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The Fertile Crescent region (area shaded green) of the ancient Middle East which is the centre of distribution of the progenitors of modern bread wheat.
Source publication
Thesis (M.Ag.Sc.) - University of Queensland, 2005. Includes bibliography.
Contexts in source publication
Context 1
... the basket had drained, the tissue and soil were discarded. The water in the tray was then slowly agitated and poured through the 20 µm sieve ( Figure 21D, p. 119). The sieve was allowed to drain and in the meantime, the inside of the plastic tub was gently rinsed all over and then the rinse water was passed through the 20 µm sieve. After the sieve had drained it was gently rinsed all over ( Figure 21E, p. 119) and the small volume of extract was then poured into a labelled 30 ml vial ( Figure 21F, p. 119). The sieve was then given a second rinse and this was also poured into the 30 ml vial. The sieve was washed thoroughly between samples to eliminate the risk of nematode carry- over. After all extractions were completed, the plastic trays, tubs and mesh were all washed with hot water to kill any remaining nematodes. The volume of extract was then determined by weighing and recorded and the samples stored in a cold room at 2°C. ...
Context 2
... the basket had drained, the tissue and soil were discarded. The water in the tray was then slowly agitated and poured through the 20 µm sieve ( Figure 21D, p. 119). The sieve was allowed to drain and in the meantime, the inside of the plastic tub was gently rinsed all over and then the rinse water was passed through the 20 µm sieve. After the sieve had drained it was gently rinsed all over ( Figure 21E, p. 119) and the small volume of extract was then poured into a labelled 30 ml vial ( Figure 21F, p. 119). The sieve was then given a second rinse and this was also poured into the 30 ml vial. The sieve was washed thoroughly between samples to eliminate the risk of nematode carry- over. After all extractions were completed, the plastic trays, tubs and mesh were all washed with hot water to kill any remaining nematodes. The volume of extract was then determined by weighing and recorded and the samples stored in a cold room at 2°C. ...
Context 3
... is the direct wild progenitor of most cultivated wheats ( Levy and Feldman, 1989). Two ecotypes of wild emmer wheat have been recognised, these are the tall, early maturing 'robust' and the short, slender 'grassy' ecotypes. Jaradat (1997a) has also identified intermediate types between the 'grassy' and the 'robust' types. Figure 10. Triticum turgidum ssp. ...
Context 4
... alimentary canal of any nematode has three major parts: stomadeum (pharynx or oesophagus), mesenteron (intestine) and the proctodeum (rectum). The stomadeum ( Figure 14) includes the lips (labial region) at the anterior-most end, stoma and oesophagus to oesophago-intestinal junction (Davies and Hodda, 1999). The labial region in Pratylenchus is not well defined, but is sometimes set off by narrowing of the body contour. The lips are supported internally by hexaradite sclerotisation. There are six lips with the lateral lips being slightly wider than the sub- dorsal and sub-ventral lips. The lips are marked by two to four annules (one to three striations) with P. thornei having three lip annules (two striations) ...
Context 5
... is one of the most important diseases of wheat on a worldwide basis. The disease causes significant losses in wheat production whenever epidemics occur. The most effective and efficient method for reducing losses in wheat production from powdery mildew is the development of resistant cultivars (Moseman et al., 1984). Gerechter- Amitai and van Silfhout (1984) found that accessions of T. turgidum ssp. dicoccoides ( Figure 11) displayed a diversity of responses to powdery mildew infection, ranging from high resistance to complete susceptibility. Many of the entries displayed distinctly differential interactions. Since the number of reaction patterns is quite considerable, it may be assumed that many different genes for resistance are involved. van Silfhout ...
Context 6
... ground, the symptoms of P. thornei can be quite variable. In most crops the initial invasion, which may take from four to six hours (Maggenti, 1981), is probably at random but other nematodes subsequently enter through the wounds (Figure 17, p. 71), perhaps attracted by the contents of the punctured cells (Fortuner, ...
Context 7
... 48 hours had passed, the basket was lifted out of the water and placed across the tub to drain ( Figure 21C, p. 119). The basket was allowed to drain for a minimum of 10 minutes or until free water had stopped dripping into the tub. Allowing soil particles to fall into the plastic tub was avoided as it would block the 20 µm sieve and also contaminate the extraction ...
Context 8
... samples were left to extract for 48 hours at 22°C in a constant temperature room ( Figure 21B, p. 119). Approximately 50% of the nematode population will be extracted in this time; it may take up to seven days to extract virtually all ...
