Varietal Improvement Research Articles

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The availability of tomato seeds adapted to local production conditions remains one of the major constraints for the tomato sector in Gabon. The development of varieties adapted to pedoclimatic conditions is necessary. An agro-morphological characterization study of ten (10) tomato lines introduced in Gabon was carried out in order to select the best lines for their use in a program of creation and varietal improvement. The objectives were to measure the agro-morphological characteristics of the lines, evaluate the yields, determine the qualities of the fruits and identify the types and levels of infestation of the plants. These lines were evaluated according to a Fisher block device with three repetitions. Univariate (ANOVA) and multivariate (ACP, CAH) analyzes of the data were carried out with the R software. The results revealed variability between the lines for all the traits studied. The flowering time varied between 26 and 36 days after sowing (DAS) and the first harvests varied between 70 and 84 DAS. Line L1 was the earliest and L9 late. For the yield, it varied between 0.6 and 26.7 t/ha. Lines L4 and L8 were the most productive with 26.7 t/ha and 20.5 t/ha respectively. The fruits with the best sizes are those of the L2 and L4 lines with respectively 87.7 g for a rounded shape and 86.6 g for an ovoid shape. Lines L1, L4, L5 and L8 are the firmest. The type of disease observed is downy mildew, spoon yellows and apical necrosis for a moderate severity index for all the lines. These results make it possible to assess the agronomic performance of the lines and to identify promising lines for varietal improvement programs in order to improve productivity for food security.

Genetic Relationship and Diversity Analysis in Arecanut (Areca catechu L.) Genotypes using Molecular Markers

Background: Arecanut (Areca catechu L.) is an important plantation crop of India belongs to the family Arecaceae. As it is a highly cross-pollinated crop there is a significant difference among the genotypes. Morphological traits used for determining diversity and relationships among genotypes or variety are prone to environmental influences. Thus, the usefulness of molecular markers has been investigated as a means of characterizing and discriminating difference more precisely. Therefore, the present study was carried out to assess the genetic relationship and diversity among the arecanut genotypes by employing RAPD, ISSR and SSR markers. Methods: A total of 11 genotypes are being grown in University of Agricultural and Horticultural Sciences (UAHS), Shivamogga, Karnataka, India, which includes both local and exotic collections. These 11 genotypes were evaluated for genetic variations using molecular markers viz., random amplified polymorphic DNA (RAPD), inter-simple sequence repeats (ISSR) and simple sequence repeats (SSR). Result: All the markers studied showed significant polymorphism among the genotypes. Jaccard’s genetic similarity coefficient values of RAPD, ISSR and SSR markers were found in the range of 0.56-0.76, 0.55-0.74 and 0.52-0.91. The higher similarity was observed between the genotypes Mohitnagar and Mangala, as well as Theerthahalli Local and Hirehalli Dwarf. The genotypes Maidan Local and Cameroon were placed in very distinct clusters, showing that they are having very distinct traits. The dendrogram prepared using SSR data separately and combining data of RAPD, ISSR, SSR markers showed similar results. Therefore, employing SSR markers for further studies will be more useful for identifying germplasm for varietal improvement programmes.

The impact of the international rice genebank’s (IRG) on rice farming in Bangladesh

