Abstract: Early blight is one of the most destructive diseases for tomato crop; traditional breeding programs
are the main way to produce new cultivars for early blight resistance. In this study, five different genotypes
namely: NCEBR-6 as a resource of early blight resistance and five domestic genotypes i.e., LA 2399, Edkawi,
UCT5, Super strain-B and Peto-82 were used and the crosses were made to produce five populations and to be
evaluated for early blight disease under nature infection of early blight during three seasons under the field and
greenhouses conditions. Results indicated that, there were significant differences in the degree of resistance (P
> 0.05) between tomato genotypes and its crosses. NCEBR-6 cultivar was resistant for early blight and F1
hybrid (Super Strain B × NCEBR-6) recorded the highest degree of resistance compared with the other crosses.
The relative potency ratio of gene set for parent showed high partial dominance in the cross (Super strain-B ×
NCEBR-6) = 0.74. There was negative complete dominance for the cross (Edkawi × NCEBR-6) value = -1
trending to smaller parent. The correlation between resistance for yield, yield components and fruit quality was
established, there were highly positive relationship between resistances for fruit set %, fruit number and were
moderate with yield. as, r = 0.949, 0.749 and 0.609 respectively. This data revealed that the cultivars did not
super pass the resistant parent. Further, this study needs more information to investigate the inheritance and
genetic analysis to improve commercial cultivars to get the completely resistance.
Keywords: Tomato breeding, Early blight Resistance, Alternaria solani, Solanum lycopersicum, Inheritance.