Evaluation of inbred lines derived from commercial hybrids and their utilization in developing high yielding field corn (Zea mays L.) hybrids

Genetic enhancement and identification of genetically broad-based inbred lines for the development of new hybrids is the pre-requisite for the heterosis breeding. Newly derived 118 inbred lines were evaluated for their morpho-physiological characters in order to identify best suitable male and female parental lines. Total 10 best inbred lines were selected after thorough evaluation of 16 stable inbred lines, identified from the pool of 118 inbred lines. These inbred lines were crossed in line × tester manner, considering three inbred lines as male andrest as female, based on the Specific Combining Ability and General Combining Ability. Hybrids thus obtained were evaluated in two diverse agroclimatic situations and best heterotic hybrids were selected based on their standard heterosis and rank obtained in Duncan's Multiple Range Test analysis. Single location ANOVA for inbred lines and combined ANOVA for hybrids showed that selected inbreds and hybrids were significantly differing from each other. Since, there exists a Genotype × Environment interaction among hybrids, PCA also taken into consideration for giving weight as classification variable for the hybrids. Further, multi-location evaluation of these hybrids is proposed to identify stable hybrids suitable for large scale commercialization

Genetic variability, combining ability and molecular diversity-based parental line selection for heterosis breeding in field corn (Zea mays L.)

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGBackground: The demand of maize crop is increasing day by day, hence to reduce the production and demand gap, there is a need to extract the high yielding parental lines to improve per se yield of the hybrids, which could help to enhance the productivity in maize crops. Methods and results: The present investigation was carried out to select the best medium maturing inbred lines, among a set of 118 inbred lines. Based on the Duncan multiple range test, out of 118 lines, 16 inbred lines were selected on the basis of its high yield per se and flowering time. The molecular diversity was carried out using SSR markers linked to heterotic QTL and up on diversity analysis it classified selected genotypes in to three distinct groups. Among the selected inbred lines, a wider genetic variability and molecular diversity were observed. A total of 39 test crosses were generated after classifying 16 inbred lines in to three testers and thirteen lines (based on per se grain yield and molecular diversity) and crossing them in line × tester manner. Conclusion: Combining ability analysis of these parental lines showed that female parents, PML 109, PML 110, PML 111, PML 114 and PML 116 showed additive effect for KRN and grain yield, whereas male parents, PML 46, and PML 93 showed epistatic effect for KRN and PML 102 showed epistatic effect for grain yield. The generated information in the present investigation may be exploited for heterosis breeding in filed corn. Key messages To tackle the balanced dietary requirement of Indian population; we focused to enhance the productivity of maize hybrids using genetically broad based, elite, diverse inbred lines. Combination of selection criterion, not only augment the productivity but also improves the quality of hybrid/s

Development of β-carotene rich maize hybrids through marker-assisted introgression of β-carotene hydroxylase allele.

Development of vitamin A-rich cereals can help in alleviating the widespread problem of vitamin A deficiency. We report here significant enhancement of kernel β-carotene in elite maize genotypes through accelerated marker-assisted backcross breeding. A favourable allele (543 bp) of the β-carotene hydroxylase (crtRB1) gene was introgressed in the seven elite inbred parents, which were low (1.4 µg/g) in kernel β-carotene, by using a crtRB1-specific DNA marker for foreground selection. About 90% of the recurrent parent genome was recovered in the selected progenies within two backcross generations. Concentration of β-carotene among the crtRB1-introgressed inbreds varied from 8.6 to 17.5 µg/g - a maximum increase up to 12.6-fold over recurrent parent. The reconstituted hybrids developed from improved parental inbreds also showed enhanced kernel β-carotene as high as 21.7 µg/g, compared to 2.6 µg/g in the original hybrid. The reconstituted hybrids evaluated at two locations possessed similar grain yield to that of original hybrids. These β-carotene enriched high yielding hybrids can be effectively utilized in the maize biofortification programs across the globe

Development of Biofortified Maize Hybrids through Marker-Assisted Stacking of β-Carotene Hydroxylase, Lycopene-ε-Cyclase and Opaque2 Genes

