Diversity, Distribution, and Evolution of Solanum bulbocastanum Late Blight Resistance Genes

Abstract

Knowledge on the evolution and distribution of late blight resistance genes is important for a better understanding of the dynamics of these genes in nature. We analyzed the presence and allelic diversity of the late blight resistance genes Rpi-blb1, Rpi-blb2, and Rpi-blb3, originating from Solanum bulbocastanum, in a set of tuber-bearing Solanum species comprising 196 different taxa. The three genes were only present in some Mexican diploid as well as polyploid species closely related to S. bulbocastanum. Sequence analysis of the fragments obtained from the Rpi-blb1 and Rpi-blb3 genes suggests an evolution through recombinations and point mutations. For Rpi-blb2, only sequences identical to the cloned gene were found in S. bulbocastanum accessions, suggesting that it has emerged recently. The three resistance genes occurred in different combinations and frequencies in S. bulbocastanum accessions and their spread is confined to Central America. A selected set of genotypes was tested for their response to the avirulence effectors IPIO-2, Avr-blb2, and Pi-Avr2, which interact with Rpi-blb1, Rpi-blb2, and Rpi-blb3, respectively, as well as by disease assays with a diverse set of isolates. Using this approach, some accessions could be identified that contain novel, as yet unknown, late blight resistance factors in addition to the Rpi-blb1, Rpi-blb2, and Rpi-blb3 genes.

DNA Markers for Selection of Late Blight Resistant Potato Breeding Lines

“…Based on the DNA sequences of the four candidate genes, a total of 24 genespecific primer pairs were selected; 15 primers were based on publications [6] …”

“…J101 (6x) was developed from a somatic fusion between S. bulbocastanum (2x) and S. tuberosum (4x). S. bulbocastanum is a wild potato variety that is resistant to P. infestans and was likely a source of the resistance genes [6]. Genomic DNA from the four parental clones was used to verify the PCR-based markers (Table 1).…”

“…However, P. infestans was able to overcome the resistance conferred by these R genes [5]. Breeding programs have also used resistance genes derived from other wild species, such as S. bulbocastanum (2n = 2x = 24) which contains several R genes [6]. Rpi-blb1 gene, also known as RB gene, is located on chromosome 8 and was found to confer broad spectrum resistance against P. infestans when introduced into potatoes [7] [8].…”

In Vitro Culture as a Stressful Factor Triggers Changes in Polyphenols, Flavonoids and Antioxidant Activity in Somatic Hybrids between Solanum tuberosum and S. bulbocastanum and their Respective Parents

“…This wild species has effective resistance mechanisms to different abiotic stress factors, but also to some biotic agents, like aphids (Alvarez et al, 2006), nematodes (Austin et al, 1993) or fungi (Lokossou et al, 2010). In this context, higher TPC, TFC and AA were actually expected for the wild species, all three physiological traits taken into consideration being actively involved in the resistance mechanisms (Lattanzio et al, 2006;Mierziak et al, 2014).…”

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

“…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). …”