THE RESISTANCE OF IRR AND RRII SERIES RUBBER CLONES TO LEAF FALL DISEASES IN INDONESIA AND ITS CORRELATION WITH STOMATA NUMBER AND CUTICLE THICKNESS
Resistance rubber clones to leaf fall diseases varies among clones. There are three major kinds of leaf fall diseases that attack rubber namely Colletotrichum, Corynespora and Oidium. Resistance level of each clone to leaf fall diseases is one of the important characters considered in the selection of superior clones. Superior clones in Indonesia are IRR 5, IRR 104, IRR 112, IRR 118, and IRR 220. While, RRII clones from India are RRII 414, RRII 417, RRII 422, RRII 429, and RRII 430. This research was conducted in hybridization garden and green house. Samples were observed from three plants on the middle leaves of one to five whorls on 7th, 14th and 21st days after the appearance of symptoms of Colletotrichum, Corynespora and Oidium. Number of stomata and cuticle thickness were observed in the crop protection laboratory. The results showed that clones, diseases and their interaction were significant after 21st days. Levels of resistance for IRR series and RRII series are moderate, moderately resistant and resistant. Resistance to all the leaf fall diseases were influenced by genetic factor. For IRR series clones the factors were h2: 0.55 and GPE: 56.79%. while for RRII 400 series they wereÂ h2: 0.68 and GPE: 25,42%. Stomata number is the character that supports resistanceÂ of each clone (h2: 0.89 and GPE: 18.04%).
Keywords: IRR series, RRII series,Â resistance, Colletotrichum, Corynespora, and Oidium