BackgroundThe International Rice Genebank (IRG) currently safeguards the largest and most diverse collection of rice genetic resources in the world. Over the past decades, genetic resources from the IRG have been used effectively to increase smallholder farmers’ rice productivity in developing economies. Bangladesh is one of the direct and indirect recipients of IRG germplasm for rice genetic improvement. This study aimed to map the impact pathways of IRG germplasm transfers to Bangladesh, evaluate the genetic contribution of IRG germplasms to rice productivity of farmers, and compute the equivalent economic benefit.MethodsImpact pathway analysis was conducted to map the IRG’s germplasm transfer for varietal improvement and seed dissemination of improved rice varieties in Bangladesh using the information collected from key informant interviews. Using data from the farm household survey conducted by the International Rice Research Institute (IRRI) in 2016 in five divisions in Bangladesh, a pedigree analysis was conducted that related the productivity changes in farmers’ fields explicitly to genebank accessions through varietal improvement. Afterward, we evaluated the economic benefit of IRG contribution in rice varietal improvement in Bangladesh using the computed marginal increases in productivity, average paddy price, and estimated total rice area.ResultsIRG’s impact pathway on germplasm transfer in Bangladesh showed that impacts for farmers were achieved through joint efforts with IRRI and the National Agricultural Research and Extension System’s research-for-development programs. On average, 52% of the improved rice varieties’ genetic composition, cultivated by farmers in Bangladesh, definitely came from IRG accessions. This contribution factor could increase up to 67% if possible contributions were taken into account. The results of the Cobb–Douglas model implied that for every 1% increase in the definite IRG contribution to an improved rice variety, there was an increase in rice yield of about 0.99%, holding other factors constant. This yield increase can be translated into an additional US$ 8,576,973 aggregated net benefit of farmers during the wet season in Bangladesh. The enhanced yield can be associated with the added important agronomic traits contributed by the accession provided by the IRG in the genetic background of the rice varieties developed for farmers in Bangladesh.ConclusionsThe findings of the study demonstrate that IRG accession forms a significant part of the ancestry of improved rice varieties which is associated with improved yield. The study highlights the valuable contribution of IRG’s conservation and distribution of genetic accessions to the research and development of improved rice varieties and rice production on farms in Bangladesh.

Genetic variability and association of yield contributing traits in advanced breeding lines of soybean

Characterization of genotypes for various traits is a basic and very essential criterion for crop varietal improvement programmes. Under the present investigation fifty seven advanced breeding lines along with three best checks (JS 20-98, JS 20-116 and JS 20-34) were evaluated to characterize 17 phenotypic and 11 yield attributing traits at JNKVV, Jabalpur. Morphological/phenotypic traits were described as per DUS guidelines. Yield attributing traits were utilized to work out various biometric parameters (Phenotypic Coefficient of Variation,(PCV), Genotypic Coefficient of Variation (GCV), heritability with genetic advance, correlation and path coefficient). Phenotypic characterization exhibited huge variability among advanced breeding genotypes for most of the descriptor traits. Semi-erect growth habit (100%), presence of peroxidase activity in ripe seed (100%), Semi-determinate growth type (95%), Yellow colour ripe seed testa (90%) and tawny colour pod hair (86.8%) were most common traits  studied in genotypes. Significant variation was also obtained for yield attributing quantitative traits. PCV was higher in magnitude than GCV for all the traits and the highest for seed yield per plant (39.10 and 36.76, respectively). The highest heritability and genetic advance as per cent of mean were recorded for biological yield per plant and seed yield per plant, respectively. Seed yield per plant demonstrated a highly significant positive relation with biological yield (0.797**) followed by 100 seed weight (0.735**) and the number of pods per plant (0.620**). Whereas, it was negatively correlated with plant height (-0.303**). The genotypic path coefficient analysis also revealed that the highest positive direct effect on seed yield per plant was due to biological yield per plant followed by 100 seed weight. Keywords: Heritability, Phenotypic traits, Correlation, Path Coefficient, soybean

Evaluation of Rapeseed Genotypes against Alternaria Blight under Field Conditions in Nawalparasi-West, Nepal

Alternaria blight disease causes both yield and quality loss in Brassica crops. A field evaluation of ten rapeseed genotypes against Alternaria blight disease was conducted during November 2018 to February 2019 in Parasi, Nawalparasi-west district. Experiment was laid out in a randomized complete block design with individual plot size of 2.25 m2 with three replications. Post-harvest in-vitro seed infection test was done in a completely randomized design with four replications. Disease scoring was done as percentage of leaf area and pod infection on individual 15 sample plants per plot at seven days intervals. Genotype ICT 2001-35 was found moderately resistant based on categorization of mean leaf AUDPC (308.52) and mean pod infection AUDPC values (391.48) with low seed infection (12.50%). Preeti, Bikash and Pragati showed highly susceptible reactions to both leaf blight and pod infection. Therefore, genotype ICT 2001-35 could be used in a varietal improvement program for disease resistance against Alternaria blight.

