The Rpi‐blb2 gene from Solanum bulbocastanum is an Mi‐1 gene homolog conferring broad‐spectrum late blight resistance in potato

Abstract

SummaryThe necessity to develop potato and tomato crops that possess durable resistance against the oomycete pathogen Phytophthora infestans is increasing as more virulent, crop-specialized and pesticide resistant strains of the pathogen are rapidly emerging. Here, we describe the positional cloning of the Solanum bulbocastanum-derived Rpi-blb2 gene, which even when present in a potato background confers broadspectrum late blight resistance. The Rpi-blb2 locus was initially mapped in several tetraploid backcross populations, derived from highly resistant complex interspecific hybrids designated ABPT (an acronym of the four Solanum species involved: S. acaule, S. bulbocastanum, S. phureja and S. tuberosum), to the same region on chromosome 6 as the Mi-1 gene from tomato, which confers resistance to nematodes, aphids and white flies. Due to suppression of recombination in the tetraploid material, fine mapping was carried out in a diploid intraspecific S. bulbocastanum F1 population. Bacterial artificial chromosome (BAC) libraries, generated from a diploid ABPT-derived clone and from the resistant S. bulbocastanum parent clone, were screened with markers linked to resistance in order to generate a physical map of the Rpi-blb2 locus. Molecular analyses of both ABPTand S. bulbocastanum-derived BAC clones spanning the Rpi-blb2 locus showed it to harbor at least 15 Mi-1 gene homologs (MiGHs). Of these, five were genetically determined to be candidates for Rpi-blb2. Complementation analyses showed that one ABPT-and one S. bulbocastanum-derived MiGH were able to complement the susceptible phenotype in both S. tuberosum and tomato. Sequence analyses of both genes showed them to be identical. The Rpi-blb2 protein shares 82% sequence identity to the Mi-1 protein.Significant expansion of the Rpi-blb2 locus compared to the Mi-1 locus indicates that intrachromosomal recombination or unequal crossing over has played an important role in the evolution of the Rpi-blb2 locus. The contrasting evolutionary dynamics of the Rpi-blb2/Mi-1 loci in the two related genomes may reflect the opposite evolutionary potentials of the interacting pathogens.

DNA Markers for Selection of Late Blight Resistant Potato Breeding Lines

“…In this study, four P. infestans resistance genes named Rpi-blb1 [8], Rpi-blb2 [15], Rpi-blb3 [16] and Rpi-bt1 [17] were used based on prior publications.…”

Why genetically modified crops?

“…Late blight caused by Phytophthora infestans is a very destructive disease of potato and tomato, resulting in $6.7 billion in annual losses worldwide [17]. Several resistance genes have been cloned from wild potato relatives that confer resistance to potato late blight [18][19][20]. Transgenic lines show resistance in the field, though it is unlikely that any one blight resistance gene will be durable, and appropriate and varying combinations of resistance genes need to be defined.…”

Agrotransformación y evaluación de la resistencia a Phytophthora infestansen Solanum tuberosum L. variedad Désirée

“…Asimismo, la búsqueda de nuevas fuentes de resistencia ha impulsado el uso de genes de la misma especie o de una familia cercana a la planta que se desee modificar (Storck et al 2012). Un ejemplo de ello son los genes R (genes de resistencia) de la familia de genes NB-LRR (Nucleotide binding and leucine-rich repeat), provenientes de la especie silvestre Solanum bulbocastanum (Collinge et al 2008, Jacobs et al 2010Pel et al 2009).…”

“…En consecuencia, la obtención de plantas con resistencia a P. infestans es apremiante. Es por este motivo, que el estudio de los genes R a tenido gran atención, como es el caso del gen Rpi-blb2, el cual presenta un amplio espectro de resistencia a P. infestans (van der Vossen et al 2005). Se ha demostrado que este gen evolucionó más recientemente que el gen RB / Rpi-blb1 y codifica una proteína de 1,267 aminoácidos, cuya secuencia génica presenta 82% de similitud con el gen Mi-1 de tomate, el cual también confiere resistencia a nematodos, áfidos y a la mosca blanca (Nombela et al 2003, Lokossou et al 2010).…”