Molecular analysis of the genetics of resistance to Rice hoja
              blanca virus and its vector Tagosodes orizicol...
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Poster78: Molecular analysis of the genetics of resistance to rice hoja blanca virus and its vector Tagosodes orizicolus

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Poster78: Molecular analysis of the genetics of resistance to rice hoja blanca virus and its vector Tagosodes orizicolus

  1. 1. Molecular analysis of the genetics of resistance to Rice hoja blanca virus and its vector Tagosodes orizicolus. Lee Calvert, Iván lozano, Natalia Villarreal, Luz E. Romero, Mónica Triana, Mathias Lorieux, Andrea Garavito y Cesar Martínez Abstract: The variety Fedearroz 2000, which is highly resistant to rice hoja blanca virus (RHBV) and intermediate resistant to its planthopper vector Tagosodes orizicolus Abstract: The variety Fedearroz 2000, which is highly resistant to rice hoja blanca virus (RHBV) and intermediate resistant to its planthopper vector Tagosodes orizicolus, , was crossed the highly susceptible line WC366, and 235 F2 lines were generated. For the analysis of resistance to RHBV, 60 F3 plants of each of the 235 lines were was crossed the highly susceptible line WC366, and 235 F2 lines were generated. For the analysis of resistance to RHBV, 60 F3 plants of each of the 235 lines were infested with RHBV viruliferous T. orizicolus The 30 most resistant and susceptible lines were analyzed using 53 polymorphic microsatellites. The microsatellite RM261 on infested with RHBV viruliferous T. orizicolus. .The 30 most resistant and susceptible lines were analyzed using 53 polymorphic microsatellites. The microsatellite RM261 on the short arm of chromosome was correlated with resistance to RHBV. Three additional microsatellites markers on the short arm of chromosome were tested and all theshort arm of chromosome 44was correlated with resistance to RHBV. Three additional microsatellites markers on the short arm of chromosome 44were tested and all were correlated with RHBV resistance. In this region of chromosome 4, potential candidate gene with CBS domain was found. This gene has homology with putative werecorrelated with RHBV resistance. In this region of chromosome 4, aapotential candidate gene with aaCBS domain was found. This gene has homology with aaputative brown planthopper induced resistance gene on chromosome 2. The variety Fedearroz 50, which is intermediate resistant to rice hoja blanca virus (RHBV) and highly brown planthopper induced resistance gene on chromosome 2. The variety Fedearroz 50, which is intermediate resistant to rice hoja blanca virus (RHBV) and highly resistant to T. orizicolus was crossed the highly susceptible line WC366, and 291 F2 lines were generated. The 30 most resistant and susceptible lines were analyzed resistant to T. orizicolus, ,was crossed the highly susceptible line WC366, and 291 F2 lines were generated. The 30 most resistant and susceptible lines were analyzed using 65 polymorphic microsatellites. A very strong correlation to resistance was found for the microsatellite RM 346 and RM 11 on the chromosome 7. Additional potential using65 polymorphic microsatellites. A very strong correlation to resistance was found for the microsatellite RM 346 and RM 11 on the chromosome 7. Additional potential QTLs were also identified in this study. QTLs were also identified in this study. Introduction Evaluation of T. orizicolus. Rice hoja blanca virus (RHBV) has been reported in Peru, Ecuador, Colombia, The 291 lines in the cross Fd 50 X WC366, 31.5% were resistant, 37.5% intermediate Venezuela, Panama, Costa Rica, Nicaragua, Honduras, El Salvador, Dominican resistant and 31% susceptible to T. oriziclous. Twenty plants per lines were evaluated Republic, Cuba, Guyana, Suriname and French Guiana. The virus is important and the rating was made when the plants of the susceptible check Bluebonnet 50 died. because it can cause severe epidemics that can cause catastrophic losses. These Cica 8 was the intermediate control and Makalioka was the resistant control. The epidemics tend to last two or three cropping seasons and then disappear for many evaluation scale shown in Table 2. years. Rice hoja blanca virus is in the genera Tenuivirus. The principal vector of RHBV *1: No symptoms or slight discoloration is the Delphacidae, Tagosodes orizicola (Muir). The virus propagates in the %DP 1 2 3 4 *2: Chlorosis of the tip and borders of the leaves planthopper and is transmitted in a circulative, persistent manner. The virus is 0 1 3 5 7 *3: Half of the plant with chlorosis or necrosis 10 1 3 5 7 *4: Stunting with more than half of the plant necrotic retained when the planthopper molts and there is transovarian transmission to the 20 3 3 5 7 %DP: percentage of dead plants progeny of an infected planthopper. 