Wheat rusts can be controlled by host resistance or chemicals. Ethiopian farmers are not widely experienced with chemicals. Sixty seven (49 bread wheat (BW) and 18 durum (DW)) non-replicated varieties were planted on 0.4 m2 plots at 22 rust hotspot locations in 2014. Kubsa and Digalu were used as susceptible checks for YR and SR, respectively. Rust severities were scored according to the modified Cobb scale. Ten YR and 12 SR hotspot locations with mean rust severities of ≥40% were used in data analyses. Kubsa had a mean 59% YR severity and Digalu, a 73% SR severity. Rust severity levels were divided into three categories, viz. low (≤35%), moderate (36-40%) and high (>40%), across locations for both diseases. The frequency of varieties with low YR severities in the BW group was 26.5%, medium 18.4% and high 55.1% compared to DW varieties at 61%, 28% and 11%, respectively. In the case of SR, both BW and DW had large proportions of entries in the high severity category at 69.4% and 72.2%, respectively. The medium and low SR severity groups were represented by 20.4% and 10.2% for BW, and 11.1% and 16.7% for DW, respectively. In summary, the top 10 widely cultivated BW and a few DW varieties categorised in the medium and high severity groups for both YR and SR, would definitely require fungicides in rust-prone areas for optimum disease control. Many cultivars released after 1974 are still cultivated indicating that susceptible varieties are only slowly replaced. Hence, development and distribution of resistant cultivars, replacement of susceptible cultivars, and training industry workers and farmers on effective field scouting and fungicide use will be paramount for sustainable wheat production in Ethiopia.
Primary Author: Hundie, Ethiopian Institute of Agricultural Research (EIAR)
With ongoing threats of rust from both internal and international sources it has become a priority at CIMMYT and for Pakistan national programs to accelerate the rate of seed increase and to popularize new Pgt race Ug99 resistant varieties to avert future disasters. Seed of Ug99 resistant varieties NARC-11, Pak-2013, Dharabi-2011 and BARS-09 was produced under the Wheat Productivity Enhancement Program (WPEP). The country-wide participatory approach involves a partnership of farmers, seed companies and research institutes. In 2014 16,020 and 6,085 kg of seed of NARC-11 and Pak-13, respectively, were distributed all over the country, including Azad Jammu Kashmir and Gilgit-Baltistan. Comparative yields across Pakistan show that the rust resistant varieties are equal, or superior, to current stem rust susceptible varieties grown by farmers. Deployment and use of these varieties by farmers in Balochistan will have a significant impact not only on productivity, but may also avert the consequences of possible introduction of race Ug99.
Primary Author: Hussain, International Maize and Wheat Improvement Center (CIMMYT) Pakistan Office
Global warming affects the environmental parameters of agro-based countries like temperature increase, melting of glaciers, floods, erratic rains, low temperature, frost and high temperature. As a result agriculture is becoming more vulnerable to global environmental shifts. In case of wheat, erratic or low rains badly affect the wheat crop of rainfed areas of the country along with high temperature at seedling or juvenile stage. Similarly, frost affects the early sown wheat crop in irrigated areas of Punjab. Lesser availability of irrigation water from water reservoirs also reduces the wheat crop productivity. Sudden increase in temperature (>30?C) during the month of March adversely affect the grain filling. High temperature during grain filling stage interferes with the photosynthetic activities of the plant due to enhanced maturity, grain become shriveled and results in low grain yield. The threat of these environmental changes can only be overcome through breeding with specific objectives which is cost effective once obtained.
Hence development of wheat varieties for frost, drought and heat tolerance is the only feasible solution to combat these stresses which is being used at Wheat Program of Ayub Agricultural Research Institute, Faisalabad, Pakistan. New emphasis is also being given to develop frost resistant wheat varieties due to changing scenario of last few years. The institute is actively involved for the development of heat, drought and frost tolerant wheat varieties. During working for tolerance against any of these stresses plant types to be breed are physiologically and morphologically modeled in such a way that they should be capable of tolerating respective stress. In addition to breeding work an extensive research is also being done at Wheat Research Institute, AARI., Faisalabad to investigate best agronomic strategies to make wheat crop best adapted to environmental stress conditions.
