Breeding creeping-rooted lucerne for the subtropics

1967 ◽  
Vol 18 (6) ◽  
pp. 891 ◽  
Author(s):  
LA Edye ◽  
KP Haydock
Keyword(s):  
Survival Rates ◽  
Adventitious Shoots ◽  
Mass Selection ◽  
Genotypic Correlation ◽  
Specific Effects ◽  
The Mean ◽  
Selection For ◽  
Successive Generations ◽  
Seed Yields ◽  
Better Than

A lucerne-breeding programme was undertaken at Lawes, south-eastern Queensland, to transfer the creeping-rooted habit from Heinrichs's Canadian strains to subtropical lucerne varieties. Before intensive selection commenced, the inheritance and association of three characters, summer yield, winter yield, and the number of extra crowns originating as adventitious shoots from roots, were determined in the F2 and F3 generations. The F2 genotypic variances for summer yield, winter yield, and number of extra crowns were predominantly additive and were respectively 81, 53, and 54% of their phenotypic variances. The genotypic correlation coefficient for winter yield and number of extra crowns was negative ( rG = –0.18), consisting of a negative additive correlation rg = –0.55 and a positive non-additive correlation rs = 0.50. In the F3 generation the approximate genotypic correlation for these two characters was small and positive and composed of a nearly zero additive correlation and a high positive non-additive correlation. Simultaneous mass selection for summer yield, winter yield. and creeping-rootedness was undertaken in the F3 generation, and the combining ability variances and covariances for these characters were studied in the F4 generation. All three variables were positively associated in their general and specific effects, and the majority of families did not differ significantly from Hunter River in winter and summer yield. The seed production of ten F4 families was studied and it was found that eight families were significantly lower seed producers than Hunter River, their seed yields ranging from 20 to 47% of the mean for Hunter River. Covariance analysis showed seed yield and number of extra crowns to be negatively associated in the F4 generation. The changes in creeping-rootedness in the successive generations F1 to F5 were 2, 9, 34, 19, and 59% compared with a mean of 4% for Heinrichs's Canadian strains at Lawes. Creeping-rooted individuals survived better than non-creeping-rooted plants of similar genotype and better than Hunter River, particularly in the F4 generation, where the respective survival rates were 75, 27, and 23% 19 months after transplanting in the field

FERTILITY OF BARLEY AUTOTETRAPLOIDS: I. FERTILITY IN SUCCESSIVE GENERATIONS OF FOUR AUTOTETRAPLOID BARLEY VARIETIES AND THE EFFECT OF SELECTION FOR FERTILITY IN THE O.A.C. 21 AUTOTETRAPLOID

1959 ◽  
Vol 39 (1) ◽  
pp. 98-107 ◽  
Author(s):  
E. Reinbergs ◽  
L. H. Shebeski
Keyword(s):  
Promising Method ◽  
Low Fertility ◽  
Fertility Level ◽  
Seed Setting ◽  
The Mean ◽  
Selection For ◽  
Successive Generations ◽  
Subsequent Selection

The differences in fertility of four colchicine-induced autotetraploid barley varieties (Brant, Montcalm, O.A.C. 21 and York) were determined and compared in four successive generations following the induction of tetraploidy. Despite a wide fertility range within each autotetraploid, the varieties tested varied considerably in their mean per cent fertility. Within each variety the mean per cent fertility remained relatively constant from generation to generation. The Montcalm tetraploid had the lowest mean fertility, fluctuating from generation to generation within a range of 6.0 to 10.1 per cent. The O.A.C. 21 tetraploid had the highest mean fertility, fluctuating within a range of 40.0 to 51.3 per cent.Significant differences in fertility of the four autotetraploid varieties were interpreted as indicating that seed-setting ability may be genetically controlled and, therefore, hybridization and subsequent selection could be a promising method for increasing fertility.Continuous selection for either high or low fertility from the C1 to C4 generation did not change the mean per cent fertility level in the O.A.C. 21 tetraploid.

MASS SELECTION FOR RESISTANCE TO SELENOPHOMA BROMIGENA IN NORTHERN AND SOUTHERN TYPES OF BROMUS INERMIS

1967 ◽  
Vol 47 (6) ◽  
pp. 679-681 ◽  
Author(s):  
J. Drew Smith ◽  
R. P. Knowles
Keyword(s):  
Disease Resistance ◽  
Leaf Spot ◽  
Bromus Inermis ◽  
Mass Selection ◽  
Progeny Testing ◽  
Smooth Bromegrass ◽  
Selection For ◽  
Better Than

