Tightly linked Rps12 and Rps13 genes provide broad-spectrum Phytophthora resistance in soybean

The Phytophtora root and stem rot is a serious disease in soybean. It is caused by the oomycete pathogen Phytophthora sojae. Growing Phytophthora resistant cultivars is the major method of controlling this disease. Resistance is race- or gene-specific; a single gene confers immunity against only a subset of the P. sojae isolates. Unfortunately, rapid evolution of new Phytophthora sojae virulent pathotypes limits the effectiveness of an Rps (“resistance to Phytophthora sojae”) gene to 8–15 years. The current study was designed to investigate the effectiveness of Rps12 against a set of P. sojae isolates using recombinant inbred lines (RILs) that contain recombination break points in the Rps12 region. Our study revealed a unique Rps gene linked to the Rps12 locus. We named this novel gene as Rps13 that confers resistance against P. sojae isolate V13, which is virulent to recombinants that contains Rps12 but lack Rps13. The genetic distance between the two Rps genes is 4 cM. Our study revealed that two tightly linked functional Rps genes with distinct race-specificity provide broad-spectrum resistance in soybean. We report here the molecular markers for incorporating the broad-spectrum Phytophthora resistance conferred by the two Rps genes in commercial soybean cultivars.

KETAHANAN BEBERAPA LADA HASIL PERSILANGAN TERHADAP Phytophthora capsici ASAL LADA

<p>ABSTRAK</p><p>Busuk pangkal batang (BPB) lada yang disebabkan oleh cendawanPhytophthora capsici merupakan masalah utama pada budidaya lada diIndonesia. Penyakit ini telah ditemukan di semua areal produksi lada diIndonesia. Sampai saat ini, saran pengendalian yang dianjurkan adalahpengendalian secara terpadu untuk mengurangi kerugian ekonomi akibatpenyakit ini. Akhir-akhir ini usaha untuk mendapatkan jenis lada yangtahan dilakukan melalui persilangan. Tujuan penelitian ini adalahmengevaluasi ketahanan F1 yang diperoleh dari persilangan beberapatetua. Penelitian dilakukan di laboratorium dan rumah kaca, BalaiPenelitian Tanaman Rempah dan Obat, Bogor, dari Januari sampaiDesember 2005. Dari 400 aksesi hasil persilangan yang ada, dipilih 15aksesi yang menunjukkan hasil yang menjanjikan pada uji pendahuluan.Tiga isolat Phytophthora yang menunjukkan virulensi yang berbedadigunakan sebagai isolat uji. Di laboratorium, helaian daun ke-3 dan 4diambil dari tiap aksesi dan diletakkan dalam kotak yang telah diberi tissuebasah untuk menjaga kelembapannya. Inokulasi secara buatan dilakukandengan meletakkan potongan koloni masing-masing isolat Phytophthorapada permukaan bawah daun. Luas nekrosa yang terbentuk pada masing-masing aksesi diukur dengan leaf area meter setelah diinkubasi selama 72jam. Percobaan di rumah kaca dilakukan dengan cara menyiramkansuspensi zoospora sebanyak 50 ml pada bibit lada dari masing-masingaksesi yang telah berumur 4 bulan. Jumlah tanaman yang mati dihitungsetelah diinkubasi selama 1 bulan. Data hasil pengukuran luas serangandianalisis dengan rancangan faktorial dengan dua faktor untuk duakegiatan di atas. Hasil penelitian menunjukkan bahwa tidak ada interaksiyang nyata antara aksesi dengan isolat Phytophthora yang digunakan, baikpengujian in vitro maupun rumah kaca. Sembilan aksesi menunjukkankerusakan kurang dari 20% saat di laboratorium maupun di rumah kaca,dan aksesi 27-1, 36-31, dan 4-5L menunjukkan kerusakan kurang dari10%. Persilangan lebih lanjut perlu dilakukan pada aksesi-aksesi tersebutuntuk mendapatkan keturunan yang mempunyai ketahanan lebih baik danstabil.</p><p>Kata kunci : Piper nigrum L., Phytophthora, ketahanan, persilangan</p><p>ABSTRACT</p><p>Resistance of Black Pepper Accessions to Phytophthora capsiciFoot rot disease of black pepper caused by Phytophthora capsici ismain constraint in black pepper cultivation in Indonesia. The diseasespread widely over all pepper producing areas in Indonesia. Integratedpest managements are suggested to reduce the economic loss due to thedisease. Recently, breeding program has been developed in Indonesiathrough hybridization to find out promising accessions resistant to foot rotdisease. The objective of the present study was to evaluate the resistanceof F1 progenies obtained from polination of various parents to foot rotdisease. Among 400 accessions of black pepper obtained from breedingprogram, 15 accessions were selected based on previous evaluation. ThreePhytophthora isolates were used as tester in the study. The research wascarried out in laboratory and glass house of Indonesian Spice andMedicinal Crops Research Institute, from January to December 2005. Invitro screening was carried out by inoculating detached third and fourthleaves of each accession. The leaves were set in boxes abaxial surfacefacing up, while wet tissue papers were used to retain air humidity in thebox. The lower leaf surface of each pepper accession was inoculated witha piece of Phytophthora colony then incubated in room temperature. Thewidth of necrotic areas was measured with leaf area meter after the leaveswere incubated for 72 hours. Each treatment was replicated 5 times. Ingreen house experiment, 4 month seedlings of each accession wereinoculated with 50 ml of zoospore suspension (10 5 zoospore/ml), replicated3 times, and each replication consisted of 5 seedlings. The number ofinoculated seedlings was counted after one month of incubation. Bothexperiments were arranged using factorial design with two factors: pepperaccession and Phytophthora isolate. There was no significant interactionbetween black pepper accession and the Phytophthora isolates, neither invitro nor green house. Nine accessions showed disease severity less than20%, and accession number 27-1, 36-31, and 4-5L showed disease severitybelow 10% in both experiments. To obtain better progeny resistant to stemrot disease and more stable, it is suggested to continue this pollinationprogram by using those promising accessions.</p><p>Key words: Piper nigrum L., Phytophthora, resistance, pollination</p>

