Genome-wide association studies for earliness, MYMIV resistance, and other associated traits in mungbean (Vigna radiata L. Wilczek) using genotyping by sequencing approach.

Yellow mosaic disease (YMD) remains a major constraint in mungbean (Vigna radiata (L.)) production; while short-duration genotypes offer multiple crop cycles per year and help in escaping terminal heat stress, especially during summer cultivation. A comprehensive genotyping by sequencing (GBS)-based genome-wide association studies (GWAS) analysis was conducted using 132 diverse mungbean genotypes for traits like flowering time, YMD resistance, soil plant analysis development (SPAD) value, trichome density, and leaf area. The frequency distribution revealed a wide range of values for all the traits. GBS studies identified 31,953 high-quality single nucleotide polymorphism (SNPs) across all 11 mungbean chromosomes and were used for GWAS. Structure analysis revealed the presence of two genetically distinct populations based on ΔK. The linkage disequilibrium (LD) varied throughout the chromosomes and at r2 = 0.2, the mean LD decay was estimated as 39.59 kb. Two statistical models, mixed linear model (MLM) and Bayesian-information and Linkage-disequilibrium Iteratively Nested Keyway (BLINK) identified 44 shared SNPs linked with various candidate genes. Notable candidate genes identified include FPA for flowering time (VRADI10G01470; chr. 10), TIR-NBS-LRR for mungbean yellow mosaic India virus (MYMIV) resistance (VRADI09G06940; chr. 9), E3 ubiquitin-protein ligase RIE1 for SPAD value (VRADI07G28100; chr. 11), WRKY family transcription factor for leaf area (VRADI03G06560; chr. 3), and LOB domain-containing protein 21 for trichomes (VRADI06G04290; chr. 6). In-silico validation of candidate genes was done through digital gene expression analysis using Arabidopsis orthologous (compared with Vigna radiata genome). The findings provided valuable insight for marker-assisted breeding aiming for the development of YMD-resistant and early-maturing mungbean varieties.

Correction to: Pollen staining is a rapid and cost­effective alternative to marker­assisted selection for recessive waxy1 gene governing high amylopectin in maize.

[This corrects the article DOI: 10.1007/s12298-022-01240-1.].

Pollen staining is a rapid and cost-effective alternative to marker-assisted selection for recessive waxy1 gene governing high amylopectin in maize.

Waxy maize is popular for food-, feed- and industrial usage. It possesses a recessive waxy1 (wx1) gene that enhances amylopectin to ~ 95-100%, compared to ~ 70-75% in traditional maize. Marker-assisted selection (MAS) is a preferred approach to converting normal maize into a waxy version. However, it requires specialized expertise, a well-equipped laboratory, and high cost. Here, pollen staining was used as an alternative approach to MAS. BC1F1, BC1F2 and BC2F2 populations in seven genetic backgrounds segregating for the wx1 gene were used. Pollens treated with iodine-potassium iodide showed that wild types (Wx1Wx1) were dark purple, while waxy pollens (wx1wx1) exhibited red colour. Heterozygotes (Wx1wx1) showed a mix of both dark purple and red colour. Staining of endosperm flour also confirmed the same findings. Wx1-based genotyping using phi022 and wx2507F/RG confirmed the same genotypic status. The average amylopectin among genotypes having red coloured pollens was 97.6%, while it was 72.5% among dark purple. Heterozygotes with both dark purple and red pollens had 85.2% amylopectin. Pollen staining showed complete agreement with the genotyping as well as amylopectin contents. Pollen staining saved 81% cost, and 54% time compared to MAS. This is the first report on the utilization of pollen staining for selecting the wx1 allele in segregating populations used for the development of waxy maize hybrids. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-022-01240-1.

Combining higher accumulation of amylopectin, lysine and tryptophan in maize hybrids through genomics-assisted stacking of waxy1 and opaque2 genes.

Waxy maize rich in amylopectin has emerged as a preferred food. However, waxy maize is poor in lysine and tryptophan, deficiency of which cause severe health problems. So far, no waxy hybrid with high lysine and tryptophan has been developed and commercialized. Here, we combined recessive waxy1 (wx1) and opaque2 (o2) genes in the parental lines of four popular hybrids (HQPM1, HQPM4, HQPM5, and HQPM7) using genomics-assisted breeding. The gene-based markers, wx-2507F/RG and phi057 specific for wx1 and o2, respectively were successfully used to genotype BC1F1, BC2F1 and BC2F2 populations. Background selection with > 100 SSRs resulted in recovering > 94% of the recurrent parent genome. The reconstituted hybrids showed 1.4-fold increase in amylopectin (mean: 98.84%) compared to the original hybrids (mean: 72.45%). The reconstituted hybrids also showed 14.3% and 14.6% increase in lysine (mean: 0.384%) and tryptophan (mean: 0.102%), respectively over the original hybrids (lysine: 0.336%, tryptophan: 0.089%). Reconstituted hybrids also possessed similar grain yield (mean: 6248 kg/ha) with their original versions (mean: 6111 kg/ha). The waxy hybrids with high lysine and tryptophan assume great significance in alleviating malnutrition through sustainable and cost-effective means. This is the first report of development of lysine and tryptophan rich waxy hybrids using genomics-assisted selection.