Four-way data analysis within the linear mixed modelling framework

Cultivars have to be evaluated under different crop management systems across agro-ecosystems and years using multi-environment trials (MET) before releasing them to the market. Frequently, data collected in METs are arranged according to cultivar (G), management (M), location, (L) and year (Y) combinations in a four-way G x M x L x Y data table that is highly unbalanced for cultivars across locations and time. Therefore, we present the restricted maximum likelihood method (REML) for linear mixed models (LMM) with a factor analytic variance-covariance matrix for assessing cultivar adaptation to crop management systems and environments based on unbalanced datasets. Such a multi-environmental trial system has been in operation in Poland for winter wheat (Triticum aestivum L.) in the form of the Post-registration Variety Testing System (PVTS). This study aimed to illustrate the use of LMM in the analysis of unbalanced four-way G x M x L x Y data. LMM analysis provided adjusted means of grain yield for 51 winter wheat cultivars bred in different regions in Europe, tested across 18 trial locations and seven consecutive cropping seasons in two crop management intensities. The application of the four-way LMM with a factor analytic variance-covariance matrix is a complementary and effective tool for evaluating the unbalanced G x M x L x Y table. Cultivars tested had different adaptive responses to the Polish agro-ecosystems separately for each of the crop management intensities. Wide adaptation in both crop management systems was exhibited by cultivars Mulan and Jenga bred in Germany

Turfgrass evaluation of native grasses

There is increasing public pressure on the turfgrass industry to reduce maintenance inputs. Grasses native to North America seem perfect candidates for low-maintenance turfgrass as they have evolved under the environmental extremes of North America. The objectives of this research were to identify native grass species suitable for use in drought, saline and low-maintenance conditions. Fifteen native grass species for a total of 31 entries were evaluated: alpine bluegrass ('Poa alpina' L.), alkali grass (' Puccinellia nuttaliana' [Schultes] Hitchc.), blue grama (' Bouteloua gracilis' [Willd. ex kunth] Lag. ex Griffiths), buffalograss ('Buchloe dactyloides' [Nutt.] Engelm.), Canada bluegrass (' Poa compressa' L.), fescue spp., fowl bluegrass ('Poa palustris ' L.), Idaho bentgrass ('Agrostis iddaensis'), inland desert saltgrass ('Distichlis stricta' [Torr.] Rydb.), marsh muhly ('Muhlenbergia racemose' [Michx.] B.S.P.), prairie junegrass ('Koeleria macrantha' [Ledeb.] LA. Schultes), rough hairgrass ('Agrostis scabra' Willd.), side-oats grama ('Bouteloua curtipendula' [Michx.] Torr.), sweetgrass ('Hierchloe odorata ' [L] Beauv.) and tufted hairgrass ('Deschampsia caespitosa ' [L.] Beauv.). The entries with high quality ratings for low-maintenance turf use were: Minnesota ecotype blue grama, 'Bismarck' and 'Sharp's Imp. II' buffalograss, inland desert saltgrass, 'Bad River' blue grama, 'Barkoel' prairie junegrass and 'Golfstar' Idaho bentgrass. The last four were also moderately tolerant of saline soil conditions. The warm season grasses entries blue grama and buffalograss were extremely drought tolerant, maintaining consistent green colour. Most entries will require a breeding and selection program before being released to the public for low-maintenance turfgrass use. This research provides useful information on a number of native grass species suitable as low-maintenance turf and the relevant drought and saline tolerance of many native grass species

Mandibular dental changes following serial and late extraction of mandibular second premolars

