Resistance Of Wheat Varieties Research Articles

Study of Inheritance and Linkage of Virulence Genes in a Selfing Population of a Pakistani Dominant Race of Puccinia striiformis f. sp. tritici.

Wheat stripe rust is a severe threat of almost all wheat-growing regions in the world. Being an obligate biotrophic fungus, Puccinia striiformis f. sp. tritici (PST) produces new virulent races that break the resistance of wheat varieties. In this study, 115 progeny isolates were generated through sexual reproduction on susceptible Himalayan Berberis pseudumbellata using a dominant Pakistani race (574232) of PST. The parental isolate and progeny isolates were characterized using 24 wheat Yr single-gene lines and ten simple sequence repeat (SSR) markers. From the one-hundred-and-fifteen progeny isolates, 25 virulence phenotypes (VPs) and 60 multilocus genotypes were identified. The parental and all progeny isolates were avirulent to Yr5, Yr10, Yr15, Yr24, Yr32, Yr43, YrSp, YrTr1, YrExp2, Yr26, and YrTye and virulent to Yr1, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, Yr27, Yr28, YrA, Yr44, and Yr3. Based on the avirulence/virulence phenotypes, we found that VPs virulent to Yr1, Yr2, Yr9, Yr17, Yr47, and YrA were controlled by one dominant gene; those to YrSp, YrTr1, and Yr10 by two dominant genes; and those to YrExp2 by two complementary dominant genes. The results are useful in breeding stripe rust-resistant wheat varieties and understanding virulence diversity.

EVALUATION OF MORPHOLOGICAL AND BIOCHEMICAL RESISTANCE PARAMETERS TO CHLORIDE SALINATION IN DIFFERENT WHEAT GENOTYPES

Determining salt tolerance potential in wheat is one of the most important problems in breeding practice for areas with primary and secondary salinity. Presence of large areas of saline soils results in inhibition of growth, development and stability in obtaining high yields of agricultural plants. Therefore, there is a need for a comprehensive studying and improving of diagnostic methods during early growth stages. Different genotypes of wheat Triticum aestivum Host. and Triticum durum Desf. were used to identify salt tolerance markers. Both morphometric and some biochemical indicators of wheat varieties were used as salt tolerance markers. At this stage, it was shown that a comprehensive description of wheat varieties is needed to assess resistance of wheat varieties to chloride salinity.

Characterization of resistance of winter wheat varieties to Fusarium head blight

In this study, naturally and artificially inoculated winter wheat varieties were studied with respect to their productivity and resistance to Fusarium head blight (FHB). We used the following set of disease assessment parameters: the percentage of visually and latent Fusarium-damaged grains (FDG); the DNA content of Fusarium fungi; the productivity of inoculated plants compared with non-inoculated plants; and the amount of mycotoxins in the grain. In case of naturally infected grains, the average FDG was found to be about 6.1 % (range of 0–15 %). The amount of DNA of Fusarium graminearum was found to be in the range of (1.1–42.7) × 10–5 ng/ng wheat DNA. The mycotoxin deoxynivalenol (DON) was detected in 15 samples of grain from plants that were grown under natural infection. The maximum DON amount was found to be 420 μg/kg. Fumonisin B1 (FB1) was not be detected in naturally infected grain. In case of artificially inoculated plants, the average FDG was found to be 25.8 % (2–54 %). The amount of F. graminearum DNA was found to be significantly higher (4.24– 49.8) × 10–3 ng/ng than it was detected in grain of non-inoculated plants. The wheat varieties inoculated with F. graminearum contained DON in high amounts from 20255 to 79245 μg/kg. Furthermore, a significant amount of FB1 was detected in all wheat varieties in the range of 980–20326 μg/kg. Among the analysed wheat varieties, Adel was characterized to be the most resistant to fungal infection as well as to the contamination by mycotoxins. Antonina, Lebed and Pamyat varieties were classified more relatively resistant than that of other varieties, and Utrish variety was found to be the most susceptible to FHB. The similar resistance of wheat varieties against F. graminearum and F. verticillioides infection was recorded, and the interactions between the fungi during the colonization of grain were shown.

