Genetic evaluation of several rubber tree clones to circular leaf fall disease

Abstract

Circular leaf fall disease (CLFD) remains a significant challenge for rubber plantations globally, with yield losses exceeding 20% observed over the past five years. One of the effective strategies to mitigate the impact of this disease is through the utilization of superior rubber tree clones. This study aimed to evaluate the resistance of selected rubber tree clones (Hevea brasiliensis) clones to CLFD using two species of Pestalotiopsis sp. The evaluation was conducted using the Detached Leaf Assay (DLA) method under controlled conditions. Disease severity was assessed based on lesion development, with the progression of symptoms observed at three, five, and seven days after inoculation (dai). The factors of isolate, rubber tree clone, and rubber tree clone x isolate interaction had a very significant effect on lesion diameter at 5 and 7 days after inoculation. The evaluation classified the rubber tree clones into three groups based on lesion diameter characteristics: resistant, moderate, and susceptible. Rubber tree clones IRR 112 and RRIC 100 exhibited resistance to circular LFD pathogens, with lesion diameter less than 10 mm. Conversely, rubber tree clones IRR 39 and PB 260 produced lesions mor than 20 mm and were classified as susceptible clones. The DLA method has the potential to be used to evaluate the response of rubber clones to circular LFD. These results can then be used as a reference for preliminary selection in future breeding programs strategies for the assembly of superior clones resistant to circular LFD.