The inheritance of resistance to bacterial spot (Xanthomonas campestris pv. vesicatoria, race T2) in tomato (Lycopersicon esculentum) was investigated in a field trial. The genotypes 'Ohio 8245' and 'Hawaii 7998' (resistant), 'CNPH 401-08' and 'CNPH 416.81.01.02' (susceptible) were crossed in a diallel scheme without reciprocals. Each cross was labeled as one family, represented by six different generations: Parent1, Parent2, F1, F2 and Backcrosses to parents (BC1 and BC2). The family 'Ohio 8245 <FONT FACE=Symbol>'</FONT> Hawaii 7998' presented the lowest disease severity, followed by the family 'Hawaii 7998 <FONT FACE=Symbol>'</FONT> CNPH 416.81.01.02' and by the family 'Ohio 8245 <FONT FACE=Symbol>'</FONT> CNPH 416.81.01.02'. These last two families showed both higher broad and narrow sense inheritability estimates and the highest prediction of selection gain. The resistance was found to be quantitative, with four to eight genes involved, depending on the family. Transgressive segregation was observed in the 'Ohio 8245 <FONT FACE=Symbol>'</FONT> CNPH 401-08', the 'Hawaii 7998 <FONT FACE=Symbol>'</FONT> CNPH 401-08' and the 'Hawaii 7998 <FONT FACE=Symbol>'</FONT> CNPH 416.81.01.02' families. The relevance of the additive effects was observed and for all the families the data fitted to additive-dominant model, with the additive component showing greater magnitude.
horizontal resistance; inheritance; Lycopersicon esculentum; Xanthomonas campestris pv. vesicatoria
