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White root rot (WRR) disease which is caused by Rigidoporus microporus is a major agricultural disease. The disease affects tropical fruits, forest trees, ornamental trees as well as rubber (Hevea brasiliensis) trees. Although WRR causes significant economic losses to planters, there is no effective method to control this disease. The understanding on the population genetics of R. microporus isolates could mitigate WRR disease in plant management. Therefore, the objective of this work was to elucidate molecular phylogeny of R. microporus isolated from rubber trees. Twenty seven R. microporus isolates were characterised using internal transcribed spacer (ITS), Beta-tubulin (β-tubulin) and translation elongation factor-α (tef1-α) sequences data. Phylogenetic tree analyses of R. microporus isolates were divided into two major groups; the Asian and African groups. However, there was no distinct geographical structuring in the Asian group, suggesting gene flow happened among the populations. Somatic Incompatibility (SI) test and Inter Simple Sequence Repeat (ISSR) marker revealed that the R. microporus in the rubber plantations partially clustered based on geographical regions. The genetic diversity of R. microporus by ISSR revealed four major groups. The findings of the present study provide a baseline data for breeders and plant pathologists to enable them strategise effective and sustainable WRR disease management.

One of the most critical aspects of marker-assisted backcross breeding is recurrent parent genome recovery (RPGR). RPGR ensures that only the genes of interest are retained without further segregation in the recombined progenies while the unwanted genomic segments are completely deleted. This experiment aimed to introgress multiple bacterial leaf blight (BLB) resistance genes against using marker-assisted backcross breeding. Four Xoo resistance genes viz: Xa21, xa13, xa5, and Xa4 from IRBB60 were introgressed into the genetic background of MR297 Malaysian, which is considered a high yield. Polymorphic functional linked markers to target genes and SSR markers were used for both foreground and background selection. The percentage of RPGR in the selected lines, a background selection was adopted using 83 approved polymorphic microsatellites markers. The study results reveal RPGR of 81.94%, 92.30%, and 95.32% at BC1F1, BC2F1, and BC2F2, respectively. Marker-assisted backcross breeding often shows a faster introgression resistance gene than traditional breeding. The introgression of four BLB resistance genes Xa21, xa13, xa5, and Xa4 in the nine newly developed lines would provide durable and broad-spectrum resistance against the bacterial leaf blight. The newly created lines were suggested for commercial production as new rice varieties.