Distribution and frequency of a gene for resistance to white pine blister rust in natural populations of sugar pine

1992 ◽  
Vol 70 (7) ◽  
pp. 1319-1323 ◽  
Author(s):  
Bohun B. Kinloch Jr.

The gametic frequency of a dominant allele (R) for resistance to white pine blister rust, a disease caused by an introduced pathogen (Cronartium ribicola), in natural populations of sugar pine was estimated by the kind of leaf symptom expressed after artificial inoculation of wind-pollinated seedlings from susceptible seed–parent genotypes (rr). Gene frequency increased clinally from near 0 in the southern Cascade Range to 0.08 in the southern Sierra Nevada, but it was not correlated with any major climatic gradient. Because R expresses a typical hypersensitivity response to pathogenesis, it has probably always functioned in disease resistance. A candidate pathogen for this function is C. occidentale, cause of pinyon blister rust, and a close relative of C. ribicola. Increase in allele frequency was positively associated with the proximity of sugar pine to single-leaf pinyon pine populations. Although sugar pine is not presently a natural host of pinyon rust, R may be a relict gene that protected sugar pine from this endemic pathogen in recent geologic epochs, when both pines are known to have been more intimately associated. Key words: Cronartium ribicola, genetic resistance, Pinus lambertiana, population genetics.

2003 ◽  
Vol 93 (6) ◽  
pp. 691-694 ◽  
Author(s):  
Bohun B. Kinloch ◽  
Richard A. Sniezko ◽  
Gayle E. Dupper

The distribution and frequency of the Cr2 gene for resistance to white pine blister rust (Cronartium ribicola) in western white pine (Pinus monticola) was surveyed in natural populations of the host by inoculation of open-pollinated seedlings from 687 individual seed parents from throughout most of the species' range. Because Cr2 is dominant and results in a conspicuous hypersensitive reaction (HR) in pine needles, the phenotype can readily be detected in offspring of susceptible seed parents fertilized by unknown Cr2 donors in the ambient pollen cloud. Gametic frequencies of Cr2 were thus determined as the proportion of total challenged seedlings that were pollen receptors exhibiting the Cr2 phenotype. Zygotic frequencies, the proportion of seed parents with progeny that segregated in Mendelian ratios for the Cr2 phenotype to the total number of parents, were a complementary, though less precise, measure. Cr2 frequency was rare overall, ranging from 0.004 to 0.008 in the Sierra Nevada to about 0.001 in the central Cascade Range; it was undetectable further north in the Cascades, as well as in the Rocky Mountains and Coast Mountains of the United States and Canada. The diminishing frequency of Cr2 from the southern and central Sierra Nevada northward mirrors that of Cr1 in sugar pine (P. lambertiana) and points to this region as the origin of both genes. We rationalize that this coincidence may have resulted from protection that these genes may have conferred on both species to an endemic pine stem rust congeneric with C. ribicola (C. occidentale) in recent geologic epochs.


Plant Disease ◽  
2010 ◽  
Vol 94 (4) ◽  
pp. 461-464 ◽  
Author(s):  
D. T. Dalton ◽  
J. D. Postman ◽  
K. E. Hummer

Hosts for the fungus Cronartium ribicola, causal agent of white pine blister rust (WPBR), include five-needle pines as aecial hosts, and currants and gooseberries as uredinial/telial hosts. Aeciospores produced on diseased pine, and urediniospores produced on diseased Ribes plants, can infect Ribes foliage. Resistance and susceptibility for both spore types have been reported for Ribes; however, the comparative infectivity of these spore types on clonal Ribes nigrum genotypes is under-described. Immunity, resistance, and susceptibility to WPBR resides at a clonal level in Ribes. Previous studies have emphasized fungal diversity or forestry considerations, rather than horticultural aspects. The objective of this study was to determine if aeciospores and urediniospores were equally infective to specific genotypes of black currant, Ribes nigrum, with differential responses. A family of 51 black currant genotypes from a cross between a known-immune cultivar containing the Cr gene and a susceptible cultivar was examined. Single-leaf softwood cuttings of each of these genotypes were artificially inoculated with a spore solution and incubated in airtight plastic containers within a growth chamber. Inoculations were replicated three times for each spore type. Twenty-two of the F1 genotypes did not develop uredia after artificial inoculation. These may be immune; 22 developed uredia after exposure to both types of inoculum, and were susceptible; whereas seven exhibited differential responses and may have some mechanism for resistance to WPBR other than the Cr gene. The infectivity of aeciospores and urediniospores was not significantly different on specific Ribes genotypes. Either spore type can therefore be considered equally effective as inoculum when screening for WPBR resistance or immunity in horticultural settings.


1996 ◽  
Vol 74 (3) ◽  
pp. 456-460 ◽  
Author(s):  
Bohun B. Kinloch Jr. ◽  
Gayle E. Dupper

Genetically pure lines of the mononucleate (haploid) stage of Cronartium ribicola can be grown by isolating mycelium from single spots on infected white pine needles or by culturing single basidiospores on defined media preconditioned by cell-free diffusates of massed germinating basidiospores. Although growth is initially slow, cultures can be increased rapidly by alternately subculturing from solid to liquid media and back again indefinitely. The ability to culture pure haploid clones has important implications for studying the genetic structure and sexual behavior of rust populations and the nature of virulence. Keywords: white pine blister rust, sugar pine, virulence.


