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.

Qualitative dynamics of waxy maize (Jikenuo 19) in different harvest times

Jikenuo 19 was used as experimental material, and six harvest times were set to study the effects of different harvest times on grain quality and gelatinization characteristics, so as to provide reference for the harvest time and quality improvement of waxy maize varieties. The results showed that when the harvest time was 27 days after pollination, the sensory and cooking quality score of Jikenuo 19 was the highest. Starch content increased with the delay of harvest time, while protein and soluble sugar content decreased. With the delay of harvest time, the peak viscosity, valley viscosity, final viscosity, disintegration value, recovery value and peak time all showed a trend of first increasing and then decreasing. Compared with starch and soluble sugar, the effect of protein in grain on gelatinization characteristics was higher. The present findings reveal that the best harvest time was 27 days after pollination, which will provide reference for determining the best harvest time and improving grain quality. Bangladesh J. Bot. 50(3): 987-992, 2021 (September) Special

Proteomics reveals the effects of drought stress on the kernel development and starch formation of waxy maize

Background Kernel development and starch formation are the primary determinants of maize yield and quality, which are considerably influenced by drought stress. To clarify the response of maize kernel to drought stress, we established well-watered (WW) and water-stressed (WS) conditions at 1–30 days after pollination (dap) on waxy maize (Zea mays L. sinensis Kulesh). Results Kernel development, starch accumulation, and activities of starch biosynthetic enzymes were significantly reduced by drought stress. The morphology of starch granules changed, whereas the grain filling rate was accelerated. A comparative proteomics approach was applied to analyze the proteome change in kernels under two treatments at 10 dap and 25 dap. Under the WS conditions, 487 and 465 differentially accumulated proteins (DAPs) were identified at 10 dap and 25 dap, respectively. Drought induced the downregulation of proteins involved in the oxidation–reduction process and oxidoreductase, peroxidase, catalase, glutamine synthetase, abscisic acid stress ripening 1, and lipoxygenase, which might be an important reason for the effect of drought stress on kernel development. Notably, several proteins involved in waxy maize endosperm and starch biosynthesis were upregulated at early-kernel stage under WS conditions, which might have accelerated endosperm development and starch synthesis. Additionally, 17 and 11 common DAPs were sustained in the upregulated and downregulated DAP groups, respectively, at 10 dap and 25 dap. Among these 28 proteins, four maize homologs (i.e., A0A1D6H543, B4FTP0, B6SLJ0, and A0A1D6H5J5) were considered as candidate proteins that affected kernel development and drought stress response by comparing with the rice genome. Conclusions The proteomic changes caused by drought were highly correlated with kernel development and starch accumulation, which were closely related to the final yield and quality of waxy maize. Our results provided a foundation for the enhanced understanding of kernel development and starch formation in response to drought stress in waxy maize.

Longevity of genepool maize seeds under model conditions

Aim. To determine genotypic features of seed longevity of different subspecieses of maize - carriers of the corresponding genes under model conditions. Methods. Accessions of the maize (Zea mays L.) gene pool: dent maize (subsp.indentata), semi-dent (subsp. semindentata), waxy (subsp.ceratina) wx, popcorn (subsp.everta), sweet maize (subsp.saccharata.) sh were investigated in the conditions of model experiment "accelerated aging". Results. The seed longevity of studied maize genotypes was established in the conditions of model experiment on indicators of germination energy, seed germination and morphophysiological indexes of sprouting. The applied conditions of accelerated aging had a negligible effect on the studied parameters, which corresponded to the initial stages of seed aging. Variations in morphophysiological indexes were observed. Conclusions. The highest sensitivity to accelerated aging was found for sweet (sh) and waxy maize (wx). Variation of morphophysiological parameters of seedlings in experimental and control variants, seed longevity of the studied varieties are discussed.Keywords: gene pool, seeds, maize, subspecies, longevity.