Marker assisted breeding in Maize, genotypic selection with the help of markers increases selection efficiency and helps in quicker advancement of breeding programmes.

1. MARKER ASSISTED BREEDING IN MAIZE
T. Nivethitha , 2020608019

2. MAS MARS MABB

3. MABB- Marker Assisted Backcross Breeding

5. Case studies
Biofortified maize enriched in pro vitamin A (proA), lysine and tryptophan -
alleviates micronutrient malnutrition.
 Traditional yellow maize - high kernel carotenoids, but provitamin A is quite low
(<2μg/g).
 Low concentration of lysine and tryptophan – low endosperm quality.
 crtRB1 (carotene hydroxylase) and lcyE (lycopene-"-cyclase) – pro vitamin A
 opaque2 (o2) – Lysine & Tryptophan

6. QPM hybrids of late maturity released in INDIA are not rich in provitamin A.
Hence, the objective was designed as,
 Stacking favorable alleles of crtRB1, lcyE and opaque2 genes into elite
inbreds/hybrids by using MABB
 Evaluate the MABB derived –inbreds/hybrids for nutritional quality,
agronomic and yield related traits.

7. S.No Hybrid Parents Maturity Days Year Area of
adaptation
1 HQPM1 HKI193-1 X HKI163 Late 88-90 2005 Zone-II,III,IV,V
2 HQPM4 HKI193-2 X HKI161 Late 95-97 2010 Zone-II,III,IV,V
3 HQPM5 HKI163 X HKI161 Late 92-93 2007 Zone-II,III,IV,V
4 HQPM7 HK1193-1 X HK1161 Late 96-97 2008 Zone-IV
QPM Parents - RP
 HKI161- 2.04
 HKI163- 1.65
 HKI193-1 – 1.84
 HKI193-2 – 1.74
Donor Parents
 HP704-22- 16.05
 HP704-23 – 15.28
Pro A - µg/g
Pro A - µg/g

9. Details of markers used for foreground selection
Details of markers used for Background selection

10. C = 543bp
L = 650bp
o2 = 165bp
Segregation pattern of three markers

11. Recovery of recipient parent genome % of proA improved
lines

12. • Individuals of each backcross- and self- generations – selected for plant, ear,
and grain characteristics for their similarity with their respective recurrent
parents.
• BC2F3 seeds from the introgressed progenies- standard light box test to
measure the intensity of opaqueness .
The seeds with similar degree of opaqueness of the original inbreds were
forwarded for further generation and for the reconstitution of hybrids.
 Selfed seeds of BC2F4 plants - Analysis of Provitamin A, Lysine, and
Tryptophan – UHPLC .
Phenotypic selection

13. Twelve improved progenies- were selected

14. Biochemical evaluation of selected introgressed progenies from selfed grains
with respective RP &DP

15. Morphological characters of selected introgressed progenies from open
pollinated plants with respective RP &DP

16. Evaluation of Reconstituted hybrids - proA

17. Evaluation of Reconstituted hybrids – Lysine &Tryptophan

18. QPM genotypes
QPM genotype

19. Polymorphism between RP &DP for crtRB1 allele
The seven inbreds are the parents-
 two extra-early-maturing [Vivek QPM-9 (VQL1 x VQL2) and Vivek Hybrid-27
(V335 x V345)]
 medium duration [HM-4 (HKI1105 x HKI323) and HM-8 (HKI1105 x HKI161)]

21. Background screening
Segregation of allele1 and allele 3 in BC2F2 generation (HKI1105 x HP467-6) using the crtRB1
gene specific marker

23. • Evaluation of improved progenies
• Evaluation of reconstituted hybrids
THIRTEEN improved progenies- were selected
VQL1
HKI1105
HKI161
Vivek hybrid 27

24. Recovery of recurrent parent genome and kernel b-carotene concentration of the
MAS-derived parental inbreds used for reconstitution of hybrids

25. Reconstituted hybrids

26. Marker-assisted recurrent selection (MARS)
• When much of the variation is controlled by minor QTLs, MABC has limited
applicability because estimates of QTL effects are inconsistent and pyramiding
becomes increasingly difficult as the number of QTLs increases.
• MARS - increase the frequency of favorable marker alleles in the population.
• MARS involves (i) defining a selection index for F2 or F2-derived progenies
with desirable alleles at target QTLs, (ii) recombining selfed progenies of the
selected individuals and (iii) repeating the procedure for a number of cycles.

27. • Although the private sector has reported significant gains through MARS
in maize (Johnson, 2004; Eathington, 2005; Crosbie et al., 2006), fewer
efforts have been undertaken in the public sector.
• Moreau et al. (2004) reported no advantage of MARS over phenotypic
selection for a multitrait performance index, probably due to the
general high heritability of traits and the limited (ca. 50%) σ2P
accounted for by QTLs.
• One shortcoming of MARS is caused by the inconsistency of QTL effects
as the genetic background changes during subsequent cycles of
selection.

28. Achievements

31. Feed specific Maize hybrids
Sweet corn + ProA+ QPM