High-yielding Cultivars Research Articles

Has yield plasticity already been exploited by soybean breeding programmes in Argentina?

This study focuses on the impact of genetic improvement of seed yield plasticity in soybean (Glycine max L.) in high-yielding environments (between 4000 kg ha-1 and 7000 kg ha-1) of Central Argentina. The association between seed yield and its plasticity was analysed with (i) a historical collection of 148 genotypes released to the market between 1980 and 2013 and (ii) 165 currently available commercial genotypes. The impact on seed yield of soybean breeding programmes in Argentina reveals higher genetic progress of the lowest (1.7% year-1) rather than the highest yielding genotypes (0.9% year-1). At the same time, seed yield plasticity has been exploited indirectly. Increased seed yield plasticity over time contributed to a reduction in genotypic seed yield variability (P<0.0001). Seed yield plasticity was related to seed yield in high-yielding environments (>5500 kg ha-1). Plastic genotypes showed a positive correlation with the length of the seed-filling period (r=0.5), suggesting that a longer seed-filling period could be required to maximize seed yield plasticity under high-yielding environments. To increase productivity, clarifying the value of plasticity will aid genotype selection for target environments, as well as the development of high-yielding cultivars specifically adapted to high-yielding conditions.

ЗБАГАЧЕННЯ ГЕНОФОНДУ ТРИТИКАЛЕ ОЗИМОГО ЗА ВНУТРІШНЬОВИДОВОЇ ГІБРИДИЗАЦІЇ

The aim of the research was to expand the genetic diversity of winter triticale samples by intraspecific hybridization and to obtain new valuable forms for their involvement in the selection process of creating high-yielding cultivars. The research was conducted during 2013–2020 at the sites of the Department of Genetics, Plant Breeding and Biotechnology of Uman National University of Horticulture, Ministry of Education and Science of Ukraine. As initial material for hybridization was used samples of hexaploid triticale of own breeding and varieties Rozivska 6, Ladne, Khlibodar Kharkivsky, Beta, Alkid, Souvenir, Raritet; octaploid triticale samples UA0602463 and UA0601654. Hybrid offspring were analyzed for morphological and economically valuable traits, including plant height, lodging resistance, ear length, grain weight from the main ear and 1000 grains, protein and gluten content in the grain and its quality indicators, yield, etc. In the studies used a systematic method of site placement. The rooms were arranged in blocks with a plant density of 400 thousand units/ha four times. In the course of researches hybridization of hexaploid forms of triticale of different ecological and geographical origin among themselves, and also hybridization of octaploid forms with hexaploid was carried out. In F2 populations, individual-family selection of low-stem forms with high ear grain was performed. In the absence of low-stem forms in the area of F2 hybrids, ear productivity was selected, and the population was transferred to a hybridization nursery for crossing plants with donors of low-stem genes. As a result of the conducted researches 23 highly productive forms of winter triticale were obtained, in particular, two dwarf samples (h = 58 cm), four – short-stemmed (h = 60–80 cm), one – early-ripening (vegetation period 285 days), nine – with high ear productivity. Sample 63 was selected, which significantly exceeded the group standard in terms of yield (7.01 t/ha), protein content (12.2 %) and gluten of the first quality group (25.4 %).

Evaluation of Local Bread Wheat Cultivars for Grain Yield and Its Attributes at Different Sowing Dates under Assiut Conditions