BrKAO2 mutations disrupt leafy head formation in Chinese cabbage (Brassica rapa L. ssp. pekinensis).

The role of BrKAO2 in leafy head formation was confirmed by using two allelic Chinese cabbage mutants. Chinese cabbage yield and quality are determined by leafy head formation. Cloning and characterising the key genes regulating leafy head formation are essential for its varietal improvement. We used an EMS-mutagenised population of the heading type 'FT' Chinese cabbage line and identified two allelic non-heading mutants, i.e. nhm3-1 and nhm3-2. Genetic analysis showed that the mutant trait was controlled by a single recessive gene. MutMap and Kompetitive Allele Specific PCR genotyping revealed that BraA05g012440.3C was the candidate gene, which encodes ent-kaurenoic acid oxidase 2 in gibberellin (GA) biosynthetic pathway. It was named BrKAO2. Two non-synonymous mutations in the second BrKAO2 exon, respectively, accounted for the mutant phenotypes of nhm3-1 and nhm3-2. BrKAO2 was expressed during all leaf development stages, and there were no significant differences between the wild type and mutants in terms of BrKAO2 expression. The mutant phenotypes were restored to the wild type via exogenous GA3 application. RNA-Seq was performed on wild-type 'FT', nhm3-1, and nhm3-1 + GA3 rosette leaves, and several key genes involved in GA biosynthesis, signal transduction, and leafy head development were identified. These findings indicate that BrKAO2 is responsible for the leafy head formation in nhm3 mutants.

Cluster analysis of Corchorus capsularis jute based on agro-morphological characters to isolate high-yielding genotypes for breeding purposes

White jute (Corchorus capsularis) is an important bast fiber producing cash crop. Its narrow genetic base due to its self-pollination nature as well as genetic incompatibility in respect of interspecific hybridization cause low morphological variability. The searching for good genotypes and their use in intraspecific hybridization is the best option to increase the yield potentiality of this crop. In this research experiment, 95 white jute genotypes including 93 accessions and two pre-released varieties (CVL-1 and BJRI Deshi Pat 9) were investigated for higher fibre yield. The experiment was laid out in an augmented design at Jute Agricultural Experiment Station, Manikgonj during 2019. Plants were harvested at 120 days age and morphological data like plant height (m), base diameter (mm), green weight with leaves (g plant-1), fiber yield (g plant-1) and stick yield (g plant-1) were recorded carefully. From the descriptive analyses of the recorded data, good fibre yields were found in A-725 (20 g plant-1) and A-2232 (16.60 g plant-1) followed by A-2224, A-248, A-07, A-675, A-2264, A-1292, A-247, A-469, A-2226, A-674, A-02, A-232, A-10, A-684 than the control varieties BJRI Deshi Pat-9 (10.80 g plant-1) and CVL-1 (9.20 g plant-1). From the hierarchical cluster analysis, the average inter-cluster distances were found higher than the average intra-cluster distances, which shows the presence of wide genetic diversity among the genotypes of different clusters than those of the same cluster. These higher fibre yielding accessions with wide genetic diversity would be used as breeding materials for varietal improvement through hybridization and selection approaches.

Resilient Fertilization Strategies to Enhance Rice Productivity in Submergence-Prone Areas

Previous efforts to mitigate the negative impacts of submergence on rice production have focused mainly on varietal improvement. Synergistic effects of submergence-tolerant rice varieties and appropriate fertilizer management strategies are critical to enhance resilience of rice to submergence.

Ecological and genomic vulnerability to climate change across native populations of Robusta coffee (Coffea canephora).

