Selection for chilling and freezing resistance in common bean

Suboptimal seedbed temperatures (<15°C) in early spring, and risk of late spring- and early fall-frosts are detrimental to dry bean (Phaseolus vulgaris L.) production on the northern prairies. This study: i) determined the effects of suboptimal seedbed temperatures on dry bean seedling emergence and yield; ii) evaluated diverse accessions of cultivated and wild bean for emergence at suboptimal temperatures; iii) investigated freezing resistance in Phaseolus species; and iv) obtained interspecific hybrids between frost sensitive P. vulgaris and frost resistant P. angustissimus. The mid May planting of dry bean cultivars in 1999 and 2000 resulted in lower emergence (74 to 89%) compared to the late May planting (93 to 95%). However, highest yield was obtained in 1999 with the mid May planting, partly because two indeterminate cultivars, failed to mature prior to the first fall frost, when planted in late May. When common bean accessions were planted on May 3, 2000, G8823 had the highest emergence at 20 days after planting. The check cultivar CDC Nighthawk was comparable to G8823 at 30 days after planting. A similar trend was observed in 2001 except emergence was higher in later sampling times due to a warmer seedbed. Accessions with low cumulative thermal units to anthesis, however, were not necessarily early in maturity. G8823 was the only accession with consistent early emergence, early anthesis and early maturity in both years. Leaflets of wild relatives of common bean showed extensive supercooling and their LT50 in the presence of external nucleators was 0.5 to 1°C lower compared to the cultivated species. Exposure to cold acclimating temperatures had no effect in enhancing freezing tolerance of Phaseolus species. Phaseolus angustissimus had the highest seedling survival (55 to 85%) in response to both the fall frost of 2000 and the spring frost of 2001 when the minimum air temperatures were below -5°C. Frost sensitive common bean was crossed as the female parent with the frost resistant P. angustissimus to obtain F1 interspecific hybrids. In reciprocal crosses, flowers aborted at three days after pollination. Interspecific hybrid plants grew to produce flowers, but failed to set seed. The mid May planting of dry bean cultivars will result in higher seed yield compared to the late May planting in years with a mid September or earlier frosts. Successful introgression of both resistance to suboptimal seedbed temperatures during emergence (accession G8823) and frost resistance (P. angustissimus) into common bean may expand the gographic distribution of bean crop to higher altitudes and latitudes

Physiology of Cold Acclimation and Deacclimation Responses of Cool-season Grasses: Carbon and Hormone Metabolism

Winter injury of cool-season turfgrasses in northern climates is a significant issue, leading to losses in turf cover and subsequent increased inputs for recovery. Despite the different potential causes for winter injury, the overall level of plant freezing tolerance has been shown to account for a majority of the variation in winter survival of grasses. Freezing tolerance is achieved through cold acclimation, based on a series of physiological and biochemical changes that increase cell stability at freezing temperatures. Winter injury can result from insufficient cold acclimation, or rapid cold deacclimation triggered by temperature fluctuations or freeze-thaw cycles. Previous research has been mostly conducted to investigate the mechanisms associated with cold acclimation, limited research was applied to deacclimation resistance. In order to enhance winter survival, and reduce turf losses and recovery costs, a better understanding of the underlying factors associated with cold acclimation and deacclimation is necessary. Therefore, the objectives of this thesis research are to: (1) evaluate the carbon metabolism factors attributing to different freezing tolerance capacity associated with cold acclimation and deacclimation of annual bluegrass and creeping bentgrass; (2) investigate the differences in hormone regulation of annual bluegrass and creeping bentgrass during cold acclimation and deacclimation; and (3) identify physiological changes in response to cold acclimation and deacclimation among perennial ryegrass genotypes contrasting in freezing tolerance. Overall, our research found that the fast up-regulation of carbon metabolism activities (chlorophyll fluorescence, photosynthesis, respiration) during deacclimation was associated with losses in freezing tolerance. In addition, changes in hormone content, such as abscisic acid, auxin, salicylic acid, and jasmonic acid, at both leaf and crown level, contributed to differences in deacclimation resistance. Lastly, increased crown moisture content during deacclimation was also found to be responsible for the losses in freezing tolerance. Although these factors may aid in a faster recovery in response to temperature increases during late winter and early spring, these physiological changes may also make the plants more susceptible to freezing injuries if plants are once again exposed to freezing temperatures

