Avaliação de competição entre pólen nas espécies de algodoeiros Gossypium hirsutum L. e G. mustelinum (Miers) Watt

Abstract

The Brazilian Northeast is the center of origin of cotton Gossypium mustelinum (Miers) Watt. This cotton has not been improved or exploited commercially, but there is evidence of their introgression into the genome of varieties of upland cotton G. hirsutum L. variety marie galante Hutch. When considering the loss of variability can be said that G. mustelinum, G. barbadense L. and G. hirsutum L. var. marie galante Hutch of extinction are very high, high and medium, respectively, requiring immediate efforts for their preservation. This study aims to determine whether there is competition between pollen G. mustelinum and herbaceous in relation to fertilization of wild species, as well as whether there are differences of competition in different proportions of pollen of these species. For both crossings were performed between the two species used the G. mustelinum mother as having been fertilized by pollen from: i) mixture of 50% G. mustelinum and 50% herbaceous ii) a mixture of 75% herbaceous and 25% G. mustelinum iii) a mixture of 25% herbaceous and 75% G. mustelinum iv) herbaceous v) G. mustelinum. The latter two were used as controls to determine the expression pattern of alleles in polyacrylamide gels and validate the crosses with mixed pollen. We obtained seeds from each cross. The molecular analysis determined the proportion of seeds from crosses inter-and intra-specific by genotyping with SSR markers of the type. The frequency of offspring in each proportion of pollen used in crosses were compared using statistical test, chi-square (x²), with expected frequencies of 50% of hybrid seeds and 50% of seeds derived from selfing, 75% of seeds hybrid and 25% of the seeds of self-fertilization, 25% seed and 75% hybrid seed selfing. Were pollinated between 10:42 Flowers in the crosses with mixed pollen. The average number of seeds obtained ranged between nine and 11. Comparing these values with the average number of seeds from the intersection with 100% of pollen of the respective species, it was found that there was little variation. There were no differences in fertility or crossability between the genotypes of G. mustelinum. The only male parent in crosses that did not get the seeds was C27, and this was possibly caused by physiological conditions unfavorable. Through the data can be seen that the higher the percentage of pollen from G. hirsutum, the greater tendency of hybrids between two species. Therefore the higher the percentage of pollen from G. mustelinum, the lower the amount of hybrids. After analyzing the results, the chi-square (x²), a 1% probability it was established that there was competition between pollen from wild species and cultivated at all levels studied.