Pyramiding of resistant genes into local rice varieties for Bacterial Leaf Blight (BLB), Gall Midge (GM) and Brown Planthopper (BPH) using Marker Assisted Selection (MAS)
Brown Planthopper (BPH) and Gall Midge (GM) are two important pests and Bacterial Leaf Blight (BLB) is one of the major diseases of rice in Sri Lanka. Development of resistant varieties is the most suitable solution to overcome these problems. However, some of the resistant rice varieties released in the recent past has become susceptible to targeted pests and diseases. Immergence of virulent populations indicates a development of new biotype(s)/pathotypes. Therefore, pyramiding resistant genes of BPH, GM and BLB will reduce out-breaks and facilitate durable resistance.
|Bacterial Leaf Blight||Gall Midge||Brown Planthopper|
To address these issues, Department of Agriculture is involved in Sri Lanka – United States Department of Agriculture (SL-USDA) project “Pyramiding of Genes for Resistance to Brown Planthopper (BPH), Bacterial Leaf Blight (BLB) and Gall Midge (GM) into new improved Rice Varieties” to develop varieties with durable resistance to BPH, GM and BLB by pyramiding major genes from different sources. The advanced breeding lines having field resistance to BPH, GM and BLB resistance were subjected to genetic analysis using molecular techniques to assist the breeding programs with Marker Aided Selection (MAS). Simultaneously, identification of new biotypes / pathotypes is also being done as a part of the project activity.
- Bg379-2 is a rice variety released by the Department of Agriculture in 1980 for commercial cultivation was resistant to BPH. However, recent BPH outbreaks in some districts showed brakes down of the resistance in Bg379-2. It was found that Bg 379-2 is moderately resistant to avirulent BPH population collected from RRDI Batalagoda and totally susceptible to virulent BPH population collected from Kegalle. (Fernando et .al, 2007)
- Generations of crosses were advanced to F7 at RRDI Bathalagoda.
- Molecular markers such as KAM4 (Bph2) and RG 457 (Bph 13) putative RAPD marker and 2 SSR markers RM 335, RM 261 were tested and KAM4 and OPA16938 showed promising results.
- This research also reveals that the need for investigation of resistant genes in Sri Lankan germplasm and need for resistant genes to Sri Lankan biotypes
- It has been reported that there were two biotypes, biotype 1 and biotype 2 in Sri Lanka. Molecular studies revealed that there is only one biotype, a new one (Biotype3?) (Fernando et al, 2005) which is genetically similar to biotype 5 reported to be present in India. However, this Emergence of a new biotype as well as absence of existed biotypes should be confirmed using host differentials
- In PCR reactions, it was found that, 10µl reaction volume of PCR mixture gave good amplification reducing the cost per reaction. Further, it was found that 1.4% Agarose gel is good enough to separate fragments with 13 bp differences.
- Specific molecular markers developed in other countries using their own parental varieties are not always reliable to screen other varieties with different origin / parents.
Eg. The GM primer F10 cannot be used to identify the presence of resistant gene GM2 in tested rice samples. (Dissanayake et. al., 2005)
- Five rice varieties Bg300, Bg352, Bg357, Bg358, Bg360 were screened at three different locations Ambalantota, Bathalagoda and Gannoruwa for BLB resistance. All these varieties were susceptible to the most virulent isolate selected from 70 isolates collected from different locations in Sri Lanka. All these isolates were resistant to rice variety IRBB60 (Fernando et. al., 2005 (iii)).
- Bg352, Bg357, Bg358, Bg360 were susceptible and Bg300 was moderately susceptible (according to the scale: >4.5cm susceptible and 3-4cm moderately susceptible) to the bacterial isolate obtained from fields of Gannoruwa. Therefore all rice varieties were selected for gene pyramiding of the BLB disease resistance. IRBB60 was selected as the donor parent for resistance to confer genes [Fernando et.al. 2005 (iii)].
- Field screening and molecular screening of F5 generation was carried out and identified Xa-21 resistant gene for BLB in the cross IRBB60 X Bg358.
- There is high variation of the Bacterial Leaf Blight causal organism at DNA level. The OPD7 primer was promising in revealing genomic information that had a relationship with geographical location of the BLB pathogen. Pathogen reactions on differentials were highly variable. Four resistant genes in one host plant conferred a broad spectrum of resistance to BLB in rice [Fernando et.al. 2005 (ii)].
Dr. K.K.S. Fernando (Principal Investigator- Biotechnology)
Dr. R.M.T. Rajapakse (Co-Investigator-Breeding & Pathology)
Dr.W.L.G. Samarasinghe (Research Officer, Biotechnology)
Mr.A.H. Gunadasa (Research Officer, Plant Breeding)
Mr.A.M.T.Abayaywickrama (Research Officer)
Ms. D.M.K.K. Dissanayake (Programme Assistant)
Mr. J.H.B.H. Bandara (Graduate Research Assistant)
Mr. E.M. D. S. B. Ekanayake (Graduate Research Assistant)
Ms. S.I. Samararatne (Graduate Research Assistant)
Ms. S.K.Hewakapuge (Graduate Research Assistant)
Ms. G.K. Wanigasekara (Technical Assistant)
Mr. Herath (Technical Assistant)
- D.M.K.K. Dissanayake, K.K.S. Fernando and J.M.R.S. Bandara. 2005. Molecular Screening of Selected Rice Varieties with Specific Markers for Gm2 and Gm4 (t) Gall Midge Resistant Genes, Tropical Agricultural Research Vol. 17: 48 - 57.
- K.K.S. Fernando, J.H.B.H. Bandara, R.M.T. Rajapakse, V.A. Sumanasinghe. 2005. Detection of Genetic variability and Pathagenicity of Xanthomonas oryzae p.v. Oryzae: Causal organism of Bacterial leaf Blight in rice. Annals of the Sri Lanka Department of Agriculture .7:95-102
- K.K.S.Fernando, J.H.B.H. Bandara and R.M.T. Rajapakse. 2005.Selection of rice varieties for gene pyramiding for Bacterial leaf Blight disease resistance. Proceeding of the 25th Annual Session, Institute of Biology, Sri Lanka.pp28
- K.K.S. Fernando and D.M.K.K. Dissanayake.2005. Molecular analysis of Asian rice Gall Midge, Orseolia oryzae (Wood-Mason), biotypes in Sri Lanka. Proceeding of the 25th Annual Session, Institute of Biology, Sri Lanka. pp 32.