The mechanism of freezing resistance in cold-acclimated winter wheat and rye crowns

The ability of cold-acclimated crowns to survive freezing is an important environmental factor limiting winter wheat (Triticum aestivum L.) expansion in Western Canada. Coldacclimation refers to the physiological and biochemical processes by which plants acquire freezing resistance. Cold-acclimation establishes an ice segregation freezing survival mechanism. The shoot apical meristem (SAM) cold-acclimates through the accumulation of dehydrins, vernalization-responsive and cold shock proteins. Modifications to the vascular transition zone (VTZ), are centered on increases in pathogenesis-related, antifreeze proteins, sugar hydrolyzing enzymes and increased cell wall glucuronoarabinoxylans. In cold-acclimated winter wheat and rye (Seacale cereale L.), magnetic resonance microimaging revealed a desiccative intermediate zone between the SAM and VTZ with reduced water mobility. Slow cooling rates (≤ 2°C h-1) are required to establish freezing injury in the VTZ prior to injury in the SAM. Infrared thermography was used to observe in the absence of an extrinsic ice nucleator that freezing initiated from the base of the crown. The first freezing event (-3°C to -5°C) corresponded with warm ice nucleation temperatures (-3.5°C) and ice formation in the leaf sheath. Removal of the leaf sheath prior to cooling reduced cold hardiness and resulted in injury to the SAM prior to the VTZ. The second freezing event (-8°C to -12°C) corresponded with non-lethal injury to the VTZ. The third freezing event (-21°C in Norstar, -27°C in Hazlet and -30°C in Puma rye) corresponded with injury to the SAM and the plant’s killing temperature based on whole plant survival tests. It is hypothesized that cold-acclimated crowns survive sub-zero temperatures through the following mechanism. The leaf sheath is established as an ice sink relative to the SAM. An intermediate zone acts as a barrier to ice propagation, allowing the SAM to supercool and avoid freezing. The VTZ acts as an ice sink within the crown. Possible differences in SAM freezing survival between rye and wheat could explain their contrasting cold hardiness

Approaches in Enhancing Antioxidant Defense in Plants

This Special Issue, “Approaches in Enhancing Antioxidant Defense in Plants” published 13 original research works and a couple of review articles that discuss the various aspects of plant oxidative stress biology and ROS metabolism, as well as the physiological mechanisms and approaches to enhancing antioxidant defense and mitigating oxidative stress. These papers will serve as a foundation for plant oxidative stress tolerance and, in the long term, provide further research directions in the development of crop plants’ tolerance to abiotic stress in the era of climate change

Fyziologická a proteomická charakterizace vlivu abiotických stresů na ozimou formu brukve řepky olejky

