Genetic Gain In Yield Research Articles

Increasing co-limitation of water and nitrogen drives genetic yield gain in Australian wheat

Abstract The interactions between nitrogen (N) and water are manifold, and the concept of co-limitation provides a quantitative framework for integration. This paper tested the hypothesis that selection for yield increased water-N co-limitation in wheat adapted to winter rainfall environments of Australia. To test this hypothesis, we measured evapotranspiration, N uptake and yield in a historic collection of varieties released between 1958 and 2007 (exp. 1) and between 1969 and 2015 (exp. 2). Crops were grown under 5 (exp. 1) or 4 (exp. 2) environmental conditions resulting from the combination of sites, seasons, and supply of N and water. Genetic gain of yield, i.e. the slope of the regression between yield and year of release was 14–24 kg ha−1 y−1 or 0.36–0.52% y−1. This yield gain was associated with a linear increase in water-N co-limitation, in turn associated with an increase in N uptake per mm of evapotranspiration at a rate of 0.0019 kg N mm−1 y−1. Our findings highlight the critical role of nitrogen for the adaptation of wheat to low rainfall environments, and the scope for further yield improvement based on traits that integrate resources.

Genetic Gain for Yield in Rice Breeding and Rice Production in India to Meet with the Demand from Increased Human Population

Genetic Gain for Yield in Rice Breeding and Rice Production in India to Meet with the Demand from Increased Human Population

Genetic Gain for Yield and Allelic Diversity over 35 Years of Durum Wheat Breeding at ICARDA

The ICARDA’s durum wheat breeding program was established in 1977 in Aleppo, Syria, where it continued its work targeted to the drylands of the developing world until 2012, when it was forced to relocate. This movement represented an occasion to measure the impact of 35 years of public breeding via a detailed genetic gain (GG) study. A total of 22 ICARDA’s historical entries representing three decades of work (1974–1984, 1985–1994, or 1995–2004), were placed in competition with elites from the most recent decade (2005–2011). A total of 10 environments and 7 sites were used for the assessment. Decade-wise GG for grain yield was measured to reveal >9% (equal 0.9% per year) at 8 of the environments, while no progress was found for the dry and cold conditions of the Atlas Mountains. Combined analysis revealed an average GG per year of 0.7%, mostly driven by earlier flowering and an increase in spike density. The germplasm was also characterized with 60 polymorphic SNPs to reveal that the breeding process has already eroded 6.3% of the original genetic diversity, and that over 3-folds reduction has occurred for rare alleles. Clustering analysis confirmed that two sub-populations have substantially disappeared under the breeding selection pressure. The results presented here show that good progress was made till now, but at the cost of reducing genetic diversity and pushing toward very early genotypes. A revamped strategy is then needed to continue delivering germplasm that is meaningful to breeders worldwide.

Long‐Term Selection in Hybrid Sorghum Breeding Programs

Estimating genetic gains in sorghum [Sorghum bicolor (L.) Moench] is necessary to assess whether the current rates of improvement will meet future production demands. The current study was conducted to determine the rate of genetic gain in yield and associated traits over the commercial hybrid era using sorghum germplasm from the Texas A&M sorghum breeding program and a US sorghum seed company. From the Texas A&M AgriLife program, 60 hybrids that represented a 50‐yr span of hybrid breeding were grown and evaluated in five environments across Texas in 2016. In a separate set of trials, 14 commercial hybrids representing a similar timespan were evaluated in three Texas environments in 2016. In both programs, grain sorghum yields increased 0.008 t ha−1 annually over their respective timespans. Traits that increased over time included yield potential per plant, heterosis, test weight, panicle size, and grain number per panicle, whereas leaf angle, days to maturity, plant height, and yield stability demonstrated little to no change. Overall, ∼60% of total yield gains in US sorghum production are attributed to genetic improvement through sorghum breeding. Compared with other major US field crops, the rate of genetic gain in sorghum has been slower, presumably due to a combination of factors, which include continually shifting production environments, changing priorities in traits, reduced research investments (compared with other crops), and less‐than‐optimized heterotic groups.

