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.

RESISTANCE TO PYRENOPHORA BROMI IN BROMEGRASS

1973 ◽  
Vol 53 (1) ◽  
pp. 93-99 ◽  
Author(s):  
J. DREW SMITH ◽  
R. P. KNOWLES
Keyword(s):  
Leaf Spot ◽  
Field Tests ◽  
Bromus Inermis ◽  
The Other ◽  
Leaf Spot Disease ◽  
Western Canada ◽  
Smooth Bromegrass ◽  
Spot Disease ◽  
Selection For ◽  
Type Strains

The resistance of strains of northern, southern, and northern/southern hybrids of smooth bromegrass (Bromus inermis) to Pyrenophora bromi, the cause of a major leaf spot disease, was determined in field tests in northern Saskatchewan from 1967 to 1971. Infection derived from natural epidemics was supplemented with that from highly susceptible infector plants spaced in the test plots to improve uniformity of inoculum supply. No bromegrass strains were completely resistant to the pathogen. Four of the eight northern/southern cultivars and three of the five southern cultivars were more resistant to P. bromi than any of the nine northern types. The best southern cultivars, Baylor and Sac, were not significantly more resistant than the cult Magna and less resistant than the S-7382 and S-7306 strains, all of northern/southern-type. Basic clones of northern/southern-type strains, adapted to Western Canada, were superior in resistance to northern clones. Parental clones were more resistant than their progeny and this resistance declined from the Syn. 1 to the Syn. 2 in two northern/southern strains. Selection for resistance to the other major leaf spot pathogen, Selenophoma bromigena, resulted in a limited improvement also in resistance to P. bromi.

Recurrent Phenotypic Selection for Resistance to Brown Leaf Spot in Smooth Bromegrass 1

Crop Science ◽  
1986 ◽  
Vol 26 (3) ◽  
pp. 533-536 ◽  
Author(s):  
Clyde C. Berg ◽  
Robert T. Sherwood ◽  
Kenneth E. Zeiders
Keyword(s):  
Leaf Spot ◽  
Phenotypic Selection ◽  
Smooth Bromegrass ◽  
Brown Leaf Spot ◽  
Brown Leaf ◽  
Selection For

SEEDLING PUBESCENCE AS A GENETIC MARKER IN SMOOTH BROMEGRASS (BROMUS INERMIS LEYSS.)

1980 ◽  
Vol 60 (4) ◽  
pp. 1163-1170 ◽  
Author(s):  
R. P. KNOWLES
Keyword(s):  
Genetic Marker ◽  
North American ◽  
Inbred Lines ◽  
Bromus Inermis ◽  
Mass Selection ◽  
Smooth Bromegrass ◽  
Leaf Stage ◽  
Temperature Conditions ◽  
Early Fall ◽  
Controlled Crosses

Seedlings of a group of North American cultivars of smooth bromegrass were examined at the three-leaf stage for pubescence under greenhouse conditions. Southern strains showed 90–98% strongly pubescent seedlings while northern strains had 60–70% strongly pubescent seedlings. Saratoga, although considered southern in type, was less pubescent than all other cultivars except Polar. The degree of pubescence was greater in spring and early fall plantings than in winter plantings, indicating that pubescence depends on good light and temperature conditions. Strains nearly pure for strong pubescence were formed by repeated cycles of mass selection. Few inbred lines showed uniformity for pubescent or smooth seedlings. Pure-breeding smooth stocks were more difficult to produce than highly pubescent strains. Controlled crosses showed partial dominace for pubescence and little difference between reciprocals. Adjacent plantings of pubescent and smooth seedling stocks showed as much as 45% off-type seedlings from seed produced at the interface of plots. Contamination declined to 10% or less at 10 m from the border.

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.

Short-term Progeny Tests and Second Generation Breeding in Slash Pine

1973 ◽  
Vol 3 (2) ◽  
pp. 165-169
Author(s):  
E. C. Franklin ◽  
A. E. Squillace
Keyword(s):  
First Generation ◽  
Second Generation ◽  
Slash Pine ◽  
Mass Selection ◽  
Progeny Testing ◽  
Family Selection ◽  
Short Term ◽  
Major Disadvantage ◽  
Selection For ◽  
Almost All

Progeny testing is the most widely used method for intensive genetic evaluation of selected forest trees, but its major disadvantage is the length of time needed to get results. To circumvent this problem in selection for a multiproduct strain of slash pine (Pinuselliottii Engelm.), a system for short-term (3-year) progeny testing was developed. Oleoresin yields of selected second-generation 19-year-old parent trees were compared with yields of their 3-year-old offspring. Both parents and offspring showed little variation and a low offspring–parent correlation (r = 0.18), but other traits based on the same parent trees when they were 25 years old and their 3-year-old offspring showed relatively large amounts of variation and moderate to strong offspring-parent correlations: height, r =.56; volume, r = 0.43; turpentine, r = 0.71; ethanol–benzene extractives, r = 0.38; specific gravity, r = 0.43; moisture content, r = 0.34. Thus, indications are that additional gains could be made in the first generation by selecting among parent trees on a progeny performance basis in all traits except oleoresin yield. Original mass selection for oleoresin yield achieved gains of 100% improvement and apparently exploited almost all of the genetic variation in the base population. In second generation selection, progeny testing will be used primarily in screening for fusiform rust resistance. Between-family plus within-family selection will be used for other traits.

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

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