Ecotypic variation in the response of Arabidopsis thaliana to Phytophthora cinnamomi

Robinson, Louise H.; Cahill, David M.

doi:10.1071/ap02064

Cited by 35 publications

(49 citation statements)

References 36 publications

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“…Phytophthora infestans, P. brassicae, P. cinnamomi, Colletotrichum trifolii, and C. higginsianum), and necrotrophs (e.g. Alternaria brassicicola and Botrytis cinerea; Holub et al, 1995;Rehmany et al, 2000;Roetschi et al, 2001;Robinson and Cahill, 2003;O'Connell et al, 2004;Thaler et al, 2004). Signaling pathways controlled by SA, JA, and/or ET are involved in controlling the interaction of Arabidopsis with these pathogens.…”

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confidence: 99%

Rice Blast Fungus (Magnaporthe oryzae) Infects Arabidopsis via a Mechanism Distinct from That Required for the Infection of Rice

et al. 2008

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Magnaporthe oryzae is a hemibiotrophic fungal pathogen that causes rice (Oryza sativa) blast. Although M. oryzae as a whole infects a wide variety of monocotyledonous hosts, no dicotyledonous plant has been reported as a host. We found that two rice pathogenic strains of M. oryzae, KJ201 and 70-15, interacted differentially with 16 ecotypes of Arabidopsis (Arabidopsis thaliana). Strain KJ201 infected all ecotypes with varying degrees of virulence, whereas strain 70-15 caused no symptoms in certain ecotypes. In highly susceptible ecotypes, small chlorotic lesions appeared on infected leaves within 3 d after inoculation and subsequently expanded across the affected leaves. The fungus produced spores in susceptible ecotypes but not in resistant ecotypes. Fungal cultures recovered from necrotic lesions caused the same symptoms in healthy plants, satisfying Koch's postulates. Histochemical analyses showed that infection by the fungus caused an accumulation of reactive oxygen species and eventual cell death. Similar to the infection process in rice, the fungus differentiated to form appressorium and directly penetrated the leaf surface in Arabidopsis. However, the pathogenic mechanism in Arabidopsis appears distinct from that in rice; three fungal genes essential for pathogenicity in rice played only limited roles in causing disease symptoms in Arabidopsis, and the fungus seems to colonize Arabidopsis as a necrotroph through the secretion of phytotoxic compounds, including 9,12-octadecadienoic acid. Expression of PR-1 and PDF1.2 was induced in response to infection by the fungus, suggesting the activation of salicylic acid-and jasmonic acid/ethylene-dependent signaling pathways. However, the roles of these signaling pathways in defense against M. oryzae remain unclear. In combination with the wealth of genetic and genomic resources available for M. oryzae, this newly established pathosystem allows comparison of the molecular and cellular mechanisms underlying pathogenesis and host defense in two well-studied model plants.

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confidence: 99%

Rice Blast Fungus (Magnaporthe oryzae) Infects Arabidopsis via a Mechanism Distinct from That Required for the Infection of Rice

et al. 2008

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“…For example, in glasshouse studies, observed this phenomenon in inoculated etiolated shoots and feeder roots across clonal avocado material of rootstock varieties 'G755', 'G1033', 'G6' and 'Duke 7'. It has also been observed in a range of other plant species , Robinson & Cahill, 2003, Allardyce et al, 2012. found that viable P. cinnamomi could be isolated up to 6 mm ahead of the lesion front after inoculation in tip-inoculated 'Duke 7' roots.…”

Section: Discussionmentioning

confidence: 76%

“…Callose deposition also appears to be an effective defence response of Arabidopsis to P. cinnamomi infection (Robinson & Cahill, 2003). The study found that the presence of callose papillae was commonly associated with a redirection of the plane of hyphal growth at 90°, but induction of callose was not closely correlated with resistance.…”

