161-49 Couderc is a V. berlandieri x V. riparia hybrid used as a rootstock. It was obtained in 1888 by Georges Couderc. It is very resistant to limestone. It prefers well drained but not arid soils. Hence in Bordeaux 161-49 Couderc is perhaps the most undervalued rootstock. It promotes accumulation of colour and sugars in both Merlot and Cabernet Franc on the humid clay of the right bank, and is steady enough to promote the longevity of the vine scion. It is equally at home on limestone. Dr Richard Smart (2015, p.628) says 161-49 has high resistance to phylloxera but is susceptible to nematodes. Scions grafted to 161/49 show slower initial development compared to 420A (another V. berlandieri x V. riparia hybrid).
Dr Richard Smart in the Oxford Companion to Wine 4th edition ed. Jancis Robinson MW and Julia Harding MW (Oxford University Press, 2015, p.628.