Wheat Breeding for Durable Rust Resistance and High Yield Potential in Historical Prospective and Current Status

Epidemics of leaf, stripe and stem rusts on wheat have induced significant losses in the past during the early nineteenth century and have destroying role in reducing product yield bringing about socio-economic variability worldwide. The old tall varieties with qualitative resistance couldn't continue for longer period because of the advancement of new virulent pathogen races. But varieties like Yaqui-50, Lyalpur-73, and Lerma Rojo-64 were released during early period of green revolution, still linked with durable resistance to stripe, leaf and stem rust. Advancement of new rust races like virulence's Yr27 and Yr9 followed by the appearance of Ug99 and its mutants lead the breeders to review their breeding plan. Breeders are presently relying upon to gather minor genes and their use in grouping with major genes to develop rust resistance in wheat varieties. The minor genes, Lr46/Yr29, Lr34/Yr18, Sr2/Yr30, are being broken in wheat breeding at CIMMYT and different region. The germplasm with this kind of resistance have shown existence stability over space and time. At Ayub Agriculture Research Institute, Faisalabad the home of green revolution in Pakistan, this approach has been established since1994-95. The durable resistance assortments were crossed in a top cross/back cross technique and the segregating populations were improved by adopting mass strategy, which brought about the advancement of material having preferred yield and rust resistance over the pre-exiting assortments (e.g., Inqlab-91, MH-97). Five varieties, Shafaq-06, Lasani-08, AARI-11, Millat-11 and Galaxy-13 from these crosses have been approved for general cultivation. Essentially, the material developed and circulated by CIMMYT, Mexico having this sort of resistance is being worldwide adopted. The simple sequence repeat markers (SSR) for above mentioned durable genes are accessible and can be used in early selection of superior varieties.

Development and characterization of marker MBH1 simultaneously tagging genes Pm21 and PmV conferring resistance to powdery mildew in wheat

Wheat-Haynaldia villosa translocations T6V#2S.6AL and T6V#4S.6DL, carriers of Pm21 and PmV, respectively, continue to contribute powdery mildew resistance in wheat varieties in China. Based on colinearity between Brachypodium distachyon and Triticeae species, genomic sequences from gene intervals of B. distachyon physically linked to a homolog of Stpk-V, a key part of Pm21, were used to design primers and screen for codominant and stable markers. An anonymous marker, MBH1, tagging both Pm21 in 6V#2S and PmV in 6V#4S was identified. It also distinguished wheat 6AS- and 6DS-derived homoeoalleles of MBH1. Sequence length comparisons showed a decreasing order of 6AS > 6DS > 6V#2S > 6V#4S. F2 segregation analyses were conducted on crosses Yangmai 18 (T6V#2S.6AL)/Yangmai 19 and Yangmai 16/Yangmai 22 (T6V#4S.6DL). MBH1 detected homozygosity of both Pm21 and PmV in segregating populations. The results also showed that T6V#2S.6AL is more transmittable than T6V#4S.6DL. Using MBH1, we reconfirmed the identities of powdery mildew resistance genes in Yangmai 21, Zhenmai 9, and Yangmai 97G59. The resistance donor to all three was T6V#2S.6AL, indicating that the published pedigrees were not correct. Pm21 in NAU419-Y15, an intercalary translocation carrying Pm21, was also tagged by MBH1. MBH1 is a broadly applicable marker for selecting and distinguishing the translocation chromosomes carrying Pm21 and PmV, which continue to be effective in China.

Characteristics of mature wheat embryos with different resistance to scab cultured in vitro with Fusarium graminearum crude toxin.

