Novel genes and tools for weeds management in faba bean

Abstract

Weeds are one of the greatest threats to faba bean (Vicia faba L.) production and herbicide application is known to be the most efficient weed control method. However, the susceptibility of the current cultivars to post emergence herbicide applications impose a limitation for weed control in faba bean. Therefore, the deployment of postemergence herbicide tolerance is desirable in faba bean. To address this, a set of 130 faba bean accessions were screened for their response to the recommended dosages of two herbicides, metribuzin at 250 g a.i. ha−1 and imazethapyr at 75 g a.i. ha−1 at Marchouch and Terbol stations during four seasons between 2014 and 2018. The herbicide damage score along with other phenological and yield related traits were recorded and analyzed to evaluate the effects of post emergence herbicide application on the tested accessions and to select the herbicide tolerant ones. Tolerance to metribuzin and imazethapyr in eight faba bean accessions was confirmed as no significant reduction in grain yield resulted from the herbicide application. Moreover, in the aim to identify superior and broad adapted herbicide tolerant faba bean genotypes and to identify the most discriminating environments for herbicide screening, 37 accessions with different levels of tolerance to the recommended dosages of metribuzin and imazethapyr were selected to further evaluate the performance and stability of their plant height and grain yield across different environments (location x season x herbicide treatment). Data collected at Marchouch and Terbol during four seasons between 2014 and 2019 were used and the evaluation was based on the following stability parameters: cultivar superiority, static stability, Wricke’s eco-valence and Finlay and Wilkinson’s regression model. Differences observed in the genotypes ranking suggest that the evaluation of performance and stability of herbicide tolerant faba beans should be based on a combination of stability parameters. Genotype * environment biplot analysis indicated that the environments representing the metribuzin treatment at Marchouch 2014–2015 and the non-treated treatment at Terbol 2018–2019 are the ideal environments for evaluating faba bean genotypes. Biplots showed also that the metribuzin and imazethapyr tolerant accession IG12983 is the ideal genotype as he showed good and stable plant height and grain yield performance across the environments. Finally, to identify molecular markers associated with key genes imparting tolerance to herbicides the same set of accessions phenotyped before was genotyped using genotyping by sequencing (GBS). The GBS yield 10,794 high quality single nucleotide polymorphisms (SNPs). 10 and 14 SNPs highly associated with phenological and yield related traits under herbicide treatments were identified after conducting Single-trait and Multi-trait Genome Wide Association Studies (GWAS) respectively. Genomic sequences containing herbicide tolerance associated SNPs were aligned against the NCBI database using BLASTX tool and default parameters to annotate candidate genes underlying the causal variants. SNPs from acidic endochitinase, LRR receptor-like serine/threonine-protein kinase RCH1, probable serine/threonine-protein kinase NAK, malate dehydrogenase, photosystem I core protein PsaA and MYB-related protein P-like were significantly associated with herbicide tolerance traits. The identified SNPs will facilitate and fasten the efficient and effective development of herbicide tolerant cultivars and can be used for introgressing herbicide tolerance into desired agronomic background.

Las malas hierbas se consideran como mayor amenaza para la producción de las habas (Vicia faba L.) ya que no se dispone de métodos efectivos de control adecuados particularmente en el estado de postemergencia. En un intento de mejorar la tolerancia a los herbicidas de postemergencia más comunes, se evaluó durante cuatro años la respuesta de una colección de 130 accesiones de habas a las dosis recomendadas de metribuzin (250 g i.a. ha−1) e imazetapir (75 g i.a. ha−1) en condiciones de campo en las estaciones experimentales de Marchouch (Marruecos) y Terbol (Líbano). Estos trabajos han permitido confirmar la tolerancia de ocho accesiones a metribuzin y a imazetapir. Asimismo, se ha estudiado la estabilidad de componentes del rendimiento de 37 accesiones de habas con diferentes niveles de tolerancia a las dosis recomendadas de ambos herbicidas en diferentes ambientes (localidad x año x tratamiento con herbicida). Los resultados mostraron que la estabilidad de la respuesta en habas tolerantes a herbicidas se basa en una combinación de efectos. Los análisis de interacción Genotipo*Ambiente mostraron el tratamiento con metribuzin en Marchouch 2014-2015 y el control sin herbicida en Terbol 2018-2019 son los ideales para evaluar los genotipos de habas con tolerancia a herbicidas. La accesión IG12983 tolerante a ambos herbicidas mostró una altura de planta y rendimiento de grano altos y estables en todos los ambientes. Finalmente, la colección de habas fue genotipada por secuenciación (Genotyping by Sequencing “GBS”), resultando en la identificación de 10.794 polimorfismos de un solo nucleótido (SNP) de alta calidad. El análisis de asociación (Genome Wide Association “GWAS”) permitió la identificación de 10 y 14 SNP altamente asociados con tolerancia a los herbicidas, según se analizara por un solo o por múltiples caracteres, respectivamente. Las secuencias genómicas que contenían SNP asociados con la tolerancia a los herbicidas se alinearon con la base de datos del NCBI utilizando y la herramienta BLASTX y parámetros predeterminados para anotar los genes candidatos subyacentes a las variantes causales. Los SNP de la endoquitinasa ácida, la serina/treonina-proteína quinasa RCH1 similar al receptor LRR, la probable serina/treonina-proteína quinasa NAK, la malato deshidrogenasa, la proteína PsaA del núcleo del fotosistema I y la “MYB”- relacionada con proteína “P-like” se asociaron significativamente con los caracteres de a tolerancia a herbicidas. Estos SNP identificados permitirán acelerar el desarrollo eficiente y eficaz de cultivares tolerantes a herbicidas.