2 pp. / Alfalfa varieties differ in fall dormancy, defined as growth during the fall. Nondormant alfalfa varieties are usually planted in mild winter areas for their ability to grow in the late fall, winter, and early spring. Select alfalfa varieties that have resistance to potential pest problems. Alfalfa varieties are available that have salt tolerance or are Roundup Ready. Ratings are provided in this publication. Many of the varieties listed in this publication have been tested for yield and final stand by the University of Arizona in small plot trials. Revised 10/2016. Most recent version 09/2015

Species inhabiting intermittent streams must have life-history traits that confer resistance or resilience to flow cessation or drying. However, we lack basic life-history information for most aquatic invertebrate species, especially those from intermittent streams. I documented the life cycle and distribution of an unusual winter stonefly species, Mesocapnia arizonensis (Capniidae). The species was first described from 6 localities in 1969, but its natural history remained enigmatic. I surveyed >90 streams across the southwestern USA, documented the life cycle of M. arizonensis at 1 locality, and experimentally rehydrated dry streambed sediment in search of dormant stoneflies at another locality. Field surveys expanded the number of localities from 22 to 98, most of which were intermittent with flow durations as brief as 3 mo/y, and extended the known range of the species by 800 km. Nymphs were abundant within days of flow resumption, grew rapidly as a single cohort, and started emerging as adults 42 d after flow resumed. The brief appearance of a 2(nd) cohort of tiny nymphs 1 mo before the stream dried indicates direct hatching of at least some eggs. I failed to find dormant stoneflies in the top 30 cm of dry stream sediment, suggesting that M. arizonensis undergoes dormancy deep in the substrate, putting it safely out of reach of scouring summer floods that occur between favorable winter seasons. The remarkable ability of M. arizonensis to survive in short-flow duration streams and to endure multiple consecutive dry years, suggests that the species is well prepared for the drier climatic conditions predicted to occur across its range.

Two populations derived by crossing LDN x LDN Dic-3A (Population I) and LDN x LDN Dic-3B (Population II) were genetically characterized for the seed dormancy present on chromosome 3A and 3B of durum wheat. The genes for seed dormancy in these two populations were contributed by the wild parent T. dicoccoides. Although the populations showed transgressive segregants for both dormant as well as nondormant parent, the populations were similar to the dormant parent at Langdon and Prosper 2006 field locations for Population I and at Langdon 2007 and Autumn greenhouse season for Population II. Genotypic and phenotypic analysis over the combined populations showed an environmental effect on expression of the trait. Different QTL were identified for both field and greenhouse season for the population derived from the cross between LDN x LDN Dic-3A. Five QTL for seed dormancy were identified on chromosome 3A for the QTL analysis performed over combined field locations. One QTL ranging between marker interval Xcfa2193 and Xcfd2a was consistently present for the 30 day period of seed germination and was also found to be linked to red grain color trait. The QTL analysis performed on the population derived from the cross between LDN x LDN Dic-3B identified only one major QTL on the long arm of chromosome 3B between the marker interval Xbarc84 and Xwmc291. This QTL was consistently present for all the field and spring greenhouse season for the seed germination period of 30 days. The QTL x E effect was also observed for this QTL, however it was very small.

Dormancy is a plausible strategy for bacteria to overcome the effects of temporal fluctuations in resources or stresses and await more “optimal” conditions to resume metabolic activity and growth. Seasonal changes in environmental conditions force microbes to adjust their metabolic activity accordingly, and community composition drastically shifts. In extreme environments, however, the overriding effects of a constant stress may constrain the need or benefit of bacteria entering dormancy. In hypersaline lakes, high metabolic activity is required to maintain adaptations that permit survival. Sampling from six lakes on a salinity gradient (0.05% – 30.3%), we measured seasonal fluctuations in bacterial dormancy patterns in summer, fall, winter, and spring of 2013-14. Dormancy was calculated based on ratios of OTU recovery between 16S rRNA-based communities (only the active bacteria) and 16S rRNA gene-based communities (all bacteria present in the community) from lake water. Dormancy was linked to lake chemistry shifts through time. We found that salinity was strongly related to relative bacterial dormancy. There was a negative linear relationship (R2 = .89 P <0.01) between total dormancy and salinity. Total phosphorus (R2 = .63, P < .001) and relative community contribution by rare taxa (R2 = .89, P < .001) were also important in structuring dormancy. Our findings suggest that temporal nutrient flux is highly influential on bacterial community composition and activity, but that the presence of an extreme variable decreases change in both through time.