Fine mapping of a Phytophthora -resistance locus RpsGZ in soybean using genotyping-by-sequencing

Background: Phytophthora root rot (PRR) caused by Phytophthora sojae ( P. sojae ), is one of the most serious limitation to soybean-production in the world. Identification of resistant gene(s) and incorporating them into elite varieties are an effective way for breeding to prevent soybean from being harmed by this disease. A valuable mapping population of 228 F 8:11 recombinant inbred lines (RILs) derived from a cross of resistant cultivar Guizao1 and susceptible cultivar BRSMG68 and a high-density genetic linkage map with an average distance of 0.81 centimorgan (cM) between adjacent bin markers in this population were used to map and explore the candidate gene(s).Results: In this study, the PRR resistance in Guizao1 was controlled by a single Mendelian locus, and was fine mapped to a 367.371-kb genomic region on chromosome 3 that harbours 19 genes, including 7 disease resistance (R)-like genes in the reference Willliams 82 genome. Quantitative real-time PCR assays of possible candidate genes revealed that Glyma.03g05300 was likely involved in PRR resistance.Conclusions: These findings of fine mapping of a novel Rps locus will serve as a basis for cloning, transferring of resistant genes and breeding of P. sojae resistant soybean cultivars through marker-assisted selection.

The CaAP2/ERF064 Regulates Dual Functions in Pepper: Plant Cell Death and Resistance to Phytophthora capsici

Phytophthora blight is one of the most destructive diseases of pepper (Capsicum annuum L.) globally. The APETALA2/Ethylene Responsive Factors (AP2/ERF) genes play a crucial role in plant response to biotic stresses but, to date, have not been studied in the context of Phytophthora resistance in pepper. Here, we documented potential roles for the pepper CaAP2/ERF064 gene in inducing cell death and conferring resistance to Phytophthora capsici (P. capsici) infection. Results revealed that the N-terminal, AP2 domain, and C-terminal of CaAP2/ERF064 protein is responsible for triggering cell death in Nicotiana benthamiana (N. benthamiana). Moreover, the transcription of CaAP2/ERF064 in plant is synergistically regulated by the Methyl-Jasmonate (MeJA) and ethephon (ET) signaling pathway. CaAP2/ERF064 was found to regulate the expression of CaBPR1, which is a pathogenesis-related (PR) gene of pepper. Furthermore, the silencing of CaAP2/ERF064 compromised the pepper plant resistance to P. capsici by reducing the transcript level of defense-related genes CaBPR1, CaPO2, and CaSAR82, while the ectopic expression of CaAP2/ERF064 in N. benthamiana plant elevated the expression level of NbPR1b and enhanced resistance to P. capsici. These results suggest that CaAP2/ERF064 could positively regulate the defense response against P. capsici by modulating the transcription of PR genes in the plant.

