HM. Clause

Davis, CA, United States

HM. Clause

Davis, CA, United States
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Lindbo J.A.,HM Clause | Falk B.W.,University of California at Davis
Phytopathology | Year: 2017

Worldwide, plant viruses cause serious reductions in marketable crop yield and in some cases even plant death. In most cases, the most effective way to control virus diseases is through genetically controlled resistance. However, developing virus-resistant (VR) crops through traditional breeding can take many years, and in some cases is not even possible. Because of this, the demonstration of the first VR transgenic plants in 1985 generated much attention. This seminal report served as an inflection point for research in both basic and applied plant pathology, the results of which have dramatically changed both basic research and in a few cases, commercial crop production. The typical review article on this topic has focused on only basic or only applied research results stemming from this seminal discovery. This can make it difficult for the reader to appreciate the full impact of research on transgenic virus resistance, and the contributions from fundamental research that led to translational applications of this technology. In this review, we take a global view of this topic highlighting the significant changes to both basic and applied plant pathology research and commercial food production that have accumulated in the last 30 plus years. We present these milestones in the historical context of some of the scientific, economic, and environmental drivers for developing specific VR crops. The intent of this review is to provide a single document that adequately records the significant accomplishments of researchers in both basic and applied plant pathology research on this topic and how they relate to each other. We hope this review therefore serves as both an instructional tool for students new to the topic, as well as a source of conversation and discussion for how the technology of engineered virus resistance could be applied in the future. © 2017 The American Phytopathological Society.


Tentchev D.,French National Institute for Agricultural Research | Verdin E.,French National Institute for Agricultural Research | Marchal C.,Clause | Jacquet M.,Vilmorin | And 2 more authors.
Journal of General Virology | Year: 2011

Tomato spotted wilt virus (TSWV; genus Tospovirus, family Bunyaviridae) genetic diversity was evaluated by sequencing parts of the three RNA genome segments of 224 isolates, mostly from pepper and tomato crops in southern Europe. Eighty-three per cent of the isolates showed consistent clustering into three clades, corresponding to their geographical origin, Spain, France or the USA, for the three RNA segments. In contrast, the remaining 17% of isolates did not belong to the same clade for the three RNA segments and were shown to be reassortants. Among them, eight different reassortment patterns were observed. Further phylogenetic analyses provided insights into the dynamic processes of the worldwide resurgence of TSWV that, since the 1980s, has followed the worldwide dispersal of the western flower thrips (Frankliniella occidentalis) tospovirus vector. For two clades composed essentially of Old World (OW) isolates, tree topology suggested a local re-emergence of indigenous TSWV populations following F. occidentalis introductions, while it could not be excluded that the ancestors of two other OW clades were introduced from North America contemporarily with F. occidentalis. Finally, estimation of the selection intensity that has affected the evolution of the NSs and nucleocapsid proteins encoded by RNA S of TSWV suggests that the former could be involved in the breakdown of resistance conferred by the Tsw gene in pepper. © 2011 SGM.


Pascal T.,French National Institute for Agricultural Research | Aberlenc R.,Japan Agro Services SA | Confolent C.,French National Institute for Agricultural Research | Hoerter M.,HM CLAUSE | And 3 more authors.
Euphytica | Year: 2017

Peach powdery mildew is one of the major diseases of the peach. Various sources of resistance to PPM have thus been identified, including the single dominant locus Vr2 carried by the peach rootstock ‘Pamirskij 5’. To map Vr2, a linkage map based on microsatellite markers was constructed from the F2 progeny (WP2) derived from the cross ‘Weeping Flower Peach’ × ‘Pamirskij 5’. Self-pollinations of the parents were also performed. Under greenhouse conditions, all progenies were scored after artificial inoculations in two classes of reactions to PPM (resistant/susceptible). In addition to Vr2, WP2 segregated for three other traits from ‘Weeping Flower Peach’: Rm1 for green peach aphid resistance, Di2 for double-flower and pl for weeping-growth habit. With their genomic locations unknown or underdocumented, all were phenotyped as Mendelian characters and mapped: Vr2 mapped at the top of LG8, at 3.3 cM, close to the CPSCT018 marker; Rm1 mapped at the bottom of LG1, at a position of 116.5 cM, cosegregating with the UDAp-467 marker and in the same region as Rm2 from ‘Rubira’®; Di2 mapped at 28.8 cM on LG6, close to the MA027a marker; and pl mapped at 44.1 cM on LG3 between the MA039a and SSRLG3_16m46 markers. Furthermore, this study revealed, for the first time, a pseudo-linkage between two traits of the peach: Vr2 and the Gr locus, which controls the red/green color of foliage. The present work therefore constitutes a significant preliminary step for implementing marker-assisted selection for the four major traits targeted in this study. © 2017, Springer Science+Business Media B.V.


