New phenotyping approaches for evaluating the common bean response to Meloidogyne incognita: use of quantitative PCR associated with nematological assessment indices.

• Grant number: 23/14857-2
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• Start date: February 01, 2024
• End date: January 31, 2026
• Field of knowledge: Agronomical Sciences - Agronomy - Plant Health
• Principal Investigator: Maria Lúcia Carneiro Vieira
• Grantee: Líllian Beatriz Januário Bibiano
• Host Institution: Escola Superior de Agricultura Luiz de Queiroz (ESALQ). Universidade de São Paulo (USP). Piracicaba , SP, Brazil
• Associated research grant: 20/02755-2 - Common bean response to the root knot nematode Meloidogyne incognita: QLT mapping, transcriptional profile and functional studies of candidate resistance genes, AP.TEM

Abstract

The use of resistant cultivars is the most effective method for managing plant-parasitic nematodes. Genetic diversity is confirmed among M. incognita isolates despite their assexual mode of reproduction. Different isolates can show unique patterns of compatibility with their hosts, which can lead to resistance breakdown. Phenotyping plays a crucial role in the evaluation of nematode-resistant genotypes. The ability to quantify the nematode infestation is important for the implementation of effective control strategies. Among nematological assessment indices, the reproduction fator (RF=FP/IP) quantifies the ratio between the final (FP) and the initial or inoculated nematode population (IP). The RF is acknowledged as one of the most reliable methods for assessing resistance. Other parameters, including the gall index (GI) and egg mass index (EMI) are crucial variables to integrate with RF values. Phenotyping is equally essential to associate genotype and phenotype for quantitative trait loci (QTL) mapping for nematode resistance. In prior experiments, phenotyping based on gall index (GI) and the number of egg masses was used in our laboratory to investigate genomic regions linked to quantitative resistance. As a result, four QTLs were identified in association with gall formation. However, no QTL was found to be linked to the number of egg masses phenotype. The application of more sensitive approaches for phenotyping, such as molecular methods based on quantitative PCR (qPCR) has the potential to uncover additional QTLs. Despite the availability of qPCR protocols for the identification of M. incognita, none of these methodologies were designed to quantify the nematode population when assessing the resistance of common bean genotypes. For the efficient selection of resistant genotypes, it is essential to validate a pathogen quantification methodology associated with the usual parameters in nematological evaluations. Therefore, the postdoctoral fellow will be responsible for coordinating the phenotyping experiments of the Recombinant Inbred Lines (RILs) derived from the biparental cross 'IAC-Tybatã' x 'Branquinho,' as well as the steps involved in the integration of resistance evaluation methods: RF, GI, EMI, the number of nematodes per gram of root, and molecular quantification by qPCR.