Resistance to root-lesion nematodes (Pratylenchus thornei and P. neglectus) in synthetic hexaploid wheats and their durum and Aegilops tauschii parents

2008 ◽  
Vol 59 (5) ◽  
pp. 432 ◽  
Author(s):  
J. P. Thompson
Keyword(s):  
Bread Wheat ◽  
Combining Ability ◽  
Aegilops Tauschii ◽  
General Combining Ability ◽  
F1 Hybrids ◽  
Pratylenchus Thornei ◽  
Lesion Nematodes ◽  
Synthetic Hexaploid Wheats ◽  
Synthetic Hexaploid ◽  
Root Lesion Nematodes

Root-lesion nematodes (Pratylenchus thornei Sher and Allen and P. neglectus (Rensch) Filipijev and Schuurmans Stekhoven) cause substantial yield loss to wheat crops in the northern grain region of Australia. Resistance to P. thornei for use in wheat breeding programs was sought among synthetic hexaploid wheats (2n = 6x = 42, AABBDD) produced through hybridisations of Triticum turgidum L. subsp. durum (Desf.) Husn (2n = 4x = 28, AABB) with Aegilops tauschii Coss. (2n = 2x = 14, DD). Resistance was determined for the synthetic hexaploid wheats and their durum and Ae. tauschii parents from the numbers of nematodes in the roots of plants grown for 16 weeks in pots of pasteurised soil inoculated with P. thornei. Fifty-nine (32%) of 186 accessions of synthetic hexaploid wheats had lower numbers of nematodes than Gatcher Selection 50a (GS50a), a partially resistant bread wheat. Greater frequencies of partial resistance were present in the durum parents (72% of 39 lines having lower nematode numbers than GS50a) and in the Ae. tauschii parents (55% of 53 lines). The 59 synthetic hexaploids were re-tested in a second experiment along with their parents. In a third experiment, 11 resistant synthetic hexaploid wheats and their F1 hybrids with Janz, a susceptible bread wheat, were tested and the F1s were found to give nematode counts intermediate between the respective two parents. Synthetic hexaploid wheats with higher levels of resistance resulted from hybridisations where both the durum and Ae. tauschii parents were partially resistant, rather than where only one parent was partially resistant. These results suggest that resistance to P. thornei in synthetic hexaploid wheats is polygenic, with resistances located both in the D genome from Ae. tauschii and in the A and/or B genomes from durum. Five synthetic hexaploid wheats were selected for further study on the basis of (1) a high level of resistance to P. thornei of the synthetic hexaploid wheats and of both their durum and Ae. tauschii parents, (2) being representative of both Australian and CIMMYT (International Maize and Wheat Improvement Centre) durums, and (3) being representative of the morphological subspecies and varieties of Ae. tauschii. These 5 synthetic hexaploid wheats were also shown to be resistant to P. neglectus, whereas GS50a and 2 P. thornei-resistant derivatives were quite susceptible. Results of P. thornei resistance of F1s and F2s from a half diallel of these 5 synthetic hexaploid wheats, GS50a, and Janz from another study indicate polygenic additive resistance and better general combining ability for the synthetic hexaploid wheats than for GS50a. Published molecular marker studies on a doubled haploid population between the synthetic hexaploid wheat with best general combining ability (CPI133872) and Janz have shown quantitative trait loci for resistance located in all 3 genomes. Synthetic hexaploid wheats offer a convenient way of introgressing new resistances to P. thornei and P. neglectus from both durum and Ae. tauschii into commercial bread wheats.

Identification of common root-lesion nematode (Pratylenchus thornei Sher et Allen) loci in bread wheat

Genome ◽  
2006 ◽  
Vol 49 (10) ◽  
pp. 1319-1323 ◽  
Author(s):  
Halil Toktay ◽  
C. Lynne McIntyre ◽  
Julie M. Nicol ◽  
Hakan Ozkan ◽  
Halil I. Elekcioglu
Keyword(s):  
Middle Eastern ◽  
Wheat Yield ◽  
Synthetic Hexaploid Wheat ◽  
Parasitic Nematodes ◽  
Resistance Locus ◽  
Natural Genetic Variation ◽  
Pratylenchus Thornei ◽  
Lesion Nematodes ◽  
Synthetic Hexaploid ◽  
Root Lesion Nematodes

