Caution drives Brazil M&A deals to worst start since 2005

* Bankers see 79 pct drop in value of deals as temporary * Conclusion of key deals put off on price disagreements * Six local banks join top-ten M&A ranks for first time By Guillermo Parra-Bernal and Aluísio Alves SAO PAULO, April 2 (Reuters) - Mergers and acquisitions activity in Brazil this year got off to its worst start since 2005 as buyers, fretting over growing state intervention and a weak economy, held off on some sizeable deals to get better terms. Companies announc