NOVELTY - Heterocyclic compound (I) or its tautomer, N-oxide, or salt is new.    USE - For controlling plant diseases caused by Oomycete fungal plant pathogens (claimed) e.g. Phytophthora infestans, Phytophthora megasperma, Phytophthora parasitica, Phytophthora cinnamomi and Phytophthora capsici; and protecting plant and seed.    ADVANTAGE - The compound is more effective, less costly, less toxic, environmentally safer and have different sites of action.    DETAILED DESCRIPTION - Heterocyclic compound of formula (I) or its tautomer, N-oxide, or salt is new.    A=e.g. -O-, -S-, -N(R7)-, -C(R8)2-;    W'=O or S;    G=5-membered heterocyclic ring (optionally substituted);    Z'=direct bond, O, C(=O), S(=O)m, CH(R12) or N(R13);    J=e.g. 5- to 7-membered ring (optionally substituted);    W2=O or S;    T'a=H or 1-3C alkyl;    T'b=CR14R15R16;    X=X1-X9, where t is connected to the carbon atom with q of compound (I), the bond which is identified with u is connected to the carbon atom with r of compound (I), and the bond which is identified with v is connected to G of compound (I);    R1=e.g. H, halogen, cyano, amino, -CHO;    R2=e.g. H, halogen, cyano;or    R1+R2+C=e.g. 3- to 7-membered ring (optionally substituted);    R3=e.g. phenyl, naphthalenyl (optionally substituted);    R4=H, 1-3C alkyl or 1-3C haloalkyl;or    R3+R4+C=3- to 6-membered saturated carbocyclic ring;    R5=halogen, cyano, hydroxy, 1-4C alkyl, 1-4C alkenyl, 1-4C haloalkyl or 1-4C alkoxy;    R6=e.g. H, halogen, cyano, hydroxy;    Z2=direct bond, O, C(=O), S(=O)m, CH(R12) or N(R13);    Q=e.g. phenyl, benzyl (all optionally substituted);    R6a=e.g. halogen, hydroxy, amino;    R6+R6a=5- to 7-membered ring containing ring members selected from carbon atoms and optionally up to 3 heteroatoms selected from up to 1 O, up to 1 S and up to 1 N atom (all optionally mono- to tri-substituted by halogen, cyano, nitro, 1-2C alkyl and 1-2C alkoxy on carbon atom ring members and cyano, 1-2C alkyl and 1-2C alkoxy on nitrogen atom ring members);    R6b=e.g. phenyl (optionally substituted);    R7=e.g. H, cyano, 1-4C alkyl;or    R2+R7=5- to 7-membered partially unsaturated ring containing ring members, in addition to the linking atoms, selected from carbon atoms and up to 3 heteroatoms selected from up to 1 O, up to 1 S and up to 1 N atom (optionally mono to tri substituted by halogen, cyano, nitro, 1-2C alkyl, 1-2C haloalkyl, 1-2C alkoxy or 1-2C haloalkoxy on carbon atom ring members and cyano, 1-2C alkyl and 1-2C alkoxy on nitrogen atom ring members);    R8=H, 1-3C alkyl or 1-3C haloalkyl;    R9 and R10=e.g. 1-5C alkyl, 2-5C alkenyl, 2-5C alkynyl;    R11=e.g. H, cyano, 1-6C alkyl;    R12=H, 1-4C alkyl or 1-4C haloalkyl;    R13=e.g. H, 1-4C alkyl, 1-4C haloalkyl;    R14=H or 1-4C alkyl;    R15=e.g. phenyl, benzyl (optionally substituted);    R16=H, cyano, nitro, 1-6C alkyl, 2-6C alkenyl or 2-6C alkynyl;    R17=e.g. H, 1-6C alkyl;    R18=e.g. 1-6C alkyl, 1-6C haloalkyl;    R19=e.g. halogen, cyano;    R16+R19=3- to 7-membered ring containing ring members selected from carbon atoms and up to 4 heteroatoms selected from up to 2 O, up to 2 S, up to 2 N and up to 2 Si atoms, where up to 2 carbon atom ring members are selected from C(=O) and C(=S), the sulfur atom ring members are selected from S(=O)s(=NR11)f, and the silicon atom ring members are selected from SiR9R10 (optionally mono- to tetra-substituted by halogen, cyano, hydroxy, 1-2C alkyl or 1-2C alkoxy on carbon atom ring members and cyano, 1-2C alkyl and 1-2C alkoxy on nitrogen atom ring members);    Z3=O, C(=O), S(=O)m or CH(R12);    m=0-2;    n=0-2;and    s and f=0-2.    Full definitions are given in the DEFINITIONS (Full definitions) section. An INDEPENDENT CLAIM is included for fungicidal composition comprising compound (I), and at least one other fungicide; or compound (I) and at least one additional component selected from surfactants, solid diluents and liquid diluents.