No description available.

No description available.

The dormancy of switchgrass (Panicum virgatum L.) seeds may be broken by a variety of treatments, including after-ripening and stratification. This study was conducted to investigate and characterize more systematically factors affecting both after-ripening and stratification effectiveness, and the aging that can occur concomitantly with after-ripening. More than one year of after-ripening at ambient temperature and humidity was necessary for germination of newly harvested seeds to increase from as low as 5% to around 80%. After-ripening was not accelerated at temperatures above ambient for seeds stored in paper bags, which permitted the loss of seed moisture at the increased temperatures. Both after-ripening and aging accelerated with increases in temperature (5 to 60°C) and seed moisture content (50 to 130 g kg⁻¹), except that there was evidence of a moisture optimum for after-ripening that shifted downward as temperature increased. For many seedlots, storage at 60°C and 50 g kg⁻¹ seed moisture content for about 1 mo broke most of the dormancy and resulted in acceptably low numbers of abnormal (aged) seedlings. Decreases in germinability caused by post-stratification drying of switchgrass seeds (described herein as "reversion", in which the reverted seeds could be made germinable again by further stratification) increased as the desiccation increased. Revertibility decreased as stratification or after-ripening time increased. Stratification and after-ripening worked additively to release switchgrass seeds from dormancy. Reversion (germination with stratification minus germination after stratification followed by drying) may reveal seedlot differences and changes over time and moisture content that can not be seen otherwise. Imbibed, dormant seeds placed at 21 or 30°C were induced into deeper dormancy, as indicated by length of stratification needed to break the dormancy. Dormancy deepened more as storage temperature and time increased for imbibed seeds. There are transitional temperature and seed moisture ranges where opposing processes (aging vs. after-ripening, stratification vs. dormancy deepening) appeared to overlap or surpass one another. Switchgrass seeds, either on a single seed level, or on the population level, responded continuously to changing temperature and moisture conditions. Less aging was observed for switchgrass seeds stored in N₂. After-ripening of switchgrass seemed not to be influenced by N₂ or air. In sum, switchgrass is revealed to be remarkably plastic in its ability to move toward both greater germinability and greater dormancy. / Ph. D.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Most South African peach and nectarine production areas lack in adequate winter chilling. To address these issues, a conventional breeding programme was started, to develop new and improved stone fruit cultivars with special emphasis on climatic adaptation and pomological attributes. This study was conducted to test the accuracy of the scientific method called the phenological method of classification, currently used by the breeding programme to classify the selections in the second phase of evaluation according to chilling requirement. During April 2000 and May 2001 and continuing until the next spring, 20 oneyear- old shoots of 30 peach and nectarine selections were harvested fortnightly from an evaluation orchard on Bien Donné Experiment Farm, Simondium, Western Cape (34° S). All selections were previously categorised as high (>800 Utah chilling units [CU]), medium (400-800 CU) or _low «400 CU) chilling requirement based on phenologic observations. According to the preliminary classification of the selections included in this study, six selections were classified as high, three as medium and 21 as low chilling requirement. Two replicate bundles of shoots of each selection were prepared and forced at 25° C with continuous illumination until no further changes in bud burst occurred for a period of five days after which the shoots were then discarded. CU in the orchard were calculated according to the Utah and Infruitec models. The hours below 12° C and 7° C were also calculated. For each selection the number of days until 20% vegetative and reproductive bud break was plotted over day of year, Utah CU, Infruitec CU, hours below 12° C, and hours below 7° C, and expressed as a parabolic function. Similarly, the inverse of the number of days until 20% bud break or the rate of bud