Sujata Vasudev

Breeding Major Oil Crops: Present Status and Future Research Needs

Oils extracted from plants have been used predominantly as edible oil. Soybean, peanut, rapeseed mustard, sunflower, safflower, Sesamum, linseed, castor and cotton seed are predominant oil crops. Global status of nine major and minor oil crops has been discussed which includes their classification, contribution, major growing countries and objectives. Major objectives in oil crop improvement are enhancement of seed and oil yield, quality of oil according to its use, i.e. edible or industrial uses, breeding of varieties which fit in different cropping systems and breeding biotic and abiotic stress resistant/tolerant varieties. Achievements in varietal development programme of nine oil crops in India have also been discussed and future research needs to meet the increasing demand have also been highlighted. This review describes developments in use of biotechnological tools in seven edible oil crops, namely, Brassica, soybean, sunflower, groundnut, Sesamum, linseed and safflower and also highlights the prospects of using markers in genetic improvement of these crops. Molecular markers reported for genetic diversity assessment, mapping and tagging genes/QTLs for different qualitative and quantitative traits and their use in marker-assisted selection have been presented.

Development and validation of functional CAPS markers for the FAE genes in Brassica juncea and their use in marker-assisted selection

Low erucic acid is a major breeding target to improve the edible oil quality in Brassica juncea. The single nucleotide polymorphism (SNP) in fatty acid elongase 1 (FAE1.1 and FAE1.2) gene was exploited to expedite the breeding program. The paralogs of FAE1 gene were sequenced from low erucic acid genotype Pusa Mustard 30 and SNPs were identified through homologous alignment with sequence downloaded from NCBI GenBank. Two SNPs in FAE1.1 at position 591 and 1265 and one in FAE1.2 at 237 were found polymorphic among low and high erucic acid genotypes. These SNPs either create or change the recognition site of restriction enzymes. Transition of a single nucleotide at position 591 and 1265 in FAE1.1, and at position 237 in FAE1.2, leads to a change in the recognition site of Hpy99I, BglII and MnlI restriction enzymes, respectively. Two CAPS markers for FAE1.1 and one for FAE1.2 were developed to differentiate low and high erucic acid genotypes. The efficiency of these CAPS markers was found 100 per cent when validated in Brassica juncea, and B. nigra genotypes and used in back-cross breeding. These CAPS markers will facilitate in marker-assisted selection for improvement of oil quality in Brassica juncea.

Oil Improvement in Maize: Potential and Prospects

High-quality maize oil, having low level of saturated fatty acids, is highly suitable for human consumption. It is considered to be better than most of other edible oils due to its fatty acid composition and stability during storage and cooking. There is about 3–4 % oil content in maize kernel. However, more than 6–7 % oil is reported in high-oil corn genotypes. High-oil lines, in general, have reduced yields. Large numbers of genes/QTLs were reported to control this trait, thus, making it difficult to improve. A combination of conventional breeding methods, marker-assisted selection and transgenic approach would help in developing high-yielding genotypes with enhanced oil content in maize.

Validation of molecular markers linked to low glucosinolate QTLs for marker assisted selection in Indian mustard (Brassica juncea L. Czern & Coss)

Six earlier reported markers closely linked to low glucosinolate QTLs of Brassica juncea, spread across ‘A’ genome (A2, A3 and A9) were validated in a recombinant inbred line (RIL) population of a cross between Pusa Mustard-21 (low erucic acid) and EC-597325 (double low) genotypes, to utilize them in marker-assisted selection (MAS). Of them, four markers viz., GER 1 amplified alleles of 650 bp and of 950 bp, GER 5 amplified 310 bp and 350 bp, At5gAJ67 amplified 500 bp and 450 bp and Myb28 amplified alleles of size 900 bp and 920 bp in EC597325 and Pusa Mustard-21, respectively and therefore differentiated low and high glucosinolate parents. These four polymorphic markers were then used to genotype the phenotyped RIL population consisting 608 plants. Marker-trait association was tested for goodness of fit using 2 test. Of the four markers, GER1 and GER5 showed higher phenotypic variance (R2 value) compared to the others, indicating their significance in determination of glucosinolates and prospects for use in MAS for development of Indian mustard genotypes with low glucosinolates content.

Inheritance of low erucic acid in Indian mustard [Brassica juncea (L.) Czern. and Coss.]

Genetics of erucic acid content was studied using six generations viz., P1, P2, F1, F2, B1 and B2 derived from the crosses, Varuna × LES-39 and Varuna × LES-1-27. The trait high erucic acid content was partially dominant over low erucic acid content in both the crosses. In both the crosses, adequacy of additive – dominance model suggested absence of non-allelic interactions. The study revealed that selection for low erucic acid would result in isolation of plants with high oleic and linoleic acids and hence, it should be possible to develop high oleic acid lines having low erucic acid content in mustard.