scholarly journals Sources of Resistance to Anthracnose in the Annual Medicago Core Collection

Plant Disease ◽  
2000 ◽  
Vol 84 (3) ◽  
pp. 261-267 ◽  
Author(s):  
Nichole R. O'Neill ◽  
Gary R. Bauchan
Keyword(s):  
Core Collection ◽  
Seedling Survival ◽  
Plant Introduction ◽  
Sources Of Resistance ◽  
Forage Crop ◽  
Colletotrichum Trifolii ◽  
Resistant Varieties ◽  
Medicago Sativa L ◽  
Annual Medicago ◽  
Medicago Species

The annual genus Medicago core collection, consisting of 201 accessions, represents the genetic diversity inherent in 3,159 accessions from 36 annual Medicago species. This germ plasm was evaluated for resistance to anthracnose caused by Colletotrichum trifolii. Anthracnose is a major disease in perennial alfalfa (Medicago sativa L.) grown in North America and disease control is based principally on the use of resistant varieties. Evaluation of the core collection was conducted using standardized environmental conditions in growth chambers, and included the M. sativa standard reference cvs. Arc (resistant) and Saranac (susceptible). The degree of resistance found among accessions within species was highly variable; however, most annual species and accessions were susceptible. Only 14 accessions from seven species exhibited resistance greater than 40% seedling survival. These included accessions of M. murex, M. muricoleptis, M. polymorpha var. brevispina, M. polymorpha var. polymorpha, M. radiata, M. soleirolii, M. truncatula, and M. turbinata. Of the 12 accessions of M. polymorpha var. polymorpha, 4 exhibited more than 50% resistance, but 3 accessions were 100% susceptible. Most of the M. truncatula and M. turbinata accessions exhibited significantly more resistance than accessions of other species. Plant introduction (PI) accession number PI 495401 of M. muricoleptis exhibited 90.3% resistance. Accessions of M. scutellata were uniformly susceptible. Histological examinations of 14 of the most anthracnose-resistant accessions revealed that C. trifolii spores germinated and produced typical appressoria, but failed to penetrate and produce the primary and secondary hyphae characteristic of susceptible interactions. Resistant reactions were similar to those found in incompatible interactions with C. trifolii and alfalfa, which have been associated with specific genes leading to the production of isoflavonoid phytoalexins. The large genetic variability in annual Medicago spp. offers potential for locating and utilizing disease resistance genes through breeding or genetic engineering that will enhance the utilization of Medicago spp. as a forage crop.

scholarly journals Reactions in the Annual Medicago spp. Core Germ Plasm Collection to Phoma medicaginis

Plant Disease ◽  
2003 ◽  
Vol 87 (5) ◽  
pp. 557-562 ◽  
Author(s):  
Nichole R. O'Neill ◽  
Gary R. Bauchan ◽  
Deborah A. Samac
Keyword(s):  
Disease Resistance ◽  
Leaf Spot ◽  
Core Collection ◽  
Germ Plasm ◽  
Severity Scale ◽  
Forage Crop ◽  
The Core ◽  
Phoma Medicaginis ◽  
Disease Severity Scale ◽  
Annual Medicago

The annual Medicago spp. core collection, consisting of 201 accessions, represents the genetic diversity inherent in 3,159 accessions from 36 annual Medicago spp. This germ plasm was evaluated for resistance to spring black stem and leaf spot caused by Phoma medicaginis. Spring black stem and leaf spot is a major destructive disease in perennial alfalfa (Medicago sativa) grown in North America, Europe, and other temperate regions. Disease control is based principally on the use of cultivars with moderate levels of resistance. Evaluation of the core collection was conducted using standardized environmental conditions in growth chambers, and included the M. sativa standard reference cultivars Ramsey (resistant) and Ranger (susceptible). The degree of resistance found among accessions within species was variable, but most annual species and accessions were susceptible. Most accessions from 10 species exhibited high disease resistance. These included accessions of M. constricta, M. doliata, M. heyniana, M. laciniata, M. lesinsii, M. murex, M. orbicularis, M. praecox, M. soleirolii, and M. tenoreana. Most of the accessions within M. arabica, M. minima, M. lanigera, M. rotata, M. rugosa, M. sauvagei, and M. scutellata were highly susceptible. Disease reactions among some accessions within species were highly variable. On a 0-to-5 disease severity scale, ratings ranged from 0.67 (PI 566873) to 4.29 (PI 566883) within accessions of M. polymorpha. Most of the M. truncatula accessions were susceptible, with a mean of 3.74. Resistant reactions were similar to those found in incompatible interactions with P. medicaginis and alfalfa, which have been associated with specific genes leading to the production of isoflavonoid phytoalexins. The large genetic variability in annual Medicago spp. offers potential for locating and utilizing disease resistance genes through breeding or genetic engineering that will enhance the utilization of Medicago spp. as a forage crop.