Section: Structural Barriersmentioning

confidence: 76%

“…In interactions between many plants and P. cinnamomi, roots of resistant species or varieties can restrict the lesion to the inoculation site, whereas unimpeded necrosis extends along susceptible roots. For example, Allardyce et al (2012) observed Z. mays to be resistant in comparison to Lupinus angustifolius, observed that lesion length correlated with susceptibility across 13 plant species classified as resistant and susceptible, observed the same phenomenon in resistant vs. susceptible lines of Eucalyptus marginata, Robinson & Cahill (2003) observed it across 20 ecotypes of Arabidopsis thaliana and found the same occurrence in clonal avocado rootstock material. In resistant plants, encystment and penetration still occur, but resistant plants are able to mount an effective defence response through biochemical or structural means.…”

Section: Mechanisms Of Resistancementioning

confidence: 84%

“…Yet, in other interactions of P. cinnamomi with different hosts, encystment of P. cinnamomi zoospores did not always correlate with host susceptibility. In histological studies on eucalypt seedlings (Malajczuk et al, 1977, Tippett et al, 1976, Arabidopsis (Robinson & Cahill, 2003) and four different Persea spp., (Ho & Zentmyer, 1977) only minor differences in P. cinnamomi zoospore attraction and encystment were observed on roots between resistant and susceptible hosts. Hinch & Weste (1979) found that in interactions between P. cinnamomi and 13 different Australian plant species, no correlation was present among penetration of the epidermis, cortex and vascular tissue, and known field susceptibility.…”

Section: Zoospore Attraction and Encystmentmentioning

confidence: 99%

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Evaluation of phytophthora root rot resistance in avocado

Neilsen¹

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Avocado trees (Persea americana) affected by Phytophthora root rot caused by Phytophthora cinnamomi produce copious amounts of small, poor quality fruit and without intervention, affected trees eventually die. Current management practices involve an integrated approach to disease management, including planting on well-draining soil with a high total cation exchange capacity, application of organic mulch, carefully monitored organic and inorganic nutrition, phosphonate applications and the use of tolerant rootstock varieties. Selection of rootstocks in breeding programs is a time consuming process involving extensive glasshouse and field screening but little is understood about the mechanisms underlying tolerance in elite selections. The overall aim of the research described in this thesis was to identify phenotypic differences across a range of avocado rootstock varieties with varying degrees of resistance/ susceptibility that may be associated with known field susceptibility.The first hypothesis tested in this thesis is that field resistant rootstock varieties have greater root regenerative ability than susceptible varieties. This hypothesis was tested using a glasshouse study of inherent root growth of seedlings as well as an inoculation study to investigate root system health and wilting in response to infection by P. cinnamomi. To investigate whether inherent root growth correlates with known field susceptibility of seedling rootstock varieties, a 2-pot root regeneration system was successfully developed and varietal differences in root: shoot ratio across nine seedling avocado varieties assessed. Seedling 'Hass' produced the greatest amount of feeder roots relative to the surface area of mature leaves, although overall differences between seedling varieties were not significant. The main finding of the glasshouse root growth studies was that there were no strong indications that inherent root growth and root system necrosis correlated with known field susceptibility.The second hypothesis tested was whether increased surface feeder root growth of mature trees and other tree physiology attributes such as stored non-structural starch, yield, tree health and growth measurements such as tree height and canopy volume have any association with known field susceptibility. At one experimental site, feeder root growth of mature trees measured over two seasons was not significantly different between rootstocks 'Dusa' and 'SHSR-04' and no significant differences or associations were found in stored starch, tree health, yield or tree growth parameters.At the second experimental site, there were also no significant differences detected in feeder root growth of rootstock varieties. Significant differences in tree physiology were detected among rootstocks with 'Velvick' having the strongest determinate vegetative growth measured and the highest level of stored non-structural starch, although it wasn't significantly higher than fieldsusceptible 'Reed'. Overall, results of field studies at both sites indicated that t...

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