Posts Tagged ‘wheat’

Biochemical and histochemical traits: a promising way to screen resistance against spot blotch (Bipolaris sorokiniana) of whea

Posted by Carelia Juarez on , in Journal Articles

Published in European Journal of Plant Pathology 137(4):805-820, 2013

Eisa, M.; Chand, R.; Joshi, A.K.

Spot blotch caused by Bipolaris sorokiniana is a serious disease of wheat in warmer and humid regions of the world. Three blighting components, area under disease progress curve (AUDPC), disease severity (DS) and lesion size along with four biochemical and histochemical factors viz., total phenol content (TPC), chlorophyll content (CHC), phenylalanine ammonia-lyase (PAL) activity and lignin deposition were studied in a recombinant inbred lines (RILs) population involving parents “Sonalika” (susceptible) and “Yangmai 6” (resistant). The objective was to identify one or more robust and reliable tools of resistance, physical, biochemical or histochemical, to facilitate selection against spot blotch. The DS, AUDPC and lesion size were higher in the susceptible parent and RILs compared to the resistant. The mean TPC (246 mg Gallic acid g−1 fresh weight) of the most resistant RIL was significantly higher than the most susceptible (181.5 mg Gallic acid g−1 fresh weight) at 48 h after inoculation (hai). The mean SPAD value for CHC varied between 48.8 in the most resistant RILs to 8.8 in the most susceptible, while the mean PAL varied between 928.4 and 96.0 μmoles Cinnamic acid mg-1 fresh weight at 48 hai in resistant and susceptible RILs, respectively. Likewise, lignin deposition was significantly higher in resistant RILs compared to the susceptible. The biochemical and histochemical parameters were significantly correlated with resistance and appeared robust for facilitating screening of breeding material and for increased precision in phenotyping against spot blotch.

CIMMYT Annual Report 2012: Agricultural research for development improves food security

Posted by Carelia Juarez on , in CIMMYT Publications

CIMMYT Annual Report 2012: Agricultural research for development improves food security. 2013. CIMMYT, Int.. : 28 p.. Mexico, DF (Mexico). CIMMYT. Series: CIMMYT Annual Report.

98208.pdfThe work of CIMMYT and its many valued partners on maize and wheat farming systems is more  important now than at any time in the organization’s history. Our planet’s expanding population,  changing diets, limited natural resources, demand for bio-fuels and increasingly variable climate  are all putting extraordinary pressure on the global food system. The evidence is all around us. In  2012, for the third time in less than six years, we faced a global food price crisis with international  maize prices reaching levels double those of just two years prior. In the wake of the Arab Spring,  two major wheat production and cereal importing areas, North Africa and the Middle East, remain  highly stressed by rising wheat prices. In recent years average wheat imports for all of Africa have  reached more than 35 million tons annually, costing the continent’s nations more than US$12 billion and threatening the supply of wheat products for resource-poor consumers.

Studies of the genetics of inheritance of stem rust resistance in bread wheat

Posted by Carelia Juarez on , in Journal Articles

Published in African Journal of Biotechnology 12 (21) : 3153-3159, 2013

Nzuve, F. M.; Tusiime, G.; Bhavani, S.; Njau, P. N.; Wanyera, R.

Pgt race TTKSK (Ug99) has a wide virulence range with respect to currently grown wheat cultivars worldwide. Aspects of migration, mutation, recombination and selection in the pathogen have led to previously deployed stem rust resistance genes being ineffective. Race TTKSK has further evolved to acquire virulence for resistance genes such as Sr24 (race Ug99 + Sr24) and Sr36 (Ug99 + Sr36). Five resistant wheat lines (KSL-2, KSL-3, KSL-5, KSL-12 and KSL-19) which were resistant in tests during 2008, 2009 and 2010 were used as parents in crosses with stem rust susceptible line CACUKE to develop genetic populations for determining the inheritance of resistance to stem rust. F3 populations were evaluated at KARI Njoro in the 2012 off season and 2012 to 2013 main season. The adult plant stem rust responses were scored using the modified Cobb’s scale. The F2:3 lines of population(s) exhibiting qualitative variation were grouped as homozygous resistant (HR), segregating (Seg) and homozygous susceptible (HS). Heavy disease pressure was present during the cropping seasons with the check CACUKE displaying 90% susceptibility. Chi square analysis revealed that the segregation data in the parent KSL-2 did not deviate significantly from the single gene model (1:2:1) suggesting that the resistance to stem rust is conditioned by a single dominant gene. The Chi square test also revealed that the stem rust resistance in the parents KSL-3, KSL-5, KSL-12 and KSL-19 was conditioned by two genes. The families from the KSL-2 and KSL-3 crosses also segregated for the presence of the pseudo black chaff implying that theSr2 gene could be present in the background of these wheat parents. The superior transgressive segregants identified in these crosses will be used in breeding.

