Mapping productivity related traits in Brassica rapa L.
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Date
2020
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Punjab Agricultural University, Ludhiana
Abstract
In the present study, a set of 130 B. rapa – B. cossoniana introgression lines (ILs) were
characterized for key productivity related traits: plant height, main shoot length, number of
primary branches per plant, number of secondary branches per plant, number of siliquae on
main shoot, siliqua length, number of seeds/siliqua, seed size, seed yield per plant and oil
content. Analysis of variances indicated significant genotypic variation among the tested
introgressed genotypes for all the traits. Correlation matrices indicated positive correlation of
secondary branches with primary branches (r = 0.581**) and seed yield per plant per se (r =
0.231**). Number of siliquae on main shoot exhibited positive association with plant height (r
= 0.332**), primary branches (0.229**), secondary branches (r = 0.167*) and main shoot
length (r = 0.417**). Seed size exhibited positive correlation with oil content (r = 0.354*) and
siliqua length (r = 0.170*). Genome wide association studies indicated significant marker trait
associations for the target traits across all the 10 chromosomes of B. rapa. It was possible to
identify 30 genes comprising two for plant height, four for main shoot length, five for primary
branches, six for secondary branches, one for siliquae on main shoot length, four for siliqua
length, three for seeds per siliqua, two for seed size and three for oil content. It could not be
possible to predict the genes for seed yield per plant per se. Gene involved in inhibiting shoot
branching (CYP711A1) and vegetative development (2-OG) were predicted for plant height,
whereas for main shoot length gene involved in flower development (ARF4, BIN2 and
AtMBD9) were predicted. Genes involved in maintenance of the shoot apical meristem
(SPC25), determinacy of floral meristem (PWR, KNU) were predicted for primary branches,
whereas for secondary branches genes involved in controlling levels of auxins (BIN2, B
ALPHA) and degradation of CKs (CKX1), maintenance of the activity of shoot meristem
(LOG1) were predicted. Gene promoting flowering in the shoot apical and axillary meristems
(AGL72) were predicted for siliquae on main shoot whereas genes involved in floral
termination (LFY) and cell wall thickening (NAC) were predicted for siliqua length. Genes
involved in embryogenesis (RCE1, FACKEL, HB2, EMB1027) were identified for seed
related traits. For oil content, gene involved in vesicle transport (EMB1441), for synthesis of
18:2 fatty acids (FAD2), seed oil accumulation (OLEO4) were predicted. The present
investigation has helped to establish phenotypic variations and prediction of candidate genes
for key productivity related traits in the introgressed genotypes of B. rapa. These genes can be
validated and exploited in future breeding programme.
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Citation
Kamboj, Shefali (2020). Mapping productivity related traits in Brassica rapa L. (Unpublished M.Sc. thesis). Punjab Agricultural University, Ludhiana, Punjab, India.