The assessment of population vulnerability under climate change is crucial for planning conservation as well as for ensuring food security. Coffea canephora is, in its native habitat, an understorey tree that is mainly distributed in the lowland rainforests of tropical Africa. Also known as Robusta, its commercial value constitutes a significant revenue for many human populations in tropical countries. Comparing ecological and genomic vulnerabilities within the species' native range can provide valuable insights about habitat loss and the species' adaptive potential, allowing to identify genotypes that may act as a resource for varietal improvement. By applying species distribution models, we assessed ecological vulnerability as the decrease in climatic suitability under future climatic conditions from 492 occurrences. We then quantified genomic vulnerability (or risk of maladaptation) as the allelic composition change required to keep pace with predicted climate change. Genomic vulnerability was estimated from genomic environmental correlations throughout the native range. Suitable habitat was predicted to diminish to half its size by 2050, with populations near coastlines and around the Congo River being the most vulnerable. Whole-genome sequencing revealed 165 candidate SNPs associated with climatic adaptation in C. canephora, which were located in genes involved in plant response to biotic and abiotic stressors. Genomic vulnerability was higher for populations in West Africa and in the region at the border between DRC and Uganda. Despite an overall low correlation between genomic and ecological vulnerability at broad scale, these two components of vulnerability overlap spatially in ways that may become damaging. Genomic vulnerability was estimated to be 23% higher in populations where habitat will be lost in 2050 compared to regions where habitat will remain suitable. These results highlight how ecological and genomic vulnerabilities are relevant when planning on how to cope with climate change regarding an economically important species.

Adoption of improved soybean and gender differential productivity and revenue impacts: Evidence from Nigeria.

Despite the considerable soybean varietal improvement and dissemination efforts in Nigeria and other parts of Sub‐Saharan Africa, empirical evidence on farm‐level yield and revenue impacts of improved soybean varieties (ISVs) from a gender perspective are limited. In this paper, we analyze the impact of the adoption of ISVs on soybean yield and net revenue, and the associated gender differential effects in northern Nigeria. We use the endogenous and exogenous switching treatment effects regression frameworks to estimate the impacts. We find that the adoption of ISVs significantly increased soybean yield and net revenue of the soybean‐producing households by 26% and 32%, respectively. In addition, we find that the gender gap in yield between male and female‐headed soybean‐producing households was small, with a yield gap of about 1%. However, we find a substantial gender gap in soybean net revenue, as the net revenue of female‐headed households was lower by about 20%, as compared to male‐headed households. Overall, our findings show that policymakers and their development partners can leverage varietal improvement to boost the yields of both male‐ and female‐headed households. However, closing the gender gap in crop income necessitates reducing the disparity in market linkages so that the female farmers can equally have better market access.

Diallel Crosses of Cotton (Gossypium hirsutum L.) from Burkina Faso and Texas A&M AgriLife Research—1-Analysis of Agronomic Traits to Improve Elite Varieties from Burkina Faso

Cotton breeding progress stagnation, changing production conditions, and continued high fiber quality demands are challenging the cotton industry in Burkina Faso. The F1 populations developed by half diallel crosses between germplasm from Texas A&M AgriLife Research and Burkina Faso were evaluated for several agronomic traits. The aim was to identify the most promising parents and hybrids for further varietal improvement. Three AgriLife parents helped improve the most important targeted traits. Parent 15-3-416 reduced days to 50% flowering (−3.14 days) and shortened plant height (−22.25 cm) in hybrids while 16-2-216FQ improved their fiber percentage (+2.68%). Hybrids with Burkina Faso elite cultivar E32 as male parent and the three best AgriLife parents as the females showed good specific combining ability (SCA). FK37 × 15-10-610-7 and FK64 × 15-10-610-7 showed heterosis for earliness by reducing, respectively, days to 50% flowering (−4.27 days) or days to 50% boll opening (−3.95 days) below parent means. E32 × 16-2-216FQ and FK64 × 16-2-216FQ increased fiber percentage by +1.75% and +2.06%, respectively. FK64 × 15-3-416 increased seed index (SI) (+0.62 g) and fiber percentage (+1.19%), while maintaining other traits at the parents’ average levels. E32 × 15-3-416 showed the most heterosis for desired improvements, reducing days to 50% flowering (−4) and increasing the number of bolls/vegetative branch (+3.05), number of bolls/fruiting branch (+6.38), number of bolls/plant (+13.49), boll weight (+1.53 g), SI (+0.40 g), and fiber percentage (+1.18%). Inter-program crosses show the potential to enhance genetic diversity in Burkina Faso’s breeding program. Subsequent selection methods must be carefully applied considering the Burkina Faso breeding objectives for future cultivars.

