Marcadores moleculares aplicados à certificação de cruzamentos, análise de pureza varietal e resistência à ferrugem em cafeeiro

Abstract

The genetic improvement of Coffea arabica through controlled hybridizations constitutes a fundamental strategy for the development of cultivars with superior agronomic traits. In this context, the verification of varietal purity of parental lines and the certification of molecular markers stands out as an efficient tool for these purposes, enabling the genetic validation of genotypes. In addition, marker-assisted selection (MAS) has been widely employed to accelerate the incorporation of resistance genes, especially against coffee leaf rust, caused by Hemileia vastatrix. This study was divided into two articles, whose objectives were to validate varietal purity and certify crosses among C. arabica cultivars, as well as to select resistant plants using molecular markers. In the article, genomic DNA was extracted from 11 parental lines and their F1 hybrids using the CTAB (cetyltrimethylammonium bromide) method, with modifications. Initially, 31 SSR (Simple Sequence Repeat) markers and five SCAR (Sequence Characterized Amplified Region) markers were screened to evaluate polymorphism among the parental lines of each cross. The primers CaEST-002, CaEST-029, CaEST-071, CaEST’-072, AJ254, SSRCa87, CM101, CaRHv10, and S235 demonstrated discriminatory capacity to differentiate molecular profiles among the parental lines of three crosses and were selected for subsequent analyses. Subsequently, to certify varietal purity, plants from each parental line were compared with previously characterized coffee plants of known genetic identity. Plants resulting from varietal mixture or contamination were identified in five of the evaluated parental lines and were discarded from further analyses. Cross certification was performed for the parental combinations Catiguá MG2’ (G12) × ‘Topázio MG1190’ (G3), ‘Villa Sarchi’ (G22) × ‘MGS Paraíso 2’ (G9), and ‘Sarchimor 8840’ (G10) × ‘IPR100’ (G6). Seventeen hybrids and one self-fertilized plant were identified in the cross between G12 x G3. In the second article, marker-assisted selection (MAS), linked to a QTL located on linkage group 2 (LG2) of C. arabica, associated with resistance to races I and II, and pathotype 001 of H. vastatrix. Through this analysis, 23 homozygous resistant plants and 15 heterozygous plants were identified and considered in the selection, as they carried the resistance allele. The results obtained in this study highlight the importance of integrating molecular tools into coffee breeding. Certification ensured the genetic identity of the populations obtained, guaranteeing reliability in generation advancement. In parallel, MAS enabled the early identification of plants carrying resistance alleles, increasing the efficiency of the selection process