Posts Tagged ‘grain yield’

Yield and agronomic performance of maize hybrids resistant to the maize weevil Sitophilus zeamais Motschulsky (Coleoptera: Curculionidae)

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Protection 46 : 94-99, 2013

Tadele Tefera, Girma Demissie, Stephen Mugo and Yoseph Beyene

This study evaluated improved maize hybrids (Zea mays L.) with varying level of resistance to the maize weevil, Sitophilus zeamais Motschulsky, for yield and agronomic traits for two seasons. A total of 22 improved maize hybrids and three commercial standards were tested. Out of the 22 tested, two hybrids CKPH08035 (7.4–9.9 t ha−1) and CKPH08039 (7.3–9.8 t ha−1) significantly out yielded the commercial standards WH505 (8.8 t ha−1) and BH140 (5.5 t ha−1). In addition to yield, the improved hybrids also possess desirable traits including good plant height, good plant and ear aspects and good husk cover. The hybrid CKPH08004 had the lowest Dobie index of susceptibility and was regarded as resistant to S. zeamais. Weevils fed with the resistant hybrids produced low numbers of F1 generation weevils, had a high median developmental time and a low percentage of grain damage and grain weight loss. An increasing number of F1 generation resulted in an increasing grain damage and grain weight loss. We found an inverse relationship between the susceptibility index and percent mortality. However, the numbers of F1 generation, percent grain damage and grain weight loss were positively correlated with the susceptibility index. The use of resistant maize hybrids should be promoted in managing S. zeamais in stored maize under subsistence farming conditions in Africa.

Genetic dissection of grain yield and physical grain quality in bread wheat (Triticum aestivum L.) under water-limited environments

Posted by Carelia Juarez on , in Journal Articles

Published in Theoretical and Applied Genetics 125 (2): 255-271, 2012

Dion Bennett, Ali Izanloo, Matthew Reynolds, Haydn Kuchel, Peter Langridge and Thorsten Schnurbusch

In the water-limited bread wheat production environment of southern Australia, large advances in grain yield have previously been achieved through the introduction and improved understanding of agronomic traits controlled by major genes, such as the semi-dwarf plant stature and photoperiod insensitivity. However, more recent yield increases have been achieved through incremental genetic advances, of which, breeders and researchers do not fully understand the underlying mechanism(s). A doubled haploid population was utilised, derived from a cross between RAC875, a relatively drought-tolerant breeders’ line and Kukri, a locally adapted variety more intolerant of drought. Experiments were performed in 16 environments over four seasons in southern Australia, to physiologically dissect grain yield and to detect quantitative trait loci (QTL) for these traits. Two stage multi-environment trial analysis identified three main clusters of experiments (forming distinctive environments, ENVs), each with a distinctive growing season rainfall patterns. Kernels per square metre were positively correlated with grain yield and influenced by kernels per spikelet, a measure of fertility. QTL analysis detected nine loci for grain yield across these ENVs, individually accounting for between 3 and 18% of genetic variance within their respective ENVs, with the RAC875 allele conferring increased grain yield at seven of these loci. These loci were partially dissected by the detection of co-located QTL for other traits, namely kernels per square metre. While most loci for grain yield have previously been reported, their deployment and effect within local germplasm are now better understood. A number of novel loci can be further exploited to aid breeders’ efforts in improving grain yield in the southern Australian environment.


Genetic yield gains of the CIMMYT international semi-arid wheat yield trials from 1994 to 2010

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Science  52 (4): 1543-1552, 2012

