Showing papers on "Plant breeding published in 2020"

Conventional and Molecular Techniques from Simple Breeding to Speed Breeding in Crop Plants: Recent Advances and Future Outlook

Abstract: In most crop breeding programs, the rate of yield increment is insufficient to cope with the increased food demand caused by a rapidly expanding global population. In plant breeding, the development of improved crop varieties is limited by the very long crop duration. Given the many phases of crossing, selection, and testing involved in the production of new plant varieties, it can take one or two decades to create a new cultivar. One possible way of alleviating food scarcity problems and increasing food security is to develop improved plant varieties rapidly. Traditional farming methods practiced since quite some time have decreased the genetic variability of crops. To improve agronomic traits associated with yield, quality, and resistance to biotic and abiotic stresses in crop plants, several conventional and molecular approaches have been used, including genetic selection, mutagenic breeding, somaclonal variations, whole-genome sequence-based approaches, physical maps, and functional genomic tools. However, recent advances in genome editing technology using programmable nucleases, clustered regularly interspaced short palindromic repeats (CRISPR), and CRISPR-associated (Cas) proteins have opened the door to a new plant breeding era. Therefore, to increase the efficiency of crop breeding, plant breeders and researchers around the world are using novel strategies such as speed breeding, genome editing tools, and high-throughput phenotyping. In this review, we summarize recent findings on several aspects of crop breeding to describe the evolution of plant breeding practices, from traditional to modern speed breeding combined with genome editing tools, which aim to produce crop generations with desired traits annually.

Physiology And Biotechnology Integration For Plant Breeding

Abstract: PHYSIOLOGICAL BASIS OF YIELD AND ENVIRONMENTAL ADAPTATION Physiology of Yield and Adaptation in Wheat and Barley Breeding J L Araus, GA Slafer, MP Reynolds, and C Royo Genetic Yield Improvement and Stress Tolerance in Maize M Tollenaar and EA Lee Physiological Basis of Yield and Environmental Adaptation in Rice S Peng and A Ismail Sorghum Physiology A Blum Pearl Millet FR Bidinger and CT Hash Comparative Ecophysiology of Cowpea, Common Bean, and Peanut AE Hall The Physiological Basis of Soybean Yield Potential and Environmental Adaptation TT VanToai and J Specht The Physiological Basis of Yield and Environmental Adaptation D M Oosterhuis and J McD Stewart APPLICATION OF BIOTECHNOLOGY TO IMPROVE CROP YIELD AND ADAPTATION Genome Mapping and Genomic Strategies for Crop Improvement PK Subudhi and HT Nguyen Marker-Assisted Utilization of Exotic Germplasm I Paran Heterosis of Yield: Molecular and Biochemical Perspectives CW Stuber Genetic Engineering for Enhancing Plant Productivity and Stress Tolerance T-hD Ho and R Wu Genome Mapping and Marker-Assisted Selection for Improving Cotton (Gossypium spp) Productivity and Quality in Arid Regions Y Saranga and AH Patterson Molecular Dissection of Abiotic Stress Tolerance in Sorghum and Rice M S Pathan, PK Subudhi, B Courtois, and HT Nguyen Genetic Dissection of Drought Resistance in Maize: A Case Study J-M Ribaut, M Banziger, T Setter, G Edmeades, and D Hoisington Physiology and Biotechnology Integration for Plant Breeding: Epilogue A Blum and HT Nguyen

Exploring the molecular basis of heterosis for plant breeding.

Abstract: Since approximate a century ago, many hybrid crops have been continually developed by crossing two inbred varieties. Owing to heterosis (hybrid vigor) in plants, these hybrids often have superior agricultural performances in yield or disease resistance succeeding their inbred parental lines. Several classical hypotheses have been proposed to explain the genetic causes of heterosis. During recent years, many new genetics and genomics strategies have been developed and used for the identifications of heterotic genes in plants. Heterotic effects of the heterotic loci and molecular functions of the heterotic genes are being investigated in many plants such as rice, maize, sorghum, Arabidopsis and tomato. More and more data and knowledge coming from the molecular studies of heterotic loci and genes will serve as a valuable resource for hybrid breeding by molecular design in future. This review aims to address recent advances in our understanding of the genetic and molecular mechanisms of heterosis in plants. The remaining scientific questions on the molecular basis of heterosis and the potential applications in breeding are also proposed and discussed.