The current research aimed to evaluate and select bread wheat stable cultivars with high ‎productivity across diverse sowing dates. Fourteen wheat cultivars were grown in a randomized ‎complete block design with three replicates at six sowing dates during two successive seasons of ‎‎2018/2019 and 2019/2020 representing twelve environments. The cultivars were evaluated for grain ‎yield and its attributes. Highly significant differences were obtained among the wheat cultivars, ‎sowing dates, and their respective interaction for all measured traits. The highest grain yield (2.992-ton ‎fed-1) was recorded on 30th November, after this date, each day delay in sowing of wheat onward ‎decreases grain yield at the rate of 21 kg fed-1 day-1. Overall, the cultivar Gemiza 11 gave the highest ‎grain yield with an average of 2.861 ton fed-1, recorded the highest 1000-GW with an average of 47.73 g, ‎highest straw yield with an average of 8.303-ton Fed-1, and was the earliest cultivar with a mean heading ‎date of 92.9 days. According to GGE biplot results, Gemiza 11, Gemiza 9, and Sakha 94 ranked in the ‎first order as high-yielding cultivars and had greater stability level overall sowing dates under ‎Assiut conditions. The most adequate cultivars for sowing in the first half of November (1st -15th ) ‎are Misr 2, Sids 12, Sakha 95, Gemiza 9, and Gemiza 11. Also, Sakha 94, Gemiza 9, and Gemiza 11 ‎can be sown after 30th November because they produce a satisfied yield, have good stability, and ‎can be considered as late sowing tolerant.‎

Assessment of Ensemble Learning to Predict Wheat Grain Yield Based on UAV-Multispectral Reflectance

Grain yield is increasingly affected by climate factors such as drought and heat. To develop resilient and high-yielding cultivars, high-throughput phenotyping (HTP) techniques are essential for precise decisions in wheat breeding. The ability of unmanned aerial vehicle (UAV)-based multispectral imaging and ensemble learning methods to increase the accuracy of grain yield prediction in practical breeding work is evaluated in this study. For this, 211 winter wheat genotypes were planted under full and limited irrigation treatments, and multispectral data were collected at heading, flowering, early grain filling (EGF), and mid-grain filling (MGF) stages. Twenty multispectral vegetation indices (VIs) were estimated, and VIs with heritability greater than 0.5 were selected to evaluate the models across the growth stages under both irrigation treatments. A framework for ensemble learning was developed by combining multiple base models such as random forest (RF), support vector machine (SVM), Gaussian process (GP), and ridge regression (RR). The R2 values between VIs and grain yield for individual base models were ranged from 0.468 to 0.580 and 0.537 to 0.598 for grain yield prediction in full and limited irrigation treatments across growth stages, respectively. The prediction results of ensemble models were ranged from 0.491 to 0.616 and 0.560 to 0.616 under full and limited irrigation treatments respectively, and were higher than that of the corresponding base learners. Moreover, the grain yield prediction results were observed high at mid grain filling stage under both full (R2 = 0.625) and limited (R2 = 0.628) irrigation treatments through ensemble learning based stacking of four base learners. Further improvements in ensemble learning models can accelerate the use of UAV-based multispectral data for accurate predictions of complex traits like grain yield in wheat.

Development and Molecular Cytogenetic Identification of a New Wheat-Psathyrostachys huashanica Keng Translocation Line Resistant to Powdery Mildew.

Psathyrostachys huashanica Keng, a wild relative of common wheat with many desirable traits, is an invaluable source of genetic material for wheat improvement. Few wheat–P. huashanica translocation lines resistant to powdery mildew have been reported. In this study, a wheat–P. huashanica line, E24-3-1-6-2-1, was generated via distant hybridization, ethyl methanesulfonate (EMS) mutagenesis, and backcross breeding. A chromosome karyotype of 2n = 44 was observed at the mitotic stage in E24-3-1-6-2-1. Genomic in situ hybridization (GISH) analysis revealed four translocated chromosomes in E24-3-1-6-2-1, and P. huashanica chromosome-specific marker analysis showed that the alien chromosome fragment was from the P. huashanica 4Ns chromosome. Moreover, fluorescence in situ hybridization (FISH) analysis demonstrated that reciprocal translocation had occurred between the P. huashanica 4Ns chromosome and the wheat 3D chromosome; thus, E24-3-1-6-2-1 carried two translocations: T3DS·3DL-4NsL and T3DL-4NsS. Translocation also occurred between wheat chromosomes 2A and 4A. At the adult stage, E24-3-1-6-2-1 was highly resistant to powdery mildew, caused by prevalent pathotypes in China. Further, the spike length, numbers of fertile spikelets, kernels per spike, thousand-kernel weight, and grain yield of E24-3-1-6-2-1 were significantly higher than those of its wheat parent 7182 and addition line 24-6-3-1. Thus, this translocation line that is highly resistant to powdery mildew and has excellent agronomic traits can be used as a novel promising germplasm for breeding resistant and high-yielding cultivars.