Combining speed breeding with traditional and genomics‐assisted breeding for crop improvement

AbstractAccelerated crop growth strategy innovations are required as we reach saturation peaks regarding the productivity of major food crops. Speed breeding (SB) is one of the most promising technologies adopted for this purpose. SB hastens crop production by reducing plant growth and development, breeding time and swift generation advancement. Prolonged daily light exposure shortens the life cycle in some long‐day or day‐neutral plants leading to early seed harvest. This approach is best suited for controlled environment prebreeding/breeding activities and analysed for several crop species. SB can be integrated with different traditional and advanced genomics‐assisted breeding technologies like marker‐assisted selection (MAS), genomic selection (GS), pollen‐based selection (PBS), overexpression/knock‐down transgenics and genome editing to achieve more precise and faster results on translational genetic enhancement. This review will discuss the approaches and strategies adopted for the SB and its potential to integrate existing crop improvement technologies to attain more efficient outcomes on major food crops' varietal improvement.

Screening of soybean genotypes for the source of soybean mosaic resistance

Soybean mosaic virus (SMV) is the major constraints for soybean cultivation in many parts of the country. Experiments were carried out to study the seed transmission of SMV and to identify the resistant sources through screening of 30 promising soybean genotypes obtained from different sources under natural infections conditions in between 2000 and 2001. Indirect-ELISA was performed against TRSV, TMV, CPMV, CMV, BBSV, BBTMV and SMV in leaf materials, both from healthy and diseased plant materials and the results showed that the seeds and the plants in the field were free from those 6 viruses. The highest seed transmission was found in Gaurab (15.07%) followed by G-2120 and the lowest (1.5%) seed transmission was found in TG-893 followed by BS-32, CM and AGS-129. Seed mottling was found related to seed transmission. No disease incidence was found in AGS-129 but there were seed mottling (1.25%). On the other hand, genotype AGS- 160 was free from mottled seeds but produced infected seedlings. Mosaic symptom became apparent 15 days after sowing (DAS), highest at 60 DAS and disappear after 90 DAS. Seeds from seed lot containing up to 20% mottled symptom could not hamper production. Screening of 30 soybean genotypes based on the natural infections revealed that AGS-129 was identified as resistant and grading 1, 10 were identified as moderately resistant (MR) considered as grading 3 and the remaining genotypes were susceptible (S) and moderately susceptible (MS) considered as grading 7 and 5, respectively. The 10 genotypes viz. CM, BS-32, ACAGS-154, G-2261, AGS-129, Durga, Williams, AGS-160, EC-1178 and PR-164 could be used for further study to locate resistant genes against soybean mosaic virus and varietal improvement in breeding purpose. Asian J. Med. Biol. Res. 2022, 8 (1), 47-62

Mungbean (Vigna radiata (L.) R. Wilczek): Progress in Breeding and Future Challenges

