Marker-Assisted Selection to Pyramid the Opaque-2 (O2) and β-Carotene (crtRB1) Genes in Maize

Abstract

Maize is an excellent nutritional source and is consumed as a staple food in different parts of the world, including India. Developing a maize genotype with a combination of higher lysine and tryptophan, along with β-carotene, can help alleviate the problem of protein-energy malnutrition (PEM) and vitamin A deficiency (VAD). This study is aimed at improving lysine and tryptophan content by transferring opaque-2 (o2) gene from donor HKI163 to β-carotene-rich inbred lines viz., UMI1200β+ and UMI1230β+. For this purpose, F1, BC1F1, BC2F1, BC2F2, and BC2F3 plants were developed using an o2 line HKI163 and two β-carotene-rich inbred lines, UMI1200β+ and UMI1230β+, as the parents. Foreground selection using the associated marker umc1066 for the o2 gene and the marker crtRB1 3′TE for the crtRB1 gene was used to select the target genes. A total of 236 simple sequence repeat (SSR) markers distributed evenly across the maize genome were employed for the background selection. To fix the crtRB1 allele in the BC1F1 stage, individual plants homozygous at the crtRB1 locus and heterozygous at the o2 locus were selected and used for backcrossing to produce BC2F1 plants. Furthermore, the selected heterozygous BC2F1 plants from both crosses were selfed to obtain the BC2F2 plants, which were then selected for the target gene and selfed to generate the BC2F3 lines. From each cross, five improved lines with homozygous marker alleles for the crtRB1 and o2 genes with a recurrent parent genome (RPG) recovery ranging from 86.75 to 91.21% in UMI1200β+×HKI163 and 80.00 to 90.08% in UMI1230β+×HKI163 were identified. The improved lines had good agronomic performance and possessed high lysine (0.294–0.332%), tryptophan (0.073–0.081%), and β-carotene (6.12–7.38 µg/g) content. These improved lines can be used as genetic resources for maize improvement.

Enhancing β-Carotene Concentration in Parental Lines of CO6 Maize Hybrid Through Marker-Assisted Backcross Breeding (MABB)

“…Following this approach, after only two generations of backcrossing, it was possible to identify the plants carrying RPGR ranging from 90.24 to 92.42% (UMI1200 × HP467-15) and 90.41–92.21% (UMI 1230 × HP467-15) in BC 2 F 3 improved lines. These results are in accordance with the previous studies ( 9 , 27 , 28 ).…”

Improvement of a Yairipok Chujak Maize Landrace from North Eastern Himalayan Region for β-Carotene Content through Molecular Marker-Assisted Backcross Breeding

“…The high degree of resemblance with their recurrent parent for the trait of plant height in the present study agreed with earlier reports of Mehta et al [ 25 ] when developing sweet corn hybrids for vitamin A fortification. The high rate of recurrent parent recovery in the BC 2 F 2 generation was also reported in previous studies [ 8 , 9 , 11 , 26 ]. The improved line CAUM66-54-9-12-24 recorded high β-carotene (8.711 μg/g) comparable to that of the donor parent (UMI285β + ) followed by the lines, viz., CAUM66-54-9-12-13 and CAUM66-54-9-12-11 which recorded 8.647 μg/g and 8.258 μg/g, respectively.…”

“…Hence, allele 1 is identified as a favorable allele that is responsible for the accumulation of a higher level of β-carotene in the maize endosperm. Many researchers used the gene-specific markers developed from the crtRB1 gene in MABC programs to increase the β-carotene content in popular elite varieties and hybrids [ 8 , 9 , 10 , 11 ]. In the NEHR of India, maize is the staple food crop and the local people cultivate the maize landraces and consume them as food.…”

Genome-Wide Characterization and Comparative Analyses of Simple Sequence Repeats among Four Miniature Pig Breeds

“…Simple sequence repeats (SSRs), also known as microsatellites or short tandem repeats (STRs), consist of 2 to 6 base-pair motifs repeated several times in tandem. As a consequence of their wide distribution and high mutation rate in eukaryotic genomes [ 1 ], SSRs have been used in genetic diversity and population structure studies [ 2 , 3 , 4 , 5 ], for discrimination among species or breeds [ 6 , 7 ], in marker-assisted selection [ 8 , 9 , 10 ] and in evolution analysis [ 11 ]. In humans, SSRs were predicted to be bound by protein-coding transcripts, long non-coding RNAs (lncRNAs) and circular RNAs (circRNAs) and affect competing endogenous RNA crosstalk [ 12 ].…”