Transforming Rice Breeding: Re-Designing the Irrigated Breeding Pipeline at the International Rice Research Institute (IRRI)

Rice breeding of inbred varieties in the public sector has hardly changed in decades. This has been a cause for concern given that the current rate of yield improvement from new varieties is not considered to be adequate to meet future global demands for rice. In this article, we describe major changes to the irrigated breeding program and former plant breeding division at the International Rice Research Institute (IRRI) headquarters by incorporating modern concepts in plant breeding and practices used in the private sector. These activities were conducted primarily within a five-year research program called “Transforming Rice Breeding” funded by the Bill and Melinda Gates Foundation. These changes were implemented with the specific objectives to increase the rate of genetic gain for yield and improve the effectiveness and efficiency of breeding operations. Key changes in the breeding program included implementing rapid generation advance, earlier multi-location trials, increased selection pressure for yield, an increase use of molecular breeding, and using variety product profiles. Regarding breeding operations, there was a concerted effort to streamline all processes and optimize logistics in order to make breeding like a “factory production line”. The Plant Breeding, Genetics and Biotechnology Division was re-organised into variety pipelines and trait research teams, with cross-cutting services to support all functions. Considerable benefits and dramatic improvements in efficiency were realized, that are expected to lead to a higher rate of genetic gain for yield in rice. These experiences are also highly relevant to many public sector plant breeding programs, especially in developing countries.

Post-green revolution genetic advance in durum wheat: The case of Spain

This paper addresses the question of whether there has been any genetic gain in yield for durum wheat released in Spain after the Green Revolution and assesses the agronomical and physiological traits associated with evolution of the crop during this time. Field experiments were carried out with a wide range of durum wheat cultivars (released in Spain from 1980 to 2009) and were conducted in different sites embracing a wide range of growing temperatures and water regimes at Aranjuez and Zamadueñas during three consecutive growing seasons (2013/14, 2014/15, 2015/16) under rainfed and supplemental irrigation and at Coria for two consecutive seasons (2014/15 and 2015/16) under rainfed conditions alone.Grain yield increased with the year of release of cultivars at a rate of 24 kg ha−1 y−1 (0.44% y−1) from 1980 to 2003, with no clear additional improvements thereafter. The moderate grain yield improvement from 1980 and 2003 was associated with kernels m−2 and kernels spike−1, with an increase of 117 kernels m−2 y−1 and 0.24 kernels spike−1 y−1, respectively. Moreover, aerial biomass at harvest and grain nitrogen yield increased with the year of release of cultivars for the entire period. However, no differences were found for thousand kernel weight, number of spikes m−2, days to heading, plant height, harvest index, canopy temperature depression, carbon isotope discrimination or grain nitrogen concentration. Overall, these results indicated that the rate of genetic progress in the yield of durum wheat in Spain after the Green Revolution has been low and has even stopped during the last decade, while no clear trend in some grain quality traits (TKW and grain N concentration) was recorded. However, the absolute and relative genetic gains estimated for yield were positively associated with the average mean and maximum daily temperatures from sowing to harvest of the testing site, which suggest that breeding has been performed under high-temperature environments.

Has Breeding Improved Soybean Competitiveness with Weeds?

Soybean yield gain over the last century has been attributed to both genetic and agronomic improvements. Recent research has characterized how breeding efforts to improve yield gain have also secondarily impacted agronomic practices such as seeding rate, planting date, and fungicide use. To our knowledge, no research has characterized the relationship between weed–soybean interference and genetic yield gain. Therefore, the objectives of this research were to determine whether newer cultivars would consistently yield higher than older cultivars under increasingly competitive environments, and whether soybean breeding efforts over time have indirectly increased soybean competitiveness. Field research was conducted in 2014, 2015, and 2016 in which 40 maturity group (MG) II soybean cultivars released between 1928 and 2013 were grown season-long with three different densities of volunteer corn (0, 2.8, and 11.2 plants m−2). Soybean seed yield of newer cultivars was higher than older cultivars at each volunteer corn density (P<0.0001). Soybean seed yield was also higher in the weed-free treatment than at low or high volunteer corn seeding rates. However, soybean cultivar release year did not affect late-season volunteer corn shoot dry biomass at either seeding rate of 2.8 or 11.2 seeds m−2. The results indicate that while soybean breeding efforts have increased yield potential over time, they have not increased soybean competitiveness with volunteer corn. These results highlight the importance of other cultural practices such as planting date and crop row spacing for weed suppression in modern soybean production systems.