scholarly journals Distribution and Virulence Phenotypes of Heterodera glycines in Missouri

Plant Disease ◽  
2003 ◽  
Vol 87 (8) ◽  
pp. 929-932 ◽  
Author(s):  
T. L. Niblack ◽  
J. A. Wrather ◽  
R. D. Heinz ◽  
P. A. Donald
Keyword(s):  
Soybean Cyst Nematode ◽  
Heterodera Glycines ◽  
Phenotypic Diversity ◽  
Research Priorities ◽  
Plant Introduction ◽  
Cyst Nematode ◽  
Population Densities ◽  
Sources Of Resistance ◽  
Resistant Varieties ◽  
Two Samples

The soybean cyst nematode, Heterodera glycines, is the most economically important pathogen of soybean in Missouri. Knowledge of the nematode's distribution and ability to adapt to resistant varieties is important for determining crop losses and establishing research priorities. No previous surveys of Missouri have provided reliable population density and phenotypic diversity data; therefore, we conducted a random survey to obtain both. Two samples from each of 200 fields were collected; 392 samples were processed for extractions of cysts and eggs. Two hundred and forty seven (63%) of the samples had detectable cyst nematode populations, which ranged from 15 to 149,700 eggs per 250 cm3 of soil. The lowest average population densities were observed in the east-central region of Missouri (2,260 eggs per 250 cm3 of soil), and the highest were observed in the northeast (9,238 eggs per 250 cm3 of soil), but among the eight regions sampled, mean population densities did not differ significantly. These population densities were potentially responsible for losses worth over $58 million in 1999 in Missouri. Race tests were conducted on populations from 183 samples. In order of frequency, races 3, 1, and 2 accounted for 86% of H. glycines populations. Nearly 60% of the populations were virulent (able to produce females) on plant introduction (PI) 88788, which is the source of resistance for most H. glycines-resistant cultivars. More than a third of the populations were virulent on cv. Peking, another common resistance source. Very few populations were virulent on PI 90763 or PI 437654, suggesting that these sources of resistance should be exploited more frequently.

scholarly journals Development and Utilization of a Core Collection in Theobroma cacao based on RAPD Marker-based Estimates of Genetic Distance

HortScience ◽  
1997 ◽  
Vol 32 (3) ◽  
pp. 513C-513
Author(s):  
Jane M. Marita ◽  
José Luis Pires ◽  
W. Martin Aitken ◽  
James Nienhuis
Keyword(s):  
Genetic Diversity ◽  
Genetic Distance ◽  
Random Sampling ◽  
Theobroma Cacao ◽  
Core Collection ◽  
Genetic Relationships ◽  
Rapd Marker ◽  
Sources Of Resistance ◽  
Resistant Varieties ◽  
Broom Disease

An increased need to understand the genetic relationships among cacao (Theobroma cacao) germplasm exists to identify cultivars that possess resistance to witches' broom disease (caused by Crinipellis perniciosa). Loss of production due to witches' broom disease in important cacao-growing areas, such as Bahia, Brazil, has generated a strong demand for disease-resistant varieties. Varieties based on single sources of resistance have been released; however, other genotypes are needed to enlarge the genetic diversity of cultivars in breeding programs. A core collection has been created to represent the range of genetic diversity available among the more than 600 cacao accessions at Centro de Pesquisa do Cacau (CEPEC). The cacao core facilitates access to the collection and is intended to enhance its use. This core collection was created from RAPD marker-based estimates of genetic distance among a subset of 270 accessions from the entire collection. The subset was sampled based on 1) witches' broom disease resistance data, 2) random sampling of the collection, and 3) random sampling of recently acquired accessions. Differences in RAPD marker frequencies were used to identify accessions in a witches' broom disease breeding program that contribute to the genetic diversity of the collection as a whole. In addition, differences in RAPD marker frequency allowed the comparison between accessions in the original collection and those acquired from new geographic regions that may expand the collection's genetic diversity.

Analysis of annual Medicago species using RAPD markers

Genome ◽  
1995 ◽  
Vol 38 (2) ◽  
pp. 362-367 ◽  
Author(s):  
E. C. Brummer ◽  
J. H. Bouton ◽  
G. Kochert
Keyword(s):  
Core Collection ◽  
Rapd Markers ◽  
Phylogeny Reconstruction ◽  
Forage Crops ◽  
Banding Patterns ◽  
Original Seed ◽  
Traditional Taxonomy ◽  
Annual Medicago ◽  
Medicago Species ◽  
Seed Collections