Context 9
... T. turgidum ssp. dicoccoides and T. turgidum ssp. carthlicum ( Figure 10) have been used for this purpose in Australian wheat breeding. T. turgidum ssp. carthlicum was initially proposed as a progenitor species of wheat ( Kerber and Bendelow, 1977;Bushuk and Kerber, 1978), however, it is now generally accepted that T. turgidum ...
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Citations
... Cre2, Cre4, Cre5, and Cre8 are partially resistant to Ha13. Similarly, sources of resistance to RLNs have been previously reported in wheat and its wild relatives including Ae. tauschii, T. urartu, T. monococcum, and T. turgidum (Sheedy 2004, Sheedy et al. 2012, Thompson and Haak 1997). Some bread wheat varieties show complete or partial resistance to Pratylenchus spp. ...
To identify loci linked to nematode resistance genes, a total of 126 of CIMMYT advanced spring wheat lines adapted to semi-arid conditions were screened for resistance to Heterodera avenae, Pratylenchus neglectus, and P. thornei, of which 107 lines were genotyped with 1,310 DArT. Association of DArT markers with nematode response was analyzed using the general linear model. Results showed that 11 markers were associated with resistance to H. avenae (pathotype Ha21), 25 markers with resistance to P. neglectus, and 9 significant markers were identified to be linked with resistance to P. thornei. In this work we confirmed that chromosome 4A (~90–105 cM) can be a source of resistance to P. thornei as has been recently reported. Other significant markers were also identified on chromosomal regions where no resistant genes have been reported for both nematodes species. These novel QTL were mapped to chromosomes 5A, 6A, and 7A for H. avenae; on chromosomes 1A, 1B, 3A, 3B, 6B, 7AS, and 7D for P. neglectus; and on chromosomes 1D, 2A, and 5B for P. thornei and represent potentially new loci linked to resistance that may be useful for selecting parents and deploying resistance into elite germplasm adapted to regions where nematodes are causing problem.
... Previous studies have reported the identification of CCN resistance genes: Cre1 and Cre8 in T. aestivum (Slootmaker et al. 1974;Williams et al. 2002), Cre2, Cre5 and Cre6 in Ae. ventricosa (Delibes et al. 1993;Jahier et al. 1996;Ogbonnaya et al. 2001a), Cre3 and Cre4 in Ae. tauschii (Eastwood 1995;Eastwood et al. 1994), Cre7 in Ae. truincialis (Romero et al. 1998), CreX and CreY in Ae. variabilis (Barloy et al. 2007) and CreR in Secale cereale (Asiedu et al. 1990). Similarly, sources of resistance to RLN have previously been reported in wheat and its wild relatives including Ae. tauschii, T. urartu, T. monococcum and T. turgidum (Thompson and Haak 1997;Sheedy 2004;Sheedy et al. 2012). A survey of several thousand Australia and overseas cultivars for resistance to PN in Australia in the 1990s resulted in the identification of superior resistance in cultivars Virest (Aus11984) from Italy and Persia 20 (Aus5205) from Iran ( Vanstone et al. 2008). ...
Soilborne pathogens such as cereal cyst nematode (CCN; Heterodera avenae) and root lesion nematode (Pratylenchus neglectus; PN) cause substantial yield losses in the major cereal-growing regions of the world. Incorporating resistance into wheat cultivars and breeding lines is considered the most cost-effective control measure for reducing nematode populations. To identify loci with molecular markers linked to genes conferring resistance to these pathogens, we employed a genome-wide association approach in which 332 synthetic hexaploid wheat lines previously screened for resistance to CCN and PN were genotyped with 660 Diversity Arrays Technology (DArT) markers. Two sequence-tagged site markers reportedly linked to genes known to confer resistance to CCN were also included in the analysis. Using the mixed linear model corrected for population structure and familial relatedness (Q?K matrices), we were able to confirm previously reported quantitative trait loci (QTL) for resistance to CCN and PN in bi-parental crosses. In addition, we identified other significant markers located in chromosome regions where no CCN and PN resistance genes have been reported. Seventeen DArT marker loci were found to be significantly associated with CCN and twelve to PN resistance. The novel QTL on chromosomes 1D, 4D, 5B, 5D and 7D for resistance to CCN and 4A, 5B and 7B for resistance to PN are suggested to represent new sources of genes which could be deployed in further wheat improvement against these two important root diseases of wheat.