growth was also plotted against all the above variables. The area under these parabolas was statistically analysed using the CANDISC procedure of SAS Release 8.1. The groupings of the CANDISC procedure were more or less consistent with the preliminary groupings obtained with the phenoligical classification method. On 16 May 2000 and 15 May 2001, 100 one-year-old shoots of the same peach and nectarine selections were harvested from the evaluation orchard on Bien Donné Experiment Farm, covered in wet paper towelling and black plastic bags and placed in a cold room kept at a temperature range between 4° C and 7° C. Two replicate bundles of 10 shoots of each selection were prepared fortnightly and forced at 25° C with continuous illumination until no further changes in bud burst occurred for a period of five days after which the shoots were then discarded. CU accumulated in the cold room at each transferral date was calculated according to the Utah model. For each selection the number of days until 20% vegetative bud break was plotted over Utah CU, and expressed as a parabolic function. Similarly, the inverse of the number of days until 20% bud break or the rate of bud growth was also plotted against the above variables. The area under these parabolas was statistically analysed using the CANDISC procedure of SAS Release 8.1. Once again, the groupings of the CANDISC procedure were more or less consistent with the preliminary groupings obtained with the phenoligical classification method. Due to the nature of the scientific method used in this study, there is room for a certain margin of experimental error to occur, which could account for the misclassifications by the CANDISC procedure, when performed on the 2001 season's data. It can be concluded that the phenological method of classifying the selections, as currently used in the breeding programme, is consistent with the results of the scientific method described here. Therefore, it is recommended that the phenological method be used in future to classify the selections according to chilling requirement (CR), as this method is less time consuming and less costly to perform. Finally the outcome of the analysis of one season's data was used as calibration data against which the other season's data was tested and the consistency of the results, using one set of discriminant functions, was tested. It can be concluded that a unique set of discriminant functions is necessary for each winter season to accurately classify selections according to CR with the CANDISC procedure. / AFRIKAANSE OPSOMMING: 'n Studie van dormansie en koue behoefte van perskes en nektariens Gebrekkige winterkoue is 'n gegewe in die meeste Suid-Afrikaanse perske en nektarien-produksie-streke. Om die gevolge hiervan aan te spreek, is 'n konvensionele teelprogram tot stand gebring om verbeterde steenvrug cultivars te ontwikkel met voortreflike pomologiese eienskappe en wat aangepas is by die plaaslike klimaatstoestande. Hierdie studie is geloods om die akkuraatheid van die wetenskaplike metode, genoem die fenologiese klassifikasie metode, soos tans deur die teelprogram gebruik, waarvolgens seleksies volgens kouebehoefte geklassifiseer word, te toets. Vanaf April 2000 en Mei 2001 tot en met die daaropvolgende lente, is 20 eenjaar-oue lote van 30 perske en nektatrien seleksies twee weekliks in 'n fase 2 evaluasie boord op Bien Donné Proefplaas, te Simondium in die Wes- Kaap (34° S) versamel. AI die seleksies was vooraf op grond van fenologiese waarnemings geklassifiseer in kategorieë van hoog (>800 Utah koue-eenhede [CU]), medium (400-800 CU) of laag «400CU) ten op sigte van kouebehoefte. Hiervolgens val ses van die seleksies wat in die studie ingesluit is in die hoë-, drie in die medium- en 21 in die lae kategorie. Lote van elke seleksie is voorberei en in twee herhalings gebondel, waarna dit geforseer is teen 25° C met deurlopende beligting totdat geen verdere knopbreek vir 'n periode van vyf dae voorgekom het nie, waarna die lote verwyder is. CU in die boord is volgens die Utah en Infruitec modelle bereken. Die aantal uur onder 12° C en onder 7° C is ook bereken. Die aantal dae wat dit elke seleksie geneem het om 20% vegetatiewe en 20% reproduktiewe knopbreek te bereik is bereken en geplot teenoor die dag van die jaar, Utah CU, Infruitec CU, aantal uur onder 12° C en aantal uur onder 7° C en uitgedruk as 'n paraboliese funksie. Die inverse van die aantal dae tot 20% knopbreek, of die tempo van knopbreek, is op soortgelyke wyse