An Analysis of Yield Gains through Breeding High-Yielding Varieties in Urdbean and Mungbean

One varietal trial each in urdbean and mungbean, each comprising 10 varieties released during succeeding years since 1975, was conducted following randomized complete blockdesign (RCBD) in three replications during kharif 2013.The analysis of variance showed significant differences among varieties in each trial. Significant genetic advances were observed for earliness in newly released varieties of both urdbean (~ 4 days) and mungbean (4.6 days), implying substantial gain in per day productivity. Newly released varieties urdbean (DBGV-5 and IPU 2-43) did not display any yield advancement over the oldest one (T-9). However, a significant genetic gain in yield (62.60 kg/ha) was recorded in mungbean due to a recently released variety ‘DGGV-1’, indicating about 60% contribution of improved varieties towards increase of national average yield (105 kg/ha) during the period 1990-2015. In conclusion, the increased area coverage underHYVs having multiple disease resistance and better agronomic practices could reasonably explain the productivity (average yield) gains in both urdbean and mungbean.

Deciphering Physiological Basis of Yield Gain in Indian Wheat Cultivars

Physiological breeding complementing the conventional approach is increasingly being explored in wheat in view of stagnating annual genetic yield gain. Designing improved plant types required knowledge about physiological traits associated with yield gain in the past. Fourteen wheat varieties including 12 historically important and popular (mega) wheat cultivars and two recently registered varieties were observed for various physiological traits for two years. Both breeding period and genotypes within breeding period accounted for significant differences for most of the physiological traits. Regression analysis indicated curvilinear trend for leaf area index (LAI), flag leaf area, and root length and root weight. Near perfect leaf area index (LAI 5.94) with semi-erect leaves and higher flag leaf area was observed in all time mega variety HD 2967 indicated the importance of plant architecture and crop canopy in yield maximization. Linear declining trend was observed for coleoptile length, number of stomata per cm2 and flag leaf length. Increasing trend for total chlorophyll content and normalized difference for vegetative indices (NDVI) at both vegetative and flowering stage indicated the importance of leaf greenness in yield improvement. Root length has continuously declined except for the latest released varieties, however no such trend was observed for root weight. We propose that grain yield stabilization at still higher level can be achieved by increasing photosynthetic capacity, optimizing the crop canopy slightly less than the optimum, and better partitioning to grain yield through directed physiological based breeding.

Genetic Gain in Common Bean with Black Grain by Indirect Estimation Methods

The objective of this study was to estimate the genetic gain for yield of black‐grained common bean (Phaseolus vulgaris L.) developed by the Embrapa breeding program of Brazil. Genetic gain estimates were generated from 403 field tests conducted in all regions of Brazil in three growing seasons over 16 yr, from 1993 to 2008. Genetic gains were estimated by two indirect methods and were compared with those found through a direct estimation method. The first methodology used the mixed model approach to calculate the best unbiased linear estimate of cycle means, as fixed effects, and the best unbiased predictor of the genotype effect within cycles, as random effects. The second methodology of generalized least squares considered a model of fixed effects, except for the error. For the direct method, 24 lines consisting of the three highest yielding of each of the eight breeding cycles were evaluated in 21 environments. The estimated percentage of annual genetic gain in grain yield by the direct method over the 16‐yr period (1.23%, P < 0.01) was significant and close to the result of the fixed model analysis (1.20%, P < 0.05) and by the mixed model (1.02%, P = 0.068). These results show that the indirect methods using a fixed model and the mixed model were consistent in determining genetic gain and can be used as an alternative to the direct method.