Puzzling out plant reproduction by haploid induction for innovations in plant breeding

Abstract: Mixing maternal and paternal genomes in embryos is not only responsible for the evolutionary success of sexual reproduction, but is also a cornerstone of plant breeding. However, once an interesting gene combination is obtained, further genetic mixing is problematic. To rapidly fix genetic information, doubled haploid plants can be produced: haploid embryos having solely the genetic information from one parent are allowed to develop, and chromosome doubling generates fully homozygous plants. A powerful path to the production of doubled haploids is based on haploid inducer lines. A simple cross between a haploid inducer line and the line with gene combinations to be fixed will trigger haploid embryo development. However, the exact mechanism behind in planta haploid induction remains an enduring mystery. The recent discoveries of molecular actors triggering haploid induction in the maize crop and the model Arabidopsis thaliana pinpoint an essential role of processes related to gamete development, gamete interactions and genome stability. These findings enabled translation of haploid induction capacity to other crops as well as the use of haploid inducer lines to deliver genome editing machinery into various crop varieties. These recent advances not only hold promise for the next generations of plant breeding strategies, but they also provide a deeper insight into the fundamental bases of sexual reproduction in plants. This Perspective summarizes recent advances made on in planta haploid induction systems and how these advances contribute to our understanding of plant reproduction and innovations of plant breeding.

Speed breeding short-day crops by LED-controlled light schemes.

Abstract: A simple and rapid speed breeding system was developed for short-day crops that enables up to five generations per year using LED lighting systems that allow very specific adjustments regarding light intensity and quality. Plant breeding is a key element for future agricultural production that needs to cope with a growing human population and climate change. However, the process of developing suitable cultivars is time-consuming, not least because of the long generation times of crops. Recently, speed breeding has been introduced for long-day crops, but a similar protocol for short-day crops is lacking to date. In this study, we present a speed breeding protocol based on light-emitting diodes (LEDs) that allow to modify light quality, and exemplarily demonstrate its effectiveness for the short-day crops soybean (Glycine max), rice (Oryza sativa) and amaranth (Amaranthus spp.). Adjusting the photoperiod to 10 h and using a blue-light enriched, far-red-deprived light spectrum facilitated the growth of short and sturdy soybean plants that flowered ~ 23 days after sowing and matured within 77 days, thus allowing up to five generations per year. In rice and amaranth, flowering was achieved ~ 60 and ~ 35 days after sowing, respectively. Interestingly, the use of far-red light advanced flowering by 10 and 20 days in some amaranth and rice genotypes, respectively, but had no impact on flowering in soybeans, highlighting the importance of light quality for speed breeding protocols. Taken together, our short-day crops’ speed breeding protocol enables several generations per year using crop-specific LED-based lighting regimes, without the need of tissue culture tools such as embryo rescue. Moreover, this approach can be readily applied to a multi-storey 96-cell tray-based system to integrate speed breeding with genomics, toward a higher improvement rate in breeding.

Natural variations of SLG1 confer high-temperature tolerance in indica rice.

Abstract: With global warming and climate change, breeding crop plants tolerant to high-temperature stress is of immense significance. tRNA 2-thiolation is a highly conserved form of tRNA modification among living organisms. Here, we report the identification of SLG1 (Slender Guy 1), which encodes the cytosolic tRNA 2-thiolation protein 2 (RCTU2) in rice. SLG1 plays a key role in the response of rice plants to high-temperature stress at both seedling and reproductive stages. Dysfunction of SLG1 results in plants with thermosensitive phenotype, while overexpression of SLG1 enhances the tolerance of plants to high temperature. SLG1 is differentiated between the two Asian cultivated rice subspecies, indica and japonica, and the variations at both promoter and coding regions lead to an increased level of thiolated tRNA and enhanced thermotolerance of indica rice varieties. Our results demonstrate that the allelic differentiation of SLG1 confers indica rice to high-temperature tolerance, and tRNA thiolation pathway might be a potential target in the next generation rice breeding for the warming globe.

