Genetic analysis and characterisation of Cmowf, a gene controlling the white petal colour phenotype in pumpkin (Cucurbita moschata D)

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Abstract

Flower colour, as an important morphological marker, plays an essential role in improving the identification efficiency of the purity seed in hybrid production. However, the molecular mechanism of white-flower trait has not been reported in pumpkin (Cucurbita moschata D.). In this study, we obtained a white-flower mutant (wf) through the ethyl methane sulfonate (EMS) mutagenesis of inbred line N87 (yellow flower). F2 populations were then constructed by crossing wf mutant and N87 plant to fine map the genes controlling white-flower trait in pumpkin. Phenotypic identification revealed that carotenoid content significantly decreased in the petals of wf mutants compared with N87 plants. Genetic analysis indicated that the white flower mutant trait was controlled by a single recessive gene, Cmowf. Using bulked segregant analysis and KASP phenotyping, Cmowf was mapped to a 762 kb region on chromosome 14 containing three annotated genes. Among them, a nonsynonymous single-nucleotide polymorphisms mutation was identified only in CmoCh14G005820 gene, which encoded a DUF1997 family protein. Compared with CmoDUF1997 amino acid sequences between the wf mutants and N87 plants, the critical amino acid mutations (early termination of amino acids) occurred in wf mutants, so CmoCh14G005820 was predicted as a potential candidate for controlling the white-flower trait. RNA-sequencing analysis revealed that the expression of CmoCh14G005820 and most genes involved in carotenoid biosynthesis was significantly downregulated in wf mutants, whereas the expression of several genes responsible for carotenoid degradation was upregulated in wf mutants. This finding suggested that carotenoid metabolism may participate in the formation of flower colour in pumpkin. Overall, our results provided a theoretical basis for understanding the genetic mechanisms underlying white-flower formation in pumpkin.

QTL mapping of nitrogen use efficiency traits at the seedling and maturity stages under different nitrogen conditions in barley (Hordeum vulgare L.)

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Abstract

Nitrogen (N) is an essential element for plant growth and development. The identification and utilization of N use efficiency (NUE) loci are essential for breeding high NUE cultivars. In this study, 15 NUE traits were measured in a recombinant inbred line population containing 121 lines derived from the cross between a cultivated barley (Baudin) and a wild barley (CN4027). The hydroponic culture was conducted with normal N and low N treatments in one-time frame, and field trials were conducted with N sufficiency and N deficiency treatments in two growing seasons. Twenty-two quantitative trait loci (QTLs) and four clusters were detected. Of them, the five stable QTLs Qgna.sau-3H for grain N concentration, Qtna.sau-3H for total N accumulation per plant, Qnhi.sau-3H for N harvest index, Qnutegy.sau-3H for N utilization efficiency for grain yield and Qanutedm.sau-3H.1 for N utilization efficiency for aboveground dry matter were co-located on chromosome 3H flanked by the markers bpb6282426 and bpb4786261. These two novel QTL clusters simultaneously controlled NUE traits at the seedling and maturity stages. Some genes related to NUE traits in intervals of the major QTLs were predicted. The significant relationships between NUE traits and agronomic and physiological traits were detected and discussed. In conclusion, this study uncovers the most promising genomic regions for the marker-assisted selection of NUE traits to improve NUE in barley.

Genome‐wide dissection and haplotype analysis identified candidate loci for nitrogen use efficiency under drought conditions in winter wheat

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Abstract

Climate change causes extreme conditions like prolonged drought, which results in yield reductions due to its effects on nutrient balances such as nitrogen uptake and utilization by plants. Nitrogen (N) is a crucial nutrient element for plant growth and productivity. Understanding the mechanistic basis of nitrogen use efficiency (NUE) under drought conditions is essential to improve wheat (Triticum aestivum L.) yield. Here, we evaluated the genetic variation of NUE-related traits and photosynthesis response in a diversity panel of 200 wheat genotypes under drought and nitrogen stress conditions to uncover the inherent genetic variation and identify quantitative trait loci (QTLs) underlying these traits. The results revealed significant genetic variations among the genotypes in response to drought stress and nitrogen deprivation. Drought impacted plant performance more than N deprivation due to its effect on water and nutrient uptake. GWAS identified a total of 27 QTLs with a significant main effect on the drought-related traits, while 10 QTLs were strongly associated with the NUE traits. Haplotype analysis revealed two different haplotype blocks within the associated region on chromosomes 1B and 5A. The two haplotypes showed contrasting effects on N uptake and use efficiency traits. The in silico and transcript analyses implicated candidate gene coding for cold shock protein. This gene was the most highly expressed gene under several stress conditions, including drought stress. Upon validation, these QTLs on 1B and 5A could be used as a diagnostic marker for NUE and drought tolerance screening in wheat.