Five wheat varieties with different resistance to scab were used to study the effect of Fusarium graminearum crude toxin on culture characteristics of mature wheat embryos in vitro. The results showed that the rate of induction and differentiation of mature embryo callus differed significantly between varieties, toxin concentration, and concentration x varieties. A low concentration (5 g/L) of F. graminearum crude toxin promoted callus formation in very resistant varieties, while high concentrations (10 and 15 g/L) hindered it, i.e., the higher the concentration, the stronger the inhibition. The rate of induction and differentiation of mature embryo callus decreased with increasing concentration of F. graminearum crude toxin, thus the lower the resistance, the lower the differentiation. At 10 g/L toxin, superoxide dismutase (SOD) activity of all five varieties was greater than that of the control group (0 g/L). At 20 g/L toxin, SOD activity of the five varieties declined; only two resistant varieties, Sumai 3 and Zheng 9023, still showed higher levels than the control, while the three susceptible varieties had lower levels than the control. Therefore, there was a relationship between SOD activity and scab resistance in wheat varieties.

Diagnosis of drought resistance of wheat varieties of different breeding on osmoregulatory properties of seeds

Seeds of Krasnodarsakaia 99, Epokha Odessa winter wheat varieties under high osmotic pressure retain significant ability to germinate. The rooting intensity, growth of embryonic roots and stems in length in seedlings decreased in all varieties with sucrose concentration increasing. Natalka variety is less exposed to the adverse effects of osmosis, which is shown in maintaining of high seed germination, oppression reducing, and growth of roots and stems of seedlings.

Characterisation of endophytic Bacillus thuringiensis strains isolated from wheat plants as biocontrol agents against wheat flag smut

To explore effective and ecofriendly means of controlling wheat flag smut (WFS) using biocontrol agents, three endophytic strains (58-2-1, 37-1 and YC-1) of Bacillus sp. were isolated from winter wheat plants in China and identified as Bacillus thuringiensis based on their 16S rDNA sequences as well as phenotypic characteristics. Four morphological (leaf length, root length, dry weight and tiller numbers) and one physiological [root vigour (RV)] parameters of wheat plants treated by strains 58-2-1 and 37-1 were significantly enhanced compared to the control. The soluble sugar contents in the roots of wheat samples treated by the two strains were significantly lower than the control. The resistance of wheat varieties to WFS was investigated by inoculation tests. Of the 12 wheat varieties tested, 6 (Yunhan-618, Bainongaikang-58, Kaimai-20, Zhengmai-9023, 04-zhong-36 and Yanzhan-4110) were identified as WFS-highly resistant (HR), 3 (Pumai-9, Jinboshi-1 and Yunong-202) WFS-moderately resistant (MR), 1 (Yubao-1) WFS-susceptible (S) and 2 (Yumai-012 and Yunong-416) WFS-highly susceptible (HS) varieties. The Urocystis tritici-induced yield loss on the S/HS varieties was significantly higher than that on the HR/MR ones. The strains 58-2-1 and 37-1 had control efficacies of 6.7–100% (av.54.8%) and 33.3–100% (av. 66.5%) on 9 and 7 out of 12 varieties, respectively. The strains 58-2-1 and 37-1 had enhanced yields of 10.2–54.9% (av. 32.9%) and 2.8–43.4% (av. 24.8%) on 10 and 8 out of 12 varieties, respectively. This is the first report on endophytic B. thuringiensis strains isolated from wheat plants with the abilities to suppress WFS and to enhance yields on multiple wheat varieties.

Disease Resistance of Wheat Varieties: Can Private Varieties Withstand the Pressure?

US wheat varieties are examined for differential disease resistance between public and private varieties, an issue for critics of plant intellectual property. Analysis using disease resistance rankings of wheat varieties from Kansas and Texas indicate that private varieties are as or more resistant. This finding was further confirmed with two years of Texas data. Thus, the results from the study reject the criticism of private breeding activities that they are more susceptible to disease compared to public varieties. However, private varieties resistance is incorporated from public offerings so that productive private wheat breeding is partly derivative.

