Independent spanning trees with small depths in iterated line digraphs

We show that the independent spanning tree conjecture on digraphs is true i f we restrict ourselves to line digraphs. Also. we construct independent sp anning trees with small depths in iterated line digraphs. From the results, we can obtain independent spanning trees with small depths in de Bruijn an d Kautz digraphs that improve the previously known upper bounds on the dept hs. (C) 2001 Elsevier Science B.V. All rights reserved.