Evolutionary aspects of direct or indirect selection for seed size and seed metabolites in Brassica juncea and diploid progenitor species
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Seed size and seed metabolites have been the targets of direct or indirect selection during domestication and subsequent crop breeding. Understanding these traits and associated genetics can prove very useful for plant translational research. Large germplasm assemblage (235) of Brassica juncea and its progenitor species (B. rapa and B. nigra) was evaluated to establish seed trait variations for seed size and seed metabolites. Seeds were smallest in B. nigra and largest in B. juncea. Australian B. juncea and Indian B. rapa var brown sarson types averaged more seed oil content. Seed size and oil content were generally higher in modern cultivars in comparison to the land races. Allelic diversity for known associated genes for seed-size and oil-content (AP2, ARF2, TTG2, GRF2, GL2, CYP78A5, CYP78A6, MINI3, IKU2, IKU1, BRI1, DGAT, GPDH, LPAAT, GPAT and DA1) was studied so as to infer the effect of domestication on seed traits. Three genes (IKU1, IKU2, AP2) in B. rapa, two (TTG2 and GL2) in B. nigra and two (IKU1 and GRF2) in natural B. juncea were identified as targets of selection on the basis of Fst outlier and/or sequence diversity tests. We report parallel divergence for seed traits between B. juncea and B. rapa. Directional selection appeared stronger for seed-size as compared to correlated seed metabolites. Positive selection on seed-size is likely to have played a significant role in structuring regional variation in the germplasm.
KeywordsBrassica rapa Brassica nigra Domestication Directional selection Calorific value Fatty acids
The studies were financially supported by the Indian Council of Agricultural Research under ICAR National Professor Project “Broadening the genetic base of Indian mustard (Brassica juncea) through alien introgressions and germplasm enhancement” awarded to S.S.B. The authors thank “Plant Gene Resources of Canada, Agriculture and Agri-Food Canada” for providing many of the germplasm lines used in our studies.
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Conflict of interest
The authors declare that they have no conflict of interest.
Research involving human participants and/or animals
This article does not contain any studies with human participants or animals performed by any of the authors.
- 13.Liu J, Hua W, Yang H-L, Zhan G-M, Li R-J, Deng L-B, Wang X-F, Liu G-H, Wang H-Z (2012) The BnGRF2 gene (GRF2-like gene from Brassica napus) enhances seed oil production through regulating cell number and plant photosynthesis. J Exp Bot 63:3727–3740. https://doi.org/10.1093/jxb/ers066 CrossRefGoogle Scholar
- 20.Appelqvist L (1968) Rapid methods of lipid extractions and fatty acid methyl ester preparation for seed and leaf tissue with special remarks on preventing the accumulation of lipids contaminants. Ark Kemi 28:551–570Google Scholar
- 21.Kaur P, Banga S, Kumar N, Gupta S, Akhatar J, Banga SS (2014) Polyphyletic origin of Brassica juncea with B. rapa and B. nigra (Brassicaceae) participating as cytoplasm donor parents in independent hybridization events. Am J Bot 101:1157–1166. https://doi.org/10.3732/ajb.1400232 CrossRefGoogle Scholar
- 22.Doyle JJ, Doyle JL (1990) Isolation of plant DNA from fresh tissue. Focus 12:13–15Google Scholar
- 30.Thompson JD, Higgins DG, Gibson TJ (1994) CLUSTALW: Improving the sensitivity of progressive multiple sequence alignment through sequence weighting, position-specific gap penalties and weight matrix choice. Nucleic Acids Res 22:4673–4680. https://doi.org/10.1093/nar/22.22.4673 CrossRefGoogle Scholar
- 34.Bots M, Laga B. Mouchel C (2014) Brassica plants comprising mutant DA1 alleles. Patent WO2014161908A1. http://www.patentsencyclopedia.com/app/20160040180
- 35.Wang JL, Tang MQ, Chen S, Zheng XF, Mo HX, Li SJ, Wang Z, Zhu KM, Ding LN, Liu SY, Li YH, Tan XL (2017) Down-regulation of BnDA1, whose gene locus is associated with the seeds weight, improves the seeds weight and organ size in Brassica napus. Plant Biotechnol J 15(8):1024–1033. https://doi.org/10.1111/pbi.12696 CrossRefGoogle Scholar
- 36.Machado HE, Lawrie DS, Petrov DA (2017) Strong purifying selection on codon usage bias. bioRxiv 106476. https://doi.org/10.1101/106476
- 37.Savadi S, Naresh V, Kumar V, Dargan S, Gupta NC, Chamola R, Bhat SR (2015) Effect of overexpression of Arabidopsis thaliana SHB1 and KLUH genes on seed weight and yield contributing traits in Indian mustard (Brassica juncea L. (Czern.)). Indian J Genet Pl Br 75:349–356. https://doi.org/10.5958/0975-6906.2015.00055.3 CrossRefGoogle Scholar