Characterization of genetic diversity of bird-of-paradise accessions

This study aimed to characterize genetic diversity in the bird-of-paradise (Strelitzia reginae) collection at the Universidade do Estado de Mato Grosso Carlos Alberto Reyes Maldonado (UNEMAT) by estimating genetic divergence among genotypes based on agronomic characteristics. Seven agronomic characters were evaluated with average Euclidean distance. The UPGMA (Unweighted Pair Group Method with Arithmetic Mean) hierarchical clustering method was used between groups, as well as Tocher’s optimization clustering method and principal component analysis (PCA), in order to classify the genotypes with maximum similarity between groups. Measures of genetic dissimilarity with average Euclidean distance verified the existence of genetic variability among accessions since the amplitude of dissimilarity values ranged from 1.09 to 36.97. Tocher’s clustering method verified the formation of two distinct groups. UPGMA hierarchical clustering, based on the dissimilarity matrix, verified the formation of three groups with 30% cutoff point. Based on the main components analysis, we verified genetic divergence between the bird-of-paradise accessions in the UNEMAT Collection. The most promising combinations for future crosses in breeding programs comprise accessions 1, 11, and 23 and accession 1 as the most divergent among the accessions evaluated.


INTRODUCTION
Tropical ornamental plants and flowers are gaining importance in floriculture owing to the attractiveness of the flowers and leaves, as well as their exotic colors, shapes, sizes and durability.Among tropical species, bird of paradise (Strelitzia reginae) has been cultivated for cut flowers based on their exotic colors and shapes, as well as vase life (durability), length of stems, and plant resistance to pests and diseases (WOOD, 1995;MACNISH et al., 2010;TERAO et al., 2005).Bird of paradise plants are frequently used in landscaping, but they are more attractive and exotic as cut flowers in arrangements and for decoration.
The bird of paradise tends toward polymorphism; thus, each plant originated from seed presents its own characteristics, especially as reflected in plant height, shape and size of leaves, stem length, and flower size, among other characteristics (TERAO et al., 2005).Species characterization has been very important to breeding programs since they provide parameters by which to identify the parents, contributing to greater heterosis in the progeny and high probability of achieving superior genotypes in segregating generations, in addition to gaining increased knowledge about the genetic basis of plant populations as a whole (FERRÃO et al., 2002).
The present study aimed to genetically characterize bird of paradise accessions from the UNEMAT Collection based on agronomic characteristics.
The accessions were evaluated according to agronomic characteristics, including plant height, as measured from the base of the soil to the tip of the last leaf extended, petiole length, length of leaves, leaf width, length/width ratio of leaf blades, diameter of the base of the petiole, diameter of the apex of the petiole and number of leaves.
Data were submitted to a multivariate analysis based on the Euclidean Mean distance to obtain the Matrix of Dissimilarity, using grouping methods, hierarchical linkage between groups (UPGMA) and Tocher's Optimization, in addition to an analysis of components to classify the genotypes that presented the highest similarity among groups.The statistical procedures were performed using the computational software GENES (CRUZ, 2013).

