Ahi Evran University, Agriculture Faculty, Plant Protection Department K?rsehir/Turkey
Nilofer Akci, Marta da Silva Lopes
Stem rust (Puccinia graminis f. sp. tritici) is a fungal disease that can significantly reduce wheat yields and quality. The goal of this study was to screen 281 winter bread wheat landraces genotypes for their reaction to stem rust disease in seedling and adult plant stage.
For seedling stage, the experiment was carried out under greenhouse conditions in Field Crops Central Research Institute in Ankara, Turkey during 2017 growing season. The genotypes were grown at 20?4?C under greenhouse condition and inoculated (avirulent on Sr24, 26, 27, and 31 resistance genes) with urediniospores in mineral oil suspension at Zadoks growth stage 11 or 12. After inoculation, the genotypes were incubated at 20?1?C with 100% humidity during 24 hours then at 18-25?C. Scoring took place after 14 days using a 0-4 scale. Infection types on the susceptible checks (cv. Gun-91 and Thatcher) were 3+ scores. For adult plant reactions, the genotypes were screened under natural epidemic conditions for Pgt (virulent on Sr5, 6, 7b, 8a, 8b, 9b, 9g, 10, 30, Tmp and Mcn resistance genes) in Seydiler-Kastamonu, Turkey. The materials were sown in a one-meter row with three replications. Stem rust development on each entry was scored using the modified Cobb scale (Little Club had reached 80-100S) in August 2017. Coefficients of infections were calculated and values below 20 were considered to be resistant.
Two (1%) (Seedling stage) genotypes and 15 (5%) (Adult stage) genotypes were resistant to Pgt. The resistance genotypes identified in this study can be used in breeding programs. SNP markers will be identified for stem rusts resistance identified in the landrace population.
Ethiopian Institute of Agricultural Research
Ashenafi Gemechu, Habtamu Tesfaye, Zerihun Tadesse, Habtemariam Zegeye, Netsanet Bacha, Ayele Badebo, Bekele Abeyo, Pablo Olivera, Matthew, Rouse
Puccinia graminis f. sp. tritici (Pgt) is the major wheat production constraint in Ethiopia causing recurrent epidemics that resulted in the withdrawal of widely grown wheat cultivars from production. Among the current Pgt races detected in Ethiopia, TKTTF is the most frequent and has caused a severe epidemic in the south wheat growing regions (Bale and Arsi) after its first detection in 2012. Therefore, to avert the current situation, identifying sources of resistance to race TKTTF in breeding germplasm is a top priority to the National Wheat Breeding Program. Hence, 82 promising bread wheat lines including five check cultivars were evaluated in Debre Zeit in a TKTTF single race nursery for three consecutive seasons, 2014-2016. Ethiopian bread wheat cultivar Digalu was used as a spreader row and was inoculated using a single isolate of race TKTTF at different growth stages. The nursery was bounded by oat to reduce interference with any other stem rust race. The 82 lines were tested in the greenhouse at Cereal Disease Laboratory and were also tested with known diagnostic molecular markers. Twenty-nine lines displayed low levels of terminal stem rust severity in the field and low coefficient of infections. Fourty-one lines were resistant to race TKTTF at the seedling stage. Bread wheat lines resistant to TKTTF are valuable sources of resistance that can be deployed in wheat growing regions of Ethiopia prone to stem rust.
Nepal Agriculture Research Council, Nepal
Dipendra Pokharel, Thakur Prasad Tiwari, Mahesh Gathala, Hari Krishna Shrestha
Conservation agricultural practices have been found to be climate and labor smart, and sustainable, agricultural production technologies. The decline in productivity, increase in the cost of cultivation, labor intensive practice affected the cereal based farming system in Nepal particularly at the Indo-Gangetic plains. SRFSI has been working in response to concerns about the sustainability of the cereal based farming system at Sunsari and Dhanusha district of Nepal. This study was conducted to assess the adoption and scaling up of conservation agriculture in addition to input usage, production, net profit, B:C ratio, labour use, etc. of CA practice in Sunsari district, eastern Indo-Gangetic plains of Nepal. The study employed structured questionnaires survey and key informant survey as the main data collection tools. Project reports were taken as secondary data. The primary data related for the semi-annual report and annual report of the SRFSI project were collected jointly by the DADO, Sunsari and RARST, Tarahara. Study revealed that farmers had several tangible advantages and getting higher productivity through these practices. This study assessed the potential of CA based practices in Rice-Wheat and Rice-Maize farming system to improve the yields, net profit for sustainability of the cereal based farming system.