Y. Manès , H. F. Gomez, L. Puhl, M. Reynolds, H. J. Braun and R. Trethowan

Genetic progress for yield has been assessed globally in the semi-arid wheat yield trials (SAWYTs) of the International Maize and Wheat Improvement Center (CIMMYT) over a 17-yr period. Grain yield expressed as a percentage of the long-term check cultivar Dharwar Dry has increased at approximately 1% yr−1 between 1994 and 2010. In real terms, yield has been increased at a rate of 31 kg ha−1 yr−1. The rate of yield increase in high-yielding environments was twice that of low-yielding environments. The average yield of low-yielding sites are significantly correlated with the average yield of high-yielding sites (p < 0.001), and many of the highest-yielding lines of the various SAWYT performed well at both low- and high-yielding sites. The key parents Attila and Pastor were consistently high yielding in several of the early SAWYT. In later trials their derivatives were also high yielding. The line Vorobey, developed by crossing Pastor with a synthetic derivative, showed outstanding yield in SAWYT 11 and 12. The performance of CIMMYT lines compared to local check cultivars was relatively stable over time. A success rate was calculated as the ratio of the number of sites where a given line is superior to the local check divided by the total number of sites. On average, the success rate of the 10% best lines was 61% in low-yielding sites and 62% in high-yielding sites.

Genetic gains for grain yield in CIMMYT spring bread wheat across international environments

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Science 52 (4): 1522-1533, 2012

R. C. Sharma, J. Crossa, G. Velu, J. Huerta-Espino, M. Vargas, T. S. Payne and R. P. Singh

The Global Wheat Program of the International Maize and Wheat Improvement Center (CIMMYT) develops and distributes improved germplasm targeted toward various wheat growing regions of developing world. The objective of our study was to quantify the genetic yield gains in CIMMYT’s spring bread wheat (Triticum aestivum L.) in the Elite Spring Wheat Yield Trial (ESWYT) distributed over the past 15 yr (1995–2009) as determined by the performance of entries across 919 environments in 69 countries. To determine the annual genetic gains, differences in mean yields of the five highest yielding entries from mean trial yield and mean yield of the widely grown international check ‘Attila’ were regressed over 15 yr of ESWYT testing. Across locations in all countries, mean yields of the five highest yielding entries showed an annual gain of 27.8 kg ha−1 (0.65%) compared to Attila. Annual yield gains in mega-environment 1 (ME1) (optimally irrigated), ME2 (high rainfall), Egypt, India, and Pakistan were 27.4 (0.55%), 21.4 (0.62%), 111.6 (1.13%), 32.5 (0.83%), and 18.5 kg ha−1 (0.5%), respectively. These results demonstrate continuous genetic yield gains in the elite spring bread wheat lines developed and distributed by CIMMYT and the positive outcomes achieved through breeding and the international exchange of elite spring wheat germplasm that have benefited national programs throughout the world.


Efficiency of managed-stress screening of elite maize hybrids under drought and low-N for yield under rainfed conditions in Southern Africa

Posted by Carelia Juarez on , in Journal Articles

Published in Crop Science  52 (3): 1011-1020, 2012

Vanessa S. Weber, Albrecht E. Melchinger, Cosmos Magorokosho, Dan Makumbi, Marianne Bänziger and Gary N. Atlin

Maize (Zea mays L.) yields in southern Africa are low, due largely to drought and low-N stress. Selection of stress-tolerant genotypes by CIMMYT is conducted indirectly under managed stress conditions, although the selection efficiency of this approach is not known. A retrospective analysis of 704 elite hybrid trials conducted from 2001 to 2009 was used to determine the relative ability of optimal, low-N, and managed drought trials to predict performance under the conditions of random abiotic stress and low-N fertility usually faced by African farmers. Well-fertilized trials in the rainy season were categorized as having experienced random abiotic stress if mean yield was <3 t ha−1 and the yield–anthesis date correlation was <0.1; otherwise they were classed as optimal. High genetic correlations were estimated between random abiotic stress and low-N or optimal conditions. Heritability was highest under optimal conditions and lowest under random abiotic stress. Indirect selection under low-N and optimal conditions was more efficient than direct selection under random abiotic stress or indirect selection under managed drought, especially for early maturing genotypes, but direct selection was most efficient for predicting performance under low N. Elite maize hybrids tolerant to random abiotic stress can be most efficiently selected under optimal and/or low-N conditions while low-N tolerant genotypes should be selected directly under low N.