RESULTS AND DISCUSSION
Genetic dissimilarity, relative to the characteristics evaluated, using the average Euclidean distance, revealed the existence of genetic variability among the bird of paradise accessions.The values of amplitude of dissimilarity ranged from 1.09 to 36.97, indicating the presence of a broad spectrum of variability among the accessions (Table 1).The most divergent accessions showed the highest dissimilarity (d ii ') of 36.97 and 36.38%, with the most divergent combinations for accessions 23 and 1 and 11 and 1, respectively.Therefore, these accessions present the highest divergence relative to all accessions evaluated.Based on the results, future genetic improvement programs can be suggested for these accessions showing high genetic divergence since their progeny would have greater genetic variability, which is desirable for plant crossings.According to Kvitschal (2009), the plant descendants of hybrids can generate seedlings with agronomic characteristics of interest and high production potential.
The combinations with the smallest distance magnitude based on values of d ii ' were accessions 20 and 17, 21 and 14, 15 and 7, 18 and 17, 23 and 7, and 22 and 16 with d ii ' values of 1.09, 1.39, 1.19, 1.72, 1.82 and 1.90%, respectively.These results indicate lower divergence relative to all evaluated accessions.Consequently, these accessions should not be recommended for genetic improvement programs since their progenies would generate low heterosis, thereby reducing the possibility of genetic gains with these combinations.
Cluster analysis using Tocher's Optimization (Table 2) revealed the formation of two distinct groups.Group I was the most numerous with 96.30% of the 27 accessions evaluated.Group II was formed by accession 1 alone, representing 3.70% of the accessions evaluated, suggesting that this group is the most divergent and, consequently, the most suitable for future genetic improvement of bird of paradise.The results of this study were similar to those obtained by Zuin et al. (2009), who evaluated the genetic divergence among cassava accessions (Manihot esculenta Crantz) in the municipality of Cianorte (PR) and verified the distribution of the most divergent accessions using Tocher's method.Puiatti et al. (2014) evaluated the productivity of garlic accessions through morphological characteristics and observed that Tocher's method divided 60 accessions into eight different groups.
Table 2. Representation of Tocher's method based on genetic dissimilarity of seven characteristics on 27 accessions of bird of paradise.

I
Table 3. Mean intra-and intergroup distances estimated by Tocher's method based on the dissimilarity matrix of seven characteristics on 27 accessions of bird of paradise.

GRUPOS
I II I 7.14 31.05

II -
Figure 1 shows that the UPGMA hierarchical grouping method, which is based on the dissimilarity matrix, resulted in the formation of of three groups with the cutoff point at 30%.The first group consisted of a large number of accessions, with 23 of the 27 accessions evaluated.Group II consisted of three accessions.Group III consisted of only one accession.In studies carried out by Rocha et al. ( 2013), who evaluated the quality of light guava nectars of different brands marketed in Lavras (MG), it was observed that the first two principal components explained about 84.08% of the total variation.PCA is used when the first components involve at least 80% of the total variation, allowing evaluation of the importance of each studied character on the total variation among genotypes (CRUZ et al., 2012).The graphical representation of genotype dispersion, which is based on the first two main components arranged in the two-dimensional space, revealed the formation of two small divergent groups, showing great similarity (Figure 2).Group I was formed by most accessions, and group II was only formed by accession 1 from Cuiabá, MT, indicating that this accession diverges from others in the study (most dissimilar) and is, therefore, the most suitable for genetic improvement programs.It is necessary to select parents who present a greater divergence in the characteristics in order to perform crosses between parents (HALLAUER and MIRANDA FILHO, 1981).
The intergroup space formed by the majority of the accessions in the dispersion graphic presented little dispersion, indicating, in turn, little divergence among them.A convergence was observed between the UPGMA and Tocher grouping methods with respect to the graphical representation of dispersion among the formed accession groups, indicating consistency in the results to identify divergent accessions.The graphical representation of dispersion simplified and complemented the interpretation of the other clustering methods used.

CONCLUSIONS
Our results show genetic variability among bird of paradise accessions in the plant collection of UNEMAT.The most promising combinations for future crosses in breeding programs comprise accessions 1, 11, and 23.Accession 1 is the most divergent among the accessions evaluated.

Figure 2 .
Figure 2. Graphical dispersion of the scores in relation to the representative axes of the first two main components (CP1 and CP2) of seven morpho-agronomic characters on 27 accessions of bird of paradise.

A
.A.S.: main author of the manuscript, performing the analysis, tabulation of data and discussion of the results.V.C.A.: assistance in the implementation of the experiment, collection, tabulation and interpretation of data and construction of tables and graphs.M.A.A.B.: statistical analysis and discussion of results.T.S.G.: assistance in the implementation of the experiment and data collection.P.B.L.: writing and discussion of the results.

Table 1 .
Genetic dissimilarity on seven characteristics of 27 bird of paradise accessions.

Table 4 .
Eigenvalues and eigenvectors associated with seven morpho-agronomic characters on 27 accessions of bird of paradise.