Accelerating Genetic Gain in Sugarcane Breeding Using Genomic Selection

Abstract: Sugarcane is a major industrial crop cultivated in tropical and subtropical regions of the world. It is the primary source of sugar worldwide, accounting for more than 70% of world sugar consumption. Additionally, sugarcane is emerging as a source of sustainable bioenergy. However, the increase in productivity from sugarcane has been small compared to other major crops, and the rate of genetic gains from current breeding programs tends to be plateauing. In this review, some of the main contributors for the relatively slow rates of genetic gain are discussed, including (i) breeding cycle length and (ii) low narrow-sense heritability for major commercial traits, possibly reflecting strong non-additive genetic effects involved in quantitative trait expression. A general overview of genomic selection (GS), a modern breeding tool that has been very successfully applied in animal and plant breeding, is given. This review discusses key elements of GS and its potential to significantly increase the rate of genetic gain in sugarcane, mainly by (i) reducing the breeding cycle length, (ii) increasing the prediction accuracy for clonal performance, and (iii) increasing the accuracy of breeding values for parent selection. GS approaches that can accurately capture non-additive genetic effects and potentially improve the accuracy of genomic estimated breeding values are particularly promising for the adoption of GS in sugarcane breeding. Finally, different strategies for the efficient incorporation of GS in a practical sugarcane breeding context are presented. These proposed strategies hold the potential to substantially increase the rate of genetic gain in future sugarcane breeding.

Genetic Analysis of Agronomic Traits and Grain Iron and Zinc Concentrations in a Doubled Haploid Population of Rice (Oryza sativa L.).

Abstract: The development of micronutrient dense rice varieties with good agronomic traits is one of the sustainable and cost-effective approaches for reducing malnutrition. Identification of QTLs for high grain Fe and Zn, yield and yield components helps in precise and faster development of high Fe and Zn rice. We carried out a three-season evaluation using IR05F102 x IR69428 derived doubled-haploid population at IRRI. Inclusive composite interval mapping was carried out using SNP markers and Best Linear Unbiased Estimates of the phenotypic traits. A total of 23 QTLs were identified for eight agronomic traits and grain Fe and Zn concentration that explained 7.2 to 22.0% PV. A QTL by environment interaction analysis confirmed the stability of nine QTLs, including two QTLs for Zn on chromosomes 5 and 12. One epistatic interaction for plant height was significant with 28.4% PVE. Moreover, five QTLs were identified for Fe and Zn that harbor several candidate genes, e.g. OsZIP6 on QTL qZn5.1. A number of QTLs were associated with a combination of greater yield and increased grain Zn levels. These results are useful for development of new rice varieties with good agronomic traits and high grain Zn using MAS, and identification of genetic resources with the novel QTLs for grain Zn.

Wheat dwarfing influences selection of the rhizosphere microbiome

Abstract: The development of dwarf wheat cultivars combined with high levels of agrochemical inputs during the green revolution resulted in high yielding cropping systems. However, changes in wheat cultivars were made without considering impacts on plant and soil microbe interactions. We studied the effect of these changes on root traits and on the assembly of rhizosphere bacterial communities by comparing eight wheat cultivars ranging from tall to semi-dwarf plants grown under field conditions. Wheat breeding influenced root diameter and specific root length (SRL). Rhizosphere bacterial communities from tall cultivars were distinct from those associated with semi-dwarf cultivars, with higher differential abundance of Actinobacteria, Bacteroidetes and Proteobacteria in tall cultivars, compared with a higher differential abundance of Verrucomicrobia, Planctomycetes and Acidobacteria in semi-dwarf cultivars. Predicted microbial functions were also impacted and network analysis revealed a greater level of connectedness between microbial communities in the tall cultivars relative to semi-dwarf cultivars. Taken together, results suggest that the development of semi-dwarf plants might have affected the ability of plants to recruit and sustain a complex bacterial community network in the rhizosphere.