Harel-Beja R.,Newe Ya'ar Research Center | Tzuri G.,Newe Ya'ar Research Center | Portnoy V.,Newe Ya'ar Research Center | Lotan-Pompan M.,Newe Ya'ar Research Center | And 26 more authors.
Theoretical and Applied Genetics | Year: 2010

A genetic map of melon enriched for fruit traits was constructed, using a recombinant inbred (RI) population developed from a cross between representatives of the two subspecies of Cucumis melo L.: PI 414723 (subspecies agrestis) and 'Dulce' (subspecies melo). Phenotyping of 99 RI lines was conducted over three seasons in two locations in Israel and the US. The map includes 668 DNA markers (386 SSRs, 76 SNPs, six INDELs and 200 AFLPs), of which 160 were newly developed from fruit ESTs. These ESTs include candidate genes encoding for enzymes of sugar and carotenoid metabolic pathways that were cloned from melon cDNA or identified through mining of the International Cucurbit Genomics Initiative database (http://www. icugi. org/). The map covers 1,222 cM with an average of 2.672 cM between markers. In addition, a skeleton physical map was initiated and 29 melon BACs harboring fruit ESTs were localized to the 12 linkage groups of the map. Altogether, 44 fruit QTLs were identified: 25 confirming QTLs described using other populations and 19 newly described QTLs. The map includes QTLs for fruit sugar content, particularly sucrose, the major sugar affecting sweetness in melon fruit. Six QTLs interacting in an additive manner account for nearly all the difference in sugar content between the two genotypes. Three QTLs for fruit flesh color and carotenoid content were identified. Interestingly, no clear colocalization of QTLs for either sugar or carotenoid content was observed with over 40 genes encoding for enzymes involved in their metabolism. The RI population described here provides a useful resource for further genomics and metabolomics studies in melon, as well as useful markers for breeding for fruit quality. © 2010 Springer-Verlag.


Mercier J.,HM. Clause | Muscara M.J.,HM. Clause | Davis A.R.,HM. Clause
Plant Disease | Year: 2014

In September and October 2012, powdery mildew was detected on watermelon (Citrullus lanatus var. lanatus) plants of various breeding lines growing in field plots in Davis, California. Plants had partially necrotic leaves, yellowing to brown in color, with white surface mycelium and faint sporulation. No teleomorph was observed. Infected leaves were collected for examination and a spore suspension of the field isolate was made in water with 0.01% Tween 20 to spray inoculate watermelon seedlings of cultivar Dixie Lee with two true leaves. Plants were incubated in a growth chamber (22 to 26°C, 12-h photoperiod) for approximately 10 days, until sporulation was apparent. Microscopic observation of conidial chains showed that they had clearly crenate edges indicative of Podosphaera xanthii (4). To confirm the identity of the pathogen, we used Podosphaera-specific primers PFITS-F (5′-CCAACTCGTGCTGAGTGT-3′) and PF5.8-R (5′-TGTTGGTTTCTTTTCCTCCG-3′) to amplify and sequence the internal transcribed spacer regions of the nuclear rDNA. The 326-bp sequence had 98% homology to the GenBank sequence (accessions JQ340082.1 and AB774158.1) for P. xanthii. Infected 'Dixie Lee' leaves were used to make a spore suspension (approximately 5 × 104 conidia/ml) as described above to inoculate watermelon, melon, and squash seedlings (2 to 3 plants per cultivar) in a greenhouse. It caused severe symptoms on all watermelon plants cv. Charleston 76, P8, and Sugar Baby in the form of a powdery mildew with surface mycelium and chains of conidia, with leaves becoming gradually more necrotic and eventually dying, with the appearance of a melting down. Non-inoculated plants did not develop symptoms. The isolate also infected all squash plants 'Zucchini Elite' and melon powdery mildew differentials Iran H and 'Védrantais.' On these plants, the pathogen produced a powdery mildew (white surface mycelium with sporulation) but did not cause extensive necrosis. All other melon powdery mildew differentials ('PMR5,' 'PMR45,' WMR29, MR1, PI 124112, and PI 313970) did not develop any powdery mildew. A follow-up test in a growth chamber (22 to 26°C, 12-h photoperiod) with the same set of species and cultivars gave the same results. Based on these results, we conclude that this isolate belongs to race 1W (1,2). The presence of race 1W could have implications in disease management for this crop in the Central Valley of California as most cultivars are not resistant to it and the disease has been shown to cause severe damage in other states (1,3). © The American Phytopathological Society.

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