Posts Tagged ‘resistance’

Response to S1 recurrent selection for resistance to two stem borers, Busseola fusca and Chilo partellus, in two tropical maize populations

Posted by gabrielamartinez on , in Journal Articles

56905Authors: Mwimali, M., Derera, J., Mugo, S.N., Tongoona, P.

Published in: Euphytica, In Press.


Stem borers, Busseola fusca and Chilo partellus, are among the key devastating lepidopteran insect pests ofmaize causing grain yield losses.Recurrent
selection studies for stem borer resistance in maize are limited. However, maize populations carrying resistance genes to these stem borers have not been exploited fully in breeding programmes. The objective of the study was to separately improve resistance to B. fusca and C. partellus stem borers for two maize populations CML395/MBR C5 Bc and CML444/MBR/MDR C3Bc and therefore grain yield after two cycles of S1 progeny recurrent selection. Cycle 0 and the advanced generations (cycle 1-susceptible, cycle 1-resistant and cycle 2-resistant) were evaluated at three locations in Kenya using a 35 9 12 a-lattice design with 2 replications. The net reductions in cumulative tunneling, number of exit holes and leaf feeding damage scores ranged from0 to 69 %for both populations after two cycles of selection. In the two populations, each cycle of selection for borer resistance improved grain yield by 0.5–0.8 t ha-1. Actual net gains in grain yield with reference to cycle 0 were 43 % for population CML395/MBRC5 Bc under B. fusca infestation and 70 % under C. partellus infestation. For population CML444/MBR/MDR C3Bc, the actual net gains in grain yield were 25 %under B. fusca infestation and 36 % under C. partellus infestation. The reductions in the injurious effects attributable to leaf feeding damage, cumulative stem tunneling and number of exit holes contributed towards the 43 and 70 % net genetic gain in grain yield under B. fusca and C. partellus infestation respectively, for both populations. Broad sense heritability (H2) for grain yield ranged from 2 to 98 % in both maize populations. The study showed that two cycles of S1 progeny recurrent selection was effective in accumulating favourable alleles for B. fusca and C. partellus stem borer resistance.

Antibiosis Mechanism of Resistance to Larger Grain Borer, Prostephanus truncatus (Horn)(Coleoptera: Bostrichidae) in Maize

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Entomology  11 (5) : 248-260, 2014

Nhamucho, E.;  Mugo, S.N.;  Kinyua, M.;  Gohole, L.;  Tadele Tefera;  Mulima, E.

Host plant resistance is a valuable component of integrated pest management in maize. Maize stored on-farm without controlled moisture content and insecticide treatment is highly susceptible to damage by Larger Grain Borer (LGB),Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae). The aim of this study was to determine the resistance of Mozambican maize genotypes against P. truncatus. Seventeen maize genotypes composed of seven experimental hybrids, one released hybrid, two improved open pollinated varieties (OPV), three landraces from Mozambique and four checks (two resistant and two susceptible) from Kenya were screened for their resistance to LGB. The F1 and F2 hybrids were evaluated at Kiboko, Kenya in a completely randomized design trial, replicated four times in a post-harvest laboratory. A selection index computed from the number of LGB, grain weight loss (%), seed damage (%) and flour weight were used to categorize the materials as either resistance or susceptible. Fifty percent of the F1 hybrids tested were resistant, 25% moderately resistant and 25% susceptible. Twenty five percent of F2 hybrids evaluated were resistant and 75% susceptible. EV8430DMRSR, an OPV and Kandjerendjere, a landrace were the most resistant genotypes with less than 10% weight loss and less than 25% seed damage. This study showed that high protein content contributed towards resistance while high starch contributed to susceptibility. It was concluded that antibiosis mechanism could contribute to LGB resistance in maize. The identified resistant genotypes could be used as cultivar or as source of resistance in maize breeding programs for resistance to LGB.