in Czech language, Ph.D. thesis - Milan Urban, 2017 V některých letech je zemědělská produkce brukve řepky olejky - významné plodiny České republiky - ohrožena (kromě biotických stresů) mrazem či suchem. V prvním přehledovém článku jsme proto věnovali pozornost proteinům, které byly nalezeny ve studiích porovnávajících genotypy s různou mírou tolerance k abiotickým stresům. V tomto článku jsme se také zaměřili na aplikaci výsledků proteomických studií ve šlechtitelských programech a při zvyšování odolnosti plodin ke stresům obecně. Vlastní výsledky jsme pozorovali u chladově aklimovaných, nejarovizovaných rostlin řepky ve fázi listové růžice. V druhém článku jsme prokázali signifikantní vztah mezi mrazuvzdorností, akumulací dehydrinů a aklimací fotosyntetického aparátu u pěti odrůd řepky. Při porovnání s dřívějšími výsledky jsme pozorovali nejen specifickou akumulaci dehydrinu D97, ale i kvalitativní změny dalších dehydrinů. Tyto výsledky naznačují, že úroveň získané mrazuvzdornosti je závislá nejen na aklimaci fotosyntézy, ale i na vyšší akumulaci ochranných složek. Stres sucha (článek č. 3) byl navozen ve fázi prodlužování stonku před kvetením, což je fáze, ve které rostlina musí přijmout větší množství vody. Pozdní jarní přísušky před nebo během kvetení výrazně snižují výnos a kvalitu produkce....- Ph.D. thesis - Milan Urban, 2017 In some years, the agricultural production of oilseed rape, an important crop in the Czech Republic, is - besides biotic stress - facing the problem of damage caused by frost or drought. Together with special attention paid to proteins revealing responses between crop genotypes with differential abiotic stress tolerance levels we reviewed possible applications of proteomic results in crop breeding programs aimed at an improvement of crop stress tolerance (paper 1). For first original result, cold temperature was imposed upon non-vernalized plants in the stage of leaf rosette. The article (paper 2) shows a significant correlation between frost tolerance (FT), dehydrin (DHN) accumulation, and photosynthetic acclimation in five cultivars (cvs). Newly, the specific DHN D97 was shown to accumulate and other DHNs were shown to have qualitative differences in accumulation. These results imply that proper FT assessment is based on rapid photosynthetic acclimation together with higher accumulation of protective compounds. Drought stress (paper 3) was imposed in the water- demanding stem prolongation phase before flowering, because late-spring drought before and during flowering decreases the yield and seed quality significantly. This paper newly describes two water-uptake...Katedra experimentální biologie rostlinDepartment of Experimental Plant BiologyPřírodovědecká fakultaFaculty of Scienc

The Genetics and Physiology of Abiotic Stress Disorder in Swede (Brassica napus var. napobrassica)

Swedes are extremely common as a root vegetable in Europe, USA, and Canada but are affected by the occasional presence of Brown Heart (BH) disorder affecting the marketable swede root. The incidence of BH has been reported worldwide however it is very difficult to breed resistance due to its sporadic occurrence with no external symptoms to select for. BH has been attributed to boron availability but attempts to link BH appearance definitively with boron deficiency have been difficult. Anecdotal evidence from breeders and growers highlighted the recent co-appearance of BH and frost injury in the field and it was postulated that if an association (physiological or genetic) can be determined between BH appearance and another more easily assessed trait such as frost susceptibility, then a frost tolerance screen may be developed as a useful surrogate method to screen for BH resistance. Frost hardiness assessment of 12 swede genotypes including some F1 hybrids was carried out. Results showed that some genotypes (like Ag31, Me77c and Or13) were more susceptible to frost (EL50 circa -7 ˚C) whilst others (like Gr19 and Ly01) were classified as more tolerant. Breeder trials data from the UK and Germany over a 10 year period showed that 85% of the BH incidence was associated with genotypes that had the frost susceptible lines Ag31, Or13 or Me77c in their parentage. To investigate this association further, frost susceptible and tolerant genotypes, together with a number of their F1 hybrids, were evaluated in a field trial for their response to boron treatments (0.00, 1.35, 1.80 and 2.70 kg B ha-1). At maturity, BH incidence and its severity was predominantly affected by genotype but could be ameliorated by boron application. Ag31 was confirmed to be the most susceptible to BH, and Or13 and Me77c were intermediate in their susceptibility. F1 hybrids between any two susceptible parents were also susceptible to BH. In contrast, genotypes Gr19 and Ly01 were confirmed to be highly resistant to BH and did not show any BH symptoms even at zero boron applied. F1 hybrids between resistant and susceptible lines demonstrated the BH resistant phenotype. Resistance to BH was therefore confirmed as a dominant trait with either a BHBH or BHbh genotype, whilst susceptibility was recessive bhbh. A degree of quantitative variation existed in the severity of the BH suggesting that BH resistance was not a single gene effect. BH severity was significantly negatively correlated (r = - 0.632) with root boron content in susceptible genotypes. The genotypes which were BH resistant in this trial were also more tolerant to frost in screening tests and this association was investigated further at a molecular level. Cold acclimation (CA) for 14 days at 4 ˚C positively affected the response of swede to frost, lowering the EL50 by -1.5˚C, and boron reduced the EL50 by -2.2˚C under non-acclimating conditions and by -1.2˚C under CA. Both boron and CA increased the catalase (CAT) and super oxidase dismutase (SOD) concentrations in swede leaves. Molecular analysis clearly demonstrated the presence of the B.napus cold response gene in swede, BN115, and was shown to be up-regulated due to both CA and boron application but differed between the two genotypes tested. The more frost resistant Gr19 showed a better response than the susceptible Ag31. Boron application reduced EL50 by -2.3˚C for Ag31 and -3.1˚C for Gr19. Given the association between frost tolerance and BH resistance it is suggested that a frost test screen could be used as a useful surrogate method to screen for BH resistance in swede breeding programmes.Ministry of Higher Education / Ira

