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

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.

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.

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 Differential expression of TLP, ERF1, and R2R3MYB in annual Medicago species under salinity conditions

2015 ◽  
Vol 14 (3) ◽  
pp. 10152-10164 ◽  
Author(s):  
F. Gharaghani ◽  
F. Rafiei ◽  
N. Mirakhorli ◽  
E. Ebrahimie
Keyword(s):  
Differential Expression ◽  
Annual Medicago ◽  
Medicago Species

An improved method for artificial hybridization in annual Medicago species

1994 ◽  
Vol 45 (7) ◽  
pp. 1329 ◽  
Author(s):  
W Pathipanawat ◽  
RAC Jones ◽  
K Sivasithamparam
Keyword(s):  
Success Rate ◽  
Fold Increase ◽  
Modified Technique ◽  
Established Method ◽  
Artificial Hybridization ◽  
Annual Medicago ◽  
Improved Technique ◽  
Medicago Species ◽  
First Time ◽  
Selection Of

An improved technique for successful artificial hybridization in annual medic (Medicago spp.) is described. Using a previously reported method, only four out of seven species were successfully crossed, with the percentage of success ranging from 3 to 22%. Initial modifications to this technique gave a 7-8 fold increase in the successful crossing rate in M. murex and M. polymorpha medic, from 9 to 64% with M. murex and from 10 to 82% with M. polymorpha. Further modifications to the technique resulted in a success rate of 100% in both species. The numbers of seeds per pod obtained from crosses in both species were also increased by using the modified techniques compared to the established method. Selection of larger, more mature flowers, differences in flower cutting position, as well as post pollination position were the main modifications which accounted for the greatly improved success rate. The modified technique was subsequently applied successfully to obtain for the first time inter-specific crosses involving M. polymorphax M. murex, M. polymorphax M. sphaerocarpos, M.murexx M. sphaerocarpos, M. solerolii x M. littoralis/M.truncatula hybrid, M. solerolii x M, tornata, and M. littoralis/M.truncatula hybrid x M. sphaerocarpos.

Strategies for control of Phoma black stem in annual Medicago species

1989 ◽  
Vol 29 (5) ◽  
pp. 635 ◽  
Author(s):  
MJ Barbetti
Keyword(s):  
Disease Severity ◽  
Medicago Truncatula ◽  
Field Trial ◽  
Subsequent Development ◽  
Field Site ◽  
Infected Seed ◽  
Annual Medicago ◽  
And Control ◽  
Medicago Species ◽  
Selection Of

Strategies for control of Phoma black stem disease in annual Medicago species through selection of cultivars with increased resistance to Phoma medicaginis, fungicidal spray applications to swards, and fungicidal control of seedborne infection, were investigated. Fiftyseven annual Medicago cultivars and lines were screened for resistance in the field in 1 m rows over 2 consecutive seasons. There were significant differences in resistance among species and also between lines and cultivars of any particular species. Three M. rugosa cultivars were very highly resistant and most cultivars and lines showed some resistance. In a field trial, the fungicides benomyl, carbendazim, flutriafol, propiconazole, thiabendazole and triadimefon were tested for their efficacy in controlling Phoma black stem disease. All fungicides reduced disease severity in the sward and, except for thiabendazole, the percentage burrs with Phoma lesions. The role and control of seed-borne P. medicaginis in causing Phoma black stem disease in Medicago truncatula and M. polymorpha var. brevispina at a field site was also investigated. Seed-borne P. medicaginis caused subsequent development of Phoma black stem disease in swards sown with infected seed. Disease appeared earlier, developed faster and became much more severe in M. truncatula cv. Cyprus than in M. polymorpha cv. Serena. Application of benomyl seed treatments (0.1 and 0.5% w/w) resulted in only a 4-5 week delay in the onset of Phoma black stem symptoms.

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.

Forage Yield and Quality of Six Annual Medicago Species in the North‐Central USA

1996 ◽  
Vol 88 (6) ◽  
pp. 955-960 ◽  
Author(s):  
Yanping Zhu ◽  
Craig C. Sheaffer ◽  
Donald K. Barnes
Keyword(s):  
Forage Yield ◽  
North Central ◽  
The North ◽  
Yield And Quality ◽  
Annual Medicago ◽  
Central Usa ◽  
Medicago Species

Stigma development and the stigmatic cuticle of Medicago scutellata

1985 ◽  
Vol 63 (4) ◽  
pp. 813-818 ◽  
Author(s):  
G. L. Kreitner ◽  
E. L. Sorensen
Keyword(s):  
Cell Walls ◽  
Light And Electron Microscopy ◽  
Single Layer ◽  
Intercellular Spaces ◽  
Self Pollination ◽  
Medicago Scutellata ◽  
Annual Medicago ◽  
Stigma Development ◽  
Medicago Species ◽  
Late Stages

The self-fertile annual Medicago species evolved from the cross-pollinated perennial species. We used light and electron microscopy to study the development and structure of the stigma in annual tetraploid Medicago scutellata (L.) Mill to help elucidate the mechanism of self-pollination. Immature stigmatic cells have extensive lipid deposits. During development, stigmatic cells become separated and cellular lipid is transferred to intercellular spaces as part of the copious stigmatic secretion. The cuticle of the stigma is lifted away from underlying cell walls and confines secretion around stigmatic cells. The cuticle is thin, about 75 nm, and is composed mainly of a single layer traversed by dense strands. The cuticle is virtually always disrupted during late stages of flower maturation, as evidenced by penetration of stain into the stigma. Self-pollination may occur without flower tripping.

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