In the epidemic years 1965 and 1966, field ratings confirmed that southern strains of smooth bromegrass, Bromus inermis Leyss, were generally less susceptible to leaf spot caused by Selenophoma bromigena (Sacc.) Sprague & A. G. Johnson than northern strains. The northern/southern hybrid S-6733, developed by mass selection and progeny testing, was found to resist S. bromigena at least as well as the southern strains Lincoln and Redpatch, and better than the southern Saratoga. It was found possible to improve resistance of the susceptible northern strain Carlton by mass selection. Northern strains probably do not have as great a potential for improvement in disease resistance as southern strains or hybrids.

scholarly journals Two-way within-family and mass selection for 8-week body weight in different mouse populations

1984 ◽  
Vol 43 (2) ◽  
pp. 191-200 ◽  
Author(s):  
Ines von Butler ◽  
Henning Willeke ◽  
Franz Pirchner
Keyword(s):  
Body Weight ◽  
Inbred Strains ◽  
Selection Response ◽  
Mass Selection ◽  
Individual Selection ◽  
Family Selection ◽  
Body Weights ◽  
Selection For ◽  
Size At Birth ◽  
Better Than

SUMMARYTwo mouse populations, randombred albino mice and a cross of four inbred strains, were divergently selected for high (H8) and low (L8) 8-week body weight over 18 generations using within-family and individual selection. The crossbreds showed asymmetry of selection response and realized heritabilities (H8 0·29 ± 0·01; L8 0·17 ± 0·01). In the randombred population realized heritabilities were symmetrical (H8 0·23 ± 0·01; L8 0·22 ± 0·02). Over the first nine generations individual selection was nearly 40 per cent better than within-family selection, as was expected from the full sib correlation in both populations. As selection progressed, within-family selection reached 82% and 61% of the responses obtained with individual selection in the crossbreds and randombred respectively. Correlated responses for 3-week (weaning) and 5-week body weights agreed with observations made on direct responses, but selection for L8 did not reduce weaning weight. Selection for L8 decreased and selection for H8 increased first litter size at birth. However, mass-selected L8-pairs had a higher life-reproduction and life-span than H8-pairs.

EARLY GENERATION SELECTION FOR PROTEIN IN Glycine max × G. soja CROSSES

1981 ◽  
Vol 61 (4) ◽  
pp. 901-908 ◽  
Author(s):  
L. R. ERICKSON ◽  
W. D. BEVERSDORF ◽  
H. D. VOLDENG
Keyword(s):  
Protein Content ◽  
Seed Protein ◽  
Glycine Soja ◽  
Mass Selection ◽  
Seed Protein Content ◽  
Family Selection ◽  
Early Generation ◽  
Early Generation Selection ◽  
The Mean ◽  
Selection For

Early generation selection for high seed-protein content would be desirable in breeding programs attempting to combine high yield and high protein content in soybeans (Gycine max (L.) Merr.). The heritability of seed-protein content in the F2 and F3 was measured in four crosses and mass and family selection for protein were compared in the F3 of these crosses. Glycine soja Sieb. and Zucc., a putative wild ancestor of the soybean, was the male parent in all crosses and selection intensity was at 10%. The heritability of protein in the F2, calculated by parent-offspring regression, was 27%. The broad-sense heritability of protein in F3 families grown over two locations in one season was 78%. Mean protein content for every selected population was greater (P ≤ 0.01) than the mean for the non-selected control population (45.3%). Mean protein contents of the F4 populations resulting from these selection methods were: mass selection in the F2 and F3, 48.0%; mass selection in the F3 following one generation of single seed descent, 48.8%; selection among F3 families, 47.6%; selection among and within F3 families, 47.5%. Either method of mass selection was superior to either method of family selection at the 0.01 level. Although early selection (mass or family) raised the mean protein content of a population, segregation continued to give rise to low-protein genotypes thereby requiring further selection.

scholarly journals Threshold selection for rust resistance in hybrid poplar: Population response to mass selection

2011 ◽  
Vol 60 (1-6) ◽  
pp. 266-276 ◽  
Author(s):  
B. J. Stanton
Keyword(s):  
Rust Resistance ◽  
Polynomial Regression ◽  
Hybrid Poplar ◽  
Directional Selection ◽  
The Other ◽  
Quadratic Functions ◽  
Mass Selection ◽  
Selection Intensity ◽  
The Mean ◽  
Selection For

