggesting that both small and large genomic regions were targeted.
The polymorphic information content (PIC) values for the SRAP markers ranged from 0.52 (SRAP m2e7) to 0.87 (SRAP m5e3), with an average of 0.74, indicating moderate to high levels of informativeness. The marker index (MI), which reflects the discriminative power of the markers, ranged from 1.56 (SRAP m2e5) to 6.14 (SRAP m5e3), with an average of 3.02. The resolving power (RP) of the primers, a measure of their ability to differentiate closely related genotypes, ranged from 15.42 (m5e3) to 39.5 (m2e7), with an average of 24.44 (Table 4). These parameters collectively suggest that SRAP markers are robust tools for distinguishing between diverse Heliconia genotypes.
ISSR marker analysis
Amplification using two ISSR primers selected from an initial screening of 25 ISSR primers yielded 15 polymorphic alleles across the 28 Heliconia genotypes, with a 100% polymorphism rate (Table 5). The polymorphic rate observed here is notably higher than the 63.64% reported by Pereira et al. (2016) for Heliconia. The allele sizes ranged from 300 bp to 800 bp, and the ISSR 811 primer generated the highest number of alleles (11), while ISSR 809 generated 4 alleles.
The PIC values for ISSR markers ranged from 0.56 (ISSR 809) to 0.85 (ISSR 811), with an average of 0.71, indicating moderate informativeness. The marker index ranged from 2.26 (ISSR 809) to 9.40 (ISSR 811), with an average of 5.83, reflecting the high discriminatory capacity of ISSR markers. The resolving power ranged from 14.90 (ISSR 811) to 38 (ISSR 809), with an average of 26.45 (Table 5), demonstrating their utility in differentiating closely related genotypes.
Comparative analysis of SRAP and ISSR markers
Despite a higher polymorphic band percentage with ISSR markers, SRAP markers exhibited a higher average PIC value (0.74) compared to ISSR (0.71), suggesting greater overall informativeness in distinguishing between Heliconia genotypes. This discrepancy may be attributed to the different genomic regions targeted by the two marker systems, with SRAP markers primarily amplifying functional regions, such as open reading frames (ORFs), and ISSR markers focusing on non-coding regions between simple sequence repeats (SSRs). These differences align with previous studies, where varying levels of marker informativeness were observed across different species and marker systems (Liu et al., 2012; Wu et al., 2014).
Pairwise Jaccard similarity coefficient values for the 28 Heliconia genotypes ranged from 0.302 to 0.943, reflecting substantial genetic variability within the species. The highest similarity (0.943) was observed between H. chartaceae ‘Temptress’ and H. angusta ‘Red Christmas’, suggesting close genetic relatedness. Conversely, the lowest similarity (0.302) was found between H. stricta ‘Lobster Claw’ and H. angusta ‘Red Christmas’, indicating significant genetic divergence (Table 6).
Cluster analysis, performed using the UPGMA method based on SRAP and ISSR marker data, revealed two main clusters (Cluster A and Cluster B) at a similarity coefficient of 59% (Fig. 2). Cluster A comprised seven genotypes, which were further subdivided into two subclusters, A1 and A2. Subcluster A1 included four genotypes: Fire Flash, Guyana 2, Golden Torch, and Alan Carle. The latter three genotypes (Golden Torch, Alan Carle, and Guyana 2) clustered closely together, sharing a common parental lineage of H. psittacorum x H. spathocircinata. In contrast, Fire Flash, which has a distinct parental background of H. densiflora, was placed further apart within this subcluster.
Subcluster A2 contained three genotypes: Temptress, Red Christmas (which shared 94% similarity), and Distans. These genotypes have diverse parental origins, including H. chartaceae, H. angusta, and H. latispatha.
Cluster B, consisting of 21 genotypes, was further divided into two subclusters, B1 and B2. Subcluster B1 was split into two groups: B1.1 and B1.2. Group B1.1 was divided into two subgroups: Group a and Group b. Within Group a, subgroups a1 and a2 were identified. Subgroup a1 contained Meccas Pink and Pedro Ortiz, which are closely related despite having different parental lineages: H. orthotricha and H. collisiana × bourgeana, respectively. Subgroup a2 included four genotypes (Tropics, Kathy, Lady Di, and Kenya Red), which are closely related, with Kathy, Lady Di, and Kenya Red sharing the common parent H. psittacorum, and Tropics being a cross of H. psittacorum x H. spathocircinata.
Group B1.2 contained two subgroups: Group b1 and Group b2. Group b1 consisted of four genotypes: Red, Jacquinii, Prince of Darkness, and Caribea, all sharing a common parental lineage of H. caribaea. Additionally, Red, Jacquinii, and Prince of Darkness share the parental cross H. caribaea x H. bihai. Group b2 comprised seven genotypes, including Ten Days, Jamaican Dwarf, and Parrot’s Beak, which are closely related and clustered with Iris and Guyana. Ten Days and Parrot’s Beak share common parents H. rostrata and H. stricta, while Jamaican Dwarf and Iris share parents H. bihai. Additionally, Dwarf and Schaefer, both sharing the common parent H. bihai, were placed together in Group B1.2.
