Line x Tester Analysis for Resistance to Cassava Anthracnose Disease

Thirteen cassava (Manihot esculenta) varieties which includes four IITA Improved used as lines and seven Landraces used as testers with various level of resistance to Colletotrichum gloeosporioides f. sp. manihotis, were crossed in a Line X tester design to determine the general (GCA) and specific (SCA) combining abilities relative to the inheritance. The Parents and the 36 F1 hybrids were evaluated in year 2003 and 2004 on an infected field. The variances due to SCA and GCA showed that both additive and non-additive, possibly epistatic gene actions are important. Majority of the crosses between the resistance sources and the susceptible lines showed intermediate reactions and various degrees of partial dominance for canker development in cassava plants. The most resistance IITA improved variety I63397, had the highest negative GCA effect for resistance among the lines. The moderately resistance TME-8 had largest significant negative GCA among the landraces. Most the crosses involving I63397 and TME-8 had significantly high negative SCA effects. The contribution of these parents to heterosis of their hybrids will be towards reduction of disease symptoms. This suggests the importance of both the additive and non-additive in the development of resistance to cassava anthracnose disease. Therefore recurrent selection with progeny evaluation is advocated for breeding for resistance to the disease.