Biology subjects

Chhetry, M.

Publications and source records attributed to Chhetry, M..

4 recordsLinked to original sources

bioRxiv2025

Buying time - increasing yield potential in wheat by extending stem elongation duration

Extending the duration of the stem elongation (SE) phase between terminal spikelet (TS) and anthesis has often been proposed as an avenue to increase wheat yield. However, accurate determination of TS is labour intensive, and existing evidence is often based on a limited number of genotypes observed under controlled conditions. Here, a Buster x Charger population comprising 108 doubled haploid lines was grown across four year-sites under UK field conditions. TS was recorded through meristem dissection and SE duration was measured as the time between TS and ear emergence (EE). Mixed model analysis across year-sites revealed high heritabilities (H2yield = 0.66, H2TS = 0.93, H2SE = 0.89, H2EE = 0.95) and strong genetic correlations between yield and the phenology traits SE and EE (rg = 0.56 and rg = 0.6, respectively). While SE duration was mainly driven by EE, independent QTL for TS suggest that SE could be modified without affecting EE. The positive effect of SE duration on yield was attributed to increased grain number per area as well as increased grain weight, through independent QTL. Although validation in broader genetic backgrounds is needed, these QTL may offer opportunities for further yield increase in a physiological breeding framework. HighlightsO_LILonger stem elongation duration increases grain number. C_LIO_LILonger stem elongation duration increases grain weight. C_LIO_LIIndependent QTL suggest the timing of stem elongation as well as its effect on yield components may be independently selectable. C_LI

genetics↗

bioRxiv2023

An improved Nicotiana benthamiana bioproduction chassis provides novel insights into nicotine biosynthesis

The model plant Nicotiana benthamiana is an increasingly attractive organism for the production of high-value, biologically active molecules. However, N. benthamiana accumulates high levels of pyridine alkaloids, in particular nicotine, which complicates the downstream purification processes. Here, we report the assembly of an improved N. benthamiana genome as well as the generation of low-nicotine lines by CRISPR/Cas9-based inactivation of berberine bridge enzyme-like proteins (BBLs). Triple as well as quintuple mutants accumulated 3-4 times less nicotine than the respective control lines. The availability of lines without functional BBLs allowed us to probe their catalytic role in nicotine biosynthesis, which has remained obscure. Notably, chiral analysis revealed that the enantiomeric purity of nicotine was fully lost in the quintuple mutants. In addition, precursor feeding experiments showed that these mutants cannot facilitate the specific loss of C6 hydrogen that characterizes natural nicotine biosynthesis. Our work delivers an improved N. benthamiana chassis for bioproduction and opens the possibility that BBLs are the sought-after coupling enzymes in nicotine biosynthesis.

plant biology↗

bioRxiv2022

Improved SpCas9 and LbCas12a genome editing systems in Brassica oleracea and Brassica napus

We report highly efficient genome editing in Brassica species. We compare the efficiency of targeted mutagenesis using four Streptococcus pyogenes Cas9 (SpCas9) systems in Brassica oleracea and Brassica napus over 3 target genes and five guides to identify two which show a striking improvement to our first published system (Lawrenson et al., 2015). Targeted mutagenesis occurred in up to 100% of T0 plants with the improved systems, compared to 20% in the original system. This is the only reported comparison of SpCas9 systems we are aware of in Brassica species. Secondly, we report the first successful use of Lachnospiraceae bacterium Cas12a (LbCas12a) in Brassica oleracea. We test three LbCas12a coding sequences and two guide architectures against one target gene using four guides. From this we identify the best performing combination of our novel, multi-intron coding sequence and a ribozyme flanked guide expression cassette. In this case 68% of T0 plants contained targeted mutations. Heritability of LbCas12a mutations is shown. We show that our two useful and novel LbCas12a coding sequences have utility in Brassica species.

genomics↗

bioRxiv2019

CONSTRUTION OF A GENETIC MAP OF RILs DERIVED FROM WHEAT (T. AESTIVUM L.) VARIETIES PAMYATII AZIEVA X PARAGON USING HIGH-THROUGHPUT SNP GENOTYPING PLATFORM KASP - COMPETATIVE ALLELE SPECIFIC PCR

The main purposes of the study were i) to develop a first mapping population for bread wheat grown in Kazakhstan, ii) to construct its genetic map for further identification of genes associated with important agronomic traits.\n\nTo the best of our knowledge this is the first segregating population and genetic map developed for Kazakh bread wheat. The work is an example of how plant breeding programs in Kazakhstan have started successfully deploying next generation plant breeding methods.\n\nThe KASP (Compatative Allele Specific PCR) technology of LGC Group and SNP DNA-markers have been exploited to genotype and build a genetic map of the segregating population. The total length of the map was 1376 cM. A total 157 out of initial 178 SNP markers used formed 26 linkage groups leaving 1 duplicated and 20 unassigned markers. The threshold distance between markers was set [≤] 30 cM. Therefore, two linkage groups were obtained for chromosomes such as 2A, 2B, 2D, 3A, 5A, 6B and 7A. Despite one duplicated and 20 unassigned markers, the 157 KASP SNP markers that were mapped spanned A, B and D genomes of wheat. Kosambi Mapping function was employed to calculate recombination units between makers. RILs were developed through SSD method up to F4 generation. Almost 97% of identified alleles were useful in evaluating the populations genetic diversity; the remaining 3% showed no outcome. As a result, 77 DNA markers were mapped for A, 74 for B and 27 for D genomes. The mapping population will be genotyped using high marker density array planform such as Illumina iSelect to obtain a genetic map with a relatively high coverage. Then, the population and high-resolution genetic map will be used to identify genes influencing wheat adaptation in Kazakhstan.

genomics↗