Mungbean (Vigna radiata (L.) R. Wilczek) is a short duration farmer preferred warm-season pulse crop. The crop has shown a balanced growth worldwide, especially in developing countries. Mungbean being a great source of protein with higher folate and iron levels attracts high demand and price on the market making the farmers happy and satisfied. Moreover, it can fix atmospheric nitrogen through symbiosis with nitrogen-fixing bacteria, making it perfect for rice based cropping systems and intercropping with other crops. Despite having so many benefits, mungbean has been a neglected crop compared to other pulses with limited efforts aiming at its breeding and development. Higher productivity, breeding for biotic and abiotic stresses resistance and nutritional quality improvement are future challenges for mungbean breeders. Several researchers are working in the direction of collecting and maintaining mungbean genetic resources. Mutation breeding and genetic engineering has also been enhanced in mungbean varietal improvement. Genomic information is limited compared to other legume species. However, the recent successful sequencing of mungbean genome has opened new vistas into the crop’s R&D. It is a self-pollinated pulse with small genome size, which could be used as a model for studying other legumes. Mungbean breeders at present times aim to identify useful alleles from diverse germplasm and markers closely associated with desirable traits. The high-throughput marker genotyping system has now made it feasible to pinpoint the exact gene locations and mutations contributing target phenotypes. In this review we present the current status of conventional and molecular breeding of the crop and summary of efforts in the utilization of genetic information and genomic resources for further mungbean improvement.

Identification of the Promising Lines of Lentil for Varietal Improvement

This study aimed to evaluate and identify promising lentil genotypes for varietal enhancement, conducted at the Nepal Agriculture Research Council (NARC), Agriculture Botany Division (ABD), Khumaltar. Eighteen genotypes sourced from the National Grain Legumes Research Program (NAGRC) and the International Centre for Agriculture Research in Dry Areas (ICARDA) was assessed. Various parameters, including plant stand, flowering duration, maturity period, plant height, yield-related traits, chlorophyll content, and disease severity, were recorded. Notable correlations were found between grain yield and key attributes such as pods per plant, 1000-seed weight, chlorophyll content, final plant stand, and branches per plant. Genotypes exhibiting high chlorophyll content, optimal plant height, increased branching, greater seed weight, more pods, enhanced plant stand, and lower disease susceptibility displayed positive correlations with grain yield. Among these, genotype ILL-10071 demonstrated the highest average grain yield, highlighting its potential for further breeding and improvement programs. Other promising genotypes included ILL-9924, ILL-3338, ILL-10265, ILL-1920, ILL-6458, ILL-6465, and RL-71, showcasing significant grain yield and warranting consideration in future varietal enhancement initiatives. These findings underscore the importance of specific traits in lentil genotypes and provide valuable insights for breeding programs aimed at enhancing lentil productivity.

Water Demand in Maize Is Projected to Decrease under Changing Climate in India

Crop stage-specific information on the impacts of projected climate change on crop and irrigation water requirements are essential for improving productivity. This study investigated the possible implications of projected climate change on the phenology, effective rainfall (Peff), crop (CWR) and irrigation water requirements (IWR) of maize in eight locations in India. CWR, Peff and IWR were estimated for seven crop stages viz., emergence, 5th leaf stage, tasseling, silking, milking, dough and maturity during the baseline (1980–2009) and near-century (2022–39) using climate data derived from a subset of 29 general circulation models. The results indicated that mean seasonal maximum temperature, minimum temperature and rainfall were projected to increase in all the locations. Hence, the total crop duration (3–7 days), CWR (8–69 mm) and IWR (1–54 mm) were projected to decrease. The study could identify the specific stages in which the greatest reduction in crop duration, CWR and IWR would occur. Such information will be of immense help to farmers and varietal improvement programs in the study regions in the near future.