Genetic gains in grain yield in spring wheat in Turkey

Genetic gain for grain yield was evaluated in 35 Turkish spring wheat varieties released between 1964 and 2010. The germplasm comprised varieties developed by the East Mediterranean Agricultural Research Institute (ARI) in Adana, the Maize Research Station in Adapazarı, and Aegean ARI in İzmir. Out of 34 varieties studied, 24 were selected from CIMMYT germplasm. The trials were conducted during 2009?2013 at the same three sites. Average yearly genetic gain for all varieties was 30.9 kg/ha or 0.62%. The top five highest yielding varieties were all released after 1998: Ziyabey, Menemen, and Meta (İzmir), and Karatopak and Ceyhan (Adana). Plant height had a clear tendency to decrease over time. Genetic gain in yield was associated with genetic gains in harvest index (0.51%), the number of spikes/m2 (0.29%), and the number of grains/spike (0.26%). Kernel size and biomass did not change over time and represent traits to be explored in the future. The newest varieties combined higher yield with yield stability. Resistance to leaf rust contributed greatly to yield genetic gain. Turkish breeders made a substantial impact on national grain supply and food security. Future breeding strategies shall combine the utilization of CIMMYT germplasm, a diverse modern gene pool, and genetic resources in an integrated national breeding program.

Phenomics: unlocking the hidden genetic variation for breaking the barriers in yield and stress tolerance

The rate of genetic gain in yield, quality, input use efficiency and adaptability of crops to biotic and abiotic stresses must be improved significantly to achieve global food and nutritional security by 2050. To achieve this goal, deciphering the physiological genetic basis and assembly of component traits through analytical breeding is necessary. The two pillars of analytical breeding are genotyping and phenotyping. Advances in genotyping technologies such as single-nucleotide polymorphism genotyping and genotyping by sequencing have made deep genotyping cheaper and quicker, while phenotyping has lagged behind and thus remains a rate limiting step. Recently, phenomics has emerged as a new way of accurately phenotyping large set of genotypes. Phenomics employ non-invasive sensors and advanced computational platforms for non-destructive and high-throughput phenotyping. The depth of component phenotypic traits and the spatio-temporal dynamic phenotypic data generated in phenomics are enormous and unparallel to the conventional phenotyping. The utility of phenomics in QTL mapping and genome-wide association studies has already been demonstrated in important food crops. Phenomics has high potential for phenome-wide association studies, genomics selection models for enhancing selection efficiency, and genetic-ecophysiological crop simulation models for prediction of genotype-phenotypes relationship, in silico phenotyping and ideotype design. With the advancement in the depth of phenome data acquisition and analyses capabilities of phenomics, phenome assisted breeding and phenomic selection is anticipated to be a reality in near future. Complementary use of conventional phenotyping and advanced phenomics is suggested to assist in fundamental discoveries and analytical crop breeding.

Soybean Genetic Gain in Maturity Groups III to V in Argentina from 1980 to 2015

Genetic progress is assessed to estimate its contribution to on‐farm yield increases and to identify traits that have been improved over some period of time. Although Argentina is a major soybean [Glycine max (L.) Merr.] producer, there is limited information about genetic progress in this system. Argentinean soybean cultivars were developed from US commercial cultivars. Because the genetic base of US cultivars is narrow, it would be expected that genetic progress in Argentina to be slower than in the United States. We assessed the genetic gain for yield and related traits in cultivars released in Argentina from 1980 to 2015. One hundred and eighty‐one cultivars belonging to maturity groups (MGs) III, IV, and V were evaluated in three environments in the northern pampas from Argentina. Genetic gain in yield was 43 kg ha−1 yr−1 and was not different across MGs. Relative genetic gain was 1.1% yr−1, similar to reports from the United States or Brazil. Newer cultivars from MGs III and IV had increased days to maturity, while cultivars from MG V showed the opposite trend. Vegetative period was also reduced in newer cultivars from MGs IV and V. Seed protein concentration was reduced over the years. Genetic progress explained 50% of total on‐farm yield increase. Results from this experiment showed that breeding programs in Argentina were able to attain a similar genetic gain to the United States even though the starting parents were only a few US cultivars selected from an already narrow genetic base.