Indirect selection for grain yield in spring bread wheat in diverse nurseries worldwide using parameters locally determined in north-west Mexico

Posted by on , in Journal Articles

Published in The Journal of Agricultural Science 150(1): 23-43, 2012

M. Gutierrez, M. P. Reynolds, W. R. Raun, M. L. Stone And A. R. Klatt

The relationships of normalized water index three (NWI-3) and canopy temperature (CT) with grain yield in north-west Mexico were determined in a set of wheat lines planted in multi-location yield trials. Advanced wheat lines developed by The International Maize and Wheat Improvement Centre (CIMMYT) were included and tested internationally in the trials including the 24th Elite Spring Wheat Yield Trial (ESWYT), the 11th Semi-Arid Wheat Yield Trial (SAWYT) and the 11th High Temperature Wheat Yield Trial (HTWYT). In north-west Mexico, NWI-3, CT and grain yield were determined in three growing seasons (2006, 2007 and 2008) and three environments (well irrigated, water-stressed and high-temperature), while grain yield was measured at international locations in the same advanced lines of the 24th ESWYT, the 11th SAWYT and the 11th HTWYT . The CIMMYT database was used to obtain grain yield from worldwide nurseries. The mean grain yield ranged from 0·8 to 12·7 t/ha for the 24th ESWYT (59 international sites), from 0·6 to 8·2 t/ha for the 11th SAWYT (28 international sites) and from 0·4 to 7·5 t/ha for the 11th HTWYT (26 international sites). NWI-3 and CT for the advanced lines in the three yield trials measured in north-west Mexico in distinct environments showed significant associations with the grain yield from a few international locations (0·12–0·23 of sites). Locations from Central Asia and North Africa had the best associations with NWI-3 and CT. The lack of more associations may be due to either an interaction of other factors (low rainfall and limited irrigations), which affected yield performance, or few of the advanced lines were well adapted to local growing conditions at each testing site, or a combination of these factors. The present results indicate that NWI-3 and CT have limited potential to predict yield performance at international sites.

Prediction of grain yield using reflectance spectra of canopy and leaves in maize plants grown under different water regimes

Posted by Carelia Juarez on , in Journal Articles

Published in  Field Crops Research  128(1): 82-90, 2012

Prediction of grain yield using reflectance spectra of canopy and leaves in maize plants grown under different water regimes

V.S. Weber, J.L. Araus, J.E. Cairns, C. Sanchez, A.E. Melchinger and E. Orsini

The ability to accurately estimate grain yield using spectral reflectance measurements prior harvest could be used to reduce phenotyping time and costs. In this study, grain yield of 300 maize testcrosses grown under different water and temperature regimes in the dry season 2010 was predicted using spectral reflectance (495–1853 nm) of both leaves and canopy measured between tassel emergence until milk-grain stage. Partial least square regression (PLSR) was used for data analysis. Coefficients of determination (R2) between predicted and actual grain yield were highest for measurements conducted at anthesis and milk-grain stage, explaining at maximum 23% and 40% of the genotypic variation in grain yield after validation, respectively. PLSR models explained a higher proportion of the genetic variation in grain yield under drought stress compared to well-watered conditions. The association between predicted and actual grain yield was stronger in spectral reflectance measurements taken at the leaf level compared to canopy level. By combining the most predictive PLSR models across trials, at maximum of 40% of the variation in grain yield could be explained in each trial with a relative efficiency of selection of 0.88 and 0.68 using leaf and canopy reflectance, respectively. The most relevant wavelengths for predicting grain yield were associated with photosynthetic capacity (495–680 nm), red inflection point (680–780 nm) and plant water status (900, 970, and 1450 nm, 1150–1260 nm, and 1520–1540 nm). Additional wavelengths based on leaf (800, 1000, and 1260–1830 nm) and canopy (988–999 nm and 1430–1640 nm) reflectance of unknown physiological relevance were also identified for prediction of grain yield. Caution must be exercised before integrating our spectral reflectance approach into a breeding program because this is a pilot study based on a single location and season.

