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Ledesma-Ramires, L.

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Ledesma-Ramires
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Ledesma-Ramires, L.

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    Relationship between the number of partial resistance genes and the response to leaf rust in wheat genotypes
    (INIA, 2018) Ledesma-Ramires, L.; Solís Moya, E.; Ramirez-Pimentel, J.G.; Dreisigacker, S.; Huerta-Espino, J.; Aguirre-Mancilla, C.L.; Mariscal-Amaro, L.A.
    The adult plant resistance conferred by genes with an additive effect is an alternative to achieve durable resistance to leaf rust caused by the fungus Puccinia triticina in wheat (Triticum spp.) The objective of this study was to know the response to this disease in bread wheat genotypes that possess the partial resistance genes Lr34, Lr46, Lr67 and Lr68. The severity level of the disease was measured in 280 wheat genotypes in three locations. The presence or absence of partial resistance genes was determined by molecular markers for each gene in 245 wheat genotypes. The different combinations of adult plant genes resulted in the genotypes were classified into nine groups. In 77 of these genotypes, the markers were negative for these genes. The Lr34, Lr46, Lr67 and Lr68 genes were identified individually in 48, 48, 5, and 14 genotypes, respectively. The combination of two genes, Lr34+Lr46, Lr34+Lr68 and Lr46+Lr68, was determined in 18, 17, and 12 genotypes, respectively. Only in six genotypes the combination Lr34+Lr46+Lr68 was identified. The genotypes with the Lr34, Lr46, Lr67 and Lr68 genes in a unique form showed 21%, 24.8%, 21.9% and 21.8% of rust severity on average, respectively. An additive effect was observed in the combinations of two genes, and higher effect in the combinations that included the Lr34 gene since genotypes with this gene combination showed on average 11.4% of rust severity. The combination of three genes Lr34+Lr46+Lr68 provide greater protection in the genotypes with 9.7% of rust severity on average.
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    Harnessing genetic potential of wheat germplasm banks through impact-oriented-prebreeding for future food and nutritional security
    (Nature Publishing Group, 2018) Singh, S.; Vikram, P.; Sehgal, D.; Burgueño, J.; Sharma, A.R.; Singh, S.K.; Sansaloni, C.; Joynson, R.; Brabbs, T.; Ortiz, C.; Solís Moya, E.; Velu, G.; Gupta, N.; Sidhu, H.S.; Basandrai, A.K.; Basandrai, D.; Ledesma-Ramires, L.; Suaste-Franco, M.P.; Fuentes Dávila, G.; Ireta Moreno, J.; Sonder, K.; Vaibhav K. Singh; Sajid Shokat; Shokat, S.; Mian A. R. Arif; Khalil A. Laghari; Puja Srivastava; Bhavani, S.; Satish Kumar; Pal, D.; Jaiswal, J.P.; Kumar, U.; Harinder K. Chaudhary; Crossa, J.; Payne, T.S.; Imtiaz, M.; Sohu, V.S.; Singh, G.P.; Bains, N.; Hall, A.J.W.; Pixley, K.V.
    The value of exotic wheat genetic resources for accelerating grain yield gains is largely unproven and unrealized. We used next-generation sequencing, together with multi-environment phenotyping, to study the contribution of exotic genomes to 984 three-way-cross-derived (exotic/elite1//elite2) pre-breeding lines (PBLs). Genomic characterization of these lines with haplotype map-based and SNP marker approaches revealed exotic specific imprints of 16.1 to 25.1%, which compares to theoretical expectation of 25%. A rare and favorable haplotype (GT) with 0.4% frequency in gene bank identified on chromosome 6D minimized grain yield (GY) loss under heat stress without GY penalty under irrigated conditions. More specifically, the ‘T’ allele of the haplotype GT originated in Aegilops tauschii and was absent in all elite lines used in study. In silico analysis of the SNP showed hits with a candidate gene coding for isoflavone reductase IRL-like protein in Ae. tauschii. Rare haplotypes were also identified on chromosomes 1A, 6A and 2B effective against abiotic/biotic stresses. Results demonstrate positive contributions of exotic germplasm to PBLs derived from crosses of exotics with CIMMYT’s best elite lines. This is a major impact-oriented pre-breeding effort at CIMMYT, resulting in large-scale development of PBLs for deployment in breeding programs addressing food security under climate change scenarios.
    Publication