Dayaniklilik Geni Cre1’ in Akdeniz Tahil Kist Nematodu, Heterodea latipons Franklin (Tylenchida: Heteroderidae)’e Karsi Etkinliginin Arastirilmasi

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Agricultural Science 20  261-268, 2014

Imren, M.; Kasapoglu, E.B.; Dababat, A.A.; Toktay, H.;Elekcioglu, I.H.

Cereal cyst nematodes (Heterodera avenae group) are important pests of wheat; they include the three most important species of cereal cyst nematodes: Heterodera avenae Wollenweber, H. latipons Franklin and H. filipjevi (Madzhidov) in Turkey that were determined in different wheat growing areas. It was reported that Mediterranean cereal cyst nematode, Heterodera latipons which is widely found in the centre of the durum wheat growing area -South-eastern Anatolia regionin our country was reaching the economical threshold in many locations. It is known that the use of resistant/tolerant wheat varieties is the most effective controlling method against cyst nematodes in the wheat cultivation. Nowadays, nine different resistance genes (Cre genes), which are transferred from wild wheat species to wheat cultivated forms are available. In this study, the efficiency of the resistance gene, Cre1, against the population of H. latipons from Gaziantep (Karkamıs) was investigated. In the study, 38 genotypes carrying Cre1 gene and 26 genomes lacking resistance genes; this gives a total 64 wheat genotypes which are produced by parental crossing of SILVERSTAR containing the resistance gene, Cre1, in its genome, SOKOLL, CALINGIRI, GOLDMARKER, CROC_1/AE.SQUARROSA(224)//OPATA,FRAME, STYLET and PASTOR were used against H. latipons in the experiment. Among the 64 genotypes; 20 were resistant, 32 were moderately resistant and 12 were moderately susceptible to the nematode. Ten resistant, 20 moderately resistant and 8 moderately susceptible lines were determined against H. latipons that these 38 lines carried the Cre1 gene in their genome. Within this study, the resistant gene, Cre1, was not found to be completely resistant against H. latipons, but its 78% efficiency rate was found to be successful: therefore, it was concluded that it can be used against H. latipons in national wheat breeding programs. Furthermore, PASTOR, SOKOLL and CROC_1/AE.SQUARROSA(224)//OPATA wheat genotypes were determined as good resistance source against H. latipons.

Evaluation of traits of resistance to postharvest insect pests in tropical maize

Posted by Carelia Juarez on , in Journal Articles

Published in International Journal of Agriculture and Crop Sciences 6(13) : 926-933, 2013

Mwololo, J.K.; Mugo, S.N.; Tadele Tefera; Munyiri, S.W.

The maize weevil Sitophilus zeamais (Motschulsky) is among the most grain damaging insect in sub-saharan Africa. The objective of the study was to determine differences in traits associated with resistance to the maize weevil in the field and in storage. Two hundred and ninenty five (295) maize genotypes comprising of 120 inbred lines, 100 hybrids and open pollinated varieties (OPVs), and 75 landraces including resistant and susceptible checks were used in the study. The test materials were planted in two rows of 5 m replicated three times in alpha lattice designs. Husk tip length (cm) was measured in 10 plants of each row. Grain texture was rated visually and mechanical hardness of grain samples determined using a force displacement meter. Grain samples of 100 grams were taken from each plot of the three replications of each of the experiments and tested in the screening laboratory for resistance to maize weevil. Analysis of variance for the individual traits, correlation analysis and weight loss (%) was performed. High phenotypic variation in traits associated with postharvest resistance was evident. Grain hardness was high in the resistant compared to the susceptible genotypes. Genotypes with flint grain texture had longer tip length. The resistant hybrids and inbred lines were flinty in texture whereas the susceptible were dent. There was a positive relationship (r = 0.77) between grain texture and husk cover. The study showed that mechanisms of resistance vary among genotypes hence resistance should not be based on a single trait.

Identification of genetic resistance to cereal cyst nematodes; Heterodera avenae (Wollenweber, 1924), Heterodera filipjevi (Madzhidov, 1981) Stelter and Heterodera latipons (Franklin, 1969) in some international bread wheat germplasms

Posted by Carelia Juarez on , in Journal Articles

Published in Turkiye Entomoloji Dergisi – Turkish Journal  of Entomology 37 (3) : 277-282, 2013

Imren, M.; Toktay, H.; Bozbuga, R.; Erginbas Orakci, G.; Dababat, A.; Elekcioglu, I.H.