Are the modern-bred rice and wheat cultivars in India inefficient in zinc and iron sequestration?

Zinc and iron deficiency is a serious global health problem in humans depending on cereal-diet and is largely prevalent in low-income countries like Sub-Saharan Africa, and South and South-east Asia. We report inefficiency of modern-bred cultivars of rice and wheat to sequester those essential nutrients in grains as the reason for such deficiency and prevalence. To substantiate, experiments were conducted with elite, high-yielding cultivars of rice (n = 16) and wheat (n = 18) released in succeeding decades since the beginning of green revolution in India. The inherent Zn and Fe sequestering capacity in grains of the cultivars, and their responses to external application of Zn and Fe fertilizers were evaluated following standard protocols. We found a downward trend in grain density of Zn and Fe in those cereals in past more than 50 years. However, we failed to notice yield-dilution as a causative effect for such unwitting downward trend. With time, the cultivars again became stubborn to Zn and Fe fertilization for enhancing their grain density. Further, we noticed that external supply of one element, to improve its density in grains, had inhibitory effect on accumulation of the other, and the effect was magnified along the succeeding decades. Our innovative research warrants an improvement in ionomes of the cereals to alleviate the said incapacitating effect and ultimately the deficiency of those elements in humans, particularly living in low-income countries.

Sugarcane Breeding in Reunion: Challenges, Achievements and Future Prospects

All over the world, sugarcane breeding programs are developing new, high-yielding cultivars that are resistant to major diseases to improve the profitability and sustainability of the sugar-energy industries they serve. In Reunion Island, sugarcane genetic improvement efforts began in 1929. Many challenges had to be overcome. Continuous breeding efforts have been made to develop varietal resistances to control some major diseases and are still going on today. Given the extreme agroclimatic diversity that characterizes the different production areas of the industry, it was necessary to gradually develop a large network of seven decentralized breeding programs to support genetic progress throughout the whole industry. This article provides an overview of the sugarcane breeding program of Reunion. It describes historical achievements and gives detailed information about germplasm development, variety exchanges, breeding program and selection scheme and procedures. A review is also made on applied genetics research activities supporting variety improvement. Further progress depends on the optimized functioning of the current breeding program, which has never been so largely extended in terms of target environments. The article discusses prospects of genomics breeding applications in the complex genetic context of sugarcane, which will require large multidisciplinary collaborations.

Vegetative and Reproductive Response to Fruit Load in Two Jojoba (Simmondsia chinensis) Cultivars

Jojoba (Simmondsia chinensis) is a wax crop cultivated mainly in arid and semi-arid regions. This crop has been described as an alternate-bearing plant, meaning that it has a high-yield year (“on-year”) followed by a low-yield year (“off-year”). We investigated the effect of fruit load on jojoba’s vegetative and reproductive development. For two consecutive years, we experimented with two high-yielding cultivars—Benzioni and Hazerim—which had opposite fruit loads, i.e., one was under an on-year load, while the other was under an off-year load simultaneously. We found that removing the developing fruit from the shoot during an off-year promotes further vegetative growth in the same year, whereas in an on-year, this action has no effect. Moreover, after fruit removal in an on-year, there was a delay in vegetative growth renewal in the consecutive year, suggesting that the beginning of the growing period is dependent on the previous year’s yield load. We found that seed development in the 2018 season started a month earlier than in the 2017 season in both cultivars, regardless of fruit load. This early development was associated with higher wax content in the seeds. Hence, the wax accumulation rate, as a percentage of dry weight, was affected by year and not by fruit load. However, on-year seeds stopped growing earlier than off-year seeds, resulting in smaller seeds and an overall lower amount of wax per seed.

