Molecular characterization and genetic diversity analysis in Indian mustard (Brassica juncea L. Czern & Coss.) varieties using SSR markers.

In this study, we evaluated genetic diversity in a panel of 87 Indian mustard varieties using 200 genomic-SSR markers. A total of 189 SSRs resulted into positive amplification with 174 (92.06%) SSRs generating polymorphic products and 15 (7.94%) SSRs producing monomorphic amplicons. A total of 552 alleles were obtained and allele number varied from 2-6 with an average number of 3.17 alleles per SSR marker. The major allele frequency ranged from 0.29 (ENA23) to 0.92 (BrgMS841) with an average value of 0.58 per SSR locus. The polymorphic information content (PIC) value ranged from 0.10 (BrgMS841) to 0.68 (BrgMS519) with 0.39 as mean PIC value. The gene diversity per locus ranged from 0.13 (BrgMS841) to 0.72 (ENA23 & BrgMS519) with a mean value of 0.48 per SSR primer pair. Both Unweighted Neighbor Joining-based dendrogram and population structure analysis divided all the 87 varieties into two major groups/subpopulations. Analysis of molecular variance (AMOVA) inferred the presence of more genetic variation (98%) among individuals than among groups (2%). A total of 31 SSRs produced 36 unique alleles for 27 varieties which will serve as unique DNA-fingerprints for the identification and legal protection of these varieties. Further, the results obtained provided a deeper insight into the genetic structure of Indian mustard varieties in India and will assist in formulating future breeding strategies aimed at Indian mustard genetic improvement.

Agro-morphological traits and SSR markers reveal genetic variations in germplasm accessions of Indian mustard - An industrially important oilseed crop.

Indian mustard is an economic and highly important industrial oilseed crop. In this study, genetic diversity among 135 Indian mustard germplasm accessions was evaluated using 11 agro-morphological descriptors and 227 SSRs. Morphological characterization of Indian mustard germplasm accessions exhibited a broad range of variation for characters including biological yield (CV = 25.63%), seed yield (CV = 23.23% and 1000-seed weight (CV = 23.14%); whereas traits such as days to maturity (CV = 2.91%) showed lowest degree of variation. Out of 227 SSR markers evaluated, a total of 159 (70.04%) SSRs produced polymorphic products and 68 (29.96%) SSRs resulted into monomorphic amplicons. The polymorphic markers amplified 575 alleles and the number of alleles ranged from 2-7 with 3.61 average number of alleles per locus. SSR markers BRMS-030, Ra2-E11, Ra2-G05, Ni4-G10 and Ol10B11 generated the highest number of alleles (7). SSR marker Ra2-G05 was having the highest allele frequency (0.84), while BRMS-002 was having the lowest major allele frequency (0.33). Polymorphism information content (PIC) values ranged from 0.24-0.61 with an average value of 0.39 per primer pair. Unweighted pair group method with arithmetic mean (UPGMA) cluster analysis based on morphological traits grouped Indian mustard genotypes into three clusters, while two clusters were obtained based on SSR based clustering. Population structure analysis provided a better estimate of genetic diversity and divided all the genotypes into five subpopulations. Genetically diverse accessions identified may be used for hybridization in Indian mustard crop improvement programs in future.

Genetic diversity in leafy mustard (Brassica juncea var. rugosa) as revealed by agro-morphological traits and SSR markers.

