The effects of environment and genotype on expression of resistance to bronze wilt was studied using ‘Suregrow 125', ‘Tamcot Sphinx', and ‘Deltapine 50' as resistant cultivars and ‘Stoneville 373', ‘Paymaster 1220 B/R' and ‘Pima S-7' as susceptible cultivars. Differences in the resistance of cultivars were affected by temperature, photoperiod, relative nitrogen content of fertilizer and fertilizer rate. The following standard screening procedure was adapted from the environmental studies: 1) Seeds are germinated in sterile germination towels wet with a bacterial suspension at 30ºC for 40-44 h; 2) Seedlings are transplanted to 500 g of a mixture of 25% Brazos clay soil (pH 8.2), 75% Brazos fine sand (pH 8.0), 5 g gypsum, and 10 g dolomitic limestone; 3) Incubation is continued at 30ºC for a total of 1 wk from seeding and the temperature is then raised to a continuous 37ºC with a 15-h photoperiod; 4) Each plant is fertilized weekly with 150 mg of Peter's 15-16-17 soluble fertilizer dissolved in 50 ml of water; and 5) After 8 wk plant parts are weighed and assessed for damage, and bacterial content of roots is determined. ‘Stoneville 373' and ‘Paymaster 1220 B/R' commercial seed, were mostly susceptible to bronze wilt also included resistant individuals. Plants that gave rise to uniformly susceptible or resistant progeny when self-pollenated were used for genetic studies. Resistance to bronze wilt caused by Agrobacterium tumefaciens strain 34B was completely dominant or overdominant to susceptibility in all hybrids. Thus, severe bronze wilt occurs only when a homozygous recessive condition is present. Cultivars carrying different bacterial blight resistance genes (B genes) also were evaluated for resistance to strain 34B. Cultivars with the B₄, B_N, B_In, and B₂,B₃ genes showed higher levels of resistance than similar cultivars that lacked these genes. The ‘DPP4' and ‘S-295' cultivars which have undefined B genes also showed higher levels of resistance to bronze wilt. Cultivars with the B₂ or B₇ gene were more susceptible to bronze wilt than the corresponding cultivar lacking these genes and behaved similar to ‘Hartz 1215.' Both cultivars that carried the B₂ gene, alone or combined with B₃, showed more blighting and defoliation of lower leaves and recovered more slowly than the 96 other cultivars when returned to temperatures below 33ºC. The possible importance of B genes in bronze wilt susceptibility is discussed. Reactions of 96 modern cultivars and lines to bronze wilt caused by A. tumefaciens strain 34B in a greenhouse screen are reported.