The role of conventional plant breeding in ensuring safe levels of naturally occurring toxins in food crops

Abstract: Background The process of selecting superior performing plants for food, feed and fiber products dates back more than 10,000 years and has been substantially refined in the last century. While the perceived risks posed by genetically engineered crop plants has been extensively addressed, the extant levels of naturally occurring plant toxins in food crops has received far less attention. Scope and approach This review discusses how conventional breeding practices are used by plant breeders to develop safe new food crop varieties. Crops are grouped into two categories: 1) crop plants with no significant plant-produced toxins; and 2) crop plants with known plant-produced natural toxins. Examples and crop case studies from each category are used to illustrate the safety considerations of breeding these economically important crops and how plant breeding practices are adjusted prior to commercialization, depending on whether the crop produces known natural toxin(s). Key findings and conclusions Conventional breeding practices, such as cross- or self-pollinating, shuffle genetic allelic combinations to produce new progeny varieties without giving rise to novel uncharacterized biosynthetic pathways. Therefore, plant breeders can fine tune their practices depending on the crop and specific known natural toxins inherent to that crop species, thereby ensuring a safe food supply for consumers. Breeders often select different varieties of a single food crop for use in disparate markets, each with unique breeding selection practices depending on the desirable characteristics and safety considerations for the portion of the plant that is consumed and the nature of the particular processing industry.

Ancient wheat varieties have a higher ability to interact with plant growth‐promoting rhizobacteria

Abstract: Plant interactions with plant growth-promoting rhizobacteria (PGPR) are highly dependent on plant genotype. Modern plant breeding has largely sought to improve crop performance but with little focus on the optimization of plant × PGPR interactions. The interactions of the model PGPR strain Pseudomonas kilonensis F113 were therefore compared in 199 ancient and modern wheat genotypes. A reporter system, in which F113 colonization and expression of 2,4-diacetylphloroglucinol biosynthetic genes (phl) were measured on roots was used to quantify F113 × wheat interactions under gnotobiotic conditions. Thereafter, eight wheat accessions that differed in their ability to interact with F113 were inoculated with F113 and grown in greenhouse in the absence or presence of stress. F113 colonization was linked to improved stress tolerance. Moreover, F113 colonization and phl expression were higher overall on ancient genotypes than modern genotypes. F113 colonization improved wheat performance in the four genotypes that showed the highest level of phl expression compared with the four genotypes in which phl expression was lowest. Taken together, these data suggest that recent wheat breeding strategies have had a negative impact on the ability of the plants to interact with PGPR.

CRISPR-mediated accelerated domestication of African rice landraces.

Abstract: African Oryza glaberrima and Oryza sativa landraces are considered valuable resources for breeding traits due to their adaptation to local environmental and soil conditions. They often possess superior resistance to endemic pests and tolerance to drought and nutrient deficiencies when compared to the “imported” high production Asian rice varieties. In contrast, “domestication traits” such as seed shattering, lodging, and seed yield are not well established in these African landraces. Therefore, the use of these African varieties for high production agriculture is limited by unpredictable yield and grain quality. We are addressing this shortcoming by developing protocols for genetically transforming African landraces to allow the use of CRISPR-Cas mediated breeding approaches. Here we use as proof of concept the cultivated African landrace Kabre to target selected known “domestication loci” and improve the agronomic potential of Kabre rice. Stable genetic transformation with CRISPR-Cas9-based vectors generated single and simultaneous multiple gene knockouts. Plants with reduced stature to diminish lodging were generated by disrupting the HTD1 gene. Furthermore, three loci shown to control seed size and/or yield (GS3, GW2 and GN1A) were targeted using a multiplex CRISPR-Cas9 construct. This resulted in mutants with significantly improved seed yield. Our study provides an example of how new breeding technologies can accelerate the development of highly productive African landrace rice varieties, an important advancement considering that Africa is a hotspot for worldwide population growth and therefore prone to food shortage.

Prospects of GWAS and predictive breeding for European winter wheat's grain protein content, grain starch content, and grain hardness.

