Genotype × environment interactions for resistance to Kabatiella caulivora in Trifolium subterraneum subspecies yanninicum

1980 ◽  
Vol 31 (6) ◽  
pp. 1111 ◽  
Author(s):  
PE Beale ◽  
NA Goodchild

Genotype x environment interactions of resistance to clover scorch in Trifoliurn subterraneurn subspecies yanninicum were studied by growing 11 subterraneum clover genotypes at three sites in Western Australia and one site in South Australia. Similar data from the previous year at one site were utilized to study genotype x season interactions. Clover scorch damage was assessed by scoring at fortnightly intervals from which total disease development was calculated. A combination of established methods called by us significant rank order, in which analysis of variance is followed by a ranking process, is developed and discussed. Interactions based on significant rank order are demonstrated, and the implications of these interactions for plant breeding strategies are discussed.

2008 ◽  
Vol 59 (6) ◽  
pp. 561 ◽  
Author(s):  
P. G. H. Nichols ◽  
M. P. You ◽  
M. J. Barbetti

Twenty-eight cultivars and 106 F6-derived breeding lines of subterranean clover (Trifolium subterraneum) were screened in the field for their response to clover scorch disease caused by race 1 of Kabatiella caulivora. Eleven of the cultivars, including Denmark and Goulburn, were classified as resistant. Breeding lines with Denmark parentage had 55% of progeny with resistance, while those of Goulburn had only 19% of resistant progeny, suggesting different modes of inheritance. Selection for resistance to race 2 of K. caulivora in the F4 generation markedly increased the probability of selecting F6-derived lines with resistance to race 1, suggesting linkage between genes for resistance to both races.


1975 ◽  
Vol 26 (4) ◽  
pp. 647 ◽  
Author(s):  
K Helms

Seedlings of six cultivars of Trifolium subterraneum were tested during germination for resistance to Kabatiella caulivora, and gave results comparable with those obtained with seedlings inoculated by spraying at 1–4 weeks after sowing. Advantages of the method were that a large number of seedlings could be screened under uniform conditions with the minimum of time and space. Within the more susceptible group of cultivars, Woogenellup and Bacchus Marsh were usually more susceptible than Yarloop and Mt. Barker; these in turn were more susceptible than Clare, and Clare more susceptible than Daliak. For all cultivars except the highly resistant cultivar, Daliak, there was a correlation between the rate of trifoliolate leaf production and susceptibility to the disease, the most susceptible being those with most leaves expanded at the time of inoculation and with most leaves present at the time of harvest. Physiologic specialization in isolates of the pathogen from different parts of Australia was demonstrated. In general, one isolate from South Australia was more pathogenic than a group of isolates from South Australia, Victoria and Western Australia; these in turn were more pathogenic than one isolate from New South Wales, which was somewhat atypical in culture, and one from Victoria which was markedly atypical in culture.


1972 ◽  
Vol 12 (59) ◽  
pp. 634 ◽  
Author(s):  
PE Beale ◽  
EJ Crawford

The growth and persistence of a number of accessions of seven species of Trifolium were measured. For the first three years the plots were grazed only to remove excess herbage after sampling. For the following three years they were grazed continuously under commercial conditions. In ungrazed swards the annual dry matter production of accessions of T. cherleri, T. globosum, and T. purpureurn was similar to T. subterraneum cultivars Yarloop and Woogenellup. T. cherleri, T. globosum, and Woogenellup made the bulk of their growth during the spring whereas T. purpureum and Yarloop produced half of their total dry matter during the winter. Good plant densities of T. argutum, T. cherleri, T. purpureum, and T. subterraneum were present at the end of three years continuous grazing, but Woogenellup and all other species were markedly inferior to Yarloop in their contribution to total production at the end of this period. Yarloop and T. purpureum were found to be very susceptible to clover scorch (Kabatiella caulivora) ; Woogenellup was moderately susceptible and the other species were unaffected in the field. All test species had low levels of formononetin in their leaves.


1990 ◽  
Vol 41 (1) ◽  
pp. 115 ◽  
Author(s):  
M Chandrashekar ◽  
GM Halloran

The disease reaction of seedlings (2 weeks old) from a field collection of subterranean clover (Trifolium subterraneum) to clover scorch (Kabatiella caulivora (Kirch.) Karak), revealed 89 immune plants out of a total of 1530. However, with adult plants (15-16 weeks old) only one plant remained immune. In the F2 population of the cross of the cultivars (Daliak X Woogenellup (D X W), seedling resistance was conditioned by a single dominant gene and in the cross (Enfield X Woogenellup) (EX W) by a single recessive gene. However, with adult plants, resistance in the (D X W) F2 was conditioned by a single recessive gene and that in the (EX W) F2 by two recessive genes. The effect of increasing age in reducing the proportion of plants resistant to clover scorch in both studies indicates that caution is needed in evaluating resistance to clover scorch in epidemiological, breeding and genetic studies.


1979 ◽  
Vol 30 (4) ◽  
pp. 651 ◽  
Author(s):  
PE Beale ◽  
N Thurling

The development of a clover scorch epidemic was studied at Denmark, W.A., by using 62 lines of Trifolium subterraneum including 29 subspecies yanninicum genotypes. Total disease development (TDD), the intrinsic rate of disease development (Rate) and time to 50% disease development (Delay) were calculated from fortnightly observations from August to December. Principal component analyses of the data lent support to the view that TDD is a good measure of disease expression. TDD ranged from 16 to 139 disease days (maximum possible 140). Nine yanninicum genotypes that had TDD values of less than 28 disease days are considered to have potential in breeding for resistance. Within these nine genotypes there was, however, considerable variation in Rate and Delay. A positive correlation between early growth and TDD, and a negative correlation between flowering date and TDD, are seen as possible problems in breeding resistant cultivars. Scoring plants once in the middle of the period of maximum disease development and also at the end of the season should provide a reasonably accurate approximation of TDD and delay.