Introduction: 15% of the general population are affected by severe dental crowding where conventional orthodontic treatment involves permanent dentition extractions. An alternative treatment method involves serial extraction in the mixed dentition. There is currently limited research on second premolar serial extraction. Objectives: To determine the changes in occlusal curves and dental tipping that occur from mandibular second premolar serial extraction and early extraction of deciduous mandibular second molars with missing mandibular second premolars. Methods: Records were collected from 85 subjects at 3 timepoints: T0, baseline for the control and serial extraction patients; T1, after extraction and physiologic drift but prior to orthodontic treatment for serial extraction patients, and pre-treatment for the late premolar extraction patients; and T2, after comprehensive orthodontic treatment. Three occlusal curves were measured on digitized mandibular casts by placing best fit spheres at specified landmarks. The long axes of the lower first molar, first premolar, canine and central incisor to the palatal plane were measured on digitized cephalometric radiographs to determine the direction and amount of tipping. Results: At T0, there were no significant differences between groups. At T1, there was significant steepening of Monson’s Sphere and the Curve of Wilson between early and late extraction groups. At T2, the differences in Monson’s sphere and the Curve of Wilson were fully corrected. At T1, there were significant differences in the tipping of lower 6’s, 4’s and 3’s between the early extraction groups compared to the late extraction and control groups. There was no difference in lower incisor tipping between any group. At T2, the differences in tipping were fully corrected. Conclusions: Serial extraction of lower second premolars, or lower deciduous second molars when second premolars were missing, produced steeper occlusal curves and significant tipping of mandibular first molars, first premolars and canines after extraction and physiologic drift (T1). The tipping of teeth and accentuated occlusal curves of Monson’s sphere and the Curve of Wilson were fully corrected following comprehensive fixed orthodontic treatment (T2). Serial extractions involving lower second premolars or lower deciduous second molars did not cause any significant lingual tipping of lower incisors following physiologic drift.Dentistry, Faculty ofGraduat

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Mandibular dental changes following serial and late extraction of mandibular second premolars

ABSTRACT Objectives: To determine changes in occlusal curves and dental tipping occurring from mandibular second premolar serial extraction, early extraction of deciduous mandibular second molars with missing second premolars, and late second premolar extraction compared with untreated controls. Materials and Methods: Information was collected from 85 subjects at three time points: T0, prior to serial extraction; T1, after serial extraction and drift prior to orthodontic treatment, and pretreatment for the late premolar extraction patients; and T2, posttreatment. Untreated age- and gender-matched controls were used for comparison. Three occlusal curves were measured on digitized mandibular casts, and dental tipping was assessed using lateral cephalograms. Results: At T0, there were no significant differences among groups. At T1, there was significant steepening of Monson's sphere and the curve of Wilson between early and late extraction and control groups. At T2, the differences in Monson's sphere and the curve of Wilson were fully corrected. At T1, there were significant differences in the tipping of mandibular 6's, 4's, and 3's between the early extraction groups compared with the late extraction and control groups. At T2, these differences in tipping were fully corrected. There were no differences in mandibular incisor tipping between groups at T1 or T2. Conclusions: Serial extraction produced steeper occlusal curves and significant tipping of mandibular first molars, first premolars, and canines after extraction and physiologic drift (T1). Accentuated occlusal curves and tooth tipping were fully corrected following orthodontic treatment (T2). Mandibular incisor position was unchanged by serial or late second premolar extraction. </jats:sec

Physiologically mediated self/non-self discrimination in roots

Recent evidence suggests that self/non-self discrimination exists among roots; its mechanisms, however, are still unclear. We compared the growth of Buchloe dactyloides cuttings that were grown in the presence of neighbors that belonged to the same physiological individual, were separated from each other for variable periods, or originated from adjacent or remote tillers on the same clone. The results demonstrate that B. dactyloides plants are able to differentiate between self and non-self neighbors and develop fewer and shorter roots in the presence of other roots of the same individual. Furthermore, once cuttings that originate from the very same node are separated, they become progressively alienated from each other and eventually relate to each other as genetically alien plants. The results suggest that the observed self/non-self discrimination is mediated by physiological coordination among roots that developed on the same plant rather than allogenetic recognition. The observed physiological coordination is based on an as yet unknown mechanism and has important ecological implications, because it allows the avoidance of competition with self and the allocation of greater resources to alternative functions