Resistance to stem rust Ug99 in six bread wheat cultivars maps to chromosome 6DS

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics, 2013

Lopez-Vera, E.E.; Nelson, S.; Singh, R.P.; Basnet, B.R.; Haley, S.D.; Bhavani, S.; Huerta-Espino, J.; Xoconostle-Cazares, B.G.; Ruiz-Medrano, R.; Rouse, M.N.;Sukhwinder Singh

More than 80 % of the worldwide wheat (Triticum aestivum L.) area is currently sown with varieties susceptible to the Ug99 race group of stem rust fungus. However, wheat lines Niini, Tinkio, Coni, Pfunye, Blouk, and Ripper have demonstrated Ug99 resistance at the seedling and adult plant stages. We mapped stem rust resistance in populations derived from crosses of a susceptible parent with each of the resistant lines. The segregation of resistance in each population indicated the presence of a single gene. The resistance gene in Niini mapped to short arm of chromosome 6D and was flanked by SSR markers Xcfd49 at distances of 3.9 cM proximal and Xbarc183 8.4 cM distal, respectively. The chromosome location of this resistance was validated in three other populations: PBW343/Coni, PBW343/Tinkio, and Cacuke/Pfunye. Resistance initially postulated to be conferred by the SrTmp gene in Blouk and Ripper was also linked to Xcfd49 and Xbarc183 on 6DS, but it was mapped proximal to Xbarc183 at a similar position to previously mapped genes Sr42and SrCad. Based on the variation in diagnostic marker alleles, it is possible that Niini and Pfunye may carry different resistance genes/alleles. Further studies are needed to determine the allelic relationships between various genes located on chromosome arm 6DS. Our results provide valuable molecular marker and genetic information for developing Ug99 resistant wheat varieties in diverse germplasm and using these markers to tag the resistance genes in wheat breeding.

Identification and mapping in spring wheat of genetic factors controlling stem rust resistance and the study of their epistatic interactions across multiple environments

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics 126 (8) : 1951-1964, 2013

Singh, A.; Knox, R.E.; DePauw, R.M.; Singh, A.K.; Cuthbert, R.D.;Campbell, H.L.; Singh, D.; Bhavani, S.; Fetch, T.; Clarke, F.

Stem rust (Puccinia graminis f. sp. tritici) is responsible for major production losses in hexaploid wheat (Triticum aestivum L.) around the world. The spread of stem rust race Ug99 and variants is a threat to worldwide wheat production and efforts are ongoing to identify and incorporate resistance. The objectives of this research were to identify quantitative trait loci (QTL) and to study their epistatic interactions for stem rust resistance in a population derived from the Canadian wheat cultivars AC Cadillac and Carberry. A doubled haploid (DH) population was developed and genotyped with DArT®and SSR markers. The parents and DH lines were phenotyped for stem rust severity and infection response to Ug99 and variant races in 2009, 2010 and 2011 in field rust nurseries near Njoro, Kenya, and to North American races in 2011 and 2012 near Swift Current, SK, Canada. Seedling infection type to race TTKSK was assessed in a bio-containment facility in 2009 and 2012 near Morden, MB. Eight QTL for stem rust resistance and three QTL for pseudo-black chaff on nine wheat chromosomes were identified. The phenotypic variance (PV) explained by the stem rust resistance QTL ranged from 2.4 to 48.8 %. AC Cadillac contributed stem rust resistance QTL on chromosomes 2B, 3B, 5B, 6D, 7B and 7D. Carberry contributed resistance QTL on 4B and 5A. Epistatic interactions were observed between loci on 4B and 5B, 4B and 7B, 6D and 3B, 6D and 5B, and 6D and 7B. The stem rust resistance locus on 6D interacted synergistically with 5B to improve the disease resistance through both crossover and non-crossover interactions depending on the environment. Results from this study will assist in planning breeding for stem rust resistance by maximizing QTL main effects and epistatic interactions.