Annual species of the genus Medicago have attracted interest as green manure and temporary forage crops. This study was conducted to determine if randomly amplified polymorphic DNA (RAPD) markers could be used to assess the variability within and among species. Several accessions of each six species (M. scutellata Mill., M. disciformis DC, M. murex Willd., M. truncatula Gaertn., M. polymorpha L., and M. rugosa Desr.) were studied. A phylogeny reconstructed with the computer program Phylogenetic Analysis Using Parsimony (PAUP) showed the same relationships as traditional taxonomy. Variation was present among accessions of all species. Several accessions were considerably different from others within the species (one of each M. scutellata and M. polymorpha) and four accessions of M. murex were differentiated by both morphology and RAPD banding patterns from the other accessions. These accessions may be useful to include in a core collection. Variation within accessions was present. Although the species are autogamous, the original seed collections may have been made from a number of plants in the same area. Also, some outcrossing or seed mixing may have occurred. Finally, at least 10 RAPD primers appear to be necessary in order to develop reliable estimates of relatedness among annual Medicago accessions.Key words: Medicago, annual medic, phylogeny reconstruction, RAPD, core collection.

Methods of developing a core collection of annual Medicago species

1995 ◽  
Vol 90 (6) ◽  
pp. 755-761 ◽  
Author(s):  
N. Diwan ◽  
M. S. McIntosh ◽  
G. R. Bauchan
Keyword(s):  
Core Collection ◽  
Annual Medicago ◽  
Medicago Species

Insecticidal Active Rotenoids from Plant Parts and Callus Culture of Medicago sativa L. from a Semiarid Region of India (Rajasthan)

2020 ◽  
Vol 16 (6) ◽  
pp. 937-941
Author(s):  
Sharad Vats ◽  
Preeti Mehra
Keyword(s):  
Medicago Sativa ◽  
Callus Culture ◽  
Point Of View ◽  
Semiarid Region ◽  
Disease Vectors ◽  
Vector Borne Diseases ◽  
Plant Parts ◽  
Resistant Varieties ◽  
Medicago Sativa L

Background: Vector-borne diseases are quite prevalent globally and are one of the major causes of deaths due to infectious diseases. There is an availability of synthetic insecticides, however, their excessive and indiscriminate use have resulted in the emergence of resistant varieties of insects. Thus, a search for novel biopesticide has become inevitable. Methods: Rotenoids were isolated and identified from different parts of Medicago sativa L. This group of metabolites was also identified in the callus culture, and the rotenoid content was monitored during subculturing for a period of 10 months. Enhancement of the rotenoid content was evaluated by feeding precursors in a tissue culture medium. Results: Four rotenoids (elliptone, deguelin, rotenone and Dehydrorotenone) were identified, which were confirmed using spectral and chromatographic techniques. The maximum rotenoid content was found in the seeds (0.33±0.01%), followed by roots (0.31±0.01%) and minimum in the aerial parts (0.20±0.05%). A gradual decrease in the rotenoid content was observed with the ageing of subcultured tissue maintained for 10 months. The production of rotenoids was enhanced up to 2 folds in the callus culture using amino acids, Phenylalanine and Methionine as precursors as compared to the control. The LC50 value of the rotenoids was found to be 91 ppm and 162 ppm against disease vectors of malaria and Dracunculiasis, respectively. Conclusion: The study projects M. sativa as a novel source of biopesticide against the disease vectors of malaria and Dracunculiasis. The use of precursors to enhance the rotenoid content in vitro can be an effective venture from a commercial point of view.

Artificial microRNA (amiRNA) induced gene silencing in alfalfa (Medicago sativa)

Botany ◽  
2013 ◽  
Vol 91 (2) ◽  
pp. 117-122 ◽  
Author(s):  
Julian C. Verdonk ◽  
Michael L. Sullivan
Keyword(s):  
Gene Silencing ◽  
Medicago Sativa ◽  
Target Gene ◽  
Target Genes ◽  
Mirna Precursor ◽  
Crop Species ◽  
Forage Crop ◽  
Ribonucleic Acids ◽  
Endogenous Gene ◽  
Medicago Sativa L

Gene silencing is a powerful technique that allows the study of the function of specific genes by selectively reducing their transcription. Several different approaches can be used, however they all have in common the artificial generation of single stranded small ribonucleic acids (RNAs) that are utilized by the endogenous gene silencing machinery of the organism. Artificial microRNAs (amiRNA) can be used to very specifically target genes for silencing because only a short sequence of 21 nucleotides of the gene of interest is used. Gene silencing via amiRNA has been developed for Arabidopsis thaliana (L.) Heynh. and rice using endogenous microRNA (miRNA) precursors and has been shown to also work effectively in other dicot species using the arabidopsis miRNA precursor. Here, we demonstrate that the arabidopsis miR319 precursor can be used to silence genes in the important forage crop species alfalfa (Medicago sativa L.) by silencing the expression of a transgenic beta-glucuronidase (GUSPlus) target gene.