Genomic Selection in Tropical Forage Grasses: Current Status and Future Applications.

The world population is expected to be larger and wealthier over the next few decades and will require more animal products, such as milk and beef. Tropical regions have great potential to meet this growing global demand, where pasturelands play a major role in supporting increased animal production. Better forage is required in consonance with improved sustainability as the planted area should not increase and larger areas cultivated with one or a few forage species should be avoided. Although, conventional tropical forage breeding has successfully released well-adapted and high-yielding cultivars over the last few decades, genetic gains from these programs have been low in view of the growing food demand worldwide. To guarantee their future impact on livestock production, breeding programs should leverage genotyping, phenotyping, and envirotyping strategies to increase genetic gains. Genomic selection (GS) and genome-wide association studies play a primary role in this process, with the advantage of increasing genetic gain due to greater selection accuracy, reduced cycle time, and increased number of individuals that can be evaluated. This strategy provides solutions to bottlenecks faced by conventional breeding methods, including long breeding cycles and difficulties to evaluate complex traits. Initial results from implementing GS in tropical forage grasses (TFGs) are promising with notable improvements over phenotypic selection alone. However, the practical impact of GS in TFG breeding programs remains unclear. The development of appropriately sized training populations is essential for the evaluation and validation of selection markers based on estimated breeding values. Large panels of single-nucleotide polymorphism markers in different tropical forage species are required for multiple application targets at a reduced cost. In this context, this review highlights the current challenges, achievements, availability, and development of genomic resources and statistical methods for the implementation of GS in TFGs. Additionally, the prediction accuracies from recent experiments and the potential to harness diversity from genebanks are discussed. Although, GS in TFGs is still incipient, the advances in genomic tools and statistical models will speed up its implementation in the foreseeable future. All TFG breeding programs should be prepared for these changes.

Transcriptome integrated metabolic modeling of carbon assimilation underlying storage root development in cassava

The existing genome-scale metabolic model of carbon metabolism in cassava storage roots, rMeCBM, has proven particularly resourceful in exploring the metabolic basis for the phenotypic differences between high and low-yield cassava cultivars. However, experimental validation of predicted metabolic fluxes by carbon labeling is quite challenging. Here, we incorporated gene expression data of developing storage roots into the basic flux-balance model to minimize infeasible metabolic fluxes, denoted as rMeCBMx, thereby improving the plausibility of the simulation and predictive power. Three different conceptual algorithms, GIMME, E-Flux, and HPCOF were evaluated. The rMeCBMx-HPCOF model outperformed others in predicting carbon fluxes in the metabolism of storage roots and, in particular, was highly consistent with transcriptome of high-yield cultivars. The flux prediction was improved through the oxidative pentose phosphate pathway in cytosol, as has been reported in various studies on root metabolism, but hardly captured by simple FBA models. Moreover, the presence of fluxes through cytosolic glycolysis and alanine biosynthesis pathways were predicted with high consistency with gene expression levels. This study sheds light on the importance of prediction power in the modeling of complex plant metabolism. Integration of multi-omics data would further help mitigate the ill-posed problem of constraint-based modeling, allowing more realistic simulation.

Substitution Mapping of a Locus Responsible for Hybrid Breakdown in Populations Derived From Interspecific Introgression Line.