Molecular basis of resistance in wheat varieties against spot blotch disease

During present investigation, among the six wheat genotypes tested against six isolates of Bipolaris sorokiniana, the genotype BOW‘S’ showed resistance response against three isolates, namely, BS-D-1, BS-DWRK-2 and BS-K-4, whereas moderately resistance response against remaining 3 isolates i.e. BS-F-3, BS-P-5 and BS-V-6.The genotype A-9-30-1 showed almost highly susceptible response against each isolate except BS-D-1 which exhibited susceptible reaction on this genotype. Thus, it is clear that genotype BOW ‘S’ has broad genetic base for resistance, whereas genotype A-9-30-1 has no gene for resistance against these six isolates tested. Remaining five genotypes showed varying response, ranging from highly susceptible, susceptible, moderately susceptible, moderately resistant and resistant against various isolates of B. sorokiniana tested.

New and Diverse Sources of Multiple Disease Resistance in Wheat

ABSTRACTTan spot (caused by Pyrenophora tritici‐repentis) and Stagonospora nodorum blotch (SNB), (caused by Phaeosphaeria nodorum) are destructive diseases of wheat (Triticum aestivum L.). The majority of currently grown wheat varieties are susceptible to both diseases, presumably because of high pathogenic variability occurring in these fungi or narrow genetic background for resistance in wheat varieties. Therefore, identifying new sources of tan spot and SNB resistance in wheat is imperative. A subset of 825 wheat accessions from the core collection of the National Small Grains Collection (NSGC) of the United States Department of Agriculture, National Plant Germplasm System (NPGS) was evaluated for resistance to tan spot and SNB at seedling stage in a growth chamber. On the basis of disease reactions, 88 wheat accessions exhibited resistance to both diseases. Data from the Germplasm Resources Information Network (GRIN) were examined for the 88 accessions to identify those that also have resistance to other key diseases and on this basis 28 accessions with multiple resistances were identified. The genetic relationship among the 88 accessions was assessed using resistance gene analog polymorphism (RGAP) primers. Wheat accessions with similar growth habit were grouped together despite differences in country of origin. Associations between agronomic traits and host resistance indicated that winter wheat habit in the studied collection was strongly associated with both SNB and tan spot resistance. This study identified genetically diverse wheat accessions with broad‐spectrum resistance that can be used in developing cultivars with high levels of resistance to multiple diseases in wheat breeding programs.

GENE-POSTULATION FOR STEM RUST RESISTANCE IN TWENTY CERTAIN EGYPTIAN WHEAT VARIETIES

Matching of sixteen monogenic lines and twenty wheat (Triticum aestivum L.) varieties representing the Egyptian germplasm inoculated with thirty different stem rust isolates to postulate stem rust resistance gene (Sr). Genes were determined according to the infection types (IT) to different Puccinia graminis f. sp. tritici isolates for seedling resistance in wheat varieties. All of the tested varieties were probably present in Sr7b and Sr8a, with the exception of Giza 160 and Sohag-3, whereas, Sr9e gene were detected in Gemmeiza-7 but it was not detected in the rest of tested varieties. Thirteen genes were probably present in Gemmeiza-7 (the highest), however Sakha 61, Sohag-3 and Sakha 160 wee included the least genes (Sr's). Sr29, Sr30, Sr36 followed by Sr7b and Sr8a were most commonly postulated and having the highest frequency, while Sr9e, Sr21, Sr26 SrTt-1 appeared in lower frequencies within the used Egyptian wheat varieties.