Primary Author: Hussain, Wheat Research Institute, Faisalabad, Pakistan
Drought and heat along with rusts are the most common biotic and abiotic stresses that affect growth, development and yield of wheat crop in Pakistan. CIMMYT in partnership with Wheat Research Institute Faisalabad (WRI-Fsd), USDA, and Kansas State University initiated an effort to develop heat tolerant, high yielding, and farmer-accepted rusts resistant wheat varieties for Pakistan. A set of 1656 wheat lines received in the form of EPCBW and SABWGPYT nurseries were tested in 2013-14 and 2014-15 wheat season, respectively. Testing of the materials at (WRI-Fsd), Pakistan under normal and late planting conditions resulted in the selection of 55 lines with higher grain yield and resistant to both leaf (LR) and yellow (YR) rusts. Among these lines, the line no. 1027 produced maximum yield (5.78 ton/ha) under normal and line no. 5030 produced maximum yield (3.38t/ha) under late planting conditions with resistance to both LR and YR. Further evaluation of the selected 55 lines as HYT-60 in 2015-16 showed the average grain yield ranged from 4.98 to 2.51 ton/ha under normal and 1.74 to 0.73 t/ha under late planting. Three lines HYT-60-57, HYT-60-7 and HYT-60-5 were included in the first year advanced yield trials to test for their potential as commercial cultivars while another seventeen lines were distributed as HYT-20 to six national wheat breeding programs for yield testing at key location which will enable national partners to combine yield potential with resistance to biotic and abiotic stresses.
Primary Author: Imtiaz, CIMMYT
Rust disease response is used to assess the resistance status of breeding lines, which is required to be tested across location and complemented with molecular markers. The current study was designed to characterize yellow rust resistance in 29 introduced advanced CIMMYT wheat lines along with three check varieties across three contrasting wheat growing regions (Peshawar, Mansehra and Lakki-Marwat) during wheat season 2015-16. A high disease pressure was observed across all three locations as favorable cold and wet climatic conditions prevailed during 2015-16. The maximum disease was recorded at Mansehra (up to 90%) followed by Peshawar (up to 50%) and Lakki-Marwat (up to 45%). There was a significant variability amongst the tested wheat lines for yellow rust severity and in yield potential. Among the advanced lines, W-SA-104, W-SA-115 and W-SA-118 had better grain and biological yield. Based on disease and yield parameters, cluster analysis of 29 wheat lines along with three checks grouped wheat lines into four clusters. None of these wheat lines showed resistance at every location (Average coefficient of infection "ACI" = 0). The maximum co-efficient of infection (55) was recorded at Mansehra whereas the minimum (0) was recorded at Peshawar and Lakki-Marwat. Twenty-six of these wheat lines were identified to possess partial resistance to yellow rust (with ACI < 20). Genotyping for the presence of resistance gene markers STS-7 (linked with Yr5), SC-Y15 (linked with Yr17) and Xwmc-44 (linked with Yr29) revealed the highest frequency of Yr17 (90.60%), followed by Yr29 (87.5%) and Yr5 (50%). The three resistant genes together were present only in 15 wheat lines (46.87%). Our results thus revealed the presence of variation in resistance response based on both field testing and molecular markers which could be utilized in wheat breeding to develop better resistance varieties to be exploited at field level.