University of Eldoret
Julius Ochuodho, Ruth Wanyera, Sridhar Bhavani, Les Szabo
Stem rust Ug99 and related race group are one of the major constraints of wheat production in Kenya. The challenge has been largely due to rapid evolution of races within lineage defeating resistance genes resulting in boom and burst cycles. Understanding of the pathogen population structure in major wheat growing regions in Kenya gives comprehensive information of the predominant races as well as capturing new races which may have potential of causing epidemics. Such information can have significant impact on effective gene stewardship in breeding resistant varieties. Using 11 Pgt Simple Sequence Repeats (SSR) markers we analyzed 104 single uredinial-pustule samples. Allele frequency distribution ranged from 2 to 6 per locus with an average of 3.27 per locus. Observed heterozygosity ranging from 0.297-1.000 (mean HO=?0.809) was significantly different (P< 0.001) than the expected heterozygosity (0.264 to 0.507; mean HE=?0.407) indicating that the population is asexual. Analysis of molecular variance (AMOVA) showed that the majority of the variation occurred within the samples (98%) rather than between regions (2%). Analysis of 104 samples identified 21 multiple locus genotypes (MLGs). MLG.19 was observed across the three region analyzed that is Central Rift, North Rift and Mount Kenya while MLG.18 was predominant in Mount Kenya. Based on SSR genotypes of reference isolates, Pgt clade IV (race TKTTF) was associated with MLG.16 in Central Rift Kenya while clade I (race TTKSK) had a unique MLG.10. These results indicated two main groups corresponding to Clade I (Ug99 race group) and Clade IV (race TKTTF race group). This minimum spanning network analysis pattern points to the Pgt population being asexual due to mutation. These preliminary results suggest that Pgt population in Kenya is asexual in nature. Further analysis is being conducted to ascertain geographical structure as well as compare the results with the 2011 data.
Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization (AREEO), Karaj, Iran
Kamal Shahbazi, Jabbar Alt Jafarby, Mohammad Sadegh Khavarinejad, Farzad Afshari, Farshad Bakhtiar, Habibollah Soghi
In this project to obtain resistant wheat breeding lines/cultivars to stem rust disease, new cultivars and lines of the north breeding program were evaluated in greenhouse with races collected in 2014 from northern regions of Iran, Moghan and Gorgan. Artificial inoculation in greenhouse indicated none of the races had virulence on Sr11, Sr13, Sr24, Sr25, Sr26, Sr27, Sr29, Sr31, Sr32, Sr33, Sr37, Sr39, Sr40, and SrTmp. In order to evaluate seedling resistance, 143 wheat cultivars and new lines under greenhouse conditions were inoculated with four isolates of stem rust in four separate experiments in a randomized complete block design with three replications. Evaluation of the northern germplasm under greenhouse conditions showed that some of the genotypes were resistant against all four isolates. The resistance of some of these new lines was also confirmed in Kenya. Regarding other desirable agronomic characteristics, some of these lines will be introduced as new cultivars in the northern region of Iran.
Institute of Agriculture and Food Research and Technology
Karim Ammar, Susanne Dreisigacker, Josí María Arjona, Conxita Royo
Understanding the effect of genetic factors controlling flowering time is crucial to fine-tune crop adaptation to each target environment and maximize yield.
A set of spring durum wheat inbred lines carrying all but one of the possible allelic combinations at Ppd-A1 and Ppd-B1 genes was developed through a collaboration between IRTA and CIMMYT. The collection was grown during several years at four sites at latitudes ranging from 19?N to 41?N in order to assess the effect of Ppd-1 genes on development, biomass production and allocation, as well as grain yield formation.
Environmental constraints were responsible for most of the observed variation for flowering time and yield components. Latitude was a main driver of flowering time, which was later in northern sites and associated with lower minimum temperatures before flowering. Data on environmental constraints explaining a large proportion of grains m-2 and kernel weight variation will be presented. The effect on flowering time of Ppd-A1 alleles conferring photoperiod insensitivity was enhanced at sites with average daylength before flowering lower than 12h. Ppd-A1 caused a stronger effect on flowering time than Ppd-B1, which was found responsible for differences in grains m-2, associated with longer photoperiods from double-ridge to terminal spikelet stages. These differences in grains m-2, however, did not result in higher yields due to kernel weight compensation. Late flowering genotypes carrying alleles conferring photoperiod sensitivity had greater biomass at anthesis but it did not confer superior yields. Early flowering times were associated with higher yields in autumn-sowing sites due to a large contribution to yield of current photosynthesis during grain filling. Early flowering genotypes tended to yield more due to higher kernel weights, and the interaction of allele combination x environment will be discussed in the context of using allelic information as environment-specific guideline in breeding efforts.
Central Research Institute for Field Crops, Yenimahalle, Ankara, Turkey
Berberis species are important alternate hosts and generate new races of stem rust fungus, Puccinia graminis f. sp. tritici and yellow (stripe) rust fungus Puccinia striiformis. Berberis species are common in Kastamonu province of Turkey. In 2016 and 2017, surveys were conducted in Kastamonu province in order to elucidate aecial infection status of Berberis species in this region. In 2016, the central region and A?l?, Ara?, Daday, ?hsangazi, Seydiler, Ta?k?pr? and Tosya regions and in 2017 central region and Ara?, Daday, Han?n?, P?narba??, Seydiler, Ta?k?pr? and Tosya regions of Kastamonu province were investigated. It appears that there are at least two different Berberis species exist in that area. Berberis species showed variation in terms of fruit color and morphological characters. In 2016, 50 Berberis plants were examined and aecia were present in 38 plants (76%). Percentage of plants parts infected with aecia ranged between 3-80%. In 2017, 64 Berberis plants were examined. Aecia were present in 34 plants (53%). Percentage of plants parts infected with aecia ranged between 3-85%. Aecia were mainly observed on leaves but also observed on other plant parts including flower parts, fruit and young twigs. The role of these aecia and Berberis spp. on rust diseases in Kastamonu province of Turkey should be investigated.