Hybrid breakdown, a form of postzygotic reproductive barrier, has been reported to hinder gene flow in many crosses between wild and cultivated rice. Here, the phenomenon of hybrid breakdown was observed as low-tillering (i.e., low tiller number) in some progeny of an interspecific cross produced in an attempt to introduce Oryza meridionalis Ng (W1625) chromosomal segments into Oryza sativa L. ssp. japonica “Taichung 65” (T65). Low-tillering lines were obtained in BC4-derived progeny from a cross between W1625 and “Taichung 65,” but the locus for low-tillering could not be mapped in segregating populations. As a second approach to map the locus for low-tillering, we analyzed an F2 population derived from a cross between the low-tillering lines and a high-yielding indica cultivar, “Takanari.” A major QTL for low-tillering, qLTN4, was detected between PCR-based markers MS10 and RM307 on the long arm of chromosome 4, with a LOD score of 15.6. The low-tillering phenotype was associated with weak growth and pale yellow phenotype; however, low-tillering plant had less reduction of grain fertility. In an F4 population (4896 plants), 563 recombinant plants were identified and the low-tillering locus was delimited to a 4.6-Mbp region between markers W1 and C5-indel3729. This region could not be further delimited because recombination is restricted in this region of qLTN4, which is near the centromere. Understanding the genetic basis of hybrid breakdown, including the low-tillering habit, will be important for improving varieties in rice breeding.

Genetic Relationships Among Physiological Processes, Phenology, and Grain Yield Offer an Insight Into the Development of New Cultivars in Soybean (Glycine max L. Merr).

Soybean grain yield has steadily increased during the last century because of enhanced cultivars and better agronomic practices. Increases in the total biomass, shorter cultivars, late maturity, and extended seed-filling period are frequently reported as main contributors for better soybean performance. However, there are still processes associated with crop physiology to be improved. From the theoretical standpoint, yield is the product of efficiency of light interception (Ei), radiation use efficiency (RUE), and harvest index (HI). The relative contribution of these three parameters on the final grain yield (GY), their interrelation with other phenological–physiological traits, and their environmental stability have not been well established for soybean. In this study, we determined the additive–genetic relationship among 14 physiological and phenological traits including photosynthesis (A) and intrinsic water use efficiency (iWUE) in a panel of 383 soybean recombinant inbred lines (RILs) through direct (path analyses) and indirect learning methods [least absolute shrinkage and selection operator (LASSO) algorithm]. We evaluated the stability of Ei, RUE, and HI through the slope from the Finley and Wilkinson joint regression and the genetic correlation between traits evaluated in different environments. Results indicate that both supervised and unsupervised methods effectively establish the main relationships underlying changes in Ei, RUE, HI, and GY. Variations in the average growth rate of canopy coverage for the first 40 days after planting (AGR40) explain most of the changes in Ei. RUE is primarily influenced by phenological traits of reproductive length (RL) and seed-filling (SFL) as well as iWUE, light extinction coefficient (K), and A. HI showed a strong relationship with A, AGR40, SFL, and RL. According to the path analysis, an increase in one standard unit of HI promotes changes in 0.5 standard units of GY, while changes in the same standard unit of RUE and Ei produce increases on GY of 0.20 and 0.19 standard units, respectively. RUE, Ei, and HI exhibited better environmental stability than GY, although changes associated with year and location showed a moderate effect in Ei and RUE, respectively. This study brings insight into a group of traits involving A, iWUE, and RL to be prioritized during the breeding process for high-yielding cultivars.

High Quantitative Trait Variability in Faba Bean Mutagenized Population for High-yielding Breeding Program in Saudi Arabia

Background: The narrow genetic base and environmental stresses are behind the low rate of faba bean yield in the past two decades. Drought stress is one of the most destructive abiotic stresses. Using induced mutagenesis on locally adapted landrace cultivar is proposed to cope with this problem. Methods: This study was conducted on faba bean landrace cultivar of Saudi Arabia, namely Hassawi 2, treated by 25 and 50 Gray gamma radiation. The genetic diversity assessment of M2 mutant populations was based on seven quantitative traits and nine Amplified Fragment Length Polymorphism (AFLP) primer combinations. Result: A total of 3419 M2 seeds were planted, of which 2782 (81.4%) seeds germinated and 2658 plants survived. A 5 to a 10-fold range of quantitative traits studied among mutant plants compared to control plants showed high variability. The number of pods per plant and seeds per plant was a valid selection criterion for a high-yielding faba bean breeding program. Nine AFLP primer combinations generated 1079 polymorphic alleles from 88 samples that comprised mutant and control plants. Shannon index (I) and expected heterozygosity (He) were 0.337 and 0.206, respectively. The AFLP results validated high variability in M2 populations. These findings will assist faba bean breeders in developing high-yielding cultivars with drought stress tolerance.

