Growth Characters, Physiology and Leaf Fall Disease Resistance in Immature Plants of Rubber (Hevea brasiliensis) IRR 400 Series Clones

Superior rubber clones have been used in Indonesia, but productivity achievements are low. The area and rubber production in 2020 was 3,316,047 ha with a productivity of 1,022 kg/ha. The low productivity is caused use of seedling materials. Adaptation testing is one of the stages for selecting superior rubber clones in various environmental conditions, the influencing factors are clone or environmental. The suitability of clones to grow in certain environments with special characteristics can be seen due to changes in growth and differences in physiological characteristics that support growth. This research is one of the test areas for adaptation to growing environmental conditions, the topography is flat, with an altitude of 34 m above sea level, rainfall is 2195 mm/year and rainy is 156 days/year. The aim of the research is to determine the growth characteristics, anatomy, physiology of plants and resistance to leaf fall diseases (Colletotrichum, Oidium, Corynespora and Pestalotiopsis) of immature plant IRR 400 series. This research was carried out at PT Socfindo Tanah Besih, physiology laboratory and protection laboratory of the unit research Sungei Putih. The IRR 400 series clones, namely IRR 425, IRR 428, IRR 434, IRR 440 and two comparison clones (PB 217 and PB 330), were planted in 2019 with a spacing of 7.5´2.5 m. The research was structured using a randomized block design (RAK) with three replications, wherein in each replication a number of 20 trees were planted. The research results showed that the IRR 434 clone had vigor growth with a girth of 40.99 cm and a girth increment of 9.06 cm/year. Resistance to leaffall disease of Corynespora, Colletotrichum, Oidium and Pestalotiopsis clone IRR 400 is moderate. The physiology analysis showed different values among clones, the highest total sugar and SOD (IRR 428), the highest proline and H₂O₂ (IRR 434), the highest chlorophyll and SOD (IRR 425), the highest APX (IRR 440).