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Abstract
In coffee (Coffea arabica L.), male sterility is a prerequisite for the exploitation of heterosis since it provides an efficient and reliable method for the production of hybrid seeds. Given its relevance, the objective of this study was to identify male-sterile genotypes within the Colombian Coffee Collection that can be used in genetic improvement. For this purpose, Ethiopian germplasm and progenies derived from hybrids between C. arabica x C. canephora were explored between 2017 and 2021. In the first stage, genotypes without visual presence of pollen were preselected in the field, followed by selection through staining and verification of male sterility and female fertility through directed crosses (directed, reciprocal and selfing). In this stage, 9,753 trees were explored, preselecting 2.4% due to visual absence of pollen. The staining of structures allowed us to confirm the lack or sporadic production of pollen in 23 individuals of Ethiopian origin. The results of the directed crosses led to the identification of 11 male-sterile and 12 partially male-sterile genotypes belonging to 15 accessions. In all cases, the individuals were characterized by the presence of anthers but with an absence or low content of pollen, which is why the male sterility is possibly of the sporogenic type. The female receptivity values were between 2.9% and 72.6%, being higher than 30% in five genotypes. These genotypes are a valuable tool for the genetic improvement of C. arabica with the potential to facilitate the use of heterosis and to allow a deeper understanding the development of male gametophytes in the species.
Highlights
Coffee (Coffea arabica) is one of the most important raw materials worldwide, with an estimated annual market value of $200–250 billion, and is the main source of income for more than 60 million people [1]
In the Colombian Coffee Collection (CCC), approximately 10,000 trees were explored in search of this male sterility, 68.5% corresponding to 482 accessions from the center of origin and diversity of C. arabica–Ethiopia, while the remaining trees were derived from 79 progeny from the hybridization between C. arabica x C. canephora
The detailed microscope observation of the anthers of the genotypes selected in the field stage evidenced the reduced or no presence of pollen grains in 24 of them, 23 of which came from 15 Ethiopian accessions of the CCC and one from interspecific hybrids
Summary
Coffee (Coffea arabica) is one of the most important raw materials worldwide, with an estimated annual market value of $200–250 billion, and is the main source of income for more than 60 million people [1]. Obtaining significant increases in agronomic traits of interest, especially yield, is one of the main objectives of genetic improvement programs, including for C. arabica given its economic importance. For this purpose, the use of the heterosis phenomenon is the main strategy employed in various species [2, 3]. The application of this strategy is conditioned by the finding of technical solutions at a moderate cost that allow it to be used commercially [4, 5].
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