Screening and QTLs detection for drought factor index trait in rubber (Hevea brasiliensis Müll. Arg.)

Climate change has an impact. Droughts will become more common in the future and as a result is the drop of rubber production. Drought tolerant rubber genotypes, may reduce drought risk, could be discovered by selection of germplasm and crossing progenies. As perennial plant, conventional rubber selection of rubber needs long time. Molecular detection such as QTL (precise and fast detection) for screening to get drought tolerant rubber genotypes is very important to be conducted. A variable widely used to screen stress tolerance genotypes is Performance Index (PI). Measurement of PI in normal, moderate, and severe drought stress enables the calculation of the Drought Factor Index (DFI). DFI as an integrative parameter for drought tolerance trait provides simple and robust method to quantify the tolerance ability of plants to withstand drought condition. This research is the first application of DFI to select drought-tolerant rubber genotypes and to identify QTLs related to DFI. This research aimed to select candidate drought-tolerant genotypes from the biparental population PB 260 × SP 217 as well as to identify QTLs related to DFI variable. One hundred and thirty-two genotypes and four control commercial clones, namely PB 260, SP 217, GT1, and RRIM 600 have been successfully screened using DFI variable. Normal, moderate, and severe drought stresses were calibrated for each plant by monitoring the fraction of transpirable soil water (FTSW). Due to the skewed distribution of DFI data that was generated in the phenotyping step, the Kruskal-Wallis non-parametric test was used to test the significance of each QTLs using MapQTL version 6 software. From this research, it can be concluded that DFI can be used as a parameter for selection of drought tolerant rubber clones. Based on DFI calculation, the top ten high DFI genotypes/clones were genotype number 34, 206, 056, 007, 205, 225, 066, 235, 109, and clone RRIM 600. Furthermore, the most significant detection of QTL for DFI variables was found in locus g5TA2155, located at 0.553 cM in LG5. It indicated that this locus contained genes controlling DFI trait.