Plant parasitic nematodes are a major biotic cause of wheat-yield loss in temperate wheat-growing regions. A major strategy to develop resistance to root-lesion nematodes (RLNs) in wheat is to assess and then exploit their natural genetic variation. This study examines RLN (Pratylenchus thornei) resistance in 1 Middle Eastern landrace (AUS4930 7.2) and 1 synthetic hexaploid wheat, CROC_1/AE.SQUARROSA (224)//OPATA (CROC), using F2 and F9 populations generated by crossing AUS4930 7.2 and CROC with the susceptible cultivar Pastor, and inoculating these crosses with P. thornei in greenhouse trials. Wheat microsatellite markers linked to previously identified quantitative trait loci (QTLs) for resistance to P. thornei and P. neglectus were used to screen both populations. In the AUS4930 7.2 × Pastor population, resistance loci on chromosomes 1B, 2B, and 6D were detected. Similarly, in the CROC × Pastor population, 2 resistance loci, located on chromosomes 1B and 3B, were identified. Interestingly, a resistance locus located on chromosome 6D was not detected. More detailed mapping is required in these 2 populations, developed using new RLN resistance sources, to determine whether the QTLs identified on these chromosomes are the same, are allelic, or are linked to different resistance loci from those previously identified, and to determine whether these 2 sources contain other novel resistance loci.

scholarly journals Inheritance of resistance to root-lesion nematode (Pratylenchus thornei) in wheat landraces and cultivars from the West Asia and North Africa (WANA) region

2011 ◽  
Vol 62 (1) ◽  
pp. 82 ◽  
Author(s):  
J. P. Thompson ◽  
N. P. Seymour
Keyword(s):  
North Africa ◽  
Doubled Haploid ◽  
Combining Ability ◽  
General Combining Ability ◽  
F1 Hybrids ◽  
Root Lesion Nematode ◽  
Components Of Variance ◽  
Pratylenchus Thornei ◽  
Lesion Nematode ◽  
Half Diallel

The root-lesion nematode Pratylenchus thornei causes substantial loss to bread wheat production in the northern grain region of Australia and other parts of the world. West Asia and North Africa (WANA) wheat accessions with partial resistance to P. thornei were analysed for mode of inheritance in a half-diallel crossing design of F1 hybrids (10 parents) and F2 populations (7 parents). General combining ability was more important than specific combining ability as indicated by components of variance ratios of 0.93 and 0.95 in diallel ANOVA of the F1 and F2 generations, respectively. General combining ability values of the ‘resistant’ parents were predictive of the mean nematode numbers of their progeny in crosses with the susceptible Australian cv. Janz at the F1 (R2 = 0.86, P < 0.001, 8 crosses), F2 (R2 = 0.83, P < 0.001, 9 populations) and F∞ (R2 = 0.71, P < 0.05, 5 doubled-haploid populations). The F2 and F∞ populations showed relatively continuous distributions. Heritability was 0.68 for F2 populations in the half-diallel of resistant parents and 0.82–0.92 for 5 ‘resistant’ parent/Janz doubled-haploid populations (narrow-sense heritability on a line mean basis). The results indicate polygenic inheritance of P. thornei resistance with a minimum of from 2 to 6 genes involved in individual F∞ populations of 5 resistant parents crossed with Janz. Morocco 426 and Iraq 43 appear to be the best of the parents tested for breeding for resistance to P. thornei. None of the P. thornei-resistant WANA accessions was resistant to Pratylenchus neglectus.

Septoria nodorum blotch resistance in Aegilops tauschii and its expression in synthetic amphiploids

2001 ◽  
Vol 52 (12) ◽  
pp. 1393 ◽  
Author(s):  
R. Loughman ◽  
E. S. Lagudah ◽  
M. Trottet ◽  
R. E. Wilson ◽  
A. Mathews
Keyword(s):  
Bread Wheat ◽  
Aegilops Tauschii ◽  
F1 Hybrids ◽  
Infection Frequency ◽  
Synthetic Wheat ◽  
Seedling Resistance ◽  
Adult Disease ◽  
Septoria Nodorum Blotch ◽  
Late Maturity ◽  
Moderate Resistance

A collection of 433 Aegilops tauschii was screened for response to infection with Stagonospora nodorum. Resistance similar or marginally superior to the range observed in spring wheat genotypes was readily identified. Three lines, RL5271, Aus18911, and Aus21712, were resistant to a range of pathogen isolates and were similar in resistance to a highly resistant French line, No.33. Accessions of Ae. tauschii assessed as resistant or susceptible as seedlings had corresponding reactions when tested as adult plants, with resistance being commonly expressed as restricted lesion development. Infection frequency differed between some Ae. tauschii lines. Seedling resistance in synthetic bread wheats was expressed partially or not at all depending on both the tetraploid and the tetraploid/Ae. tauschii combination. Assessment of adult responses among a range of synthetics showed occasional expression of moderate resistance around the level observed among reference bread wheat cultivars of similar maturity. Disease escape associated with late maturity was common. One synthetic wheat, #231, derived from a resistant Ae. tauschii, exhibited low adult disease expression associated with late maturity. This line was resistant in seedling tests and seedling resistance was dominant in F1 hybrids to bread wheat.