1999 ◽  
Vol 89 (3) ◽  
pp. 192-196 ◽  
Author(s):  
Bohun B. Kinloch ◽  
Gayle E. Dupper

Tests for Mendelian segregation of virulence and avirulence in Cronartium ribicola, causal agent of white pine blister rust, to a major gene (R) for resistance in sugar pine were made using haploid basidiospore progenies from single diploid telia as inoculum on resistant genotypes. The telia were sampled from a small deme in the Siskyou Mountains of northern California, where a few mature sugar pines known to be Rr genotypes had become infected after withstanding the chronic blister rust epidemic for several decades and where intermediate frequencies of virulence in the ambient basidiospore population were subsequently measured. Infection type on inoculated seedlings with R was qualitative: all progenies of 81 single telia tested over 3 different years were either virulent (compatible) or avirulent (inducing hypersensitive necrosis), never a mixture of both reactions. The complete absence of heterozygotes in the telia population is strong evidence that virulence is not controlled by a nuclear gene. The data are consistent with earlier tests showing that basidiospore inoculum derived from aeciospores isolated from infected Rr trees produced mostly (>90%) virulent reactions on R— seedlings. The evidence indicates that transmission of virulence is uniparental via the cytoplasm of aeciospores. Exchange of spermatia between haploid thalli does not appear to be involved.


1996 ◽  
Vol 72 (6) ◽  
pp. 637-638 ◽  
Author(s):  
Jean A. Bérubé

White pine seedlings were treated with triadimefon two weeks prior to natural inoculation with Cronartium ribicola and were observed for two growth seasons. During the second growth season in the greenhouse the incidence of blister rust symptoms was 70.8% for the untreated controls, whereas only 3.8% of the treated seedlings showed symptoms of blister rust. Triadimefon offers effective protection against white pine blister rust infection and would enable the production of bare root seedlings in areas prone to blister rust infection.


2002 ◽  
Vol 92 (3) ◽  
pp. 278-280 ◽  
Author(s):  
Bohun B. Kinloch ◽  
Gayle E. Dupper

Four of eight white pine species native to western North America surveyed for resistance to white pine blister rust by artificial inoculation showed classical hypersensitive reactions (HR) at frequencies ranging from very low to moderate. Mendelian segregation, indicating a single dominant allele for resistance (Cr3), was observed in southwestern white pine (Pinus strobiformis), as it was previously in sugar pine (P. lambertiana, Cr1) and western white pine (P. monticola, Cr2). HR was present at a relatively high frequency (19%) in one of five bulk seed lot sources of limber pine (P. flexilis), and was also presumed to be conditioned by a single gene locus, by analogy with the other three species. HR was not found in whitebark pine (P. albcaulis), Mexican white pine (P. ayacahuite), foxtail pine (P. balfouriana), or Great Basin bristlecone pine (P. longaeva), but population and sample sizes in these species may have been below the level of detection of alleles in low frequency. When challenged by (haploid) inocula from specific locations known to harbor virulence to Cr1 or Cr2, genotypes carrying these alleles and Cr3 reacted differentially, such that inoculum virulent to Cr1 was avirulent to Cr2, and inoculum virulent to Cr2 was avirulent to Cr1. Neither of these two inocula was capable of neutralizing Cr3. Although blister rust traditionally is considered an exotic disease in North America, these results, typical of classic gene-for-gene interactions, suggest that genetic memory of similar encounters in past epochs has been retained in this pathosystem.


2009 ◽  
Vol 85 (5) ◽  
pp. 745-755 ◽  
Author(s):  
Pengxin Lu ◽  
Darren Derbowka

White pine blister rust (caused by Cronartium ribicola J.C. Fisch.) is a primary cause of poor survival and growth of eastern white pine (Pinus strobus L.) and has contributed to the species’ decline across its range. Genetic resistance to C. ribicola is generally weak in eastern white pine, possibly owing to the absence of meaningful resistance alleles. Integrating major resistance genes from Eurasian 5-needle pine species to P. strobus has been demonstrated to be effective through traditional plant breeding approaches. This paper provides a review of progress after more than half a century of breeding and testing in Ontario. Key words: Pinus strobus, white pine blister rust, genetic resistance, interspecific hybridization


1977 ◽  
Vol 55 (9) ◽  
pp. 1148-1155 ◽  
Author(s):  
Bohun B. Kinloch Jr. ◽  
Julia L. Littlefield

Resistance to white pine blister rust in sugar pine is simply inherited and can be identified by distinct needle spot morphs. After artificial inoculation at 2 years of age, seedlings from selfed and full-sib families developed either 'fleck' spots, characterized by a pale, yellow margin with a necrotic fleck in the center, or they developed typical yellow or red spots (or both). Seedlings segregated for needle spot reaction in monohybrid ratios with fleck dominant. Mycelium in secondary needle tissues of fleck spots, in contrast to yellow and red spots, was relatively sparse and confined by dense tannin deposits. Bark infection and mortality was heavy on seedlings with yellow and red spots. On seedlings with fleck spots, no bark symptoms developed from secondary needle infection but small, abortive cankers did develop on some of these seedlings as a result of primary needle infection. These atypical cankers did not sporulate or spread extensively, and had healed by the 2nd year after inoculation. The gene responsible for the fleck reaction thus elicits a hypersensitive response in secondary needles and, apparently, in bark tissues as well.


PLoS ONE ◽  
2016 ◽  
Vol 11 (5) ◽  
pp. e0154267 ◽  
Author(s):  
Jun-Jun Liu ◽  
Danelle Chan ◽  
Yu Xiang ◽  
Holly Williams ◽  
Xiao-Rui Li ◽  
...  

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