Abstract
The high degree of variability of the fungus Colletotrichum sublineolum, causal agent of sorghum anthracnose, has hindered the development of resistant hybrids. The objective of this research was to compare the aggressiveness of different fungal isolates and evaluate the genetic resistance (vertical and horizontal resistance) of various sorghum lines and hybrids. Twelve isolates, collected from different regions, were inoculated on 87 lines and 63 hybrids in the field and disease severity was evaluated. The diallel crossing method provided information about the vertical and horizontal resistance of the host, as well as the aggressiveness/ virulence of the pathogen. This genetical method was very promising for the identification of horizontal resistance in the sorghum- Colletotrichum sublineolum pathosystem, and for the prediction of anthracnose resistance in hybrids in the absence of vertical resistance. Dilatory resistance was detected in 14.94% of the inbred lines, and in 19.04% of the hybrids. Significant differences in aggressiveness and virulence of the isolates were also observed.
Highlights
Sorghum (Sorghum bicolor (L.) Moench) is one of the most important cereals planted in the world, and Brazil is among the ten top producers worldwide (Rodrigues 2008, CONAB 2009)
There are several sources of resistance that are intensely used in sorghum breeding programs to obtain anthracnose-resistant cultivars
A better ability to predict the relationship between pathogen population variability in aggressiveness and virulence and genetic resistance of available hybrids is essential to increase thestability and durability of anthracnose resistance in the field
Summary
Sorghum (Sorghum bicolor (L.) Moench) is one of the most important cereals planted in the world, and Brazil is among the ten top producers worldwide (Rodrigues 2008, CONAB 2009). A better ability to predict the relationship between pathogen population variability in aggressiveness and virulence and genetic resistance (vertical and horizontal) of available hybrids is essential to increase thestability and durability of anthracnose resistance in the field. The objective of this work was to evaluate the performance of the model developed by Melo and Santos (1999) for predicting the resistance (vertical and horizontal) of sorghum hybrids to anthracnose in in the experiment.
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