Posts Tagged ‘Euphytica’

Parental genome contribution in maize DH lines derived from six backcross populations using genotyping by sequencing

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2014

Ogugo, V.Fentaye Kassa SemagnBeyene, Y.Runo, S.Olsen, M.Warburton, M.L.

Molecular characterization of doubled haploid (DH) maize lines and estimation of parental genome contribution (PGC) may be useful for choosing pairs of DH lines for hybrid make up and new pedigree starts. Six BC1-derived DH populations created by crossing two donor with three recurrent parents were genotyped with 97,190 polymorphic markers with the objectives of: (i) understanding genetic purity, genetic distance and relationship among 417 maize DH lines; (ii) estimating PGC of the DH lines derived from different genetic backgrounds; and (iii) understanding the correlation between donor parent introgression and testcross performance for grain yield and anthesis-silking interval (ASI) under managed drought and optimum environments. The DH lines were 97 % genetically pure, with <2 % heterogeneity; only two DH lines showed heterogeneity >5 %, which is likely to be due to errors during seed multiplication or maintenance. Genetic distance between pairwise comparisons of the 417 DH lines ranged from 0.055 to 0.457; only 0.01 % showed a genetic distance <0.100, indicating large genetic differences among the DH lines. Both populations 1 and 6 showed significantly lower (p < 0.001) donor introgression than the other four populations. Donor parent contribution was significantly (p < 0.001) higher in the CML444 genetic background than CML395 and CML488. The average donor and recurrent PGC across all 417 DH lines was 31.7 and 64.3 %, respectively. Donor genome introgression was higher than expected in 82 % of the DH lines in the BC1 generation, possibly due to artificial selection during the DH process, during the development of F1 or BC1 seed, or during initial agronomic evaluation of the DH lines. Donor parent introgression up to 32 % showed significant positive correlation with grain yield under drought (r = 0.312, p < 0.001) and optimum (r = 0.142, p < 0.050) environments but negative correlation with ASI under drought (r = −0.276, p < 0.001). Additional multi-environment phenotype data under managed drought are needed to confirm the correlations reported in this study and to map the specific genomic regions associated with such correlations.

Variation at glutenin subunit loci, single kernel characterization and evaluation of grain protein in East African bread wheat varieties

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2014

Macharia, G.K.; Peña Bautista, R.J.; Simsek, S.; Anderson, J.A.

Wheat breeding programs worldwide aim at developing cultivars that meet end user quality attributes demanded by producers, processors, and consumers. Selecting from breeding populations created from well characterized parental germplasm provides the best opportunity of identifying cultivars that combine the best alleles and grain phenotypes for the desired technological applications. In this study, 216 bread wheat lines associated with Ethiopian and Kenyan breeding programs including a few founder lines were profiled for high molecular weight glutenin subunits and low molecular weight glutenin subunits by SDS-PAGE. Additionally, total crude protein, relative puroindoline content by SDS-PAGE, kernel diameter, kernel weight and kernel hardness by SKCS were determined. Extensive allelic variation at the glutenin subunit loci was found, with GluB1 and GluB3 having highest diversity across subpopulations. Relative to wild type cultivar ‘Alpowa-1-soft’, the founder line BW21 had the lowest puroindoline content. The frequencies of soft and very soft wheat classes were lowest in the Ethiopian subpopulation and highest among the Kenyan lines. Accordingly, 12 lines considered to have optimal combinations of glutenin subunit alleles and kernel characteristics were highlighted and recommended for cultivar improvement.

Genetic analysis of drought tolerance in adapted × exotic crosses of maize inbred lines under managed stress conditions

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica 196 (2) : 261-270, 2014

Adebayo, M.A.; Menkir, A.; Blay, E.; Gracen, V.; Danquah, E.; Hearne, S.