Primary Author: Iqbal, The University of Agriculture, Peshawar, Pakistan
Stripe rust caused by Puccinia striiformis f.sp.tritici, is one of the major diseases of wheat in the world. Experiments were carried out at two sites in Ethiopia (Kulumsa and Meraro) during the 2015 cropping season to evaluate the response of 198 elite bread wheat genotypes and two checks to the prevailing races of stripe rust at adult plant and seedling stage. The genetic profile of these genotypes was assessed using 13006 SNP markers and an association mapping was explored to determine marker?trait association. About 72.5% and 42.5% of the lines exhibited resistance at Kulumsa and Meraro, respectively. Out of 198 genotypes tested in the greenhouse, 31% exhibited common resistance for Kubsa and mixed stripe rust isolate. Only 8966 of the SNPs were polymorphic, only these were used for association mapping analysis. These markers spanned an average density of 3.47 cM per marker, with the poorest density on the D genome. Almost half of these markers were on known chromosomes, but had no position on the consensus map of bread wheat. Analysis of population structure revealed the existence of three clusters and the estimated genomic wide Linkage Disequilibrium (LD) decay in this study ranged from 0 to 50 cM. 53 SNPs in ten genomic regions located on wheat chromosome 1AL, 2AL, 2BL, 2DL, 3BL, 4BL, 4DL, 5AS, 7AL and 7BL were identified. Thirty nine SNP markers in five genomic regions at Kulumsa and 14 SNP markers in six genomic regions at Meraro explained more than 25.5% and 35.1% of phenotypic variability respectively. For seedling stage, 21 markers in ten genomic regions located on wheat chromosomes 1B, 2A, 2B, 3A, 3B, 4B, 4D, 5A, 6B and 7B were associated with resistant. These loci may be useful for choosing parents and incorporating new resistance genes into locally adapted cultivars.
Primary Author: Isehtu, Ethiopian Institute of Agricultural Research (EIAR)
In the current scenario of climatic change, exploration and development of new stable genotypes performing better under stressed and non stressed environmental conditions is the priority of wheat breeders for exploiting genetic variability to improve stress tolerant cultivars. Late planting is one of the major abiotic stresses, seriously influencing wheat production. In the current study, twenty eight bread wheat genotypes were evaluated independently under normal (optimal) and late (stress) planting conditions at Cereal Crops Research Institute (CCRI), Pirsabak Nowshera Khyber Pakhtunkhwa Pakistan during 2013-14. Analysis of variance revealed highly significant (P < 0.01) differences among the genotypes, planting (sowing dates), and genotype ? sowing dates interactions effects for the studied traits. Generally, reduction in plant height (0.41 to 10.91%) and grain yield (0.36 to 53.35%) was observed among the tested genotypes under late planting as compared to normal (optimal) planting. Least % reduction in grain yield was recorded for genotypes BWL-23 (0.36%), BWL-4(0.76%), BWL-16(1.22%) and BWL-13 (1.78%) and were found tolerant to late planting stress as compared to check (Pirsabak-2008). Eight stress selection indices i.e. Mean productivity (MP), Tolerance (TOL), Geometric Mean Productivity (GMP), Harmonic mean (HM), Stress selection Indices(SSI), Stress Tolerance Index (STI), Yield Index (YI) and Yield Stability Index (YSI) were determined based on mean performance of genotypes evaluated under normal and late planting conditions. Analysis of correlation revealed that plant height and grain yield under normal and late planting conditions, had significant positive correlation with stress selection indices i.e. GM, HM, SSI and YI. These selection indices could be effective in identification of lines/ genotypes to late planting stress tolerant conditions. Based on MP, GMP, HM, STI and YI genotypes i.e. Pirsabak-2008, BWL-23 and BWL-27 were found late planting stress tolerant and could be recommended for sowing in both normal and late planting.
Primary Author: Ishaq, Cereal Crops Research Institute (CCRI), Pirsabak Nowshera Khyber Pakhtunkhwa-Pakistan
Resistance breeding for wheat leaf rust requires testing of breeding materials under field conditions, which must be complemented with diagnostic molecular makers. A set of 28 exotic wheat lines from advanced CIMMYT material along with three check varieties (Siran, Atta-Habib, Ghanimat-e-IBGE) were tested at three contrasting locations (Peshawar, Mansehra and Lakki-Marwat) and were genotyped with markers linked to three Lr genes (LrPr, Lr37, and Lr34). The overall leaf rust pressure was low during the wheat season of 2015-16, with the maximum disease observed at Lakki-Marwat (up to 70%), followed by Peshawar (up to 50%) and the minimum disease at Mansehra (up to 30%). Despite the overall low leaf rust pressure, the germplasm behaved variably in terms of leaf rust resistance as revealed through average co-efficient of infection (ACI). According to ACI value, 16 out of 28 genotypes were completely resistant, while few genotypes showed partial resistance. The maximum CI value was recorded for wheat line W-SA-87, which was 55 at Lakki Marwat, 33 at Peshawar and 15 at Mansehra, while 18 lines had CI value of zero across the three locations. Variability existed in yield parameters with W-SA-84, W-SA-78 and W-SA-79 producing the better grain yield. Genotyping with Lr linked markers viz., STS-7 (LrPr), SC-Y15 (linked with Lr37) and csLV34 (linked with Lr34) revealed that among the tested lines LrPr was the most frequent (83.8%), present in 26 lines; followed by Lr37 (77.4%), present in 24 lines, while Lr34 was present in 16 lines (71.1%). All three genes were detected in 45% of the germplasm. Cluster analysis grouped the germplasm in four clusters based on both phenotypic and molecular markers data. The information generated in the present study would be valuable in resistance breeding for a better control of leaf rust disease in Pakistan.
