When ppQQrr is crossed with PpQqRR then the ratio of hybrid for all the genes is:

ppQQrr x PpQqRRApplying product rule:pp x PpProbability of hybrid (Pp)= 1/2 QQ x QqProbability of hybrid (Qq)=1/2 rr x RRProbability of hybrid (Rr)= 1 Therefore, ratio of hybrid for all the three genes is= ½ (Pp) x ½ (Qq) x 1(Rr)                                                                        = ¼ PpQqRr