Authors:B. Husenov, S. Asaad, H. Muminjanov, L. Garkava-Gustavsson, A. Yorgancillar, and E. Johansson
Wheat seed-borne diseases are among the major constraints reducing crop yield and the quality of seed and grain. In this study we aimed to evaluate the type and prevalence of fungal seed-borne diseases in Tajik wheat seed samples. Particular emphasis was given to common bunt resistance in advanced wheat breeding materials. Furthermore, we aimed to identify options for improving the seed quality. Seed samples collected from two different locations in Tajikistan were tested by conventional seed-health testing methods for presence of seed-borne diseases. Nineteen advanced wheat breeding lines and three varieties collected from the Tajik wheat breeding program were screened using an artificial inoculation test for their response to common bunt. Significant differences were found between the locations and genotypes concerning presence of common bunt and black point. Fourteen fungal species, where most of them are pathogenic for wheat, were identified in the seed samples. Tilletia laevis, T. tritici, Bipolaris sorokiniana, Stemphylium spp., and Drechslera spp. were the major pathogenic fungi observed in collected wheat samples. Common bunt was predominantly represented by T. laevis. No strong resistance was found in the studied Tajik wheat material, although a low percentage of infection was found in one line (SHARK/ F4105W2.1), while the material was evaluated for common bunt resistance. In managing seed-borne diseases, breeding of resistant varieties should be given a priority, while cultural practices such as preventing contamination and monitoring seed health status should also be considered, as a last resort the use of chemical seed treatments are advised.
Authors:N. Yekelo, L. Rothmann, C.M. Bender, Z.A. Pretorius, and W.H.P. Boshoff
Triticale is derived from a cross between wheat and rye and the leaf rust pathogen of wheat, Puccinia triticina (Pt), and that of rye, P. recondita sensu stricto (Pr), can potentially cause disease in this crop. Recent studies showed that wheat rust fungi could adapt to warmer temperatures. In this paper, we report on the comparative virulence of three Pt races and one Pr isolate (all were collected in South Africa) on triticale as well as their in vitro response to temperature. Seedling infection types (SITs) of 169 triticale entries to Pt races 3SA144 (North American code SDDN), 3SA145 (CCPS) and 3SA248 (CFPS) and Pr isolate UVPr2 revealed that 3SA144 is the most virulent with 106 triticale entries found susceptible to this race. The three Pt races were avirulent to the four rye cultivars included as controls. UVPr2 was avirulent on all the triticale entries and 49 entries were considered resistant to the Pt races tested. Freshly harvested urediniospores of the above isolates were tested at constant temperature regimes of 10 °C, 22.5 °C and 35 °C to study germination characteristics. Mean urediniospore germination percentages as determined for 3SA144 (61.3%) and UVPr2 (62.6%) were significantly lower when compared to 3SA145 (83.7%) and 3SA248 (84.9%). Race 3SA144 was most sensitive to the higher temperature regime of 35 °C (5.2% germination). Among the investigated races, 3SA144 showed significantly lower mean germ tube elongation rates at all three incubation temperatures. This is the first report of differences in temperature adaptation between Pt races from SA.
Authors:M.S. Gurjar, A. Jogawat, M.S. Saharan, and R. Aggarwal
Karnal bunt of wheat (Tilletia indica) is an important internationally quarantined disease from food security point of view. For understanding host specificity and host-pathogen interaction, putative pathogenicity-related genes were analysed in Tilletia indica in response to host factor at different time points. Highest radial mycelia growth (3.4 cm) was recorded in media amended with susceptible host factor followed by resistant host (2.6 cm) and control (2.0 cm) at 30 days after incubation significantly. Fourteen homologous sequences of putative pathogenicity-related genes, viz. TiPmk1, TiKss1, TiHog1, TiHsp70, TiKpp2, TiCts1, TiHos2, TiChs1, TiPrf1, TiSid1, TiSsp1, TiSte20, TiUbc4 and TiUkc1, were identified in T. indica by in silico analysis. Some of the pathogenicity-related genes were highly expressed significantly in T. indica in response to susceptible host factor as compared to resistant host factor. TiPmk1, TiHog1, TiKss1 were found highly upregulated up to 26-fold (3 days), 20-fold (3 days) and 18-fold (4 days), respectively, significantly in presence of susceptible host factor. The TiCts1 and TiChs1 showed transcripts up to 26-fold (4 days) and 20-fold (3 days) in the presence of susceptible host factor. Further, the TiUbc4 and TiUkc1 were found upregulated up to 20-fold and 7-fold at 8 days and 3 days post incubation. This study provided the insight on expression of putative pathogenicity-related genes in T. indica which will help in understanding the infection mechanism and basis for further functional genomics approach.
Authors:C.C. Dweba, H. Shimelis, T. Tapera, and T.J. Tsilo
Fusarium head blight (FHB) is an important disease of wheat causing significant yield and quality losses globally. Breeding for host plant resistance is an economic approach to FHB control and management. The aim of this study was to identify potential sources of resistance from newly developed recombinant inbred lines (RILs) of wheat. A total of 778 RILs were developed through a bi-parental mating design followed by continuous selfing and selection. The RILs along with their eight parental lines (Baviaans, Buffels, Duzi, #910, #936, #937, #942 and #1036) and FHB resistant check cultivar ‘Sumai 3’ and susceptible check ‘SST 806’ were field evaluated across four environments in South Africa. Fusarium graminearum isolates were artificially inoculated to initiate infection and disease development. The percentage of wheat spikes showing FHB symptoms were scored. The research identified six percent of the RILs with disease resistance. Heritability for FHB resistance was the highest (64%) indicating the possibility of achieving higher selection gains for FHB resistance across the selected environments. The following five RILs were identified as potential sources of resistance: 681 (Buffels/1036-71), 134 (Duzi/910-8), 22 (Baviaans/910-22), 717 (Baviaans/937-8) and 133 (Duzi/910-7) with mean FHB scores of 6.8%, 7.8%, 9.5%, 9.8% and 10%, respectively. The selected lines expressed comparatively similar levels of resistance compared with that of Sumai 3. The identified RILs are useful genetic resources for resistance breeding against FHB disease of wheat. Since the presence of the F. graminearum is associated with deoxynivalenol (DON) accumulation, the DON levels amongst the selected lines should be determined to ensure the release of improved wheat cultivars with reduced levels of DON accumulation.
Koch, C. (1999) Cystic fibrosis - pathogenesis of the lung disease caused by Pseudomonas aeruginosa. Clinical Microbiology and Infection 5 (Suppl. 5): 5 S2-5 S3.
Cystic fibrosis - pathogenesis of the lung disease caused by
., Lachance, D. (1987) Large infection center of scleroderris canker (European race) in Québec province. Plant Disease 71 , 1041-1043.
Large infection center of scleroderris canker (European race) in Québec province