Introduced maize (Zea mays L.) germplasm can serve as sources of favorable alleles to enhance performance in new maize varieties and hybrids under drought stress conditions. In the present study, the combining abilities of 12 exotic maize inbred lines from CIMMYT and 12 adapted maize inbred lines from IITA were studied for grain yield and other traits under controlled drought stress. The inbred lines from each institution were separated into groups using SSR-based genetic diversity and were intercrossed using a factorial mating scheme to generate 96 hybrids. These hybrids were evaluated under both controlled drought stress and well-watered conditions at Ikenne in Nigeria in 2010 and 2011. Average mean yields of hybrids under drought stress represented 23 % of the average yield of hybrids under full irrigation. General combining ability (GCA) effects accounted for 49–85 % of the observed variation for several traits recorded under both well-watered and drought stress conditions. Specific combining ability effects for grain yield, though positive in most hybrids, were not significant under drought stress conditions. All the twelve exotic and nine adapted lines had positive GCA effects (female, male, or both) for grain yield under either drought stress or full irrigation, or both environments. EXL03 and EXL15 that had positive and significant female and male GCA effects for grain yield under both environments can be used to improve their adapted counterparts for grain yield and drought tolerance. Normalized difference vegetation index had weak but significant correlation with grain yield.

Characterization of Chinese wheat germplasm for resistance to Fusarium head blight at CIMMYT, Mexico

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2013

He Xinyao; Singh, P.K.; Schlang, N.; Duveiller, E.; Dreisigacker, S.; Payne, T.; He Zhonghu.

Fusarium head blight (FHB) poses a challenge for wheat breeders worldwide; there are limited sources of resistance and the genetic basis for resistance is not well understood. In the mid-1980s, a shuttle breeding and germplasm exchange program launched between CIMMYT-Mexico and China, enabled the incorporation of FHB resistance from Chinese bread wheat germplasm into CIMMYT wheat. Most of the Chinese wheat materials conserved in the CIMMYT germplasm bank had not been fully characterized for FHB reaction under Mexican environments, until 2009, when 491 Chinese bread wheat lines were evaluated in a FHB screening nursery in Mexico, and 304 (61.9 %) showed FHB indices below 10 %. Subsequent testing occurred in 2010 for plant height (PH), days to heading (DH), and leaf rust response. In 2012, 140 elite lines with good agronomic types were further evaluated for field FHB reaction and deoxynivalenol (DON) accumulation. Most of the tested lines showed good resistance: 116 (82.9 %) entries displayed FHB indices lower than 10 %, while 89 (63.6 %) had DON contents lower than 1.0 ppm. Significant negative correlations were observed between FHB traits (FHB index, DON content, and Fusarium damaged kernels) and PH, DH, and anther extrusion. A subset of 102 elite entries was selected for haplotyping using markers linked to 10 well known FHB quantitative trait loci (QTL). 57 % of the lines possessed the same 2DL QTL marker alleles as Wuhan 1 or CJ 9306, and 26.5 % had the same 3BS QTL allele as Sumai 3. The remaining known QTL were of low frequency. These materials, especially those with none of the above tested resistance QTL (26.5 %), could be used in breeding programs as new resistance sources possessing novel genes for FHB resistance and DON tolerance.

Climate change at winter wheat breeding sites in central Asia, eastern Europe, and USA, and implications for breeding

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2013

A. Morgounov, S. Haun, L. Lang, S. Martynov and  K. Sonder

Key weather parameters (monthly minimum and maximum temperature, precipitation) were extracted for 35 winter wheat breeding sites in central Asia, eastern Europe and Great Plains of USA from 1961 to 2009. Autumn and winter warming happened gradually, over a long period of time, but mostly before 1991. Climate changes after 1991 were mainly expressed through higher temperatures in spring, May, and June. Clear regional differences were observed for air temperature variation. Breeding sites in the USA seemed to be least subjected to climate change. There were no significant linear trends in yearly, seasonal, or monthly precipitation. Changing climates expressed through rising temperatures during critical stages of winter wheat development have already negatively affected yield gains in several countries, especially in eastern Europe. There are some positive changes associated with warmer winters, which may not require additional investment in traits associated with winter survival. Rising temperatures in spring are of particular concern since their effect on yield is negative in some regions. They certainly accelerate wheat development and shift heading to earlier dates. The interaction of higher temperatures in spring with the rate of crop development and yield is a fundamental issue which requires research. Rising temperatures in June are detrimental for grain development and filling and heat tolerance warrants high priority in breeding  programs.

