Working group session:
Germplasm and Genetic Stocks
Presentation type:
poster
Authors:
Barroso, Paulo A. V.; Pereira, Guilherme da Silva ; Sousa, Romero Lima de ; Hoffmann, Lúcia Vieira ; Silva, Edson Ferreira da
Presenter:
Barroso, Paulo A. V.
Correspondent:
Barroso, Paulo A. V.
Abstract:
In Brazil, it is possible to perform in situ conservation of G. barbadense and G. mustelinum. G. barbadense plants are maintained for several domestic uses. The vast majority are isolated from cultivated upland cotton, although cotton fields are located at distances that permit gene flow in some restricted areas. G. mustelinum occurs only in the northeast region of the country, and there is no sympatry with upland cotton crops. Just few upland cotton plants derived from kernels used to feed cattle or spread via dispersal during transportation can be found near some G. mustelinum populations. Although gene flow could be a problem for in situ conservation in the places where sympatry is present, natural hybrids do not occur or occur in very low frequencies in situ in Brazil. We evaluated the presence of pollen competition as a pre-zygotic barrier in crosses between upland cotton (used exclusively as pollen donor) and G. barbadense and G. mustelinum. We found that a pollination of stigmas of G. barbadense using a mixture of 50% upland cotton and 50% G. barbadense resulted in 24.5% of hybrids on average. Similarly, stigmas of G. mustelinum pollinated with mixtures containing pollen from G. mustelinum and upland cotton in proportions of 25%:75%, 50%:50% and 75%:25% produced interspecific hybrids at frequencies of 61.4%, 23.8% and 3.6%, respectively. These low rates of hybrids demonstrate that pollen competition is present with G. mustelinum and G. barbadense and confirms this mechanism as a sexual barrier. Knowledge regarding pollen competition among cultivated and non cultivated cottons in Brasil are being used to design methods for in situ preservation of sympatric, permitting less restrictive conditions for maintaining the genetic identity of non-cultivated species.