Characterization of post‐haustorial resistance to sunflower broomrape

Abstract

The development of durable resistance to broomrape (Orobanche cumana Wallr.) in sunflower (Helianthus annuus L.) requires detailed characterization of the genetic and physiological bases of resistance. The objective of the present study was to map the resistance gene accurately, and to characterize the mechanism of resistance to broomrape observed in a sunflower inbred line (PHSC1102). PHSC1102, which was consistently resistant against race F and race G populations of broomrape, was crossed with PHSC1201, which was susceptible to races F and G. A mapping population of 150 F 2 genotypes was phenotyped by evaluating F 2:3 families for resistance to broomrape races F GV and G TK . The use of single nucleotide polymorphism (SNP) markers mapped the Or SII gene to Linkage Group 4 (LG4) of the sunflower genome. Minirhizotron and histological studies of the resistant line revealed that the attachment of broomrape to host roots was similar in both the resistant and susceptible lines and that the resistance was observed at a late stage (i.e., after tubercle development). Interestingly, the resistance of the PHSC1102 line was associated with the production of phenolic compounds, which were hypothesized to restrict the parasite's growth. This research provides novel and valuable information about the host-parasite interactions between sunflower and broomrape.Abbreviations: DAB, 3,3-diaminobenzidine; LG, linkage group; LOD, logarithm of odds; PBS, phosphate-buffered saline; PCR, polymerase chain reaction; QTL, quantitative trait loci; SNP, single nucleotide polymorphism; TBO, toluidine blue O.

Genetic and physiological characterization of sunflower resistance provided by the wild-derived OrDeb2 gene against highly virulent races of Orobanche cumana Wallr

“…Although low germination-inducing varieties can be resistant to broomrape infection, and their identification is an obvious target for breeding (Yoder and Scholes 2010), results from this study indicated that resistance conferred by Or Deb2 is not related to low induction of O. cumana germination, since germination of O. cumana seeds was similarly stimulated by exudates of the resistant line DEB2 and the rest of the sunflower lines tested, including the susceptible line B117. These results agree with those reported for the resistance genes Or3, Or7, and Or SII (Antonova and Ter Borg 1996;Duriez et al 2019;Martín-Sanz et al 2020), and also with those indicated for the proprietary race F resistant genotype HE-399999 (Echevarria-Zomeño et al 2006), whose genetics has not been reported. Our study has however detected varietal differences for germination induction of P. ramosa, a broomrape species with a broad host range that can infect sunflower (Parker et al 2013) and whose seeds do not germinate with low concentrations of sunflower-specific sesquiterpene lactones (Cala et al 2017) as it occurs in other Phelipanche species (Joel et al 2011).…”

“…Second, it has been shown that the sunflower region on Chr3 in which the O. cumana resistance gene Or5 was initially mapped, carries in fact different non-allelic genes controlling also resistance to O. cumana (Imerovski et al 2013(Imerovski et al , 2016(Imerovski et al , 2019. Third, another major gene (Or SII ) conferring resistance to this parasitic weed has also been mapped to sunflower Chr4 (Hassan et al 2008;Martín-Sanz et al 2020). This gene confers post-attachment resistance to races F and G of O. cumana and was mapped between the two SNP markers HT298 and HT183, which map, respectively, 6.6 and 1 cM distal and proximal to Or SII (Hassan et al 2008), and between non-published proprietary markers (Martín-Sanz et al 2020).…”

Image analysis for the automatic phenotyping of Orobanche cumana tubercles on sunflower roots

“…The density of rhizotrons was 166 plants/m 2 under our conditions, meaning that 1992 plants/m 2 could be screened per year. However, even though the RhizOSun system allows information on resistance at early stages of the interaction, it has not been tested for phenotyping late stages of resistance, such as posthaustorial resistance [ 13 ], affecting emergence development. Therefore, phenotyping with RhizOSun and phenotyping in pots/fields are complementary approaches.…”

“…Some resistance genes act on the early stages of the interaction, such as incompatible attachment [ 12 ] or tubercle necrosis [ 2 ]. Posthaustorial/secondary resistances affect later stages of the interaction as the Orobanche shoot develops [ 13 ]. Although no information is available on most resistance genes, HaOr7, a race F resistance gene, has recently been identified and encodes a leucine-rich-repeat receptor-like kinase [ 12 ].…”

The Effect of Virulence and Resistance Mechanisms on the Interactions between Parasitic Plants and Their Hosts

“…This showed that the number of healthy tubercles at stage 3 is the trait best correlating with the number of emerged broomrape shoots in the field. Other researchers have counted the necrotic tubercles (post-haustorial/secondary resistances) in the resistant line or the number of successfully established radicles allowing the development of root tubercles on the susceptible line [32][33][34]. Another strategy to determine the successful infection by parasitic plants is to measure host plant parameters such as height, weight/biomass, photosynthesis, leaf CO 2 assimilation rates, transpiration rate, stomatal conductance, vapor pressure deficit, and leaf carbon, nitrogen, potassium, phosphorus, and magnesium levels [35][36][37].…”