 

Genetic interrelationships among medium to late maturing tropical maize inbred lines using selected SSR markers

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica 191 (2) : 269-277, 2013

Abera Wende, Hussein Shimelis, John Derera, Worku Mosisa, Jedidah Danson and Mark D. Laing

Understanding the genetic relationships among breeding lines is fundamental in crop improvement programs. The objectives of this study were to apply selected polymorphic single sequence repeat (SSR) DNA markers and cluster medium to late maturing tropical elite maize inbred lines for effective hybrid breeding. Twenty elite inbred lines were genotyped with 20 SSR markers. The analysis detected a total of 108 alleles. The unweighted pair group method with arithmetic mean allocated the inbred lines into five clusters consistent with the known pedigrees. The tested inbred lines that were adapted to mid-altitude, sub-humid agro-ecologies were classified in different clusters, except for a few discrepancies. The greatest genetic distance was identified between the clusters of lines CML-202 and Gibe-1-91-1-1-1-1. The analysis determined the genetic grouping present in the source population, which will assist in effective utilization of the lines in tropical hybrid maize breeding  programs to exploit heterosis.

QTL for yield, yield components and canopy temperature depression in wheat under late sown field conditions

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2013

R. Esten Mason, Dirk B. Hays, Suchismita Mondal, Amir M. H. Ibrahim and Bhoja R. Basnet

A wheat (Triticum aestivum L.) recombinant inbred line (RIL) population was used to identify quantitative trait loci (QTL) associated with yield, yield components, and canopy temperaturedepression (CTD) under field conditions. The RIL population, consisting of 118 lines derived from a cross between the stress tolerant cultivar ‘Halberd’ and heat stress sensitive cultivar ‘Karl92’, was grown under optimal and late sown conditions to impose heat stress. Yield and yield components including biomass, spikes m−2, thousand kernel weight, kernel weight and kernel number per spike, as well as single kernel characteristics were determined. In addition, CTD was measured during both moderate (32–33 °C) and extreme heat stress (36–37 °C) during grain-filling. Yield traits showed moderate to high heritability across environments with a large percentage of the variance explained by genetic effects. Composite interval mapping detected 25 stable QTL for the 15 traits measured, with the amount of phenotypic variation explained by individual QTL ranging from 3.5 to 27.1 %. Two QTL for both yield and CTD were co-localized on chromosomes 3BL and 5DL and were independent of phenological QTL. At both loci, the allele from Halberd was associated with both higher yield and a cooler crop canopy. The QTL on 3BL was also pleiotropic for biomass, spikes m−2, and heat susceptibility index. This region as well as other QTL identified in this study may serve as potential targets for fine mapping and marker assisted selection for improving yield potential and stress adaptation of wheat.

Evaluation of open pollinated varieties of maize for resistance to the maize weevil in a controlled temperature and humidity laboratory in Zimbabwe

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2013

R. T. Masasa, P. S. Setimela and Z. A. Chiteka

Maize weevil (Sitophilus zeamais Motschulsky) is one of the major maize storage pests among smallholder farmers in eastern and southern Africa (ESA), thereby, reducing total on-farm maize harvests. Experiments were conducted in a controlled temperature and humidity (CTH) laboratory at CIMMYT-Zimbabwe to compare the resistance of new maize open pollinated varieties (OPVs) from regional trials undertaken in ESA to maize weevils. Twenty maize OPVs were shelled and cleaned before being placed in a deep freezer at −20 °C to kill any pests and eggs in the grain from the field. Fifty grams of grain from each OPV was measured after 3 weeks and placed in the CTH lab for conditioning. The samples were placed in 250-mL jars with brass-screened lids and then infested with 32 maize weevils aged between 10 and 14 days. Data were collected for kernel hardness prior to weevil infestation, as kernel hardness to confer resistance to weevils. The components of maize weevil resistance considered were: median development period, Dobie index of susceptibility, weevil emergence, weevil mortality, weevil fecundity, grain weight loss, kernel damage and germination. There were highly significant differences in maize kernel characteristics and median development period (P < 0.001) among the maize OPVs. There were significant differences in the number of damaged kernels, grain weight loss (P < 0.01), weevil mortality and germination (P < 0.05) among the maize OPVs. There were no significant differences found for weevil progeny emergence (F1), Dobie index of susceptibility and weevil fecundity, the last of which was positively and significantly correlated with kernel damage (P < 0.001). The DIS was positively and significantly correlated with weight loss and F1 (P < 0.001). The maize OPVs 07WEEVIL, Chitedze6, Strigoff126, Strigoff128 and ZM625 were found to be resistant; on the other hand, Strigoff140, Strigoff125, Strigoff133, VP05199 and VP074 varieties were highly susceptible.

