Estratégias de avanço no melhoramento genético de trigo: enriquecimento do germoplasma brasileiro com introgressões de Aegilops speltoides e o QTLoma da resistência à giberela

Abstract

Agriculture needs to double its production by 2050, to meet the food demand of a growing population. Breeding and wheat (Triticum aestivum L.) have fundamental role on this process. The advances in this cereal breeding, since its domestication, have been expressive, as well as the future perspectives, which deserve a dedicated bibliographic review, which is the theme of the initial part of this Thesis, entitled “Wheat breeding: a brief overview from the beginning to the near future, with emphasis on the present”. Wheat has a naturally restrict genetic diversity, somewhat aggravated by the breeding, which is a cause of stagnation of the breeding progress and genetic vulnerability. An alternative to this problem is the utilization of species from the secondary gene pool, in introgression programs. Among these species, Aegilops speltoides has shown great potencial to contribute with important traits to wheat. Thus, the Chapter I, “The enrichment of the Brazilian wheat germplasm with the introgression of genomic segments from Aegilops speltoides”, aimed to introgress chromatin from this species into a Brazilian wheat cultivar, as distinct introgression lines and to generate information for future use of this genetic diversity by breeding programs. Thus, a backcrossing program assisted by genotyping methods was conducted. A genetic map of Ae. speltoides was generated, containing 537 markers. A total of 236 segments were introgressed into the lines, from all chromosomes of the wild species and into all three wheat genomes. This genetic diversity and the information generated will allow the progress of this program, until the use of this lines by breeding. Fusarium head blight is one of the most devastating wheat diseases and the most efficient type of control is the genetic resistance. Although a high number of QTL related to this trait has been mapped on this crop, this information has to be refined to be more efficiently used by breeding and for the advance of the research. It can be achieved through a meta-analysis. “The QTLome of Fusarium Head Blight resistance in wheat as a reference map for the breeding” is the title of the Chapter II of this masterpiece. The objective of this work was to analyse globally and deeply the universe of loci related to the resistance of this cereal to this disease. An extensive bibliographic review was carried out, searching for information about these QTL in wheat. A total of 556 loci were found, distributed on all genomes and chromosomes of this crop. From these, 365 QTL could be projected into the consensus map generated and 327 went through meta-analysis, forming 72 meta-QTL, in 15 linkage groups. An expressive reduction of the redundancy was obtained in number and length of loci, facilitating the mining of candidate genes. This QTLome will serve as a reference map for breeding and the advance on the understanding of the mechanisms conferring resistance to this crop against this and other diseases. New strategies for wheat breeding advance are crucial to allow this crop meet its role today and in the future feeding the humankind.