Characterization of resistance of wheat varieties and breeding lines against common bunt (Tilletia tritici) and dwarf bunt (T. controversa)

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Resistance of wheat varieties cultivated in Mie Prefecture to Fusarium head blight

Resistance of wheat varieties cultivated in Mie Prefecture to Fusarium head blight

Effect of bunt infection on the frost resistance of wheat varieties and of lines containing Bt genes

AbstractIn artificial infection experiments carried out in the nursery in Martonvásár in 1991, 1992 and 1993, studies were made on the bunt infection of wheat varieties bred in Martonvásár and of monogenic lines containing known resistance genes (Bll to Btl0, respectively). This was followed in 1993 by tests on the frost resistance of healthy wheat seedlings and wheat seedlings artificially infected with bunt in the frost‐testing chamber of the Martonvásár phytotron.During the period of the experiment, the local pathogen population was avirulent to genes Bt9 and Btl0, and virulent to Bt7. Monogeniclines containing resistance genes Bt4, Bt5, Bt6 and Bt8 had good resistance, while that of lines containing Bt1, Bt2 and Bt3 was only moderate. Among the cultivated varieties, only three proved to be moderately resistant (Martonvásári 17′,‘Martonvásári 23′,‘Fatima 2′), while the remainder were susceptible or very susceptible. The frost resistance of plants infected with bunt was significantly lower, over an average of the varieties, than that of healthy plants. A close (r = 0.890) correlation was found between the bunt susceptibility of the varieties tested and the increase in frost kill due to infection, while no correlation was observed in this respect for monogenic lines containing various resistance genes (Bt).

Differential Aluminum Resistance of Wheat Varieties and Organic Acid Secretion

Differential Aluminum Resistance of Wheat Varieties and Organic Acid Secretion

Studies on Resistance of Wheat Varieties to Scab (Gibberella zeae (Schw.) Petch.) : X. The improved method of inoculation by either conidiospores or hyphae of the scab cultured on potato agar medium

In the field, the primary infections of scab to the heads of wheat occurred by the natural inoculation with ascospores or conidiospores flying in the air; whereas the artificial inoculation of scab is usually carried out by spraying a mixed suspension of spores and hyphae of the fungus. In this experiment of the improved method of scad inoculation, the possibility was tested that the hyphae alone might be infected to leaf blade or ears, as spores do. For this purpose, the hyphae as well as the spores were taken from the scad cultured on the potato agar medium. It was found that the infection could be also obtained by inoculating the hyphae alone, though the conidiospores were successfully used in the infection, of course. The materials (wheat varieties; Nobeoka-bouzu and Wheadling) used in this experiment were much more resistant to scab than the variety Shin-chunaga, which is recognized one of the most resistant varieties in Japan. Nevertheless, no difference was seen in the susceptibility to scab between these resistant varieties and the less resistant ones reported in our previous papers. This fact supports our previous assumption that both the resistant varieties and the susceptible ones show the nearly same degree of infection when the scab was inoculated into leaf blade. From the results of our previous studies concerning the scab infections to leaf blade, head and rachis of wheat by the improved method of inoculation, the conclusions with regard to the mechanisms of infection, resistance or susceptibility to scab were drawn as follows: (1) The absence of natural infection of scab on the leaf blade of wheat in the field may well be due to the fact that it has no morphological and histological factors (steps) to promote the germination of scab spores and the subsequent intrusion of hyphae into the tissue of leaf blade. But by the improved method of inoclation, scab fungus is able to intrude easily into leaf blade, and to show a symptom of scab infection on it, owing to the supply of moisture and nutrient. (2) The fact that the natural infection of scab to wheat is restricted to heads suggests the existence of various morphological and histological factors (steps), which are needed for the intrusion of scab into heads of wheat. Such factors as number of anthers caught by glumes, pollens, number and size of stomata on the inner parts of outer glumes were recognized as the important factors influencing the entrance of scab into heads. Furthermore, the resistance or susceptibility of wheat varieties to scab might be attributable mainly to the characteristic differences of these factors on the head of each variety. (3) The foliage lesion of scab inoculated by the improved method was similar in both the resistant and susceptible varieties. This similarity was explained by the fact that any of the wheat varieties is never immune or even highly resistant to scab constitutionally, and that all the varieties are equally susceptible rather than resistant to scab. (4) The degrees of lesion in various varieties infected by the improved method of inoculation on heads or rachises did not always coincide with those of the varieties whose resistances were judged by the degrees of damages received in the field. The possible explanation of this fact may be that when the tissues of heads or rachises were directly inoculated by the improved method, the tissues permit the entrance and spreading of fungus without the aid of any of the factors above-mentioned. In spite of this fact, however, the existence of slight but recognizable differences of varietal resistance in the predisposition cann't be completely excluded. The available data do not permit the definite conclusion, and these phenomena are open for further research.