30 3 5 7 9 40 5 5 7 9 There are resistant varieties but little is known of the importance of resistance to 50 5 5 9 9 the virus versus the resistance to the vector. This study was undertaken to better 60 7 7 9 9 understand the basis of resistance and the virus/plant/vector interaction. 70 7 7 9 9 80 9 9 9 9 90 9 9 9 9 The Crosses. 100 9 9 9 9 For the analysis of resistance to RHBV the variety Fedearroz (Fd) 2000 was crossed wth WC366 and 231 F2 lines were generated. The F3 progeny were 1,3: resistant; 5: intermediate resistant; 7,9: susceptible evaluated. For the analysis of resistance to T. Orizicolus the variety Fedearroz (Fd) 50 was Table 2. Evaluation for T.orizicolus (IRRI 1996) crossed line WC366 and 291 F2 lines were generated. The F3 progeny were evaluated. Genotypic Evaluation using Micro-satellite for T. orizicolus in Fedearroz 50 Reaction For the analysis of resistance to T. orizicolus the 30 most resistant and susceptible Variety lines were analyzed. The F2 lines of the cross Fd 2000 X WC 366 were analyzed RHBV T.orizicolus using 65 polymorphic microsatellites. The microsatellites the microsatellites RM11 WC 366 S S S: Susceptible y RM346 on chromosome 7 were associated with resistance with a maximum LOD Colombia 1 R S R: Resistant score of 21. Fig. 3 HR: highly resistant Fedearroz 50 R HR Fedearroz HR R 2000 Table 1. Varieties with resistance to RHBV and T.orizicolus RM11 RM346 Evaluation for resistance to RHBV. The evaluation for resistence to was made in the greenhouse, using 3 replications of 20 plants were used to evaluate the lines of the F3 generation. Twenty-five days RM11 after planting, the rice lines were infested with a dosage of approximately 1.5 viruliferous insects per plant. After three weeks, each plant was evaluated for RM346 symptoms of RHBV (figure 1). 0.0 6.2Mb 21.32 3.0 Of the 231 lines in the cross Fd 2000 X WC366, 5.6% were resistant, 74.5% intermediate resistant and 19.9% susceptible to RHBV. LOD Fig. 3 Molecular markers associated with resistance to T. orizicolus in Fedearroz 50 The association of the microsatellites were measure using an F statistic, significance at least 5%. In the cross Fd50 X WC366, the results indicate that there may be more QTLs involved in the resistance to RHBV and T. orizicolus. Similar results were obtain using the cross Fd2000 X WC366. Additional markers will be used to test the hypothesis that these regions are QTLs for resistance. Table. 3 Resistance to RHBV Resistance T. orizicolus SSR F (1, n-2) SSR F (1, n-2) Chr. 1 RM84 4.284 Chr. 5 RM178 5.062 RM241 9.360 Chr. 4 RM348 4.810 Fig. 1. Symptoms of Rice Hoja Blanca virus RM349 4.446 RM253 4.975 RM202 5.313 Chr. 6 Genotypic Evaluation using Micro-satellite for resistance to RHBV in RM162 4.290 Chr. 11 RM229 4.794 RM21 6.421 Fedearroz 2000 For the analysis of resistance to RHBV the 30 most resistant and susceptible lines were analyzed. The F2 lines of the cross Fd 2000 X WC 366 were analyzed using 53 Table 3. Other potential QTLs for resistance to RHBV or T. polymorphic microsatellites. The microsatellites RM261, RM335, RM518 and orizicolus. RM6770 on the short arm of chromosome 4 were associated with resistance to RHBV (figure 2) Conclusions RM335 •Identification of a QTL on the short arm of chr. 4 associated with resistance to RHBV RM518 •Identification of QTL on chr. 7 associated with resistance of T. orizicolus RM6770 •A candidate gene for resistance RHBV was identified •Progress toward a Marker Aided Selection method for RHBV and T. orizicolus RM261 resistance 5.7 Mb Next steps •Saturation of the gene for both crosses with additional microsatellites •Continued fine mapping of chromosome 4 and 7. A gene with a CBS •Cloning the CBS domain candidate gene RHBV for study diversity domain is a candidate •Transformation of the CBS candidate gene for proof of concept gene for resistance •Identification the candidate genes on chromosome 7 BIBLIOGRAPHY 1. YANG H., H. REN, Q. WENG, L. ZHU, G. HE. 2002. Molecular mapping and genetic analysis of a rice brown planthopper (Nilaparvata lugens Stål) resistance gene. Hereditas 136 (1): 39-43. Fig. 2. Molecular markers associated with resistance to RHBV in 2. McCOUCH S., X.CHEN.,O.PANAUD, S.TEMNYKH, Y. XU, Y.G. CHO, N.HUANG, T.ISHII, and M. BLAIR.(1997). Microsatellite marker development, mapping and application in rice genetics and breeding. Fedearroz 2000 Plant Mol. Biol.35:89-99

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