Oryza rufipogon is one of wild rice species that may be used as a source of gene (s) in rice varietal improvement program. Backcross (BC5) and double haploid populations had been developed from a cross between IR64 and O. rufipogon in order to exploit the useful genes for blast disease resistance. These two populations were used to map blast resistant genes and to develop durably resistant varieties. This study has been conducted in collaboration with CIRAD with the following objectives: (1) to identify resistance genes to blast, Pir4(t), originated from O. rufipogon and Pir7(t) originated from IR64, on chromosome 2, and (2) to evaluate the durable resistance of double haploid lines generated from BC2F3 of IR64 x O. rufipogon to blast. Result of the previous study indicated that Pir (4&7) was mapped in the position between two Simple Sequence Repeat (SSR) markers RM263-RM250, with the distance of 28.5 cM (Utami et al, 2005). Fine map is to be established to detect the exact position of the target genes. For this purpose, two lines BC5 population, namely 317-25-1-6 and 317-25-1-3 were selected as lines with the needed level of introgression for fine mapping and target gene identification. In order to complement and to enhance candidate gene analysis at the target position the insilico analysis was applied at the target fragment region peak between RM263-RM250 markers, which resulted in consecutive order 25 putative resistance genes in this fragment region. These putative genes were further analyzed by sequencing the bases of the selected genes above to design specific primer on the basis of TIGR gene genome browser. These designed primers are Single Nucleotide Polymorphism (SNP) that has high polymorphism levels to be used to enhance fine mapping development activities.
Result of the interval mapping analysis (CIM) on BC5F2 population the highest LOD value obtained was 17.1, while on the BC2F3 population was only 3.59. GLM analysis result for the association test indicated significance between PiSNP4 primer, at 110.9 cM position and blast isolate ID31 having avr2 allele (CM28) of blast avr gene ACE1. Anotherprimer is PiSNP7, with LOD value 7.3 which is significant for ID9 blast isolate having the different ACE1 avr allele, avr1 (PH14). Result of progeny contrast test for the two target genes shown that IR64 resistant to ID9 (PH14) blast isolate but recessive to ID31 (CM28) isolate. Whereas O. rufipogon wasresistant to ID31 isolate but recessive to ID9 isolate. On the basis of introgression analysis on BC5F2 progenies it was indicated that NIL 317-25-1-6 that has the introgression of IR 64 at the Pir7 position resistant to ID9 isolate. While NIL 317-25-1-3 that has the introgression of O. rufipogon at the Pir4 position resistant to ID31 isolate. Resistance of these two lines derived from BC5 population similar to of their parents, IR64 and O. rufipogon. Until now the identification of Pir4 and Pir7 genes on the basis nucleotide sequence for detecting the presence of insertion or deletion is still underway.
Results of the evaluation of blast durable lines showed that BIO 46 which contained Pir4 was selected as a candidate blast durable line due to on this consistent resistant on many blast isolates and also many field condition (Jasinga, Sukabumi, Lampung and CIRAD). Nevertheless, the agronomical performance of this line still needed selection to fit as a new plant type released variety. Based on agronomical performance selected, among the 12 selected lines of DH population which contained the Pir4 and Pir7, BIO 61 showed the best performance on blast resistance in upland field rice condition in Yogyakarta. ( ICABIOGRAD:Dwinita WU, I. Hanarida, AD Ambarwati, S. Moeljopawiro, Santosa; CIRAD: D. Tharreau, J.B. Morel, J.L.Nottegheim )
Presentasi di katalog online : http://perpus.biotek.lipi.go.id/index.php?p=show_detail&id=15794&keywords=blast
Disusun oleh Ahmad S.S. (pustakawan)