Cytomorphological studies in induced tetraploid G. arboreum and its interspecific hybrid with tetraploid G. hirsutum L.

Polyploidy was induced in the diploid cotton species G. arooreum (2n = 26), and the tetraploid was crossed with G. hirsutum (2n = 52), giving rise to a new interspecific hybrid (2n = 52). The new hybrid produced 27.6% fertile pollen. The leaf shape, plant habit, petal spot, petal colourand pollen colour of F₁ plants were similar to those of G. arooreum, while bud and flowersize resembled G. hirsutum. The F₁ hybrid was tolerant to the sucking pest complex. The F₁ males with 2n = 52, crossed with male sterile G. hirsutum lines, gave some seed set. With the available materials it may be possible to undertake introgression of favourable genes of the diploid and tetraploid Gossypium species in one species after wide crossing.