Identification of robust yield quantitative trait loci derived from cultivated emmer for durum wheat improvement

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Abstract

Durum wheat (Triticum turgidum ssp. durum L.) is an important world food crop used to make pasta products. Compared to bread wheat (Triticum aestivum L.), fewer studies have been conducted to identify genetic loci governing yield-component traits in durum wheat. A potential source of diversity for durum is its immediate progenitor, cultivated emmer (T. turgidum ssp. dicoccum). We evaluated two biparental populations of recombinant inbred lines (RILs) derived from crosses between the durum lines Ben and Rusty and the cultivated emmer wheat accessions PI 41025 and PI 193883, referred to as the Ben × PI 41025 (BP025) and Rusty × PI 193883 (RP883) RIL populations, respectively. Both populations were evaluated under field conditions in three seasons with an aim to identify quantitative trait loci (QTLs) associated with yield components and seed morphology that were expressed in multiple environments. A total of 44 and 34 multi-environment QTLs were identified in the BP025 and RP883 populations, respectively. As expected, genetic loci known to govern domestication and development were associated with some of the QTLs, but novel QTLs derived from the cultivated emmer parents and associated with yield components including spikelet number, grain weight, and grain size were identified. These QTLs offer new target loci for durum wheat improvement, and toward that goal, we identified five RILs with increased grain weight and size compared to the durum parents. These materials along with the knowledge of stable QTLs and associated markers can help to expedite the development of superior durum varieties.

Understanding role of roots in plant response to drought: Way forward to climate‐resilient crops

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Abstract

Drought stress leads to a significant amount of agricultural crop loss. Thus, with changing climatic conditions, it is important to develop resilience measures in agricultural systems against drought stress. Roots play a crucial role in regulating plant development under drought stress. In this review, we have summarized the studies on the role of roots and root-mediated plant responses. We have also discussed the importance of root system architecture (RSA) and the various structural and anatomical changes that it undergoes to increase survival and productivity under drought. Various genes, transcription factors, and quantitative trait loci involved in regulating root growth and development are also discussed. A summarization of various instruments and software that can be used for high-throughput phenotyping in the field is also provided in this review. More comprehensive studies are required to help build a detailed understanding of RSA and associated traits for breeding drought-resilient cultivars.

New liguleless (lg2) maize stocks: Genetic resources for leaf architectural and haploid induction rate assessment studies

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Abstract

Liguleless mutants produce defective ligules and auricles and, consequently, have more upright leaves than their ligulate counterparts, making them useful genetic material for plant architectural studies. Besides, owing to the recessive nature and amenability of the liguleless trait to phenotyping at the seedling stage, liguleless mutants are popularly used for ‘proof-of-concept’ demonstration and assessment of haploid induction rate (HIR) of haploid inducer lines (HILs) in maize. The commonly used liguleless testers in maize are of temperate origin and are challenging to use and maintain under tropical/sub-tropical conditions. In the present study, liguleless lines (V 601, V 602, V 603 and V 604) derived from crosses between agronomically superior locally adapted tropical ligulate lines (V 407 and CM 152) and liguleless donors of temperate origin (PDH-3 and PDH-8) were evaluated for different agro-morphological traits. Liguleless line V 602 was also used as a tester to assess the HIR of haploid inducer line EC937890 (CIM2GTAILP2). The results showed a mean HIR of 12.42% for EC937890, consistent with the HIR reported in other studies, thus demonstrating the efficacy of V 602 as a tester for determining HIR. The agronomically superior liguleless maize lines reported in this study will, therefore, be a valuable resource for leaf architectural studies, assessment of HIR of candidate HILs and maintenance of high HIR in the HILs presently in wide use in the doubled haploid (DH) programmes. Additionally, these genetic stocks carry the liguleless trait in genetic backgrounds with known heterotic affinity with early maturity Indian public maize germplasm and, therefore, can be used directly as parents in hybrid development programmes.

New Melastomataceae hosts of Chrysoporthe species in Brazil

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Abstract

The angiosperm Melastomataceae family is one of the most abundant plant families worldwide and in the Brazilian cerrado, with significant environmental importance in regenerating degraded areas, especially those previously occupied by pastures. Recently, Chrysoporthe Gryzenhout & M. J. Wingf. species were reported in Brazil, causing canker, branch dieback, and mortality in native Melastomataceae. This leads to the demand for further investigation and understanding of these pathosystems. During field surveys, typical signs and symptoms associated with Chrysoporthe infection were found in Rhynchanthera grandiflora (Aubl.) D C. and Miconia theaezans (Bonpl.) Cogn. in southern Minas Gerais. Through phylogenetic analysis of the BT1 and BT2 fragments of the β-tubulin gene and morphological characterization of the isolates obtained, it was possible to identify C. doradensis Gryzenh. & M. J. Wingf. occurring in R. grandiflora and C. puriensis M. E. S. Oliv., T. P. F. Soar. & M. A. Ferr. occurring in R. grandiflora and M. theaezans. Furthermore, pathogenicity assays confirmed the pathogenicity of both species to their hosts.