Corn Era Hybrid Response to Nitrogen Fertilization

Agronomy Journal 108:473–486 (2016). doi:10.2134/agronj15.0314 Two sentences in the second paragraph of page 481 (left column) have been corrected below. Appearance of singlecross hybrids introduced in 1990s increased genetic yield gain to 0.11 Mg ha−1 yr−1 (Duvick, 1997). For the hybrids from the 1960s through 2000s in our study, GY increase (YAONR) was 0.13 Mg ha−1 yr−1, and GY N response (YAONR minus GY with no N applied) 0.091 Mg ha−1 yr−1. — Krishna P. Woli krishnawoli@gmail.com

Genetic variation in winter barley and selection of high yielding lines

Barley (<italic>Hordeum vulgare</italic> L.) is an important crop with excellent nutritious feed and food grain. Winter barley, in particular, is predominantly grown in highland under rainfed systems due to its ability to tolerate cold. However, it has low productivity due to complex genetic mechanisms and limitations in determining an optimal environment for its selection and evaluation. This study evaluated the genetic variability, heritability and genetic gain for yield in barley, using preliminary un-replicated yield trials in 2011 at two locations and followed by replicated sets of yield trials in 2012, all in Syria. Significant genotypic variability was found at both stages of the evaluation/selection. During 2011, the best linear unbiased predictor means of test genotypes adjusted for spatial variability were found in the range of 1.75–3.75 t/ha at Tel Hadya and 0.03–1.58 t/ha at Breda. A set of 22 advanced yield trials comprising a total of 601 lines at Tel Hadya in 2012 yielded in the range of 1.85–3.13 t/ha. Based on the mean over these set of trials, the highest heritable trait was days to heading (broad-sense heritability on mean-basis= 0.64) followed by yield (the heritability = 0.30). The yield gain due to selection, at 20% intensity of selection, was 5.66% at Tel Hadya and 27.1% at Breda in 2011 using un-replicated genetic material, while it was 7.01 % for the replicated trials at Tel Hadya in 2012. We recommend use of the best lines selected in 2012 at Tel Hadya for further exploitation in genotype × environment interaction studies for high yield and specific and broad adaptation.

Genetic progress and potential of common bean families obtained by recurrent selection

Abstract The objective of this study was to estimate the genetic gain of two recurrent selection cycles in common bean breeding and identify families with the potential to generate superior lines. The base population, cycle zero (C0), was obtained by combining 20 carioca bean parents, populations with favorable phenotypes for several agronomically important traits. The parents were recombined in a circulant diallel scheme, in which each parent participated in two crosses, generating 20 populations. From these populations, families were derived and evaluated for three seasons in the generations F2:3, F2:4 and F2:5. The same procedures of recombination and evaluation in C0 were performed in cycle one (CI). The genetic gain for yield, estimated from the simultaneous evaluation of the 40 best families of each cycle, was 8.6%. Families with potential to generate superior lines to cultivar Pérola were identified, especially among the CI families.

Genetic gains in wheat in Turkey: Winter wheat for irrigated conditions

The study estimated genetic gain for yield and other traits in winter wheat released for irrigated environments in Turkey from 1963 to 2004. Yield trials including 14 varieties were grown in 16 environments from 2008 to 2012 in provinces of Konya, Eskişehir, Ankara, and Edirne. The highest yields were achieved by recent varieties Kinaci-97 (5.48tha−1), Cetinel-2000 (5.39tha−1), Alpu-2001 (5.44tha−1), Ahmetaga (5.35tha−1), and Ekiz-2004 (5.42tha−1) compared to older varieties Yektay-406 (4.17tha−1) and Bezostaya-1 (4.27tha−1) released in the 1960s. The progress reached in grain yield in 20years was 1.16tha−1 or 58kgha−1 (1.37%) per year. This gain was mainly achieved through shorter plant height and increased harvest index. There was no clear tendency of changes in specific yield components demonstrating that new high-yielding varieties may have different ways to reach their yield potentials. The yield gains were accompanied by improved stripe rust and leaf rust resistances primarily based on adult plant resistance genes. The grain quality of the new varieties did not deteriorate over time although most of them were inferior to the bread-making quality check Bezostaya-1, a feature that may require attention in future breeding.

