Towards Molecular Breeding Of Pigeonpea Cajanus Cajan L' Millspaugh

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Towards Molecular Breeding Of Pigeonpea Cajanus
Cajan (L.) Millspaugh

• Damaris Achieng Odeny

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Pigeonpea

• Sixth most important legume the world over
• Grown mainly in Asia (India and Myanmar)
• Also sub-Saharan Africa, Latin America and the
  Caribbean

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Why Pigeonpea

• A unique crop
• Drought tolerance
• Enhances C, N and P of the soil (Fujita et al.
  2004)
• Inter-cropped with no negative impact
• High protein content (upto 28)
• Used in more diverse ways
• As food, feed, fodder, fuel wood, rearing lac
  insects, hedges, windbreaks, soil conservation,
  green manure, roofing,baskets
• Long life cycle and out-crossing nature
• Little concerted research effort

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Strategy

• Develop more efficient improvement methods
• Need to complement existing conventional methods
  with molecular methods
• Change focus from phenotypic to genotypic
  breeding
• Use of molecular markers

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Research Questions

• Is there a better and more efficient option that
  would complement the already existing methods and
  eventually enhance pigeonpea breeding?
• How do we approach such an option?

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Plausible options

• Molecular breeding
• Detailed information of the genome
• Dense set of molecular markers (genetic tools
  with the ability to show differences between
  individuals at randomly spaced positions across
  the genome)
• Microsatellites/Simple Sequence Repeats (SSR),
  markers of choice

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Microsatellites

• Tandem repeats of small segments of DNA (2-6
  bp).. CACACACACACA GAAGAAGAAGAA.
  TTATTTATTTATTTATetc
• Conserved flanking regions but varying number of
  repeats among genotypes - polymorphism

.TTTAGGGTGGCTGTTTGGA(CA)12TCCTAATAGTCCTACT1 .T
TTAGGGTGGCTGTTTGGA(CA)20TCCTAATAGTCCTACT2

• Have been shown to be linked to several genes of
  economic importance

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Objectives

• Develop a robust set of microsatellites
• Characterise and test their application in
  various breeding programs
• Assess the transferability of the new markers to
  wild pigeonpea germplasm
• Test soybean (Glycine max) SSRs for amplification
  in pigeonpea

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Methodology

• Isolation de novo
• 73 SSRs developed
• Transferability from soybean (Glycine max L.)
• 39 out of 220 tested

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Application of the SSRs

• In wild relatives of pigeonpea
• Currently a source of cytoplasmic male sterility
  for hybrid pigeonpea development.
• Contain several important traits, for example

• In determining diversity of various genotypes
  randomly selected from the breeder and from the
  gene bank
• Resistance to Fusarium wilt

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Cultivated species
Genetic Diversity Assessment
Wild species
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Towards Mapping of Resistance to F. wilt

• A mapping population (F6 RILs) was developed for
  resistance to F. wilt
• 9 markers showed easily-scorable differences
  between parents

Linkage groups
9cM
23.6cM
6cM
CCttc012
CCac006
CCttc002
CCat006
25.5cM
CCttc005
CCac030
6cM
CCtta006
CCac010
???
???
CCttc019
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Lessons for underutilized species

• There is need to improve these plants
• Molecular tools promise to facilitate improvement
  efforts
• Need to complement these tools with conventional
  skills for optimum results

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MANY THANKS
QUESTIONS?????