Cluster B2 included two genotypes, Lobster Claw and Upright, which share a genetic similarity of 0.83, despite having different parental origins: H. stricta and H. rauliniana.
Implications for genetic diversity and conservation
The high levels of polymorphism and genetic diversity observed using SRAP and ISSR markers highlight the extensive genetic variability within Heliconia genotypes. This genetic diversity underscores the need for conservation efforts to preserve Heliconia genetic resources. The results of this study provide valuable insights into the genetic structure of Heliconia, which will be crucial for breeding programs aimed at enhancing the species’ genetic pool, adaptability, and resilience in changing environmental conditions.
In conclusion, both SRAP and ISSR markers have proven to be powerful tools for assessing genetic diversity and population structure in Heliconia genotypes. These findings contribute to a better understanding of the genetic resources available, facilitating the development of effective conservation and breeding strategies for the sustainable management of Heliconia species.
Patterns of agro-morphological differentiation among genotypes
To investigate the patterns of agro-morphological traits and identify the major sources of variation among Heliconia genotypes, a Multifactorial analysis (MFA) was conducted using quantitative data. Descriptive statistics, including the maximum, minimum, mean values, and standard deviations for the estimated traits, are presented in Table 7.
The correlation between variables and factors grouped the 28 genotypes into several distinct factors, with the first four factors accounting for approximately 85.02% of the total variation observed (Table 8). Factor 1 (F1) explained the largest portion of the variation, approximately 47.7%, and was primarily associated with agronomic traits such as plant height, leaf length, leaf width, and leaf petiole length. Factor 2 (F2), which explained 15% of the variation, was closely linked to rachis length, bract length, and the number of flowering shoots per plant. Factor 3 (F3), accounting for 13.2% of the variation, was predominantly influenced by bract width. The final factor, Factor 4 (F4), explained 9.2% of the variation and was mainly associated with spike length.
The MFA plot (Fig. 3) visually represents the relationships between different genotypes based on various agro-morphological attributes, including leaf length, leaf width, plant height, spike length, leaf petiole length, rachis length, bract length, bract width, flowering shoots per plant, bracts per floret per spike, and internodal length between florets per bract. Genotypes with similar traits clustered together, while those exhibiting contrasting traits were positioned further apart.
In the first and second quadrants of the MFA plot, genotypes such as Upright, Temptress, Lobster Claw, Alan Carle, Iris, H-25, H. Red, Jacquinii, Parrot’s Beak, Ten Days, Tropics, Guyana 2, Metallica, and Caribea clustered closely together. These genotypes shared common traits related to leaf morphology (length and width), plant height, leaf petiole length, bract length, rachis length, bract width, spike length, bracts per floret per spike, and internodal length between florets per bract. Notably, Lobster Claw, Alan Carle, and H-25 were closely positioned in the first quadrant, sharing attributes such as bract length, rachis length, spike length, and internodal length between florets. Additionally, H-Red and Jacquinii formed a close cluster due to similarities in bract width. In quadrant two, Ten Days and Guyana 2 were closely associated, exhibiting similarities in leaf length, leaf width, plant height, and leaf petiole length.
On the opposite side of the MFA plot, genotypes such as Guyana, Kenya Red, Lady Di, Kathy, Meccas Pink, Red Christmas, Schaefer, Golden Torch, Dwarf, Fire Flash, Jamaican Dwarf, Distans, Prince of Darkness, and Pedro Ortiz were characterized by traits related to the number of flowering shoots per plant (Fig. 3 and 4). This provided a clear visualization of the differentiation and relationships between the genotypes based on their agro-morphological attributes, revealing specific patterns of association.
To further examine agro-morphological differentiation, hierarchical cluster analysis was performed, estimating dissimilarity among genotypes using distance to centroid based on phenotypic data (Fig. 5). The dendrogram divided the genotypes into two major clusters: Cluster 1 and Cluster 2.
Cluster 1 contained 17 genotypes, including Fire Flash, Pedro Ortiz, Tropics, Distans, Temptress, Lobster Claw, Upright, H. Red, Jacquinii, Caribea, Ten Days, Parrot’s Beak, Iris, Guyana 2, H-25, Metallica, and Alan Carle. Within this cluster, Alan Carle and Guyana 2 exhibited close genetic similarity due to their shared parental lineage of H. psittacorum x H. spathocircinata. Similarly, Ten Days and Parrot’s Beak showed a close relationship, sharing the same parent (H. rostrata). Additionally, H. Red, Jacquinii, and Caribea were grouped together, sharing a common parental background of H. caribaea x H. bihai.
Cluster 2 included 11 genotypes: Meccas Pink, Guyana, Red Christmas, Kathy, Lady Di, Kenya Red, Dwarf, Schaefer, Prince of Darkness, Jamaican Dwarf, and Golden Torch. Among these, Kathy and Lady Di were closely related, having the same parental lineage of H. psittacorum. These results were consistent with molecular analysis, further supporting the relationships observed in the agro-morphological data.
The hierarchical clustering and MFA provided a detailed understanding of the agro-morphological differentiation among Heliconia genotypes. The observed groupings were largely influenced by shared parental lineages and specific trait characteristics. This analysis is crucial for guiding breeding programs and conservation efforts, as it highlights the genetic diversity and potential for selective improvement within the Heliconia genotypes studied.