Expression profiling across wild and cultivated tomatoes supports the relevance of early miR482/2118 suppression for Phytophthora resistance

Plants possess a battery of specific pathogen resistance ( R- )genes. Precise R- gene regulation is important in the presence and absence of a pathogen. Recently, a microRNA family, miR482/2118, was shown to regulate the expression of a major class of R- genes , nucleotide-binding site leucine-rich repeats ( NBS-LRRs ). Furthermore, RNA silencing suppressor proteins, secreted by pathogens, prevent the accumulation of miR482/2118, leading to an upregulation of R- genes. Despite this transcriptional release of R -genes, RNA silencing suppressors positively contribute to the virulence of some pathogens . To investigate this paradox, we analysed how the regulation of NBS-LRRs by miR482/2118 has been shaped by the coevolution between Phytophthora infestans and cultivated and wild tomatoes. We used degradome analyses and qRT-PCR to evaluate and quantify the co-expression of miR482/2118 and their NBS-LRR targets. Our data show that miR482/2118-mediated targeting contributes to the regulation of NBS-LRRs in Solanum lycopersicum. Based on miR482/2118 expression profiling in two additional tomato species—with different coevolutionary histories with P. infestans —we hypothesize that pathogen-mediated RNA silencing suppression is most effective in the interaction between S. lycopersicum and P. infestans . Furthermore, an upregulation of miR482/2118 early in the infection may increase susceptibility to P. infestans .

Моделювання природної еволюції видів роду Solanum L. cекції Petota Dumort. за фітофторостійкістю

<p>The article presents the theoretical substantiation and experimental data, confirming the natural evolution of potato species from the standpoint of the stability and effectiveness of genetic control of resistance to late blight. Resistant samples of wild potato species which were differ in the appearance of the trait were used as the initial material for research. Artificial infection of seedlings obtained from self-pollination of potato samples with the race of phytophthora (<em>Phytophtora infestans </em>(Mont.) De Bary) 1-11X, Y, Z (25-30 conidia in the view of the microscope, 120 x), which made it possible to identify various types of resistance to fungus. The evolutionary changes of the species, relating their response to the changing of phytopathological situation in their areas have been experimentally proven. The intraspecific variety of <em>S. demissum </em>Lindl and <em>S. stoloniferum </em>Schlechtd. samples by resistance to phytophthora, which manifested both among I1 and among I2, has been identified. Depending on the evolution of the samples, differences in the genetic control of resistance to the pathogen were found, which was manifested in the frequency of appearance of offspring with high resistance, hypersensitivity, high, medium and low field resistance, as well as complete damage of seedlings. In the species of <em>S. demissum</em> the sample was found, in its progeny the seedlings with extremely high resistance to the pathogen were not isolated, but in the case of the UK sample No 27-19 the part of such material was 94.2%. The lower level of genetic control in this species was characterized by the type of supersensitive resistance. Variation in the offspring samples by this type of resistance was observed in the range of 0-78.4%, and the splitting of seedlings with high field stability was even smaller and was within 0-45%. Similar data were obtained for the species of <em>S. stoloniferum</em>. A similar type of conjugate evolution of phytophthora resistance in the testing species has been experimentally proved. There were no differences in the manifestation of hypersensitive resistance or they were very insignificant. The maximum differences between species were 4% in the class with the offspring frequency of 81-100%. Based on the results of the phytophthora resistance evaluation of various samples of potato species in I2, it was assumed that under epiphytotic conditions in the area of species growth, samples with effective genetic control of the trait, i.e., with an extremely high degree of resistance, will be evolutionally promising. </p>

Multiple Disease Resistance Loci Affect Soilborne Disease Resistance in Tobacco (Nicotiana tabacum)

Phytophthora nicotianae and Ralstonia solanacearum are two of the most important pathogens affecting tobacco worldwide. Greater insight regarding genetic systems controlling resistance to these two soilborne pathogens, as well as identification of DNA markers associated with genomic regions controlling this resistance, could aid in variety development. An evaluation of 50 historical tobacco lines revealed a high positive correlation between resistances to the two pathogens, preliminarily suggesting that some genomic regions may confer resistance to both pathogens. A quantitative trait loci (QTL) mapping experiment designed to investigate the genetic control of soilborne disease resistance of highly resistant ‘K346’ tobacco identified four QTL significantly associated with resistance to P. nicotianae (explaining 60.0% of the observed phenotypic variation) and three QTL to be associated with R. solanacearum resistance (explaining 50.3% of the observed variation). The two QTL with the largest effect on Phytophthora resistance were also found to be the QTL with the greatest effects on resistance to Ralstonia. This finding partially explains previously observed associations between resistances to these two pathogens among U.S. current cultivars and within breeding populations. Further study is needed to determine whether these relationships are due to the same genes (i.e., pleiotropy) or favorable coupling-phase linkages that have been established over time.