Responses to low temperature stress in phaseolus species

Expansion of common bean (Phaseolus vulgaris L.) crops in the northern Great Planes has been hampered due to the lack of cultivars demonstrating sufficient vitality under low temperature conditions. Phaseolus angustissimus L., a wild bean species, has been previously shown to possess the ability to survive low temperatures in field trials. Freezing tolerance experiments under controlled conditions resulted in P. angustissimus demonstrating a greater capacity for freezing tolerance than P. vulgaris, as all P. vulgaris plants studied were dead at -2.5oC while most P. angustissimus plants treated to the same conditions survived. Exposure to chilling temperatures over five days resulted in stunted growth in both species, but the cultivated bean suffered more compared to the wild bean, as noted by a marked loss in tissue water content over the first three days of chilling. Interspecific macroarray hybridizations of a cDNA library from cold acclimated Medicago sativa L. using cDNAs derived from non-chilled and three-day chilled P. vulgaris and P. angustissimus plants showed that P. vulgaris showed more changes in gene expression after three days of chilling. Also, P. vulgaris showed a general trend towards down-regulation of the transcripts sampled on the third day of chilling compared to P. angustissimus. RT-PCR experiments were conducted using cDNAs from plant tissues exposed to various durations of chilling to confirm the results from the macroarray experiment. These time-course RT-PCR experiments revealed expression patterns across various chilling durations in genes identified from the macroarray. Data from these experiments suggest that P. vulgaris and P. angustissimus seedlings respond differently to low temperature exposure, and that some of the changes in P. angustissimus transcripts monitored here may be useful for researchers in better understanding how Phaseolus species can respond better to chilling temperatures

Molecular and Physiological Responses of Soybean (Glycine max) to Cold and the Stress Hormone Ethylene