COMBINING ABILITY FOR YIELD OF SYNTHETIC HEXAPLOID WHEATS

1974 ◽  
Vol 54 (2) ◽  
pp. 235-239 ◽  
Author(s):  
R. J. BAKER ◽  
P. L. DYCK
Keyword(s):  
Triticum Aestivum ◽  
Seed Yield ◽  
Combining Ability ◽  
Genetic Variance ◽  
Additive Genetic Variance ◽  
Triticum Aestivum L ◽  
Kernel Weight ◽  
Specific Combining Ability ◽  
Synthetic Hexaploid Wheats ◽  
Synthetic Hexaploid

Four hexaploid spring wheats (Triticum aestivum L.), which differ only in their D genomes, were crossed in all combinations. Heterosis was expressed in F1 and F2 for number of spikes, kernel weight, and seed yield. Failure to detect significant specific combining ability among F1 progeny suggests that only additive genetic variance is involved in the inheritance of these traits. Competition between single-spaced plants was detected.

scholarly journals Heterosis, Combining Ability, Genetic Diversity and their Interrelationship in Pigeonpea [Cajanus cajan (L.) Millspaugh]

2021 ◽  
Author(s):  
D. Chandra ◽  
S.K. Verma ◽  
A.K. Gaur ◽  
C. Bisht ◽  
A. Gautam ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Combining Ability ◽  
High Frequency ◽  
Block Design ◽  
General Combining Ability ◽  
F1 Hybrids ◽  
Randomized Block Design ◽  
Degree Of Dominance ◽  
Correlation Result ◽  
Per Se

Background: The development of superior hybrids is must to break the existing yield plateau ( less than 800 kg/ha) in pigeonpea and hence, the genetic mechanism governing the heterosis in pigeonpea must be decoded. Methods: The present study was laid down using randomized block design during kharif 2018-19 at GBPUAT, Pantnagar with 36 genotypes (8 parents and 28 F1 hybrids) of pigeonpea. The estimates of combining ability were evaluated by using the Griffing’s, Method II, Model I. The observations recorded for yield and related traits were subjected to the estimation of genetic diversity (GD) using the D2 statistics. The correlation between heterosis and different parameters viz., parental mean (PM), specific combining ability (SCA), mean of general combining ability (MGCA) and genetic diversity (GD) were estimated by using Pearson’s correlation. Result: High estimates of SCA variance and more than unity ( greater than 1) average degree of dominance for all the characters indicated the presence of over dominance. The SCA followed by MGCA were found to be most reliable parameters to predict the heterosis. The parents having high x low or high x high per se performance, good x poor GCA effects and with medium genetic diversity resulted in high frequency of heterotic hybrids.

scholarly journals Study of heterosis and combining ability for earliness and vegetative traits in Cucumber (Cucumis sativus L.)

2016 ◽  
Vol 8 (2) ◽  
pp. 999-1005
Author(s):  
Rajni Tiwari ◽  
Dinesh Kumar Singh
Keyword(s):  
Combining Ability ◽  
Female Flower ◽  
General Combining Ability ◽  
Fruit Yield ◽  
Specific Combining Ability ◽  
F1 Hybrids ◽  
Cucumis Sativus L ◽  
Node Number ◽  
Vegetative Traits ◽  
Significant Yield

The present investigation was undertaken to investigate the extent of heterosis and combining ability on earliness, vegetative traits and yield of Cucumber. A field experiment was designed in line x tester mating design with 11 parents (including 8 parthenocarpic lines namely Pant parthenocarpic cucumber-2, Pant parthenocarpic cucumber-3, Nun-3139, Nun-3121, Nun-3141, Infifnity, Isatis, Kian, and 3 monoecious testers namely PCUC-8, PCUC-15, Pant Kheera -1 {also known as PCUC-28}) and their 24 F1 hybrids to work out the heterosis and combining ability for earliness and yield characters. All traits pertinent to earliness and yield showed significant values for heterosis and combining ability. Appreciable heterosis in desirable direction was found over better parent and check parent by the cross PCUCP-3 x PCUC-15 for earliness characters viz. days to first female flower (-71.18 & -70.31), days to first harvest (-3.40 & -22.01) whereas Cross Kian x PCUC-15 showed maximum number of fruits per plant (8.36 & 106.35) and fruit yield (86.34 & 210.74 respectively). The crosses PCUCP-3 x PCUC-15 and Nun-3139 x PCUC-8 showed significant specific combining ability for earliness and yield characters. Cross Nun-3139 x PCUC-8 showed significant yield regarding heterosis and SCA. Regarding general combining ability for earliness parent Isatis and for yield characters parent Kian stood in top. Cross Nun-3139 x PCUC-8 showed Maximum specific combining ability for node number to first female flower (-0.98), number of fruits per plant (3.39) and fruit yield (220.57).

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