RAPD and cytomorphological analyses of F₁, F₂ and amphidiploid (A₁) generations of Gossypium arboreum x Gossypium capitis-viridis

The wild diploid species Gossypium capitis-viridis Mauer (2n=2x=26 B ₄B₄) of Cape Verde Islands possess good fibre quality in addition to resistance to pest and diseases. Its narrow bracts ensure clean picking in cultivated cotton. An attempt was made to cross Gossypium arboreum var. MPKV GMS with Gossypium capitis viridis and doubled its chromosomes. The Chromosomes constitution of parents, F₁, F₂ and amphidiploid was confirmed. The hybridity of cross was confirmed on the basis of cytomorphological studies, pollen test and RAPD analysis. Cytological studies revealed that interspecific hybrid showed anomalous behavior of univalent and the formation of a single and double chromatin bridges at metaphase II that led to abnormal microspore formation in F₁ and reduction in fertility. On an average chromosome association at metaphase were 0.976^I+10. 138^II+0.06^III+1.142^IV and 0.84 ^I+10.549^II+0.053^III+0.976^IV in F₁ and F₂ of G. arboreum x G. capitis-viridis, respectively. However, in amphidiploid generation mean chromosome conjugation formed were 0.832^I+21.253^II+0.05^III+2.128 ^IV. Random Amplified Polymorphic DNA (RAPD) analysis was employed to characterize the F₁ interspecific hybrid of G. arboreum GMS x G. capitis-viridis, the doubled offspring and six segregants (designated 1-6). The 19 primers, selected from 43 initially screened, generated 250 amplification products of which 232 (92.8%) amplicons were polymorphic. Statistical analysis was carried out using NTSYS-pc software and a dendogram was generated using Jaccard's similarity coefficients. The values for similarity ranged from 0.31 to 0.66. Cluster analysis showed 3 main clusters. Cluster 1 consists of G. arboreum GMS, segregant 1, 2 and 4; cluster II comprises of G. arboreum GMS x G. capitis-viridis F₁ and doubled offspring, segregant 5 and segregant 6 and cluster III consists of segregant 3 and G capitis-viridis.