Traditional yellow maize though contains high kernel carotenoids, the concentration of provitamin A (proA) is quite low (<2 μg/g), compared to recommended level (15 μg/g). It also possesses poor endosperm protein quality due to low concentration of lysine and tryptophan. Natural variant of crtRB1 (β-carotene hydroxylase) and lcyE (lycopene-ε-cyclase) cause significant enhancement of proA concentration, while recessive allele, opaque2 (o2) enhances the level of these amino acids. Development of biofortified maize enriched in proA, lysine and tryptophan thus holds significance in alleviation of micronutrient malnutrition. In the present study, marker-assisted stacking of crtRB1, lcyE and o2 was undertaken in the genetic background of four maize hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) popularly grown in India. HP704-22 and HP704-23 were used as donors, while four elite QPM parents viz., HKI161, HKI163, HKI193-1, and HKI193-2 were used as recipients. CrtRB1 showed severe segregation distortion, while lcyE segregated as per the expectation. Recovery of recurrent parent genome (RPG) among selected backcross progenies ranged from 89 to 93%. Introgressed progenies possessed high concentration of proA (7.38–13.59 μg/g), compared to 1.65–2.04 μg/g in the recurrent parents. The reconstituted hybrids showed an average of 4.5-fold increase in proA with a range of 9.25–12.88 μg/g, compared to original hybrids (2.14–2.48 μg/g). Similar plant-, ear-, and grain- characteristics of improved versions of both inbreds and hybrids were observed when evaluated with their respective original versions. Mean lysine (0.334%) and tryptophan (0.080%) of the improved hybrids were at par with the original versions (lysine: 0.340%, tryptophan: 0.083%). Improved hybrids also possessed similar grain yield potential (6,301–8,545 kg/ha) with their original versions (6,135–8,479 kg/ha) evaluated at two locations. This is the first study of staking crtRB1-, lcyE-, and o2-, favorable alleles in single genetic background. The improved inbreds can be effectively used as potential donor for independent and/or simultaneous introgression of crtRB1, lcyE, and o2 in the future breeding programme. These biofortified maize hybrids, rich in proA, lysine and tryptophan will hold great promise for nutritional security

Marker-assisted backcross breeding scheme adapted for the introgression of <i>allele 1</i> of the <i>crtRB1</i> 3′TE gene in to elite parent (V335 and V345) of the maize hybrid Vivek Hybrid-27 (RP: Recurrent Parent; DP: Donor Parent).

<p>Marker-assisted backcross breeding scheme adapted for the introgression of <i>allele 1</i> of the <i>crtRB1</i> 3′TE gene in to elite parent (V335 and V345) of the maize hybrid Vivek Hybrid-27 (RP: Recurrent Parent; DP: Donor Parent).</p

Structure of the alleles of <i>crtRB1</i> gene causing variation in β-carotene concentration of maize.

<p>E: Exon; I: Intron; TE: Transposable element. <b>A</b>: No TE insertion at 6^th Exon causing favourable <i>allele 1</i> (543 bp amplicon); <b>B</b>: 325 bp TE insertion at 6^th Exon causing unfavourable <i>allele 2</i> (296+875 bp amplicon); <b>C</b>: 1250 bp TE insertion at 6^th Exon causing unfavourable <i>allele 3</i> (296+1221+1880 bp amplicon).</p

Segregation pattern of alleles of the <i>crtRB1</i> gene in different backcross- and selfed- generations across seven crosses.

<p>*significant at <i>P</i><0.05.</p><p>Segregation pattern of alleles of the <i>crtRB1</i> gene in different backcross- and selfed- generations across seven crosses.</p

Kernel β-carotene concentration and agronomic performance of reconstituted hybrids developed through MAS at Delhi and Dharwad.

<p>DEL: Delhi; DWD: Dharwad; g: gram; t/ha: tonnes/hectare.</p><p>Kernel β-carotene concentration and agronomic performance of reconstituted hybrids developed through MAS at Delhi and Dharwad.</p

Plant-, tassel- and ear- characteristics of original and β-carotene rich versions of the parental inbreds.

<p><b>A</b>: VQL1; <b>B</b>: Improved VQL1; <b>C</b>: HKI1105; <b>D</b>: Improved HKI1105; <b>E</b>: HKI161; <b>F</b>: Improved HKI161.</p

Pedigree details of recurrent and donor parents used in the study.

<p>Pedigree details of recurrent and donor parents used in the study.</p