A Core Collection for the United States Annual Medicago Germplasm Collection

Crop Science ◽  
1994 ◽  
Vol 34 (1) ◽  
pp. 279-285 ◽  
Author(s):  
Noa Diwan ◽  
Gary R. Bauchan ◽  
Marla S. McIntosh
Keyword(s):  
United States ◽  
Core Collection ◽  
Germplasm Collection ◽  
The United States ◽  
Annual Medicago

scholarly journals Screening of the Argentinean INTA peanut core collection with a molecular marker associated with resistance to Sclerotinia minor Jaggar

2020 ◽  
Vol 47 (1) ◽  
pp. 9-16
Author(s):  
K.D. Chamberlin ◽  
J.J. Baldessari ◽  
E.M.C. Mamani ◽  
M.V. Moreno
Keyword(s):  
Molecular Marker ◽  
Core Collection ◽  
Field Tests ◽  
Field Testing ◽  
Blight Resistance ◽  
Phenotypic Traits ◽  
Sources Of Resistance ◽  
Sclerotinia Minor ◽  
Sclerotinia Blight ◽  
Potential Sources

ABSTRACT Cultivated peanut, the third most important oilseed in the world, is consistently threatened by various diseases and pests. Sclerotinia minor Jagger (S. minor), the causal agent of Sclerotinia blight, is a major threat to peanut production in many countries and can reduce yield by up to 50% in severely infested fields. Host plant resistance will provide the most effective solution to managing Sclerotinia blight, but limited sources of resistance to the disease are available for use in breeding programs. Peanut germplasm collections are available for exploration and identification of new sources of resistance, but traditionally the process is lengthy, requiring years of field testing before those potential sources can be identified. Molecular markers associated with phenotypic traits can speed up the screening of germplasm accessions. The objective of this study was to genotype the peanut core collection of the Instituto Nacional de Tecnología Agropecuaria (INTA) Manfredi, Argentina, with a molecular marker associated with Sclerotinia blight resistance. One hundred and fifty-four (154) accessions from the collection were available and genotyped using the Simple Sequence Repeat (SSR) marker. Accessions from each botanical variety type represented in the core collection were identified as new potential sources of resistance and targeted for further evaluation in field tests for Sclerotinia blight resistance.

scholarly journals A linkage of gene of resistance to a broomrape race G with microsatellite loci of a sunflower linedonor RGP1 of VNIIMK’s breeding

2021 ◽  
Vol 186 (2) ◽  
pp. 3-9
Author(s):  
S.Z. Guchetl ◽  
◽  
D.L. Savichenko ◽  
Keyword(s):  
Microsatellite Loci ◽  
Physical Map ◽  
Pcr Analysis ◽  
Sources Of Resistance ◽  
Resistant Varieties ◽  
Literary Sources ◽  
Ssr Loci ◽  
Environmentally Safe ◽  
Yield Formation ◽  
Sunflower Genome

Broomrape (Orobanche cumana Wallr.) is one of the main biotic factors limiting high sunflower yield formation. The most effective and environmentally safe method of protection is cultivation of resistant varieties and hybrids of sunflower. Development of resistant sunflower genotypes includes search and usage of sources of resistance in breeding process as well as accurate and productive procedures of material assessment. The purpose of the research is to analyze a linkage of a gene Or7 with microsatellite loci of the line-donor of resistance to broomrape race G from the VNIIMK’s collection. The objects of the research are the line RGP1 – a donor of resistance to broomrape race G and a susceptible to this race line VR 678 from the VNIIMK’s collection. Sunflower plants were crossed in field to produce F1. Also we conducted self-pollination of F1 plants to obtain F2 progeny. Plants were tested in a greenhouse in soil infected with seeds of broomrape race G using a method of early diagnostic. Sunflower DNA was extracted from the top leaves of the young sprouts of the vegetative plants. For PCR-analysis we used three SSR-primers demonstrated polymorphism in parental lines: ORS 683, ORS 1040, and ORS 1112. We tested joint inheritance of the gene Or7 and these loci, and inheritance between SSR-loci. An independent inheritance of the gene Or7 with DNA-loci ORS 683, ORS 1040, and ORS 1112, as well as SSR-loci between ORS 1040 and ORS 1112, ORS 1040 and ORS 683 was showed. Loci ORS683 – ORS 1112 are linked with a frequency of recombination of 0.27 ± 0.41 (27 cM). As a result of our research location of the gene Or7 in the nearest area to microsatellite loci ORS 683, ORS 1040, and ORS 1112 was excluded. Basing on studied literary sources and a representative sunflower genome HanXRQr2.0-SUNRISE we made a partial physical map LG3 for determination of an area for the further search of a localization of the Or7 and DNAmarkers co-segregating with this gene.

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