1975 ◽  
Vol 26 (3) ◽  
pp. 511
Author(s):  
K Helms

The effects of moisture conditions on disease development and plant growth were examined in subterranean clover plants which were inoculated with K. caulivora 4 weeks after sowing and were maintained after inoculation at 20°C and with a light intensity of 2000 f.c. In plants which received 100% relative humidity (RH) with free water on leaves, for at least 4 days after inoculation, 15–20% of leaves developed lesions within 11 days. In plants which received continuously 90% RH with free water on leaves, or 100% RH without free water on leaves, less than 1.5% of leaves developed lesions within 11 days. There was no evidence of spread of infection in plants maintained for 11 or 25 days after inoculation. The effects of light intensities of 2000, 500 and 125 f.c. on disease development and plant growth were examined in plants which received 100% RH with free water on leaves and were grown for 25 days after inoculation, either in simulated swards or in standard pots. In most treatments a reduction in light intensity from 2000 to 500 f.c. reduced the growth of plants but had no effect on the percentage of diseased leaves, whereas a reduction in light intensity from 500 to 125 f.c. reduced growth and increased the percentage of diseased leaves of plants grown in swards from 30 to 70% and in standard pots from 10 to 35%. There were mortalities among both inoculated and control plants grown under 125 f.c. : in swards, 80–90% of inoculated plants and 30–40% of control plants died, whereas in standard pots 20–30% of inoculated plants and only occasional control plants died. The data show that environmental conditions favourable for the development of the disease were unfavourable for growth of control plants.


1975 ◽  
Vol 15 (75) ◽  
pp. 541 ◽  
Author(s):  
DL Chatel ◽  
CM Francis

The resistance of 307 varieties of subterranean clover (Trifolium subterraneum) to the clover scorch disease pathogen was assessed in three locations in south west Australia. Disease intensity as measured by visual ratings of sward damage was found to vary with variety and location. Resistance was independent of subspecies groupings but dependent on country of origin. Spanish and Portugese varieties were generally less susceptible than North African selections. Disease severity was also related to plant characters by correlation and multiple regression analysis. Late maturing varieties were most resistant under the test conditions and rapidly growing earlier varieties, with large pale leaves and thick petioles, were least resistant.


1975 ◽  
Vol 26 (3) ◽  
pp. 511
Author(s):  
K Helms

The effects of moisture conditions on disease development and plant growth were examined in subterranean clover plants which were inoculated with K. caulivora 4 weeks after sowing and were maintained after inoculation at 20°C and with a light intensity of 2000 f.c. In plants which received 100% relative humidity (RH) with free water on leaves, for at least 4 days after inoculation, 15–20% of leaves developed lesions within 11 days. In plants which received continuously 90% RH with free water on leaves, or 100% RH without free water on leaves, less than 1.5% of leaves developed lesions within 11 days. There was no evidence of spread of infection in plants maintained for 11 or 25 days after inoculation. The effects of light intensities of 2000, 500 and 125 f.c. on disease development and plant growth were examined in plants which received 100% RH with free water on leaves and were grown for 25 days after inoculation, either in simulated swards or in standard pots. In most treatments a reduction in light intensity from 2000 to 500 f.c. reduced the growth of plants but had no effect on the percentage of diseased leaves, whereas a reduction in light intensity from 500 to 125 f.c. reduced growth and increased the percentage of diseased leaves of plants grown in swards from 30 to 70% and in standard pots from 10 to 35%. There were mortalities among both inoculated and control plants grown under 125 f.c. : in swards, 80–90% of inoculated plants and 30–40% of control plants died, whereas in standard pots 20–30% of inoculated plants and only occasional control plants died. The data show that environmental conditions favourable for the development of the disease were unfavourable for growth of control plants.


2007 ◽  
Vol 47 (2) ◽  
pp. 223 ◽  
Author(s):  
P. G. H. Nichols ◽  
M. J. Barbetti ◽  
G. A. Sandral ◽  
B. S. Dear ◽  
C. T. de Koning ◽  
...  

Coolamon is a mid-season to late-season flowering F4-derived crossbred subterranean clover of var. subterraneum, developed by the collaborating organisations of the National Annual Pasture Legume Improvement Program. It is a replacement for Junee and has been selected for release on the basis of its greater herbage production and persistence, and its resistance to both known races of clover scorch. Coolamon is recommended for sowing in Western Australia, New South Wales, Victoria, South Australia and Queensland. It is best suited to well-drained, moderately acidic soils in areas with a growing season of 6.5–8 months that extends into November. Coolamon is best suited to phase farming and permanent pasture systems. It can also be used in cropping rotations, but at least 2 years of pasture are required between crops. Coolamon has been granted Plant Breeders Rights in Australia.


2018 ◽  
Author(s):  
K K VINOD

Breeding nutrient use efficient crop varieties has become a contemporary necessity to arm against the future threats in agriculture. This article comments on the necessity and ways to contemplate newer plant breeding strategies for this endeavor.


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