Primary Author: Ismail, The University of Agriculture, Peshawar, Pakistan
Under changing climatic conditions, the emergence of new diseases or new races of existing diseases is a serious threat to global wheat production. Particularly, the presence of wheat blast in Bangladesh and stem rust race Ug99 in Iran, created a fearsome and intractable situation for Pakistan. A study was planned for monitoring and surveillance of the wheat blast and rust pathogens in wheat growing districts of Punjab, Pakistan during the cropping season 2016-17 as vigilance program. During the survey, one hundred and seventy one wheat fields of upper and central Punjab region were monitored and two types of Rusts (Leaf Rust & Yellow Rust) were recorded in varying intensity on different varieties of wheat. Out of 171 locations 86 spots were free from both types of rusts i.e. Leaf Rust & Yellow Rust, while the remaining locations were found to be infected with both leaf and yellow rust. However, all the surveyed fields were free from the stem rust infestation. Among the infected fields, 23 were infected by Leaf Rust while 63 fields were infected by Yellow Rust.The susceptible type of rust attack was noticed on old/ banned/ unapproved wheat varieties. Moderately resistant to resistant reaction was observed on newly approved varieties. The rust infected samples having S or MS type infection were collected for race analysis. Similarly, blast suspected samples were analyzed in laboratory and none of the tested samples showed the presence of wheat blast pathogen, which indicates no need to panic but vigilant in future.
Primary Author: Javaid, Ayub Agricultural Research Institute, Faisalabad, Pakistan
Synthetic hexaploid wheat (SHW), generated by crossing Triticum turgidum (AABB) with Aegilops tauschii (DD), has been exploited in improving various traits in cultivated wheat. A number of recent studies decomposed the additive variance of different traits captured by multiple sets of variants (e.g. single nucleotide polymorphisms (SNPs) located on different chromosomes or genic/intergenic regions) in both human and animal quantitative genetics studies. In this research, we dissected the additive variance explained by the three subgenomes and seven homoeologous sets of chromosomes in SHW germplasm to gain a better understanding of trait evolution in newly synthesized wheat. Our SHW germplasm lines generated by crossing improved durum parents (AABB) with Aegilops tauschii (DD) parents were phenotyped for ten fungal/nematode resistance traits. The lines were genotyped by genotyping-by-sequencing and 6,176 SNPs were mapped with missing data of less than 20%. The D subgenome dominated the additive effects and this dominance affected the A more than the B subgenome. The D subgenome exhibited a 1.8-fold higher contribution than the A subgenome across all traits. This dominance was not inflated by population structure or by longer linkage disequilibrium blocks observed in the D subgenome. The cumulative effects of the three homoeologs in each set had a significant positive correlation with their cumulative explained additive variance. Moreover, an average of 70% for each chromosomal group cumulative additive variance came from one homoeolog that had the highest explained variance within the group across all ten traits. We hypothesize that structural and functional changes during diploidization may explain chromosomal group relationships as allopolyploids maintain a balanced dosage for many genes. Our results contribute to a better understanding of trait evolutionary mechanisms in SHW, and will facilitate effective utilization of wheat relatives in breeding.
Primary Author: Jighly, La Trobe University