... Previous studies have reported the identification of CCN resistance genes: Cre1 and Cre8 in T. aestivum (Slootmaker et al. 1974; Williams et al. 2002), Cre2, Cre5 and Cre6 in Ae. ventricosa (Delibes et al. 1993; Jahier et al. 1996; Ogbonnaya et al. 2001a), Cre3 and Cre4 in Ae. tauschii (Eastwood 1995; Eastwood et al. 1994), Cre7 in Ae. truincialis (Romero et al. 1998), CreX and CreY in Ae. variabilis (Barloy et al. 2007) and CreR in Secale cereale (Asiedu et al. 1990). Similarly, sources of resistance to RLN have previously been reported in wheat and its wild relatives including Ae. tauschii, T. urartu, T. monococcum and T. turgidum (Thompson and Haak 1997; Sheedy 2004; Sheedy et al. 2012). A survey of several thousand Australia and overseas cultivars for resistance to PN in Australia in the 1990s resulted in the identification of superior resistance in cultivars Virest (Aus11984) from Italy and Persia 20 (Aus5205) from Iran (Vanstone et al. 2008). ...
Soilborne pathogens such as cereal cyst nematode (CCN; Heterodera avenae) and root lesion nematode (Pratylenchus neglectus; PN) cause substantial yield losses in the major cereal-growing regions of the world. Incorporating resistance into wheat cultivars and breeding lines is considered the most cost-effective control measure for reducing nematode populations. To identify loci with molecular markers linked to genes conferring resistance to these pathogens, we employed a genome-wide association approach in which 332 synthetic hexaploid wheat lines previously screened for resistance to CCN and PN were genotyped with 660 Diversity Arrays Technology (DArT) markers. Two sequence-tagged site markers reportedly linked to genes known to confer resistance to CCN were also included in the analysis. Using the mixed linear model corrected for population structure and familial relatedness (Q+K matrices), we were able to confirm previously reported quantitative trait loci (QTL) for resistance to CCN and PN in bi-parental crosses. In addition, we identified other significant markers located in chromosome regions where no CCN and PN resistance genes have been reported. Seventeen DArT marker loci were found to be significantly associated with CCN and twelve to PN resistance. The novel QTL on chromosomes 1D, 4D, 5B, 5D and 7D for resistance to CCN and 4A, 5B and 7B for resistance to PN are suggested to represent new sources of genes which could be deployed in further wheat improvement against these two important root diseases of wheat.
... A number of attempts have been made to screen wheat germplasm against the root lesion nematode (P. thornei) in order to find sources of resistance (Vanstone et al., 1998; Thompson et al., 1999; Nicol 2004; Sheedy et al., 2004; Toktay et al., 2006). Improved screening methods could further facilitate and enhance genetic engineering studies for incorporation of resistance genes against this nematode into wheat. ...
The root lesion nematode, Pratylenchus thornei (Sher et Allen) is a polyphagous and economically important
nematode in wheat production systems, particularly in rainfed environments. Chemical management of this nematode is not economically or environmentally sound, leaving cultural practices like crop rotation as the most widely accepted option. Long-term control is best achieved in established wheat monoculture systems through genetic improvement, which provides both economic and environmental benefits to the growers. Intensive screening under controlled conditions can facilitate and accelerate the identification of resistance and its subsequent deployment in commercial wheat cultivars. In this study, a number of variables were assessed to optimize P. thornei screening, including initial nematode density, soil type, container size, reference cultivars, harvest time and watering regime with perlite. Growth room experiments showed clear separation between the resistant and susceptible cultivars, using sandy growth medium (70:29:1 sand, field soil and organic matter), small container (15 mm diameter x 100 mm in long), inoculation density with 400 individuals per plant, 9 week growing period and bottom perlite irrigation system.
... Initial screening experiments by Thompson and Haak (1997) found resistance to P. thornei in virtually all taxonomic subgroups of Ae. tauschii and later observations Thompson 2008) with synthetic hexaploids (ABD genomes) and durums (AB genomes) suggested that at least two resistance genes were involved. Sheedy (2004) screened more wild wheats, including Triticum urartu (A u genome), T. monococcum (A m genome) and T. turgidum (A u B genomes), and confirmed the presence of one or more resistance genes to P. thornei in the A genome. Aegilops speltoides (S genome) which is considered to be the B genome donor of modern wheat also had resistant accessions. ...
... Aegilops speltoides (S genome) which is considered to be the B genome donor of modern wheat also had resistant accessions. Additionally, a valuable genetic pool of potential resistance genes to P. thornei has been identified in the Watkins Collection of land race wheats from West Asia and North Africa (WANA) (Seymour and Thompson 2001) and in an extensive collection of Iranian landrace wheat accessions obtained from CIMMYT (Sheedy 2004). ...
