Anil Dhirubhai Ambani Group firm Reliance Mutual Fund retained its position as the country's largest fund house with assets of over Rs 48,000 crore even as the collective asset under management (AUM) of all the fund houses soared past Rs 3.50 lakh crore.Reliance MF's assets under management swelled to Rs 48,828 crore in April gaining Rs 2,521 crore from Rs 46,307 crore last month, according to the latest figures released by Association of Mutual Funds in India (AMFI).The combined AUM of the 30 fund houses rose over Rs 24,017 crore during the month to a total of Rs 3,50,441 crore in April as against Rs 3,26,425 crore in March.ICICI Prudential MF posted a growth of over 11% in AUM to Rs 42,268 crore maintaining its second position among fund houses for the month.Public sector fund house UTI MF was at the third slot with an AUM of Rs 35,517 crore - a drop of about Rs 66 crore from last month.