Induction and identification of Stylosanthes guianensis tetraploids.

Stylosanthes guianensis is an elite and important forage legume species, which is extensively cultivated in tropical areas. Polyploid breeding via exposure to colchicine is a conventional and practical method to improve varieties of S. guianensis. Terminal buds of S. guianensis Reyan No.5 seedlings were treated with different concentrations of colchicine (0.00, 0.05, 0.10, 0.15, 0.20, and 0.25%) for 24, 48, and 72 h. Morphological and cytological variants were observed at a frequency of <96% among transplanted seedlings. The cytogenetic analysis of young leaf cells was conducted on all variants to identify their ploidy levels. The most efficient procedure for tetraploid production was the treatment of seedling apical buds with 20% colchicine for 48 h, with the tetraploid induction rate being 10%. This is a relatively simple and reliable method for the production of tetraploidy in S. guianensis.

Physical localization of molecular markers and assignment of the 15th linkage group to chromosome 11 of the karyotype in cassava (Manihot esculenta Crantz) by primed in situ labeling.

Physical localization of molecular markers and assignment of the 15th linkage group to chromosome 11 of the karyotype in cassava (Manihot esculenta Crantz) were achieved using primed in situ labeling. Amplified signals for both the EST507-1 and SSRY13-5 markers were consistently observed in different stages of cell division. A comparison of the length, arm ratio, and other morphological characteristics of somatic metaphase chromosomes in karyotype analysis indicated that the EST507-1 and SSRY13-5 markers were localized on the short and long arm of cassava chromosome 11 with the relative map positions of 41.67 and 23.07, respectively. The physical localization of the 2 markers on chromosome 11 of the karyotype corresponds to their positions on the 15th linkage group in cassava.