* Lula cancels G20 appearance; said to be shocked by floods
* Flood region is a vote stronghold ahead of Oct election
* Finance Minister Mantega to represent Brazil at G20 (Recasts, adds more flood details)
By Natuza Nery
TORONTO, June 25 (Reuters) - Brazilian President Luiz Inacio Lula da Silva will skip the Group of 20 leaders summit in Toronto this weekend to deal with the aftermath of severe flooding in northeastern Brazil that has killed 51 people.
The northeast region is a political stronghold for Lula's government ahead of presidential elections in October in which the popular Lula wants Brazilians to elect his former chief of staff, Dilma Rousseff.
"He doesn't want to be away from Brazil at this difficult moment," a source from Brazil's G20 delegation said on Friday. The government later confirmed that Lula would miss the summit.
The Brazilian source said that Lula, whose home state of Pernambuco is one of those affected by the disaster, had been shocked by the destruction he saw when flying over flooded areas on Thursday.
The G20 is meeting Saturday and Sunday to seek a consensus on how quickly to shrink government deficits, how best to strengthen banks so that they can withstand any new downturn, and how to harmonize financial regulatory reforms.
Brazil is one of the rising powers among the world's emerging economies that have helped lead a global recovery from recession. Brazilian Finance Minister Guido Mantega will instead represent Brazil at the summit.
The floods in the states of Alagoas and Pernambuco have killed at least 51 people and devastated many towns that were struck by torrents of water from burst river dams. The state of Alagoas initially said that about 600 people were missing, but had revised that figure down to 76 by Friday.
The G20 groups the world's biggest economies and covers two-thirds of the world's population. It includes Australia, Argentina, Brazil, Indonesia, Japan, Mexico, Russia, Korea, Saudi Arabia, South Africa, Turkey and China in addition to the big European economies, the United States and Canada. (Additional reporting by Eduardo Simoes in Sao Paulo; Writing by Jason Lange and Stuart Grudgings; Editing by Mario Di Simine)