The cereal cyst nematodes, Heterodera avenae group, are known as parasites of cereals worldwide. In Turkey, the cereal cyst nematodes, Heterodera filipjevi, H. avenae and H. latipons, are the three known species infested wheat fields and cause high yield losses. The using of resistance varieties is one of the most effective methods for controlling cereal cyst nematodes. Recently, resistance genes (Cre genes) which are obtained from wild wheat genotypes have been transferred into bread wheat varieties to control the cereal cyst nematodes species. In this study, the efficiency of some sources of resistance (CreR, Cre1, Cre2, Cre3, Cre7 and Cre8) in wheat against some Turkish H. avenae, H. filipjevi and H. latipons populations was investigated in-vitro conditions. According to results, the effect of resistance genes showed variation depending on different Cereal cyst nematode populations; H.avenae, H. filipjevi and H. latipons. Although Cre1 gene was only found as completely resistant to all (three) nematode species, Cre3 and Cre7 were found resistant to H. avenae and H. latipons. Cre R was also determined as resistant to H. filipjevi and H. latipons populations but Cre8 was only found resistant against to H. filipjevi population. No resistance was found in Cre 2 gene against to all nematode populations. Additionally, 2 resistance gene-free variety and lines were found resistant to H. avenae; 3 wheat lines to H. filipjevi and 11 wheat genotypes were found moderately resistant to H. latipons.

Evaluation of macroscopic and microscopic components of partial resistance to leaf rust in durum wheat

Posted by Carelia Juarez on , in Journal Articles

Published in Journal of Phytopathology, 2013

Soleiman, N.H.; Solis, I.; Sillero, J.C.; Herrera-Foessel, S.A.; Ammar, K.; Martinez, F.

Leaf rust, caused by the fungus Puccinia triticina, is considered one of the most important foliar diseases in durum wheat. Hypersensitive resistance (HR) may be rapidly overcome by the pathogen when resistant cultivars are grown on a large acreage or following changes in virulence in the pathogen population. Prolonging the durability of the resistance requires uses of other types of resistance such as partial resistance (PR). In this study, six durum wheat lines provided by the International Center for Corn and Wheat Improvement (CIMMYT) with a high level of PR to leaf rust were studied in monocyclic tests in a growth chamber. Inoculations were performed on both primary and fifth leaves using the Spanish race DGB/BN. UV fluorescence microscopy was employed to determine microscopic components of the resistance, such as the number of early aborted infection units not associated with plant cell necrosis (EA−) and relative colony size (RCS) of the established infection units. Macroscopic components of PR such as latency period, infection frequency and uredinium size were measured as well. All six resistant lines were characterized by a higher EA− and smaller RCS respect to the susceptible control ‘Don Rafael’. Line 3 showed the highest level of PR. It had 22% of EA− compared with 4% in the susceptible control, and the smallest RCS (17% respect to RCS of ‘Don Rafael’) at adult plant stage. Both EA− and RCS had a high heritability (more than 97%) and the correlation with macroscopic parameters (latency period and uredinium size) was also high (significant at 0.001 level). Hence, PR to leaf rust in these durum wheat genotypes has been revealed at microscopic level (higher EA− and smaller RCS).