AbstractElevenPopulus×generosapopulations were developed in the Pacific Northwest by annual controlled hybridization ofP. deltoidesandP. trichocarpabetween 1991 and 2001. Mass selection forMelampsoraleaf rust resistance was observed in the field as a threshold character in identifying seedling phenotypes for clonally replicated evaluation. The effectiveness of the approach was assessed for each annual population by comparing the distribution of phenotypes in unselected seedling populations with the distribution of selected genotypes in the clonal field tests established in successive years and evaluated at the approximate same level of disease severity using two selection thresholds corresponding to chlorotic and healthy tissue. Bi-directional selection was used as an initial check on the efficacy of the procedure and resulted in a wide separation in liability between the positive (0.06 threshold units (T.U.)) and negative (−2.45 T.U.) selection groups when tested as clones. The other 10 seedling populations that were subjected solely to directional selection exhibited a mean increase in incidence above the first selection threshold at the clonal stage (47 versus 81%) that was accompanied by an improvement in population liability (−0.06 versus 0.50 T.U.) and a reduction in population standard deviation (0.83 versus 0.54 T.U.). The change in liability was strongly related by polynomial regression to selection intensity and a grouping of populations based on infection-season precipitation (r2=0.98). The mean liability of four of the 10 seedling populations observed during years of high infection-season rainfall was six-fold lower than the mean liability of those populations observed during the other six years of lower infection-season rainfall (−0.12 T.U. versus −0.02 T.U., respectively), indicating that populations undergoing evaluation during years of heavy precipitation experienced more intense rust exposure. Moreover, quadratic functions showed that populations undergoing rust evaluation during years of high rainfall were more responsive to increases in selection intensity above the vertex of the function (i.e. 13.20 versus 3.43 T.U.). Realized heritability averaged 0.63 for all ten populations subjected solely to directional selection.

scholarly journals Genetic variation for tolerance to defoliation in Cirsium arvense (Californian thistle)

2017 ◽  
Vol 70 ◽  
pp. 324
Author(s):  
M.G. Cripps ◽  
C.A. Dowsett ◽  
S.D. Jackman ◽  
A.D.L. Noble ◽  
G.J. Houliston
Keyword(s):  
Final Height ◽  
Adventitious Shoots ◽  
Shoot Density ◽  
Cirsium Arvense ◽  
Management Implications ◽  
Shoot Height ◽  
Plant Experiment ◽  
The Mean ◽  
Selection For ◽  
Californian Thistle

The pasture weed, Cirsium arvense (Californian thistle), is notorious for its ability to tolerate defoliation by herbivores, mowing, or herbicides, which is facilitated by the growth of adventitious shoots from its extensive clonal underground root system. In an outdoor potted-plant experiment, we examined the tolerance of 36 unique genotypes of C. arvense to defoliation by establishing pairs of clonal replicates that were assigned to a clipped, or unclipped treatment. Three clipping treatments were applied, and the final height, number of shoots, and biomass, were measured to compare the fitness between the clipped and unclipped clones. The majority of genotypes were negatively affected by clipping and showed a reduction in most final fitness measurements. However, some genotypes were equivalent or even greater than their unclipped counterparts indicating a large genetic range for tolerance to defoliation. The mean range in tolerance ratios (clipped/ unclipped) was 0.17 to 1.3 for shoot height, 0.26 to 1.2 for shoot density, and 0.6 to 1.2 for biomass (where a ratio of 1 indicates equivalence to the unclipped state). Since repeated defoliation is recommended for control of this weed, selection for more tolerant genotypes is possible, which may have management implications.

Genetic parameters and provenenance variation of Pinus caribaea var. hondurensis in 48 international trials

2001 ◽  
Vol 31 (3) ◽  
pp. 496-511 ◽  
Author(s):  
G R Hodge ◽  
W S Dvorak
Keyword(s):  
First Generation ◽  
Genetic Parameters ◽  
Volume Growth ◽  
Environment Interaction ◽  
Pinus Caribaea ◽  
Genotype Environment Interaction ◽  
The Mean ◽  
Selection For ◽  
Similar Growth ◽  
Better Than

A total of 23 provenances or sources of Pinus caribaea var. hondurensis (Sénécl) Barr. et Golf. were tested in 48 provenance–progeny trials in Colombia, Brazil, and Venezuela. In Brazil and Venezuela, 8-year heights were approximately 12 m, while in Colombia, mean 8-year height was less than 8 m. The growth rates of the unimproved material correspond approximately to volumes of 14–15 m3·ha–1·year–1 of wood on sites in Brazil and Venezuela, and 4–5 m3·ha–1·year–1 in Colombia. Provenances had similar growth rankings in the different countries, with a type-B provenance correlation of 0.63. The best native provenances were Limón and Guanaja, Honduras. Improved first-generation sources from Queensland, Australia and Zululand, South Africa, were 5–12% better than the mean of the unimproved provenances, depending on country where planted. Mean single-site heritability for volume growth is approximately 0.18. Potential genetic gain for volume at 8 years from selection within provenance is around 30%. Foxtailing is also under moderate genetic control with heritability around 0.15. Genotype × environment interaction for volume growth is generally higher for tests located in different countries than in the same countries. Selection for age-8 volume using age-5 data would be 93% as effective as selection at age 8.