The accumulation of recombinant miraculin is independent of fruit size in tomato.

The taste-modifying protein miraculin (MIR) has received increasing interest as a new low-calorie sweetener. In our previous study using the tomato variety 'Micro-Tom,' it was shown that in transgenic tomatoes in which MIR was expressed by using the cauliflower mosaic virus 35S promoter (p35S) and a heat shock protein terminator (tHSP) cassette (p35S-MIR-tHSP), higher levels of miraculin accumulated than when MIR was driven by the nopaline synthase terminator (tNOS) cassette (p35S-MIR-tNOS). 'Micro-Tom' is a dwarf tomato used for research and shows a low yield. To achieve high productivity of MIR, it is essential to improve the MIR accumulation potential by using high-yielding cultivars. In this study, we evaluate whether the high MIR accumulation trait mediated by the tHSP appears even when fruit size increases. A line in which the p35S-MIR-tHSP cassette was introduced into a high-yielding variety was bred by backcrossing. The line homozygous for MIR showed higher accumulation of MIR than the heterozygous line. Despite large differences in fruit size, the MIR level in the backcross line was similar to that in the p35S-MIR-tHSP line (background 'Micro-Tom'). It was approximately 3.1 times and 4.0 times higher than those in miracle fruits and the p35S-MIR-tNOS tomato line 5B ('Moneymaker' background, which exhibits the highest miraculin productivity achieved thus far), respectively. These results demonstrate that the high MIR accumulation trait mediated by the tHSP appears even when fruit size is increased.

Variability, association and path analysis of centellosides and agro-morphological characteristics in Iranian Centella asiatica (L.) Urban ecotypes

Centella asiatica (L.) Urban (Apiaceae) is a commercial medicinal plant, which is rich in pentacyclic triterpenes (PTs) named centellosides including asiaticoside and madecassoside as triterpene saponins in addition to their corresponding sapogenins (asiatic acid and madecassic acid). These are well-known bioactive compounds in C. asiatica due to their extensive applications in medicinal and cosmetic industries. In the present study, variability and association of agro-morphological and phytochemical traits in the three Iranian C. asiatica ecotypes were studied to select the best ecotype for further domestication, breeding, and commercial exploitation programs. Among the studied samples, Aziz-Kian showed the highest content of the total PTs, asiaticoside, and madecassoside. The highest leaf length, leaf width, and content of PTs especially asiatic acid were determined in Abkenar ecotype. The highest correlation (0.99) was obtained between asiaticoside and madecassoside. Internode length, leaf length, petiole diameter, petiole length, root diameter, and root length were significantly correlated with total PTs. Cluster analysis based on phytochemical and phenotypical data allocated ecotypes into three different groups. Principle component analysis revealed that leaf length, leaf width, petiole diameter, petiole length, root per node, and asiatic acid had the highest contribution in classification. The studied samples were divided into two distinct chemotypes including I (asiaticoside and madecassoside) and II (asiatic acid and madecassic acid). Based on path analysis, internode length, root diameter, and leaf length can be highly recommended for the plant breeding purposes. These findings can be considered in further breeding programs to release high-yielding cultivar of C. asiatica rich in centellosides.

