Marker assisted identification of tospovirus resistant tomato genotypes in segregating progenies Identificação de genótipos de tomateiro resistentes a tospovirus em progênies segregantes com marcador molecular

The SCAR (Sequence Characterized Amplified Region) 'Sw-421' molecular marker is located at 1.0 cM from the Sw-5 allele, originated from Lycopersicon peruvianum (L.), which confers resistance to the tomato spotted wilt virus (TSWV). However, it had not been tested yet in advanced tomato populations. The goal of this study was to distinguish resistant homozygotes (Sw-5/Sw-5) and heterozygotes (Sw-5/Sw-5+) from susceptible (Sw-5+/Sw-5+) plants in crossing populations with the Stevens cultivar and advanced backcrossing populations by using 'Sw421' SCAR marker. The amplification of 940 bp and 900 bp bands characterized the resistant homozygotes and susceptible controls, respectively. A two band pattern (900 bp and 940 bp) was observed in heterozygote genotypes (Sw-5/Sw-5+), which confirmed the co-dominant inheritance mechanism of the marker. Fifty seven plants from the isogenic progenies were characterized based on bands pattern: 18 plants (31.6%) were identified as resistant homozygotes, 8 plants (14.0%) as resistant heterozygotes and 31 plants (54.4%) were characterized as susceptible. The SCAR 'Sw-421' marker is an important tool for selection and pyramid resistance alleles, mainly when other resistance sources to the TSWV are available, such as the Rey de los Tempranos source.<br>O marcador molecular SCAR 'Sw-421' é localizado a 1,0 cM do alelo Sw-5, proveniente de Lycopersicon peruvianum (L.), que confere resistência ao vira-çabeça em tomateiro. Contudo, o mesmo ainda não havia sido testado em populações avançadas de tomateiro. O objetivo do trabalho foi distinguir plantas resistentes homozigotas (Sw-5/Sw-5), resistentes heterozigotas (Sw-5/Sw-5+) e suscetíveis (Sw-5+/Sw-5+) pelo marcador SCAR 'Sw-421'. As amplificações de bandas de 940 pb e 900 pb caracterizaram os genótipos resistentes homozigotos e suscetíveis, respectivamente. Duas bandas (900 pb e 940 pb) foram observadas nos genótipos heterozigotos, confirmando a herança codominante do marcador. De 57 plantas das progênies isogênicas avaliadas 18 (31,6%) plantas foram caracterizadas como resistentes, 8 (14,0%) como heterozigotas e 31 (54,4%) plantas suscetíveis. O marcador molecular SCAR 'Sw-421' constitui importante ferramenta para seleção e piramidação de alelos de resistência, especialmente quando se utilizam outras fontes de resistência ao vira-cabeça, como por exemplo, a fonte Rey de los Tempranos.