Otimização da amplificação de um marcador SCAR ligado à apomixia para seleção precoce em híbridos de Urochloa spp. (Poaceae)

Abstract

Brazil, followed by China, has the world's largest cattle herd, with approximately 226 million heads of cattle. Grasses of the genus Urochloa, from Africa, are the most forage used in Brazilian soils for cattle feed due to their resistance to trampling, ease of dispersion and reproduction, and high nutritional value. To supply the high agropastoral demand, the genetic improvement of this forage becomes extremely important. Genetic improvement can be achieved by crossing sexual with apomictic genotypes and selecting apomictic hybrids in F1. Plants with apomictic reproduction generated clones, thus ensuring that the characteristic of interest is fixed for the launch of new cultivars. The use of molecular markers to identify traits of interest is known as SAM (molecular marker-assisted selection). These markers allow the previous selection of the generated apomictic hybrids, providing greater efficiency in the breeding program, assistance, and time in the selection process. The objective of this work was to optimize the amplification of a SCAR marker ("SequenceCharacterized Amplified Region") p779/p780, a chromosomal region linked to apospory, called aposporic specific genomic region (ASGR). Two types of PCR (Polymerase Chain Reaction) were evaluated, traditional and touchdown. We evaluated the results of traditional PCR with annealing temperatures of 56ºC and 57°C and touchdown PCR with annealing temperatures of 60 to 56ºC and 61 to 57°C. The results revealed that the best PCR products were obtained with the 61 to 57°C touchdown PCR. Of the 43 plants tested, this marker efficiently identified the type of reproduction (sexual or apomictic) in 95% of them, being, therefore, a promising tool for the precocious identification of apomictic Urochloa ssp. hybrids.