PHENOTYPIC AND GENOTYPIC EVALUATIONS FOR CBB   RESISTANCE IN COMMON BEAN POPULATIONS       L. Kachulu, M.S. Mwala, R. Chir...
Bean Production areas in        Africa                       Expanding to                       tropical                 ...
Major production biotic constraints ofbeans in Africa (Wortmann, et al. 1998)       Constraint      Yield loss ton (p.a.) ...
Common bacterial blight (CBB)   CBB –a worldwide seed-    borne disease of common    bean- yield loss of up to    40%.  ...
Breeding for CBB resistance   •   CBB resistance breeding -constrained by the       instability of resistance because of i...
Breeding for CBB resistance   SCAR markers BC420, SU91, and SAP6 are tightly-    linked with three major QTLs on chromoso...
Objective of the study   The study was carried out to evaluate the    reaction of F4.6 lines to CBB and validate the    p...
Materials and Methods    The crosses were made from CBB resistant    sources of Meso (VAX3, VAX6 ) and Andean    (RMX2, R...
Materials and Methods   Exp2: Genotypic screening for CBB    resistance-DNA was extracted from the    greenhouse plants, ...
Results :                            EXP1:Phenotypic screening-Level of resistance for CBB in the populations were interme...
Results :CBB scores for the advanced lines within populationsrevealed presence of some resistant (1-3) genotypes,as well a...
Results from Exp. 2Parent   SU91   SAP6   BC420VAX 3      +      +       _VAX6       +      +       _                     ...
The SCAR markers were easily scored as present (+)   or absent (-) of a single band on agarose gel.Population     -SAP6/- ...
Conclusion...   The findings of this study show that, 43 F4.6 lines    were resistant to CBB. These will further be    us...
Conclusion...   The findings of the study provide a basis for    advancing lines with improved levels of    resistance to...
THANK YOU FORLISTENING
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PHENOTYPIC AND GENOTYPIC EVALUATIONS FOR CBB RESISTANCE IN COMMON BEAN POPULATIONS

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PHENOTYPIC AND GENOTYPIC EVALUATIONS FOR CBB RESISTANCE IN COMMON BEAN POPULATIONS

  1. 1. PHENOTYPIC AND GENOTYPIC EVALUATIONS FOR CBB RESISTANCE IN COMMON BEAN POPULATIONS L. Kachulu, M.S. Mwala, R. Chirwa and L. Madubanya 10th African Crop Science Society Conference 10-13 Oct, 2011, Maputo, Mozambique
  2. 2. Bean Production areas in Africa Expanding to tropical lowland areas of western Africa Source: Bean Atlas, 1998
  3. 3. Major production biotic constraints ofbeans in Africa (Wortmann, et al. 1998) Constraint Yield loss ton (p.a.) Angular leaf spot 384,200 Anthracnose 328,000 Bean stem maggot 297,100 Root rots 221,100 CBB 220,400
  4. 4. Common bacterial blight (CBB) CBB –a worldwide seed- borne disease of common bean- yield loss of up to 40%. Contaminated seed (internal or external) acts as primary source of inoculum can survive for extended period 10 years Quantitative trait controlled by more than one gene of QTLs
  5. 5. Breeding for CBB resistance • CBB resistance breeding -constrained by the instability of resistance because of its quantitative nature • Despite the instability-resistance QTLs have been introgressed into breeding lines • Markers (SCARs) for these QTLs are available and employed in MAS as a way to improve the selection of cultivars with CBB resistance
  6. 6. Breeding for CBB resistance SCAR markers BC420, SU91, and SAP6 are tightly- linked with three major QTLs on chromosomes, B6, B8, and B10 respectively. Different chromosomal positions of these SCAR markers makes them attractive sources for introgressing independent QTLs conditioning resistance to CBB into susceptible bean lines
  7. 7. Objective of the study The study was carried out to evaluate the reaction of F4.6 lines to CBB and validate the presence of SCAR markers SU91700, SAP6820 and BC420900
  8. 8. Materials and Methods The crosses were made from CBB resistant sources of Meso (VAX3, VAX6 ) and Andean (RMX2, RMX19 & RMX20), and susceptible recipient parents of Andean origin Exp1: Phenotypic screening for CBB resistance- Conducted in the G/house using isolates Xf260 and Xf410. Fully expanded trifoliate leaves were inoculated using multiple needle method and scored at 1-9 CIAT scale after
  9. 9. Materials and Methods Exp2: Genotypic screening for CBB resistance-DNA was extracted from the greenhouse plants, template DNA was used in PCR reaction to amplify SCAR markers SU91, SAP6 and BC420. Presence or absence of the resulting fragments for each marker was determined using agarose gel electrophoresis
  10. 10. Results : EXP1:Phenotypic screening-Level of resistance for CBB in the populations were intermediate.Average population scores of 5 and 6- due to segregation
  11. 11. Results :CBB scores for the advanced lines within populationsrevealed presence of some resistant (1-3) genotypes,as well as intermediate and susceptiblePopulation Number of lines and reaction to CBB Resistant (1-3) Intermediate (4-6) Susceptible (7-9)BRB211/VAX3 3 19 4BRB214/VAX3 10 17 9BRB215/VAX6 0 7 3BRB265/VAX6 6 8 6CMB107/RMX2 0 6 10RMA70/RMX20 0 13 6RMA72/VAX6 21 45 22BRB264/VAX3 3 5 10RMA72/RMX19 0 9 18
  12. 12. Results from Exp. 2Parent SU91 SAP6 BC420VAX 3 + + _VAX6 + + _ • SU91 marker was present in the VAXRMX2 _ + _ parents,RMX19 _ + _ • Andean parentsBRB211 _ + _ possessed SAP6.BRB214 _ _ _ • SAP6 was alsoBRB215 _ _ present in someBRB265 _ + _ susceptible cultivars.CMB107 _ _ _ • None of theRMA70 _ _ _ parents carriedRMA72 _ + _ the BC420 markerBRB264 _ _ _
  13. 13. The SCAR markers were easily scored as present (+) or absent (-) of a single band on agarose gel.Population -SAP6/- SAP6 SU91 +SAP6/ SU91 +SU91 Some resistant genotypes*BRB211/VAX3 1 2 lacked both SCAR markersBRB214/VAX3 10 SU91 marker was associatedBRB264/VAX3 1 2 with genotypes that showedRMA72/VAX6 8 13 higher levels of phenotypic resistance to CBB.BRB265/VAX6 6*BRB264/VAX3 2 7 1 SAP6 was found inRMA70/RMX20 3 3 susceptible genotypesCMB107/RMX2 3 7 *Resistant genotypesRMA72/RMX19 9 9 *Susceptible genotypesRMA72/VAX6 8 7
  14. 14. Conclusion... The findings of this study show that, 43 F4.6 lines were resistant to CBB. These will further be used as donor parental lines in the breeding programmes or evaluated for yield perfomance 28 of the resistant lines possessed SU91 , 2 lacked both markers and 13 had a combination of the two markers i.e. SU91 and SAP6.
  15. 15. Conclusion... The findings of the study provide a basis for advancing lines with improved levels of resistance to CBB and reducing the number of lines that need to be verified in the field Given the absence of BC420 marker in the study populations, resistance could be enhanced further by crossing with resistance sources carrying the BC420marker Need to find other markers for resistance to CBB other than SU91, SAP6 or BC420
  16. 16. THANK YOU FORLISTENING

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