Search Results (4)

Alfalfa (Medicago sativa L.) is an extensively grown perennial forage legume, and although it is relatively drought tolerant, it consumes high amounts of water and depends upon irrigation in many regions. Given the progressive decline in water available for irrigation, as well as an escalation in climate change-related droughts, there is a critical need to develop alfalfa cultivars with improved drought resilience. M. sativa subsp. falcata is a close relative of the predominantly cultivated M. sativa subsp. sativa, and certain accessions have been demonstrated to exhibit superior performance under drought. As such, we endeavoured to carry out comparative physiological, biochemical, and transcriptomic evaluations of an as of yet unstudied drought-tolerant M. sativa subsp. falcata accession (PI 641381) and a relatively drought-susceptible M. sativa subsp. sativa cultivar (Beaver) to increase our understanding of the molecular mechanisms behind the enhanced ability of falcata to withstand water deficiency. Our findings indicate that unlike the small number of falcata genotypes assessed previously, falcata PI 641381 may exploit smaller, thicker leaves, as well as an increase in the baseline transcriptional levels of genes encoding particular transcription factors, protective proteins, and enzymes involved in the biosynthesis of stress-related compounds. These findings imply that different falcata accessions/genotypes may employ distinct drought response mechanisms, and the study provides a suite of candidate genes to facilitate the breeding of alfalfa with enhanced drought resilience in the future. Full article

Yellow-flowered alfalfa (Medicago sativa subsp. falcata) (also known as sickle medic) has been the cornerstone for breeding alfalfa for dual grazing and hay production in the semiarid regions of the northern Great Plains in the US and Canada. Most, if not all, of the cultivars developed for the northern Great Plains during the 20th century, had parentage tracing back to introductions by Niels Ebbesen Hansen that were obtained from expeditions to Russia, primarily the province of Siberia, on behalf of the United States Department of Agriculture during the early 1900s. The M. falcata genome contains alleles for high levels of drought-tolerance, winter hardiness, and tolerance to grazing, but is generally deficient for commercial seed production traits, such as non-shatter, compared with common alfalfa (M. sativa). A naturalized population, tracing to USDA plant introductions to Perkins County South Dakota by N.E. Hansen in early 1900, and subsequently, facilitated by the determined seed increase and interseeding of a population by a local rancher, Norman ‘Bud’ Smith, has shown highly desirable in situ characteristics for improving rangelands in the northern Great Plains. This includes adequate seed production to build a seed bank in the soil for natural seedling recruitment and population maintenance/expansion and support the production of a commercial seed source. This review documents the seminal events in the development of cultivars to date and describes novel germplasm with potential for new cultivars in the future. Full article

Cytogenetic research in Medicago sativa subsp. sativa L., the cultivated tetraploid alfalfa (2n = 4x = 32), has lagged behind other crops mostly due to the small size and the uniform morphology of its chromosomes. However, in the last decades, the development of molecular cytogenetic techniques based on in situ hybridization has largely contributed to overcoming these limitations. The purpose of this study was to extend our knowledge about the chromosome structure of alfalfa by using a combination of genomic in situ hybridization (GISH) and fluorescence in situ hybridization (FISH) techniques. The results of self-GISH (sGISH) suggested that a substantial part of the repetitive fraction of the genome of subsp. sativa is constituted by tandem repeats typical of satellite DNA. The coincidence of sGISH and C-banding patterns supported this assumption. The FISH mapping of the Arabidopsis-type TTTAGGG telomeric repeats demonstrated, for the first time, that the alfalfa telomeres consist of this type of sequence and revealed a massive presence of interstitial telomeric repeats (ITRs). In the light of this finding M. sativa appears to be a suitable material for studying the origin and function of such extra telomeric repeats. To further exploit this result, investigation will be extended to the diploid subspp. coerulea and falcata in order to explore possible connections between the distribution of ITRs, the ploidy level, and the evolutionary pathway of the taxa. Full article

The role of nitric oxide (NO) signaling in the cold acclimation of forage legumes was investigated in this study. Medicago sativa subsp. falcata (L.) Arcang. (hereafter M. falcata) is a forage legume with a higher cold tolerance than Medicago truncatula, a model legume. Cold acclimation treatment resulted in increased cold tolerance in both M. falcata and M. truncatula, which was suppressed by pretreatment with tungstate, an inhibitor of nitrate reductase (NR), and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO), a scavenger of NO. Likely, NITRATE REDUCTASE 1 (NIA1), but not NIA2 transcript, NR activity, and NO production were increased after cold treatment. Treatments with exogenous NO donors resulted in increased cold tolerance in both species. Superoxide dismutase (SOD), catalase (CAT), and ascorbate-peroxidase (APX) activities and Cu,Zn-SOD2, Cu,Zn-SOD3, cytosolic APX1 (cAPX1), cAPX3 and chloroplastic APX1 (cpAPX1) transcript levels were induced in both species after cold treatment, which was suppressed by tungstate and 2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide (PTIO). Treatment with exogenous NO resulted in enhanced activities of SOD, CAT, and APX. Moreover, higher levels of NIA1 transcript, NR activity, NO production, and antioxidant enzyme activities and transcripts were observed in M. falcata as compared with M. truncatula after cold treatment. The results suggest that NR-derived NO production and upregulated antioxidant defense are involved in cold acclimation in both species, while the higher levels of NO production and its derived antioxidant enzymes are associated with the higher cold tolerance in M. falcata as compared with M. truncatula. Full article