Increasing Planting Density of Maize Trough Double Row Cropping System to Improves Seed Yield

Maize as the second major crop in Indonesia has an important role in the national economy. Maize production in Indonesia is potentially to be improved by the use of appropriate cultivars and cropping system. The aims of study were to evaluate the yield performances of high-yielding maize cultivars under two different cropping system. An RCBD field experiment using five high-yielding maize cultivars, namely NK212, P21, BISI 2, BISI 18 and Bima 14 were conducted at Banjar Sub-district, Pandeglang District, Banten Province, Indonesia from April to July 2020. The plants were arranged into a single row (70 × 25 cm; 5.7 plant m−2; J1) or double row (25 × 25 × 90 cm; 6.9 plant m−2; J2) cropping system. Plant growth, yield and yield components for each cultivars and cropping system were observed. Across the cultivars, the seed yield of J2 (1.34 kg m−2) was higher than that of J1 (1.71 kg m−2) due to higher number of plant m−2 that resulted greater ear number and seed number m−2. Even though J2 resulted smaller ear size (weight, length, diameter and seed weight ear−1) as compared to J1, but those were offset with greater ear number per m2 of J2. Across two cropping system, cultivar NK212 (1.75 kg m−2) was superior in seed yield, and followed with BISI 18 (1.57 kg m−2). All cultivars were consistently better under J2 than that of J1. We concluded that increasing planting density using double row cropping system, in combination with high-yielding cultivars resulted better seed yield, which is a promising way to improve maize production in Indonesia.

Genetic Diversity and Population Structure Analysis of Triticum aestivum L. Landrace Panel from Afghanistan.

Landraces are a potential source of genetic diversity and provide useful genetic resources to cope with the current and future challenges in crop breeding. Afghanistan is located close to the centre of origin of hexaploid wheat. Therefore, understanding the population structure and genetic diversity of Afghan wheat landraces is of enormous importance in breeding programmes for the development of high-yielding cultivars as well as broadening the genetic base of bread wheat. Here, a panel of 363 bread wheat landraces collected from seven north and north-eastern provinces of Afghanistan were evaluated for population structure and genetic diversity using single nucleotide polymorphic markers (SNPs). The genotyping-by-sequencing of studied landraces after quality control provided 4897 high-quality SNPs distributed across the genomes A (33.75%), B (38.73%), and D (27.50%). The population structure analysis was carried out by two methods using model-based STRUCTURE analysis and cluster-based discriminant analysis of principal components (DAPC). The analysis of molecular variance showed a higher proportion of variation within the sub-populations compared with the variation observed as a whole between sub-populations. STRUCTURE and DAPC analysis grouped the majority of the landraces from Badakhshan and Takhar together in one cluster and the landraces from Baghlan and Kunduz in a second cluster, which is in accordance with the micro-climatic conditions prevalent within the north-eastern agro-ecological zone. Genetic distance analysis was also studied to identify differences among the Afghan regions; the strongest correlation was observed for the Badakhshan and Takhar (0.003), whereas Samangan and Konarha (0.399) showed the highest genetic distance. The population structure and genetic diversity analysis highlighted the complex genetic variation present in the landraces which were highly correlated to the geographic origin and micro-climatic conditions within the agro-climatic zones of the landraces. The higher proportions of admixture could be attributed to historical unsupervised exchanges of seeds between the farmers of the central and north-eastern provinces of Afghanistan. The results of this study will provide useful information for genetic improvement in wheat and is essential for association mapping and genomic prediction studies to identify novel sources for resistance to abiotic and biotic stresses.