geplot teenoor al bogenoemde veranderlikes. Die oppervlakte onder die parabole is statisties ontleed met behulp van die CANDISC prosedure van die SAS program (Vrystelling 8.1). Die groeperings wat met die CANDISC prosedure verkry is het grootliks ooreengestem met die groeperings volgens die fenologiese klassifikasie metode. Op 16 Mei 2000 en 15 Mei 2001, is 100 eenjaar-oue lote van dieselfde perske en nektarien seleksies in die evaluasie boord op Bien Donné versamel, toegedraai in klam handdoekpapier, in swart plastiek sakke geplaas en in 'n koelkamer geplaas waarvan die temperatuur konstant gehou is tussen die grense van 4° C en T" C. Twee herhalings van 10 lote elk, van elke seleksie, is twee weekliks voorberei en geforseer by 25° C met deurlopende beligting totdat geen verdere knopbreek vir 'n periode van vyf dae plaasgevind het nie, waarna die lote verwyder is. Op elke oordragdatum is die aantal CU, wat in die koelkamer geakkumuleer het, volgens die Utah model bereken. Die aantal dae wat dit elke seleksie geneem het om 20% vegetatiewe knopbreek te bereik is bereken en geplot teenoor die Utah CU en uitgedruk as 'n paraboliese funksie. Die inverse van die aantal dae tot 20% knopbreek , dus die tempo van groei, is op soortgelyke wyse bererken en geplot teenoor bogenoemde veranderlikes. Die oppervlak onder die paraboliese funksies is statisties ontleed met behulp van die CANDISC procedure. Die groeperings van die CANDISC prosedure het weereens grootliks ooreengestem met die groeperings wat met die fenologiese metode van klassifikasie verkry is. Weens die aard van die wetenskaplike metode wat tydens hierdie studie gebruik is, kom daar 'n sekere mate van eksperimentele fout voor, wat moontlik die misklassifikasies van die CANDISC prosedure kan verklaar, wanneer dit op die 2001 seisoen se data uitgevoer word. Die gevolgtrekking kan gemaak word dat die resultate van die fenologiese metode, soos dit tans deur die teelprogram gebruik word, ooreenstem met die resultate wat deur die wetenskaplike metode, wat hier beskryf word, verkry is. Dus word daar aanbeveel dat die fenologiese metode in die toekoms gebruik word om die seleksies te klassifiseer volgens koue behoefte (CR), aangesien hierdie metode minder tyd in beslag neem en goedkoper is om uit te voer. Laastens is die resultaat van die analise van een seisoen se data gebruik as kalibrasiedata waarteen die data van die ander seisoen getoets is om so ooreenstemmendheid van die resultate te toets as slegs een stel diskriminant funksies gebruik word. Die slotsom was dat 'n unieke stel diskriminantfunksies nodig is vir elke winter seisoen om die seleksies akkuraat met behulp van die CANDISC prosedure volgens koue-behoefte te klassifiseer.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Delayed foliation is commonly observed in apple and pear producing countries with warm and/or short winter climates, resulting in less synchronised budburst, of fewer buds and reduced yield. Applications of rest-breaking agents minimise the symptoms of delayed foliation. According to chilling models used in fruit producing areas of the world, the climate of South Africa is not suitable for deciduous fruit production, however fruit has been successfully produced here for a long time. This study aimed to quantify the effects of freezing temperatures, different chilling temperatures and the period of chilling, to obtain a better knowledge of bud dormancy release on apple and pear shoots. The chilling period was the most important factor influencing the progression of dormancy. While in some cases the chilling temperature and the freeze treatment effects were significant, the contribution to differences in the progression of dormancy was negligible. Our findings indicate that currently used chilling models should emphasise the time of exposure to low temperatures more than the difference in temperatures between I to ro-c. The South African apple and pear industry made good progress in moving towards high density plantings, but large variation in soil types, non-optimum growing conditions, replant situations and a lack experience with dwarfing rootstocks limited further development. However, there is sti II an urgency to obtain higher early yields of good quality fruit applying the most efficient production practices. We aimed to quantify the field performance of locally available apple and pear rootstocks, in particular from data outside of previously reported local trials, as well as early production of newly planted trials. Information obtained form the industry indicates that BPI and BP3 are the preferred pear rootstocks. From production records of 'Packham's Triumph' pears, it appeared that BP3 and OHxF97 produced the best yields compared to the other rootstocks. Production of 'Doyenne du Cornice' was the best on QA and BP3. In newly planted 'Rosemarie', 'Flamingo', and 'Forelle' trials, different rootstocks were evaluated. 