Heritability and Genetic Control of Resistance Against Black POD Disease because of P.Palmivora Infection in Cacao

Abstract

In previous experiment, cacao clones that are resistance against P. palmivora have been identified. One of the known resistance cacao clone are the ICCRI 1 and ICCRI 3. The ICCRI 1 and ICCRI 3 clones were individually selected based on their high yielding and resistance against P. palmivora from a population of F1 hybrid derived from hybridization of high yielding DR 1 and P. palmivora resistance SCa 6. Five clones have been used to generate F1 arrays in a semi-dialel crosses by control pollination. The general objectives of these experiment were to analyse genetic control and heritability of P. palmivora resistance characters in cacao. The specific objectives were: to evaluate the individual response of the F1 arrays against P. palmivora and to determine genetic control and heritability of P. palmivora resistance in cacao. Seeds derived from the control crosses were germinated in the glasshouse, the seedlings were maintained in the glasshouse, and inoculated with P. palmivora when they were 1.5 months after germination. The P. palmivora inoculation was conducted using either agar plug containing mycelia or using spore of P. palmivora. The occurrences of symptoms of P. palmivora infection were recorded at 7 – 21 days after inoculation. The broad and narrow sense heritabilities of black pod resistance character were medium—high. GCA of TSH858, Sca6, and ICCRI3 were high. Crosses among ICCRI3xSca6, DR1xICS13, TSH858xICS13 and TSH858xDR1 exhibited the best SCA for black pod resistance. Black pod resistance in cacao was most probably controlled by at least two genes and one of them was recessive.