Molecular mapping of high temperature tolerance in bread wheat adapted to the Eastern Gangetic Plain region of India

Posted by Carelia Juarez on , in Journal Articles

Published in Field Crops Research, 2013

Tiwari, C.; Wallwork, H.; Kumar, U.; Dhari, R.; Arun, B.; Mishra, V.K.; Reynolds, M.P.; Joshi, A.K.

The inheritance of tolerance to high temperature stress during the grain filling period was investigated via a QTL analysis based on 138 doubled haploid progeny of a cross between the wheat cultivars Berkut and Krichauff. Performance data were collected from three seasons, in each of which the material was planted both at the conventional time and a month later. A heat sensitivity index (HSI) was also used to monitor the effect of high temperature on grain yield, thousand grain weight, grain filling duration and canopy temperature. Using composite interval mapping, seven stable QTL were identified for HSI of traits, mapping to chromosomes 1D, 6B, 2D and 7A. Three of the QTL related to HSI of grain filling duration, two to thousand grain weight and one each to grain yield and canopy temperature. A region of chromosome 1D harbored a QTL determining HSI of both thousand grain weight and canopy temperature. The QTL analysis for the direct traits GY, TGW, GFD and CT led to detection of 22 QTLs spread over to 17 chromosomal regions. Of these 13 QTLs were shown under normal sown, while 9 under the heat stress. A QTL for TGW on chromosome 6B under normal sown co-located with HSI(TGW) QTL QHTgw.bhu-6BL. QTL × environment interactions were not observed for any of the grain filling duration associated loci.

Lower tendency of allelic variation of Glu genes and absence of 1BL-1RS translocation in modern Pakistani wheats

Posted by Carelia Juarez on , in Journal Articles

Published in Cereal Research Communications, 2013

Rehman, A.; Sajjad, M.; Khan, S.H.; Peña Bautista, R.J.; Khan, N.I.

The allelic variation for Glu-1Glu-3 loci and presence of IBL-1RS translocation was determined in 126 spring wheat accessions. The most common alleles at Glu-1 loci wereGlu-A1b (59.52%), Glu-B1c (41.26%), and Glu-D1d (57.14%) and at Glu-3 loci were Glu-A3c (56.45%), Glu-B3j (29.36%), and Glu-D3b (76.98%). Modern Pakistani wheat varieties carried superior alleles at Glu-1 and Glu-3 loci for bread-making quality and had no negative influence of secalin protein-synthesized by 1BL-1RS translocation. For LMW-GS, the most common combination was Glu-A3cGlu-B3j and Glu-D3b. The loci Glu-B1 andGlu-B3 had the highest allelic diversity of Glu-1 and Glu-3 loci, respectively.

Insights into genotype × tillage interaction effects on the grain yield of wheat and maize

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Science 53 (5) : 1845-1859, 2013

J.M. Herrera, N. Verhulst, R.M. Trethowan, P. Stamp and B. Govaerts

No tillage or zero tillage (NT) is the extreme form of reduced tillage; NT with residue retention is a main component of conservation agriculture. Using a literature survey and meta-analysis, this study aimed to (i) summarize the results of studies comparing the grain yield of wheat [Triticum aestivum L. and Triticum turgidum L. subsp. durum (Desf.) Husn. (syn. Triticum durum Desf.)] and maize (Zea mays L.) genotypes under contrasting tillage, (ii) identify sources of variation in the grain yield response of wheat and maize genotypes to tillage practices, and (iii) identify potential traits for NT breeding programs. Grain yield was compared under NT and conventional tillage (CT) for 112 wheat genotypes (44 spring, 60 winter, and eight durum wheat genotypes) across 12 locations and 24 yr and for 93 maize hybrids across six locations and 5 yr. Most of these studies showed slightly higher grain yields under CT for maize (+5%) and winter (+5%) and spring (+2%) wheat. In the few studies where selection had been conducted under NT, the effect of tillage on the grain yield was modified significantly by genotypes. Traits associated with the emergence of vigorous seedlings and resistance to a changed spectrum of diseases increase genotype performance under NT. There is a need to evaluate genotypes developed under NT and extend the research on genotype performance under NT to locations with reduced input use and, in addition to tillage, investigate other factors that differentiate conservation agriculture from conventional practice.