Quantitative trait loci of stripe rust resistance in wheat

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics 126 (10) : 2427-2449, 2013

Rosewarne, G.M.; Herrera-Foessel, S.A.; Singh, R.P.; Huerta-Espino, J.; Lan Caixia; He Zhonghu

Over thirty publications during the last 10 years have identified more than 140 QTLs for stripe rust resistance in wheat. It is likely that many of these QTLs are identical genes that have been spread through plant breeding into diverse backgrounds through phenotypic selection under stripe rust epidemics. Allelism testing can be used to differentiate genes in similar locations but in different genetic backgrounds; however, this is problematic for QTL studies where multiple loci segregate from any one parent. This review utilizes consensus maps to illustrate important genomic regions that have had effects against stripe rust in wheat, and although this methodology cannot distinguish alleles from closely linked genes, it does highlight the extent of genetic diversity for this trait and identifies the most valuable loci and the parents possessing them for utilization in breeding programs. With the advent of cheaper, high throughput genotyping technologies, it is envisioned that there will be many more publications in the near future describing ever more QTLs. This review sets the scene for the coming influx of data and will quickly enable researchers to identify new loci in their given populations.

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.

QTL for spot blotch resistance in bread wheat line Saar co-locate to the biotrophic disease resistance loci Lr34 and Lr46

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics 126 (3) : 711-719, 2013

Morten Lillemo, Arun K. Joshi, Ravindra Prasad, Ramesh Chand and Ravi P. Singh

Spot blotch caused by Bipolaris sorokiniana is a major disease of wheat in warm and humid wheat growing regions of the world including south Asian countries such as India, Nepal and Bangladesh. The CIMMYT bread wheat line Saar which carries the leaf tip necrosis (LTN)-associated rust resistance genes Lr34 and Lr46 has exhibited a low level of spot blotch disease in field trials conducted in Asia and South America. One hundred and fourteen recombinant inbred lines (RILs) of Avocet (Susceptible) × Saar, were evaluated along with parents in two dates of sowing in India for 3 years (2007–2008 to 2009–2010) to identify quantitative trait loci (QTL) associated with spot blotch resistance, and to determine the potential association of Lr34 and Lr46 with resistance to this disease. Lr34 was found to constitute the main locus for spot blotch resistance, and explained as much as 55 % of the phenotypic variation in the mean disease data across the six environments. Based on the large effect, the spot blotch resistance at this locus has been given the gene designation Sb1. Two further, minor QTL were detected in the sub-population of RILs not containing Lr34. The first of these was located about 40 cM distal to Lr34 on 7DS, and the other corresponded to Lr46 on 1BL. A major implication for wheat breeding is that Lr34 and Lr46, which are widely used in wheat breeding to improve resistance to rust diseases and powdery mildew, also have a beneficial effect on spot blotch.

Identification and characterization of international Fusarium head blight screening nurseries of wheat at CIMMYT, Mexico

Posted by Carelia Juarez on , in Journal Articles

Published in European Journal of Plant Pathology 136 (1) : 123-134, 2013

Xinyao He, Pawan K. Singh, Etienne Duveiller, Norbert Schlang, Susanne Dreisigacker and Ravi P. Singh

Fusarium head blight (FHB) is a major threat to wheat production globally, causing not only yield losses but also food and feed contamination. FHB research began at the International Maize and Wheat Improvement Center (CIMMYT) in the early 1980’s, and since then, large-scale FHB screening has been conducted to identify and incorporate new resistance genes into elite CIMMYT germplasm. Promising lines with good FHB resistance were regularly compiled as a Fusarium Head Blight Screening Nursery (FHBSN) and distributed worldwide. The first FHBSN was assembled in 1985, and the most recent two were the 13th and 14th FHBSN that were released in 2011 and 2012, respectively. Candidate lines for a FHBSN came mainly from different CIMMYT wheat breeding programs and were tested for three consecutive years before being included in an FHBSN. FHBSN screening was conducted under strictly standardized field conditions at El Batán, where CIMMYT headquarters is located, using artificial inoculation of F. graminearum strains, whose aggressiveness and DON chemotypes had been previously identified. FHB index was scored at 31 days after inoculation for all lines and DON concentration was measured only for elite lines in their 2nd and 3rd year of evaluation. Haplotyping is a new tool for genetic characterization of FHBSN entries and helps to identify new resistance sources with novel resistance genes and to better target crosses toward diversifying and/or pyramiding resistance. The 13th FHBSN was taken as an example in this paper to show the procedure and strategy for the development of new FHB resistant lines.