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

Posted by on , in Journal Articles

Published in Euphytica 171(1): 53-64, 2010

Identifying high yielding stable winter wheat genotypes for irrigated environments in Central and West Asia

Ram C. Sharma, Alexei I. Morgounov, Hans J. Braun, Beyhan Akin, Mesut Keser, David Bedoshvili, Ahmet Bagci, Christopher Martius and Maarten van Ginkel

Improved winter wheat (Triticum aestivum L.) cultivars are needed for the diverse environments in Central and West Asia to improve rural livelihoods. This study was conducted to determine the performance of elite winter wheat breeding lines developed by the International Winter Wheat Improvement Program (IWWIP), to analyze their stability across diverse environments, and to identify superior genotypes that could be valuable for winter wheat improvement or varietal release. One hundred and one advanced winter wheat breeding lines and four check cultivars were tested over a 5-year period (2004–2008). Grain yield and agronomic traits were analyzed. Stability and genotypic superiority for grain yield were determined using genotype and genotype × environment (GGE) biplot analysis. The experimental genotypes showed high levels of grain yield in each year, with mean values ranging from 3.9 to 6.7 t ha−1. A set of 25 experimental genotypes was identified. These were either equal or superior to the best check based on their high mean yield and stability across environments as assessed by the GGE biplot analysis. The more stable high yielding genotypes were ID800994.W/Falke, Agri/Nac//Attila, ID800994W/Vee//F900K/3/Pony/Opata, AU//YT542/N10B/3/II8260/4/JI/Hys/5/Yunnat Esskiy/6/KS82W409/Spn and F130-L-1-12/MV12. The superior genotypes also had acceptable maturity, plant height and 1,000-kernel weight. Among the superior lines, Agri/Nac//Attila and Shark/F4105W2.1 have already been proposed for release in Kyrgyzstan and Georgia, respectively. The findings provide information on wide adaptation of the internationally important winter wheat genotypes, and demonstrate that the IWWIP program is enriching the germplasm base in the region with superior winter wheat genotypes to the benefit of national and international winter wheat improvement programs.

How yield relates to ash content, Delta 13C and Delta 18O in maize grown under different water regimes

Posted by on , in Journal Articles

Published in Annals of Botany 104(6): 1207-1216

How yield relates to ash content, Delta 13C and Delta18O in maize grown under different water regimes

Llorenç Cabrera-Bosquet, Ciro Sánchez and José Luis Araus

Background and Aims: Stable isotopes have proved a valuable phenotyping tool when breeding for yield potential and drought adaptation; however, the cost and technical skills involved in isotope analysis limit its large-scale application in breeding programmes. This is particularly so for Delta 18O despite the potential relevance of this trait in C4 crops. The accumulation of minerals (measured as ash content) has been proposed as an inexpensive way to evaluate drought adaptation and yield in C3 cereals, but little is known of the usefulness of this measure in C4 cereals such as maize (Zea mays). The present study investigates how yield relates to ash content, Delta 13C and Delta 18O, and evaluates the use of ash content as an alternative or complementary criterion to stable isotopes in assessing yield potential and drought resistance in maize.

Methods: A set of tropical maize hybrids developed by CIMMYT were subjected to different water availabilities, in order to induce water stress during the reproductive stages under field conditions. Ash content and Delta 13C were determined in leaves and kernels. In addition, Delta 18O was measured in kernels.

Key Results: Water regime significantly affected yield, ash content and stable isotopes. The results revealed a close relationship between ash content in leaves and the traits informing about plant water status. Ash content in kernels appeared to reflect differences in sink–source balance. Genotypic variation in grain yield was mainly explained by the combination of ash content and Delta 18O, whilst Delta 13C did not explain a significant percentage of such variation.

Conclusions: Ash content in leaves and kernels proved a useful alternative or complementary criterion to Delta 18O in kernels for assessing yield performance in maize grown under drought conditions.