Studies on Resistance of Wheat Varieties to Scab (Gibberella zeae (Schw. ) Petch.) : VIII. Infection of scap hyphae by the improved method of inoculation to the ligule or the inside of the leaf sheath just under the ligule

In this experiment. the inoculation of scad into the ligule or the delicate parts inside the uppermost leaf sheath just below the ligule was carried out, using the wheat plants (Variety. Wheat Norin No. 12) which were water-cultured after being pulled out from the field. Only the hyphae, cultured on the potato agar medium, were applied, instead of the conventional method of spore inoculation. The treated plants were at or just after the heading stage. After the inoculation, they were grown in the glass-covered thermostat (23°C) in the room. The clear lesions were observed on the treated parts. From the results of this study, the conclusion was drawn that the hyphae of scab, even without spore, can be successfully applied in the attempt of inoculating the scab into the wheat plants.

Studies on Resistance of Wheat Varieties to Scab (Gibberella zeae (Schw.) Petch.) : VII. Scab infection of rachis of wheat head by the improved method of inoculation and varietal differences in resistance

The previous report (vid. Proc. Crop Sci. Japan. Vol.35: 3.4) revealed that any floret of a wheat head can be infected by the improved method of inoculation, though no agreement was observed between the spread of scab lesion and the degree of damage in the field. In this study, it was attempted to inoculate scab onto the rachis, using several varieties resistant and susceptible to scab, to know whether or not the degree of lesion by the artificial inoculation reflects the varietal response. The rachis could be inoculated with success by the following way. 1. Two little holes are pricked with a pin in a segment of a rachis from which all the spikelets had been removed. 2. The treated segment is inoculated with scab and wound with a piece (7×20 mm) of a boiled spinach leaf. 3. The inoculated rachis is wrapped with wrap film all over the length. 4. The treated plant is kept at 20∼25°C. In this case it must be noted that the number of segment in a rachis was limited to 12∼13 and only the terminal segment was inoculated, for the convenience of comparison of varietal responses. Negative results were obtained as in the case of inoculation onto head, that is, the degree of lesion by the artificial inoculation was not always in parallel with the degree of damage in natural conditions.

Studies on Resistance of Wheat Varieties to Scab (Gibberella Zeae (Schw.) Petch.) : VI. Scab infection of wheat heads by the improved method of inoculation and varietal differences in resistance

The previous report (vid. Proc. Crop Sci. Japan. Vol.35: 3.4) revealed that any floret of a wheat head can be infected by the improved method of inoculation, though no agreement was observed between the spread of scab lesion and the degree of damage in the field. In this study, it was attempted to inoculate scab onto the rachis, using several varieties resistant and susceptible to scab, to know whether or not the degree of lesion by the artificial inoculation reflects the varietal response. The rachis could be inoculated with success by the following way. 1. Two little holes are pricked with a pin in a segment of a rachis from which all the spikelets had been removed. 2. The treated segment is inoculated with scab and wound with a piece (7×20 mm) of a boiled spinach leaf. 3. The inoculated rachis is wrapped with wrap film all over the length. 4. The treated plant is kept at 20∼25°C. In this case it must be noted that the number of segment in a rachis was limited to 12∼13 and only the terminal segment was inoculated, for the convenience of comparison of varietal responses. Negative results were obtained as in the case of inoculation onto head, that is, the degree of lesion by the artificial inoculation was not always in parallel with the degree of damage in natural conditions.