RESUMO
Global chickpea production is restricted by Ascochyta blight caused by the necrotrophic fungi Ascochyta rabiei. Developing locally adapted disease-resistant cultivars is an economically and environmentally sustainable approach to combat this disease. However, the lack of genetic variability in cultivated chickpeas and breeder-friendly markers poses a significant challenge to Ascochyta blight-resistant breeding efforts in chickpeas. In this study, we screened the mini-core germplasm of Cicer reticulatum against a local pathotype of A. rabiei. A modified mini-dome screening approach resulted in the identification of five accessions showing a high level of resistance. The mean disease score of resistant accessions ranged between 1.75 ± 0.3 and 2.88 ± 0.4 compared to susceptible accessions, where the mean disease score ranged between 3.59 ± 0.62 and 8.86 ± 0.14. Genome-wide association study revealed a strong association on chromosome 5, explaining â¼58% of the phenotypic variance. The underlying region contained two candidate genes (Cr_14190.1_v2 and Cr_14189.1_v2), the characterization of which showed the presence of a DNA-binding domain (cl28899 and cd18793) in Cr_14190.1_v2 and its orthologs in C. arietinum, whereas Cr_14190.1_v2 carried an additional N-terminal domain (cl31759). qPCR expression analysis in resistant and susceptible accessions revealed â¼3- and â¼110-fold higher transcript abundance for Cr_14189.1 and Cr_14190.1, respectively.
RESUMO
The Ph1 gene is the principal regulator of homoeologous chromosome pairing control (HECP) that ensures the diploid-like meiotic chromosome pairing behavior of polyploid wheat. The HECP control was speculated to have evolved after the first event of polyploidization. With the objective to accurately understand the evolution of the HECP control, wild emmer wheat accessions previously known to differ for HECP control were characterized for the structure and expression of the candidate Ph1 gene, C-Ph1. The C-TdPh1-5A and 5B gene copies of emmer wheat showed 98 and 99% DNA sequence similarity respectively with the corresponding hexaploid wheat copies. Further, the C-TdPh1-5B carried the C-Ph1-5B specific structural changes and transcribed three splice variants as observed in the hexaploid wheat. Further, single nucleotide changes differentiating accessions varying for HECP control were identified. Analyzed by quantitative expression analysis, the wild emmer accessions with HECP control showed ~ 10,000-fold higher transcript abundance of the C-TdPh1-5B copy during prophase-I compared to accessions lacking the control. Differential transcriptional regulation of C-TdPh1-5B splice variants further revealed that C-Ph1-5Balt1 variant is mainly responsible for differential accumulation of C-Ph1-5B copy in accessions with HECP control. Taken together, these results showed that the HECP control evolved via transcriptional regulation of splice variants during meiosis.
Assuntos
Processamento Alternativo , Pareamento Cromossômico , Meiose , Proteínas de Plantas/genética , Poliploidia , Triticum/genética , Cromossomos de Plantas , Evolução Molecular , Dosagem de Genes , Regulação da Expressão Gênica , Genes de PlantasRESUMO
Development of nutrient efficient cultivars depends on effective identification and utilization of genetic variation. We characterized a set of 276 pre-breeding lines (PBLs) for several traits at different levels of nitrogen application. These PBLs originate from synthetic wheats and landraces. We witnessed significant variation in various traits among PBLs to different nitrogen doses. There was ~ 4-18% variation range in different agronomic traits in response to nitrogen application, with the highest variation for the biological yield (BY) and the harvest index. Among various agronomic traits measured, plant height, tiller number, and BY showed a positive correlation with nitrogen applications. GWAS analysis detected 182 marker-trait associations (MTAs) (at p-value < 0.001), out of which 8 MTAs on chromosomes 5D, 4A, 6A, 1B, and 5B explained more than 10% phenotypic variance. Out of all, 40 MTAs observed for differential nitrogen application response were contributed by the synthetic derivatives. Moreover, 20 PBLs exhibited significantly higher grain yield than checks and can be selected as potential donors for improved plant nitrogen use efficiency (pNUE).