Continuous estimation of rice (Oryza sativa (L.)) canopy transpiration realized by modifying the heat balance model

An estimation of canopy photosynthetic activities is needed in order to better understand biomass production of field crops. Thermal imaging techniques and the heat balance model enable us to estimate canopy diffusive conductance (gc) and canopy transpiration rate (E) of crops under field conditions. However, because conventional methods are unstable when wind velocity is very low, it is difficult to apply this model directly to field-grown crops. In this study, we modified the conventional model by measuring aerodynamic resistance in rice (Oryza sativa (L.)) under windless conditions (ra∗). The ra∗ ranged from 9.50 to 35.40 s m−1 among the genotypes. By introducing the concept of ra∗ to the original heat balance model, the stability when wind velocity is under 3.0 m s−1 improved greatly. Using seven rice genotypes, we evaluated genotypic differences in E with higher temporal resolution. The daily cumulative transpiration ranged from 2.32 kg m−2 d−1 to 10.29 kg m−2 d−1 depending on genotype and weather conditions. High-yielding cultivars consistently showed greater transpiration rates under various weather conditions. We confirmed the relationship between estimated E and final grain yield, especially during the daytime. Our modified model is useful as a monitoring tool for rice canopy transpiration.

QTL mapping of agronomic traits in wheat using the UK Avalon × Cadenza reference mapping population grown in Kazakhstan

BackgroundThe success of wheat production is largely dependent on local breeding projects that focus on the development of high-yielding cultivars with the use of novel molecular tools. One strategy for improving wheat productivity involves the deployment of diverse germplasms with a high potential yield. An important factor for achieving success involves the dissection of quantitative trait loci (QTLs) for complex agronomic traits, such as grain yield components, in targeted environments for wheat growth.MethodsIn this study, we tested the United Kingdom (UK) spring set of the doubled haploid (DH) reference population derived from the cross between two British cultivars, Avalon (winter wheat) and Cadenza (spring wheat), in the Northern, Central, and Southern regions (Karabalyk, Karaganda, Kyzylorda) of Kazakhstan over three years (2013–2015). The DH population has previously been genotyped by UK scientists using 3647 polymorphic DNA markers. The list of tested traits includes the heading time, seed maturation time, plant height, spike length, productive tillering, number of kernels per spike, number of kernels per meter, thousand kernel weight, and yield per square meter. Windows QTL Cartographer was applied for QTL mapping using the composite interval mapping method.ResultsIn total, 83 out of 232 QTLs were identified as stable QTLs from at least two environments. A literature survey suggests that 40 QTLs had previously been reported elsewhere, indicating that this study identified 43 QTLs that are presumably novel marker-trait associations (MTA) for these environments. Hence, the phenotyping of the DH population in new environments led to the discovery of novel MTAs. The identified SNP markers associated with agronomic traits in the DH population could be successfully used in local Kazakh breeding projects for the improvement of wheat productivity.

Characterizing reduced height wheat mutants for traits affecting abiotic stress and photosynthesis during seedling growth.

Most high-yielding, semidwarf wheat (Triticum aestivum L.) grown around the world contains either Rht1 or Rht2 genes. The success of these high-yielding cultivars is greatest in the most productive farming environments but provide marginal benefits in less favorable growing conditions such as shallow soils and low-precipitation dryland farming. Further, growing evidence suggests semidwarf genes not only affect early seedling growth but limit grain yield, especially under abiotic stress conditions. There are 23 other reduced-height mutants reported in wheat, most of which have not been functionally characterized. We evaluated these mutants along with their parents for several traits affecting seedling emergence, early seedling growth, and photosynthetic efficiency. Two- to seven-fold differences in coleoptile length, first leaf length, root length, and root angle were observed among the genotypes. Most of the mutations had a positive effect on root length, while the root angle narrowed. Coleoptile and first leaf lengths were strongly correlated with emergence. A specialized deep planting experiment identified Rht5, Rht6, Rht8, and Rht13 with significantly improved seedling emergence compared to the parent. Among the mutants, Rht4, Rht19, and Rht12 ranked highest for photosynthetic traits while Rht9, Rht16, and Rht15 performed best for early seedling growth parameters. Considering all traits collectively, Rht15 showed the most promise for utilization in marginal environments followed by Rht19 and Rht16. These wheat mutants may be useful for deciphering the underlying molecular mechanisms of understudied traits and breeding programs in arid and semiarid regions where deep planting is practiced.