Indiana University-Purdue University Indianapolis (IUPUI)Abiotic stresses, such as cold, are serious agricultural problems resulting in substantial crop and revenue losses. Soybean (Glycine max) is an important worldwide crop for food, feed, fuel, and other products. Soybean has long been considered to be cold-intolerant and incapable of cold acclimation. In contrast to these reports, this study demonstrates that cold acclimation improved freezing tolerance in the domestic soybean cultivar ‘Williams 82’ with 50% enhancement of freezing tolerance after 5.2 +\- 0.6 days of cold exposure. Decreases in light dependent photosynthetic function and efficiency accompanied cold treatment. These decreases were due to an increase in photon dissipation likely driven by a decrease in plastoquinone (PQ) pool size limiting electron flow from photosystem II (PSII) to photosystem I (PSI). Cold-induced damage to operational photosynthesis began at 25 minutes of cold exposure and maximal photosynthesis was disrupted after 6 to 7 hours of cold exposure. Cold exposure caused severe photodamage leading to the loss of PSII reaction centers and photosynthetic efficiency. Comparisons of eight cultivars of G. max demonstrated a weak correlation between cold acclimation and northern cultivars versus southern cultivars. In the non-domesticated soybean species Glycine soja, the germination rate after cold imbibition was positively correlated with seedling cold acclimation potential. However, the overall cold acclimation potential in G. soja was equal to that of domestic soybean G. max reducing the enthusiasm for the “wild” soybean as an additional source of genetic diversity for cold tolerance. Despite being relatively cold intolerant, the soybean genome possesses homologs of the major cold responsive CBF/DREB1 transcription factors. These genes are cold-induced in soybean in a similar pattern to that of the cold tolerant model plant species Arabidopsis thaliana. In Arabidopsis, EIN3, a major component of the ethylene signaling pathway, is a negative transcriptional regulator of CBF/DREB1. In contrast to AtEIN3 transcript levels which do not change during cold treatment in Arabidopsis, we observed a cold-dependent 3.6 fold increase in GmEIN3 transcript levels in soybean. We hypothesized that this increase could prevent effective CBF/DREB1 cold regulation in soybean. Analysis of our newly developed cold responsive reporter (AtRD29Aprom::GFP/GUS) soybean transgenic lines demonstrated that inhibition of the ethylene pathway via foliar sprays (AVG, 1-MCP, and silver nitrate) resulted in significant cold-induced GUS activity. Transcripts of GmEIN3A;1 increased in response to ethylene pathway stimulation (ACC and ethephon) and decreased in response to ethylene pathway inhibition in the cold. Additionally, in the cold, inhibition of the ethylene pathway resulted in a significant increase in transcripts of GmDREB1A;1 and GmDREB1A;2 and stimulation of the ethylene pathway led to a decrease in GmDREB1A;1 and GmDREB1B;1 transcripts. To assess the physiological effects of these transcriptional changes; electrolyte leakage, lipid oxidation, free proline content, and photosynthesis were examined. Improvement in electrolyte leakage, a measure of freezing tolerance, was seen only under silver nitrate treatment. Only 1-MCP treatment resulted in significantly decreased lipid oxidation. Transcripts for CBF/DREB1 downstream targets (containing the consensus CRT/DRE motifs) significantly decreased in plants treated with ethylene pathway stimulators in the cold; however, ethylene pathway inhibition generally produced no increase over basal cold levels. To identify if GmEIN3A;1 was capable of binding to GmDREB1 promoters, the negative regulator GmEIN3A;1 and the positive regulator GmICE1A were cloned and expressed in Escherichia coli (E. coli). Preliminary binding results indicated that GmEIN3A;1 can bind to a double stranded section of the GmDREB1A;1 promoter containing putative EIN3 and ICE1 binding sites. GmICE1A is capable of binding to the same section of the GmDREB1A;1 promoter, though only when single stranded. Additional experiments will be required to demonstrate that GmEIN3A;1 and GmICE1A are capable of binding to the GmDREB1A;1 promoter and this work provides the tools to answer these questions. Overall, this work provides evidence that the ethylene pathway transcriptionally inhibits the CBF/DREB1 pathway in soybean through the action of GmEIN3A;1. Yet when GmCBF/DREB1 transcripts are upregulated by ethylene pathway inhibition, no consistent change in downstream targets was observed. These data indicate that the limitation in cold tolerance in soybean is due to a yet unidentified target downstream of CBF/DREB1 transcription

Genetic analysis of developmental traits associated with enhanced winter survival in autumn-seeded rye (Secale cereale L.).

The abstract of this item is unavailable due to an embargo