ESTIMATING VARIABILITY, HERITABILITY, AND GENETIC ADVANCE OF RICE GENOTYPES IN MID-HILLS OF NEPAL

<p>Rice is an essential staple food in Nepal but researches and varietal improvement programs are rarely carried out due to inadequate variability study. The field study was carried to diagnose the influence of genetic and environmental factors on yield traits to aid future rice breeding programs. Twelve genotypes were arranged in randomized complete block design with three replications from July to November 2019 at the research field of the Institute of Agriculture and Animal Science, Tribhuvan University, in the hilly area of Nepal. Analysis of variance showed significant difference for days to 50% booting, days to 50% flowering, plant height, panicle length, flag leaf area, filled grains per panicle, unfilled grains per panicle, fertility percentage, effective tillers m<sup>-2</sup>, straw yield, grain yield, 1000-grain weight, and harvesting index indicating the presence of variation in genotypes. LPN BR-1615 was the most promising genotype in grain yield. The values of Phenotypic Coefficient of Variation (PCV) were higher than Genotypic Coefficient of Variation (GCV) for each trait and low difference between them was found for days to 50% booting, days to 50% flowering, plant height, panicle length, grain yield, thousand-grain weight, fertility percentage, and harvesting index. Plant height, effective tillers m<sup>-2</sup>, and grain yield showed high heritability (i.e. 93.2%, 60.5% and 92.6%, respectively) and higher genetic advance as percentage of mean (i.e. 46.5, 34.6 and 50.1, respectively) . Thus, the experiment revealed that selections favoring plant height, effective tillers m<sup>-2</sup>, and grain yield would help in effective breeding programs of rice in future.</p>

The Multipartite Mitochondrial Genome of Marama (Tylosema esculentum).

Tylosema esculentum (marama bean), a wild legume from tropical Africa, has long been considered as a potential crop for local farmers due to its rich nutritional value. Genomics research of marama is indispensable for the domestication and varietal improvement of the bean. The chloroplast genome of marama has been sequenced and assembled previously using a hybrid approach based on both Illumina and PacBio data. In this study, a similar method was used to assemble the mitochondrial genome of marama. The mitochondrial genome of the experimental individual has been confirmed to have two large circles OK638188 and OK638189, which do not recombine according to the data. However, they may be able to restructure into five smaller circles through recombination on the 4 pairs of long repeats (>1 kb). The total length of marama mitogenome is 399,572 bp. A 9,798 bp DNA fragment has been found that is homologous to the chloroplast genome of marama, accounting for 2.5% of the mitogenome. In the Fabaceae family, the mitogenome of Millettia pinnata is highly similar to marama, including for both the genes present and the total size. Some genes including cox2, rpl10, rps1, and sdh4 have been lost during the evolution of angiosperms and are absent in the mitogenomes of some legumes. However, these remain intact and functional in marama. Another set of genes, rpl2, rps2, rps7, rps11, rps13, and rps19 are either absent, or present as pseudogenes, in the mitogenome of marama.

Variation for Nitrogen Use Efficiency Traits in Wheat Under Contrasting Nitrogen Treatments in South-Eastern Europe.

Wheat cultivars differ in their response to nitrogen (N) fertilizer, both in terms of its uptake and utilization. Characterizing this variation is an important step in improving the N use efficiency (NUE) of future cultivars while maximizing production (yield) potential. In this study, we compared the agronomic performance of 48 diverse wheat cultivars released between 1936 and 2016 at low and high N input levels in field conditions to assess the relationship between NUE and its components. Agronomic trait values were significantly lower in the low N treatment, and the cultivars tested showed a significant variation for all traits (apart from the N remobilization efficiency), indicating that response is genotype-dependent, although significant genotype × environment effects were also observed. Overall, we show a varietal improvement in NUE over time of 0.33 and 0.30% year–1 at low and high N, respectively, and propose that this is driven predominantly by varietal selection for increased yield. More complete understanding of the components of these improvements will inform future targeted breeding and selection strategies to support a reduction in fertilizer use while maintaining productivity.

Bayesian Hierarchical Models for Measuring Varietal Improvement in Tobacco Yield and Quality

AbstractWe measure the economic impact of varietal improvement and technological change in flue-cured tobacco across quantity (e.g., yield) and quality dimensions under a voluntary quality constraint. Since 1961, flue-cured tobacco breeders in the United States have been subject to the Minimum Standards Program that sets limits on acceptable quality characteristics for commercial tobacco varieties. We implement a Bayesian hierarchical model to measure the contribution of breeding efforts to changes in tobacco yields and quality between 1954 and 2017. The Bayesian model addresses limited data for varieties in the trials and allows easy generation of the necessary parameters of economic interest.