'Rosemarie' showed indications 01 incompatibility with QA and QC5 I, but on BPI and QA with a 'Beurre Hardy' interstock produced good initial yields although BPI induced slightly larger trees. 'Flamingo' on QA and QC51 produced the best yields. 'Forelle' on BPI, BP3, and QA produced similar yields up to the 4th leaf. For apples M793 seems to be the preferred rootstock in the South African industry. From production records of 'Golden Delicious' and 'Granny Smith' apples, it appeared that M793 and MM 106 produced the best yields when compared to Seedling rootstock. In a 'Cripps' Pink' trial, MMI09, M793 and M25 were more vigorous than M7, MMlll and MMI06. MMI06 was cumulatively, over four years from planting, the most yield efficient, although no consistent trend regarding fruit quality was observed between the rootstocks evaluated. / AFRIKAANSE OPSOMMING: Vertraagde bot word algemeen opgemerk in appel en peer produserende lande met n' warm enlof kort winter klimaat, wat veroorsaak dat bot van minder knoppe, meer ongelyk plaasvind en gevolglik lei tot swakker opbrengste. Toediening van rus-breek middels beperk die simptome van vertraagde bot. Volgens koue modelle wat in vrugte produserende areas in die wereld gebruik word, is Suid Afrika se klimaat nie geskik vir die verbouing van sagtevrugte nie alhoewel sagtevrugte al vir n lang tyd met groot sukses hier verbou word. Hierdie studie is daarop gemik om die effek van vries temperature, verskillende koue temperature en die periode van koue op die vrystelling van dormansie op knoppe van appel en peer lote te kwantifiseer. Die peri ode van koue was die mees belangrikste faktor wat die ontwikkeling van dormansie beinvloed het. In sommige gevalle was die effek van die koue temperature betekenisvol, maar die bydrae tot die verskille in die ontwikkeling van dormansie was weglaatbaar klein. Ons bevindinge dui aan dat die huidige koue modelle wat gebruik word, meer klem moet le op die periode van blootstelling aan koue as aan die effek van verski llende temperature tussen 1 en 10°e. Die Suid Afrikaanse appel en peer bedryf het goeie vordering in die beweging na hoe digtheid aanplantings gemaak, maar groot verskille in grond tipes, sub-optimale groei toestande, herplant probleme en n' tekort aan ondervinding met dwergende onderstamme het verdere ontwikkeling beperk. Ten spyte hiervan is daar steeds n' dringendheid om hcer produksies, van goeie kwaliteit vrugte so vroeg as moontlik te kry deur die toepassing van die mees effektiewe produksie praktyke. Ons het gepoog om die prestasie van plaaslik beskikbare appel en peer onderstamme te kwantifiseer, in besonder deur data wat nog nie van tevore oor verslag gedoen is nie en ook deur te meld van vroee produksies op nuut aangeplante proewe. lnformasie uit die bedryf het aangedui dat BP 1 en BP3 die voorkeur peer onderstamme is. Deur na die produksie geskiedenis van 'Packham's Truimph' pere te kyk kom dit voor of BP3 en OHxF97 die beste produksies in vergelyking met die ander onderstamme gelewer het. Die produksie van 'Doyenne du Com ice' was die beste op QA en BP3. In nuut geplante 'Rosemarie', 'Flamingo', en 'Forelle' pro ev e was verskillende onderstammc gecvalueer. 'Rosemarie' het tekens van onverenigbaarheid getoon met QA en Q 51, maar op BP 1 en QA met n 'Beurre Hardy' tussenstam het 'Rosemarie' goeie aanvanklike opbrengste gel ewer, al was bome op BP 1 effens grater. 'Flamingo' op QA en QCS 1 het die beste opbrengste gelewer. 'Forelle' op BP 1, BP3, en QA het ongeveer ewe veel tot die 4dc blad geproduseer. By appels is M793 die voorkeur onderstam van die Suid-Afrikaanse appel bedryf. M793 en MM 106 gee beter opbrengste as Saailing onderstam wanner die produksie geskiedenis van 'Golden Delicious' en 'Granny Smith' appels evalueer word. In n' 'Cripps' Pink' proefwas MMI09, M793 en M2S meer groeikragtig as M7, MMlil en MMI06. MM I 06 het kumulatief meer geproduseer en was ook meer produsie doeltreffend tot en met die 4de blad na plant. Daar was egter geen konstante neiging rakende vrug kwaliteit tussen die verskillende onderstamme wat getoets is nie.