Corynespora leaf fall (CLF) disease caused by Corynespora cassiicola (Berk & Curt.) Wei. has emerged as major leaf disease of Hevea rubber infecting cultivated clones and causes economic losses. Sixty two cultivated Hevea clones were...
moreCorynespora leaf fall (CLF) disease caused by Corynespora cassiicola (Berk & Curt.) Wei. has emerged as major leaf disease of Hevea rubber infecting cultivated clones and causes economic losses. Sixty two cultivated Hevea clones were tested for CLF disease resistance under natural infection in the field and in the nursery. It was found that 10 clones in the main field and 4 clones in nursery showed no infection during initial screening, but subsequently they also showed differential reaction. Based on the average disease intensity across years, popular high yielding clone RRII 105 was found highly susceptible and commercially cultivated clones, RRIM 600 and GT l were classified under resistant group (PDI <5), while popular clones like RRII 208, PB 252, PB 5/51 and PB 213 were grouped as tolerant clones (PDI 5-l 0). Analyses of variance revealed significant variations among clones, year and clone x year's interaction components. Though average performance of clones vacillated across years, their susceptibility rankings remained relatively constant. Cluster analyses reveled natural grouping of five distinct clusters. The most susceptible clones, including RRII 105 remained very susceptible throughout the study period. None of the clones tested showed true genetic resistance bordering immunity. About 63% of clones in nursery and 68% in field tests were classed in the first cluster which showed some tolerance or lesser susceptibility to the disease (PDI 5-25). Clones in the remaining clusters were susceptible (PDI >25). As availability of suitable sources of resistance is a basic tool for the breeder, information generated is useful in successful resistance breeding programmes for CLF disease.