 

 

Breeding progress for yield in winter wheat genotypes targeted to irrigated environments of the CWANA region

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2013

W. Tadesse, A. I. Morgounov, H. J. Braun, B. Akin, M. Keser, Yuksel Kaya, R. C. Sharma, S. Rajaram, M. Singh, M. Baum and M. van Ginkel

The international winter wheat improvement program (IWWIP), an alliance between Turkey–CIMMYT–ICARDA, has distributed improved germplasm to different National Agricultural Research Systems (NARS) partners through international nurseries and yield trials for the last 25 years. This study was carried out in order to determine the rate of breeding progress for yield and yield related traits at IWWIP using data of the international winter wheat yield trials (IWWYT), IWWYT 1–13, collected from 1997 to 2010 in irrigated environments across different countries. The relative grain yield of the best line expressed as percent of the best check (Kinaci-97), widely grown cultivar (Bezostaya) and trial mean (TM) increased at a rate of 0.6, 1.6 and 0.2 %/year, each non-significant (P > 0.05), respectively. Regression analysis indicated that TM has increased at a rate of 91.9 kg/ha/year (P = 0.007). The net realized breeding progress was estimated by accounting the variability due to management and weather conditions using surrogate variables such as integrated biological indices taken as means of common checks. The net realized gain for the BL was 66.2 ± 19.7 kg/ha/year (P = 0.01). Success rate of the BL, per cent of sites where the BL exceeds the local check in grain yield, ranged from 50 to 87 % across trials. To date, more than 55 varieties of IWWIP origin have been released in 10 countries of Central and West Asia including Afghanistan, Turkey, Iran, Uzbekistan and Tajikistan. Some varieties, such as Solh and Kinaci-97, have been released under different names in different countries indicating their broad adaptation. Cluster analysis of IWWYT sites indicated that IWWIP sites in Turkey and Syria are associated with most of the testing sites in Central and West Asia and North Africa (CWANA) region. The recently identified high yielding genotypes are recommended for direct release and/or parental purposes by the respective NARS.

 

Genetic distance among doubled haploid maize lines and their testcross performance under drought stress and non-stress conditions

Posted by Carelia Juarez on , in Journal Articles

Published in Euphytica, 2013

Yoseph Beyene,  Stephen Mugo, Kassa Semagn, Godfrey Asea, Walter Trevisan, Amsal Tarekegne, Tadele Tefera, James Gethi, Barnabas Kiula, John Gakunga, Haron Karaya and Andrew Chavangi

In contrast to conventional inbreeding that takes up to seven generations to develop inbred lines, the doubled haploid (DH) technology allows production of inbred lines in two generations. The objectives of the present study were to: (a) evaluate testcross performance of 45 doubled haploid lines under drought stress and non-stress conditions (b) estimate heritabilities for grain yield and other traits and (c) to assess the genetic distance and relationship among the DH lines using 163,080 SNPs generated using genotyping-by-sequencing (GBS). The 45 hybrid and five checks were evaluated using a 10 × 5 alpha lattice in six drought stress and nine well-watered environments in Kenya, Uganda, and Tanzania. Differences in trait means between the drought stress and well-watered conditions were significant for all measured traits except for anthesis date. Genetic variances for grain yield, grain moisture, plant height and ear height were high under well-watered environments while genetic variance for anthesis date, root lodging and stalk lodging were high under drought stress environments. Combined analyses across drought stress and well-watered environments showed that ten top hybrids produced 1.6–2.2 t/ha grain yield under well-watered condition and 1–1.4 t/ha under drought stress condition higher than the mean of the commercial checks. Genetic distance between pairwise comparisons of the 38 of the 45 DH lines ranged from 0.07 to 0.48, and the overall average distance was 0.36. Both cluster and principal coordinate analysis using the genetic distance matrix calculated from 163,080 SNPs showed two major groups and the patterns of group was in agreement with their pedigree. Thirteen (13) of the best hybrids are currently in National Performance Trials testing, an important step towards commercialization in Kenya, Tanzania and Uganda.