Leafy mustard (B. juncea var. rugosa) constitutes an important group of vegetable mustard crops in India and is mainly cultivated in home-backyard and hilly regions of Uttarakhand and some North-eastern states. In the present study, various agro-morphological traits, physiological and biochemical traits along with SSR markers were used for genetic diversity evaluation in a germplasm collection of leafy mustard. This study revealed a significant variation among 59 accessions of leafy mustard in both qualitative and quantitative agro-morphological traits indicating the accessions' promising potential for consumption purpose and for use in breeding programs. Maximum variability was recorded for leaf area elongation rate (CV = 53.12%), followed by total plant weight (TPW) (CV = 50.63%) and seed yield per plant (CV = 44.33%). In molecular analysis, 155 SSRs evaluated resulted in 482 alleles and the number of alleles varied form 1 to 8 with an average of 3.11 alleles per marker. A total of 122 (78.70%) SSRs resulted into polymorphic amplicons. PIC value varied from 0.32 to 0.77 with an average value of 0.44 per SSR locus. The unweighted neighbour-joining-based dendrogram analysis divided all the 59 accessions into two major groups on the basis of both agro-morphological traits and SSR markers, whereas, three subpopulations/subgroups were predicted by population STRUCTURE analysis. AMOVA indicated the presence of more variability within population than among population. Overall, agro-morphologically better performing and genetically diverse genotypes have been identified which could be further used as donors for leafy mustard improvement programs.

Current achievements and future prospects of genetic engineering in Indian mustard (Brassica juncea L. Czern & Coss.).

MAIN CONCLUSION: Transgenic technology in Indian mustard has expedited crop improvement programs. Further, there is a need to optimize gene editing protocols and find out the suitable target genes to harvest the benefits of gene editing technology in this important edible oilseed crop. Brassica juncea is an economically and industrially important oilseed crop being grown mainly in India and in some parts of Canada, Russia, China and Australia. Besides being consumed as edible oil, it also has numerous applications in food and paint industry. However, its overall production and productivity are being hampered by a number of biotic and abiotic stress factors. Further, its oil and seedmeal quality needs to be improved for increasing food as well as feed value. However, the lack of resistant crossable germplasm or varieties necessitated the use of genetic engineering interventions in Indian mustard crop improvement. A number of genes conferring resistance to biotic stresses including lectins for aphids' control, chitinase, glucanase and osmotin for disease control and for abiotic stresses, CODA, LEA and ion antiporter genes have been transferred to Indian mustard. Both antisense and RNAi technologies have been employed for improving oil and seedmeal quality. Efforts have been made to improve the phytoremediation potential of this crop through genetic engineering approach. The deployment of barnase/barstar gene system for developing male sterile and restorer lines has really expedited hybrid development programs in Indian mustard. Further, there is a need to optimize gene editing protocols and to find out suitable target genes for gene editing in this crop. In this review paper, authors have attempted to review various genetic transformation efforts carried out in Indian mustard for its improvement to combat biotic and abiotic stress challenges, quality improvement and hybrid development.

Genetic engineering strategies for biotic and abiotic stress tolerance and quality enhancement in horticultural crops: a comprehensive review.

Genetic engineering technique offers myriads of applications in improvement of horticultural crops for biotic and abiotic stress tolerance, and produce quality enhancement. During last two decades, a large number of transgenic horticultural crops has been developed and more are underway. A number of genes including natural and synthetic Cry genes, protease inhibitors, trypsin inhibitors and cystatin genes have been used to incorporate insect and nematode resistance. For providing protection against fungal and bacterial diseases, various genes like chitinase, glucanase, osmotin, defensin and pathogenesis-related genes are being transferred to many horticultural crops world over. RNAi technique has been found quite successful in inducing virus resistance in horticultural crops in addition to coat protein genes. Abiotic stresses such as drought, heat and salinity adversely affect production and productivity of horticultural crops and a number of genes encoding for biosynthesis of stress protecting compounds including mannitol, glycine betaine and heat shock proteins have been employed for abiotic stress tolerance besides various transcription factors like DREB1, MAPK, WRKY, etc. Antisense gene and RNAi technologies have revolutionized the pace of improvement of horticultural crops, particularly ornamentals for color modification, increasing shelf-life and reducing post-harvest losses. Precise genome editing tools, particularly CRISPR/Cas9, have been efficiently applied in tomato, petunia, citrus, grape, potato and apple for gene mutation, repression, activation and epigenome editing. This review provides comprehensive overview to draw the attention of researchers for better understanding of genetic engineering advancements in imparting biotic and abiotic stress tolerance as well as on improving various traits related to quality, texture, plant architecture modification, increasing shelf-life, etc. in different horticultural crops.