Heritable Chilling Tolerance Improvement in Rice Through Somaclonal Variation and Cell Line Selection

1996 ◽  
Vol 44 (1) ◽  
pp. 91 ◽  
Author(s):  
P Bertin ◽  
JM Kinet ◽  
J Bouharmont
Keyword(s):  
Oryza Sativa L ◽  
Chilling Stress ◽  
Survival Rates ◽  
Mass Selection ◽  
Heritable Variation ◽  
Higher Plant ◽  
Rice Varieties ◽  
Successive Generations ◽  
Tolerance Improvement

Embryo-derived calli of four rice varieties (Oryza sativa L.) were submitted to different continuous or discontinuous periods of chilling stress at 4°C, with a total length varying from 2 to 6 weeks. Other calli were cultivated during different times without cold stress. The reduction of plant regeneration percentages induced by low temperature was more pronounced in the more cold-sensitive varieties. Regenerated plants (R0) and their descendants in R1, R2 and R3 generations were cold-screened together with control plants. A mass selection was applied to the control plants during three successive generations. In all varieties, significantly higher chilling survival rates were obtained in R3 with in vitro grown plants than with control plants. Higher plant survival rates were obtained with the more chilling-sensitive varieties when a short discontinuous chilling treatment or no treatment had been applied, with the intermediate variety with short or intermediate treatments, and with the more cold-tolerant variety with longer, continuous treatments. The relative importance of pre-existing versus in vitro-induced variation and of epigenetic versus heritable variation, along with the significance of such cold tolerance improvement for breeding purposes are discussed.

Root Repair Versus Partial Meniscectomy for Medial Meniscus Posterior Root Tears: Comparison of Long-term Survivorship and Clinical Outcomes at Minimum 10-Year Follow-up

2020 ◽  
Vol 48 (8) ◽  
pp. 1937-1944 ◽  
Author(s):  
Kyu Sung Chung ◽  
Jeong Ku Ha ◽  
Ho Jong Ra ◽  
Woo Jin Yu ◽  
Jin Goo Kim
Keyword(s):  
Medial Meniscus ◽  
Survival Rates ◽  
Partial Meniscectomy ◽  
Clinical Failure ◽  
Kaplan Meier ◽  
The Mean ◽  
Repair Group ◽  
Better Than

Background: The importance of repair in medial meniscus posterior root tears (MMPRTs) has been increasingly recognized because it restores hoop tension. However, no study has compared the long-term outcomes between meniscectomy and repair. Hypothesis: Survivorship and clinical outcomes of repair would be better than those of meniscectomy after long-term follow-up. Study Design: Cohort study; Level of evidence, 3. Methods: Between 2005 and 2009, patients with MMPRTs who had been followed up for at least 10 years after partial meniscectomy (n = 18) or pullout repair (n = 37) were recruited. Clinical assessments, including the Lysholm score and International Knee Documentation Committee (IKDC) subjective score, were evaluated preoperatively and at the final follow-up. The final results in each group were compared with the preoperative results, and the final results of the groups were compared. Clinical failure was defined as conversion to total knee arthroplasty (TKA), and the final clinical scores were assessed just before TKA. Kaplan-Meier survival analysis was used to investigate the survival rates of surgical procedures. Results: Mean ± SD follow-up period was 101.4 ± 45.9 and 125.9 ± 21.2 months in the meniscectomy and repair groups, respectively ( P = .140). The mean Lysholm and IKDC scores, respectively, in the meniscectomy group were 50.8 ± 7.7 and 37.6 ± 7.0 preoperatively and 58.2 ± 22.1 and 44.4 ± 19.0 postoperatively ( P = .124; P = .240). In the repair group, the mean Lysholm score and IKDC score, respectively, significantly increased from 52.3 ± 10.9 and 41.0 ± 9.6 preoperatively to 77.1 ± 24.0 and 63.7 ± 20.6 postoperatively ( P < .001; P < .001). The final Lysholm and IKDC scores in the repair group were significantly better than those in the meniscectomy group ( P = .004; P = .003). In cases of clinical failure, 10 patients (56%) in the meniscectomy group and 8 patients (22%) in the repair group converted to TKA in the follow-up period ( P = .016). According to Kaplan-Meier analysis, the 10-year survival rates for the meniscectomy and repair groups were 44.4% and 79.6%, respectively ( P = .004). Conclusion: In MMPRTs, root repair was superior to partial meniscectomy in terms of clinical results for at least 10 years of follow-up. From a long-term perspective, repair with restoration of hoop tension is more effective management than meniscectomy.

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