Soil water capture trends over 50 years of single-cross maize (Zea mays L.) breeding in the US corn-belt.

Breeders have successfully improved maize (Zea mays L.) grain yield for the conditions of the US corn-belt over the past 80 years, with the past 50 years utilizing single-cross hybrids. Long-term improvement for grain yield under water-limited conditions has also been reported. Grain yield under water-limited conditions depends on water use, water use efficiency, and harvest index. It has been hypothesized that long-term genetic gain for yield could be due, in part, to increased water capture from the soil. This hypothesis was tested using a set of elite single-cross hybrids that were released by DuPont Pioneer between 1963 and 2009. Eighteen hybrids were grown in the field during 2010 and 2011 growing seasons at Woodland, CA, USA. Crops grew predominantly on stored soil water and drought stress increased as the season progressed. Soil water content was measured to 300cm depth throughout the growing season. Significant water extraction occurred to a depth of 240-300cm and seasonal water use was calculated from the change in soil water over this rooting zone. Grain yield increased significantly with year of commercialization, but no such trend was observed for total water extraction. Therefore, the measured genetic gain for yield for the period represented by this set of hybrids must be related to either increased efficiency of water use or increased carbon partitioning to the grain, rather than increased soil water uptake.

Industry‐Scale Evaluation of Maize Hybrids Selected for Increased Yield in Drought‐Stress Conditions of the US Corn Belt

ABSTRACTMaize (Zea mays L.) is among the most important grains contributing to global food security. Eighty years of genetic gain for yield of maize under both favorable and unfavorable stress‐prone drought conditions have been documented for the US Corn Belt, yet maize remains vulnerable to drought conditions, especially at the critical developmental stage of flowering. Optimum AQUAmax (Dupont Pioneer) maize hybrids were developed for increased grain yield under drought and favorable conditions in the US Corn Belt. Following the initial commercial launch in 2011, a large on‐farm data set has been accumulated (10,731 locations) comparing a large sample of the AQUAmax hybrids (78 hybrids) to a large sample of industry‐leading hybrids (4287 hybrids) used by growers throughout the US Corn Belt. Following 3 yr (2011–2013) of on‐farm industry‐scale testing, the AQUAmax hybrids were on average 6.5% higher yielding under water‐limited conditions (2006 locations) and 1.9% higher yielding under favorable growing conditions (8725 locations). In a complementary study, 3 yr (2010–2012) of hybrid‐by‐management‐by‐environment evaluation under water‐limited conditions (14 locations) indicated that the AQUAmax hybrids had greater yield at higher plant populations when compared to non‐AQUAmax hybrids. The combined results from research (2008–2010) and on‐farm (2011–2013) testing throughout the US Corn Belt over the 6‐yr period from 2008 to 2013 indicate that the AQUAmax hybrids offer farmers greater yield stability under water‐limited conditions with no yield penalty when the water limitations are relieved and growing conditions are favorable.

Agronomic performance and genetic progress of selected historical soybean varieties in the southern USA

AbstractThis study was conducted to compare recently developed and historical soybean varieties and evaluate genetic gain in yield and other agronomic traits in the southern USA. A total of 45 southern varieties from public breeding programs, which were released from 1928 to 2008, were used in this study. Three experiments were conducted in 2007 and 2008 at Keiser, Stuttgart, and Marianna in Arkansas (USA). Varieties with maturity groups (MG) late IV to early V had a yield gain of 21.7 kg/ha/yr from the 1950s to the 2000s, mid to late MG V had a yield gain of 16.4 kg/ha/yr from the 1940s to the 2000s, and MG VIs had a yield gain of 12.4 kg/ha/yr from the 1920s to the 2000s. Yield increased linearly for all combined experiments by 16.8 kg/ha/yr. Plant height remained steady over time for most experiments. No significant changes were observed in maturity. Lodging scores decreased, protein concentration decreased, and oil concentration increased linearly over time for all combined experiments. Hutcheson, Narrow, R97‐1634, and Young were recommended as parent lines in future soybean breeding efforts.