This study was supported by General Directorate of Agricultural Research and Policies, Turkey (Project No: TAGEM-BS-15\12-01\02-02).
University of the Free State, South Africa
Nelzo Ereful, Botma Visser, Lesley Boyd, Zakkie Pretorius
Adult plant resistance (APR) to stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is often conferred by multiple minor genes and has the potential to be durable. A preceding project identified two Kenyan wheat lines (W1406 and W6979) from the Genome Resource Unit (Norwich, UK) that exhibit APR to Pgt. The aim of this study was to investigate the APR response to Pgt race PTKST in W1406 and W6979 compared to 37-07, a susceptible control line. Histological investigation of inoculated flag leaf sheaths indicated a significant and quantifiable decrease in Pgt colony size in the APR lines at 120 hours post inoculation (hpi). Molecular analysis supported the observed fungal biomass decrease in the APR lines at 120 hpi. RNAseq analysis identified 169 transcripts differentially expressed in W1406 and 166 transcripts in W6979 when comparing 24 and 72 hpi to 0 hpi. In W1406 transcripts encoding putative pectinesterases, lipid-transfer proteins and leucine-rich repeat-like proteins were induced at 72 hpi. In W6979 only a corresponding putative pectinesterase encoding transcript was identified. Although the induced defence response in the two APR lines exhibited some dissimilarity, it potentially involves cell wall modification in both lines. Two independent sets of peroxidases were induced at 24 and 72 hpi in both lines, suggesting independent signalling events. Expression analysis suggests the occurrence of two phases of gene expression, one at 24 hpi and another at 72 hpi; the latter seeming to correspond to the inhibition of Pgt growth, manifesting as the observed APR phenotype.
School of Agricultural Biotechnology, Punjab Agricultural University, Ludhiana-141004 India
Ahmed Elkot, Satinder Kaur, Parveen Chhuneja
Stripe rust and leaf rust are two most widely distributed diseases of wheat despite the fact that major emphasis has been made globally to develop rust resistant varieties. The wild tetraploid wheat Triticum araraticum (AAGG) evolved in the eastern part of Fertile Crescent is a source of useful traits for the improvement of wheat including resistance to disease. T. araraticum acc. pau4692 and a derived advanced backcross introgression line (IL) in susceptible T. durum cv. Malvi local background showed high level of seedling resistance against Indian pathotypes of leaf rust and stripe rust. The F5 Single seed descent (SSD) population developed from the crosses between T. araraticum IL with T. durum cultivar PBW114 was screened with commonly prevalent pathotypes of leaf rust and stripe rust in India at the seedling stage. The genetic analysis indicated that the leaf rust resistance is conditioned by two genes and stripe rust resistance by a single gene. The SSR markers mapped on A and B genome were used for parental polymorphism along with resistant and susceptible bulks for leaf rust and polymorphic markers between bulks were used on the whole population. The molecular marker data using single marker analysis showed that leaf rust resistance genes were mapped on chromosome 2A and 7A linked to SSR markers Xwmc149 and Xbarc49, respectively. The genes have been temporarily named as LrAr1 and LrAr2. Bulked segregant analysis (BSA) for mapping stripe rust resistance is in progress.
University of Minnesota
Ayele Badebo, Worku Bulbula, Matthew Rouse, Yue Jin
Our research objective is to identify new resistance genes in durum wheat that are effective against TTKSK and other significant stem rust pathogen races that could be utilized in durum breeding. We characterized 8,000 accessions for stem rust response in the field (Debre Zeit, Ethiopia, and St. Paul, MN). Accessions with resistant to moderately resistant responses in multiple field evaluations were evaluated at the seedling stage for resistance to races TTKSK, TRTTF, TTTTF, JRCQC, TKTTF, and six representative U.S. races. We identified 438 durum accessions resistant to moderately resistant in all field evaluations. Among the field-resistant accessions, 273 were resistant to all races used in seedling evaluations. Accessions susceptible at the seedling stage are being evaluated for the presence of adult plant resistance genes. The highest frequencies of resistant lines include landraces from East and North Africa (Ethiopia and Egypt) and advanced breeding lines and cultivars from North America (Mexico and USA). DNA markers will be performed to identify the presence of durum stem rust resistance genes, including Sr13, Sr8155B1, Sr11, and Sr8a. Nineteen resistant accessions were selected to investigate the genetics of TTKSK and TRTTF resistance. Results from evaluating F2 and F2:3 generations from biparental crosses revealed that resistance to race TTKSK was conferred mostly by one or two genes with dominant and recessive actions. Additional resistance genes were identified when populations were evaluated against race TRTTF. A bulk segregant analysis approach is being used to map the resistance in selected lines using the 90K SNP platform.