Análisis molecular de 79 accesiones de maíz (<i>zea mays</i> l.) recolectadas en la provincia de el oro

Abstract

Maize (Zea mays L.) is one of the crops with a great genetic diversity, which can be exploited mainly for plant breeding programs, food production and identity conservation. The objective of this work is the genotyping of 79 maize accessions using ISSR molecular markers. The research work was carried out in the province of El Oro, the accessions to be used were obtained from the germplasm bank of the Semillero de Investigación en Recursos Fitogenéticos (SIRF), the fresh leaf samples were sent to the molecular identification laboratory (IDgen), the methodology used was DNA extraction and amplification by conventional PCR. The banding patterns obtained with the ISSR primers analyzed the genetic relationships between the 79 maize accessions, and a pairwise similarity matrix was calculated using the Dice coefficient, which was used to make a dendrogram by the method of groups of unweighted pairs with arithmetic averages, which showed a high difference between them due to the low cophenetic correlation (r = 0.3). It is observed that with a coefficient of cophenetic correlation of 0.32, the evaluated accessions form six main groups. The first group was composed of those that showed high divergence, among them SIRF 62, SIRF 52 and SIRF 37. However, the second group was the one that presented the most divergent accession among all, composed only by SIRF 20. The third group is formed by two subgroups, the first one is composed by SIRF 22, SIRF 23 and SIRF 21, the second subgroup is established by only two accessions SIRF 38 and SIRF 07. The fourth group is formed by two subgroups, the first one is located from SIRF 66 to SIRF 64, the second subgroup is formed by several associations and is composed from SIRF 79 to SIRF 17. The fifth group was established from accession SIRF 60 to SIRF 53. The sixth and last group is made up of the majority of the accessions, forming two large subgroups, the first is made up of several associations and is established from SIRF 46 to SIRF 16, the second large subgroup is constituted from SIRF 30 to SIRF 01. The accessions that showed the greatest similarity were SIRF 18 and SIRF 19 with a correlation coefficient of 0.85, SIRF 48 and SIRF 50 presented a coefficient of 0.83. However, the most interesting ones to take advantage of in a conservation and plant improvement program are those that presented greater divergence in relation to the others, as was the case of SIRF 20 with a correlation coefficient of 0.34, and SIRF 37 with a coefficient of 0.36 associated with SIRF 52 and SIRF 62. Likewise, an analysis of principal coordinates in the plane of two dimensions was carried out, with the purpose of corroborating the results obtained in the dendrogram, visualizing a separation in all the accessions, being the positive quadrant of coordinate 1 and negative of coordinate 2, where most of them were located, followed by the negative quadrant of coordinate 1 and negative of coordinate 2. It should be noted that the accessions that presented greater divergence in the dendrogram SIRF 37, SIRF 52, SIRF 62 and SIRF 20, in terms of the analysis of principal coordinates were observed distant from each other, with the exception of SIRF 37 and 62 that were located in the positive quadrant of coordinate 1 and negative of coordinate 2, SIRF 20 was located nearby. However, SIRF 52 was the most dissimilar to the others, as were SIRF 68, SIRF 55 and SIRF 28, all in different quadrants. However, SIRF 17, SIRF 25, SIRF 30, SIRF 07 and SIRF 26 had the highest degree of similarity with the exception of the others. SIRF 18 and SIRF 19 that showed more similarity in the dendrogram were located in the same quadrant, close to coordinate 1 and negative to coordinate 2. The 3D plane (Figure 7), allows us to visualize in a better way the genetic variability that exists among the accessions of study, in the same way the two-dimensional plane is ratified with respect to SIRF 52, SIRF 55, SIRF 68 and SIRF 28 that remained distant in their quadrants, in the same way it is verified that SIRF 17, SIRF 25, SIRF 30, SIRF 07 and SIRF 26 are found with a greater improvement with respect to the others. It is concluded that the results of variability that exist within the germplasm bank of SIRF suggest the conservation of those accessions, especially those that presented greater dissimilarity, in order to carry out genetic improvement programs in the maize crop.