Association mapping and nucleotide sequence variation in five drought tolerance candidate genes in spring wheat

Posted by Carelia Juarez on , in Journal Articles

Published in Plant Genome 6 (2) : 13, 2013

Erena A. Edae, Patrick F. Byrne, Harish Manmathan, Scott D. Haley, Marc Moragues, Marta S. Lopes and Matthew P. Reynolds

Functional markers are needed for key genes involved in drought tolerance to improve selection for crop yield under moisture stress conditions. The objectives of this study were to (i) characterize five drought tolerance candidate genes, namely dehydration responsive element binding 1A (DREB1A), enhanced response to abscisic acid (ERA1-B and ERA1-D), and fructan 1-exohydrolase (1-FEH-A and 1-FEH-B), in wheat (Triticum aestivum L.) for nucleotide and haplotype diversity, Tajima’s D value, and linkage disequilibrium (LD) and (ii) associate within-gene single nucleotide polymorphisms (SNPs) with phenotypic traits in a spring wheat association mapping panel (n = 126). Field trials were grown under contrasting moisture regimes in Greeley, CO, and Melkassa, Ethiopia, in 2010 and 2011. Genome-specific amplification and DNA sequence analysis of the genes identified SNPs and revealed differences in nucleotide and haplotype diversity, Tajima’s D, and patterns of LD. DREB1A showed associations (false discovery rate adjusted probability value = 0.1) with normalized difference vegetation index, heading date, biomass, and spikelet number. Both ERA1-A and ERA1-B were associated with harvest index, flag leaf width, and leaf senescence. 1-FEH-A was associated with grain yield, and 1-FEH-B was associated with thousand kernel weight and test weight. If validated in relevant genetic backgrounds, the identified marker–trait associations may be applied to functional marker-assisted selection.

Earliness in wheat: A key to adaptation under terminal and continual high temperature stress in South Asia

Posted by Carelia Juarez on , in Journal Articles

Published in Field Crops Research 151 : 19-26, 2013

S. Mondal, R.P. Singh, J. Crossa, J. Huerta-Espino,  I. Sharmac, R. Chatrath, G.P. Singh, V.S. Sohu, G.S. Mavi, V.S.P. Sukaru, I.K. Kalappanavarg, V.K. Mishra, M. Hussain, N.R. Gautam, J. Uddin, N.C.D. Barma, A. Hakim and  A.K. Joshi

High temperatures are a primary concern for wheat production in South Asia. A trial was conducted to evaluate the grain yield performance of high yielding, early maturing heat tolerant CIMMYT wheat lines, developed recently in Mexico for adaptation to high temperature stresses in South Asia. The trial, comprised of 28 entries and two checks, was grown in 13 locations across South Asia and two environments in Mexico. Each location was classified by mega environment (ME); ME1 being the temperate irrigated locations with terminal high temperature stress, and ME5 as warm, tropical, irrigated locations. Grain yield (GY), thousand kernel weight (TKW), days to heading (DH) and plant height (PH) were recorded at each location. Canopy temperature (CT) was also measured at some locations. Significant differences were observed between ME for DH, PH, GY, and TKW. The cooler ME1 locations had a mean DH of 83 days, compared to 68 days mean DH in ME5. The ME1 locations had higher mean GY of 5.26 t/ha and TKW of 41.8 g compared to 3.63 t/ha and 37.4 g, respectively, for ME5. Early heading entries (<79 days, mean DH) performed better across all locations, with GY of 2–11% above the local checks and 40–44 g TKW. Across all locations the top five highest yielding entries had 5–11% higher GY than the local checks. The early maturing CIMMYT check ‘Baj’ also performed well across all locations. In the Mexico location, CT was associated with GY, thereby suggesting that cooler canopies may contribute to higher GY under normal as well as high temperature stress conditions. Our results suggest that the early maturing, high yielding, and heat tolerant wheat lines developed in Mexico can adapt to the diverse heat stressed areas of South Asia.