... This ectoparasitic species is associated with wheat, barley and oats throughout the region and is the dominant plantparasitic nematode on some farms. Population densities as high as 70 nematodes/g soil in crop have been recorded and they are much higher than those recently associated with a reduction in wheat yields in the Pacific Northwest of the United States (Smiley et al. 2006). Thus, some research on this nematode is also warranted, particularly with regard to its pathogenicity on the most important grain crops of the region. ...
Two species of root-lesion nematode (predominantly Pratylenchus thornei but also P. neglectus) are widespread pathogens of wheat and other crops in Australia's northern grain belt, a subtropical region with deep, fertile clay soils and a summer-dominant rainfall pattern. Losses in grain yield from P. thornei can be as high as 70% for intolerant wheat cultivars. This review focuses on research which has led to the development of effective integrated management programs for these nematodes. It highlights the importance of correct identification in managing Pratylenchus species, reviews the plant breeding work done in developing tolerant and resistant cultivars, outlines the methods used to screen for tolerance and resistance, and discusses how planned crop sequencing with tolerant and partially resistant wheat cultivars, together with crops such as sorghum, sunflower, millets and canaryseed, can be used to reduce nematode populations and limit crop damage. The declining levels of soil organic matter in cropped soils are also discussed with reference to their effect on soil health and biological suppression of root-lesion nematodes.
... Likewise, much progress and promise exist for breeding wheat varieties with sufficiently high tolerance and(or) resistance to stabilize yields and reduce the reproductive efficiency for P. thornei (Nicol et al., 2003). Numerous sources of improved genetic resistance to P. thornei were recently identified in wheat and closely related species (Hollaway et al., 2000;Nicol et al., 1999Nombela and Romero, 1999;Sheedy, 2005;Thompson et al., 1999;Zwart et al., 2004a,b). Of particular interest are lines, such as GS50A and AUS4930, that convey high levels of tolerance as well as resistance to P. thornei (Hollaway et al., 2000;Nicol et al., 1999). ...
Pratylenchus thornei reaches high population densities in non-irrigated annual cropping systems in low-rainfall regions of the Pacific Northwest. Two spring wheat varieties with different levels of tolerance and susceptibility to P. thornei were treated or not treated with aldicarb in three experiments. Grain yield was inversely correlated (P < 0.05) with pre-plant populations of P. thornei in soil and with P. thornei density in mature roots. As population of P. thornei increased, yield of the moderately tolerant/moderately susceptible variety Krichauff was generally more stable than for the intolerant/susceptible variety Machete. The reproductive factor (Pf/Pi) was generally lower (P < 0.05) for Krichauff than Machete. Aldicarb improved wheat yield (P < 0.05) in highly infested fields by an average of 67% for Krichauff and 113% for Machete. Aldicarb increased (P < 0.05) numbers of headed tillers, plant height, and grain test weight and kernel weight, and reduced (P < 0.05) the density of P. thornei in mature wheat roots, variability in height of heads, and leaf canopy temperature. Aldicarb did not improve yield in a soil with a low population of P. thornei. This is the first report that P. thornei causes economic damage to wheat in the Pacific Northwest.
Wheat is one of the important staple crops of the world. Its grain yield is affected by various factors including genotype and planting time. An experiment was conducted to study the yield performance of 10 different wheat advanced genotypes (PR-133, PR-135, PR-136, PR-137, PR-138, PR-139, PR-140, Khaista-17, Gulzar-19 and Pirsabak-19) at different sowing times of 15-days interval. A pooled analysis across the same environment revealed a significant difference (P≥ 0.01) for all the parameters i.e. days to heading, days interval, plant height, flag leaf area, tillers m-2, spike length, spikelet spike-1, grain spike-1, thousand grain weight, grain yield and biological yield across three planting dates i.e. early, normal, and late respectively. Differences between wheat genotypes and genotype-environment interaction were also highly significant (P≥ 0.01) for studied traits, indicating that genotypes performed differently in three sowing times. Under early, normal and late planting, genotypes PR-138, PR-140 and Gulzar-19 had the highest grain yield respectively. PR-138 performed outstandingly across three sowing times for seed yield. Hence, it is concluded from the present study that delayed sowing progressively decreases the yield performance of the studied genotypes and the most suitable sowing time is from 15th October to 15th November.