Abstract: Grain quality traits determine the classification of registered wheat (Triticum aestivum L.) varieties. Although environmental factors and crop management practices exert a considerable influence on wheat quality traits, a significant proportion of the variance is attributed to the genetic factors. To identify the underlying genetic factors of wheat quality parameters viz., grain protein content (GPC), grain starch content (GSC), and grain hardness (GH), we evaluated 372 diverse European wheat varieties in replicated field trials in up to eight environments. We observed that all of the investigated traits hold a wide and significant genetic variation, and a significant negative correlation exists between GPC and GSC plus grain yield. Our association analyses based on 26,694 high-quality single nucleotide polymorphic markers revealed a strong quantitative genetic nature of GPC and GSC with associations on groups 2, 3, and 6 chromosomes. The identification of known Puroindoline-b gene for GH provided a positive analytic proof for our studies. We report that a locus QGpc.ipk-6A controls both GPC and GSC with opposite allelic effects. Based on wheat's reference and pan-genome sequences, the physical characterization of two loci viz., QGpc.ipk-2B and QGpc.ipk-6A facilitated the identification of the candidate genes for GPC. Furthermore, by exploiting additive and epistatic interactions of loci, we evaluated the prospects of predictive breeding for the investigated traits that suggested its efficient use in the breeding programs.

New Insight into the Composition of Wheat Seed Microbiota.

Abstract: Endophytes are associated with host plants throughout their life history from seed germination to fruit development One of the most important plant organs colonized by endophytic microbiota is the seed The aim of this study was to determine the structure of the seed core microbiome inhabiting the endosperms and embryos of eight wheat cultivars with the use of a culture-independent technique The seeds of Triticum aestivum L cv Hondia, Wilejka, STH, Opcja, Tybalt, Euforia and Triticum spelta L cv Rokosz and Schwabencorn (producer: Plant Breeding Strzelce Sp z oo Group IHAR) were studied Rokosz and Hondia were cultured in vitro and in vivo to identify obligatory bacterial endophytes A restrictive analysis of reads originating from the in vitro plants has demonstrated that the bacterial genera Paenibacillus and Propionibacterium inhabiting Rokosz and Hondia plants have a status of obligatory microorganisms Greater biodiversity of seed-borne endophytes was found in the seed endosperms than in the embryos The multiple comparison analysis of the OTU abundance indicated that the seed part significantly influenced the relative abundance The seed-born microbiome is not statistically significantly dependent on the wheat cultivars; however, it cannot be claimed that every wheat seed is the same

Green revolution 'stumbles' in a dry environment: Dwarf wheat with Rht genes fails to produce higher grain yield than taller plants under drought.

Abstract: Rht genes control reduced height in wheat, and two identified loci, Rht1 (Rht-B1b) and Rht2 (Rht-D1b) and mutants thereof, were central in achieving the much celebrated \"Green revolution\". Dwarf and semi-dwarf wheat plants have thicker and shorter stems and are less prone to lodging in irrigated fields, resulting in much higher grain yield. Serious limitations, however, have begun to emerge following cultivation of dwarf or semi-dwarf wheat plants in drier environments. A clear grain yield penalty in dwarf and semi-dwarf compared to taller wheats has been reported for young plants, particularly under early and severe drought. Shorter coleoptiles, smaller leaves with altered thickness, and insensitivity to gibberellic acid were identified as the major biological factors responsible for an increased vulnerability to drought in dwarf or semi-dwarf wheat seedlings. This means that, in dry conditions, tall and fast-growing wheat plants with good tolerance to drought may offer higher grain yields than \"Green revolution\" wheat. In a future climate where drier environments are more likely, tall wheat genotypes, or those only moderately reduced in stature that carry alternative or novel Rht genes and alleles, may be better suited to many wheat-growing regions. Dwarf and semi-dwarf wheat genotypes are likely, however, to remain the best choice for irrigated or well-watered and fertilised fields where their high yield potential can be realised. This article is protected by copyright. All rights reserved.

Population structure and genetic diversity analyses of common bean germplasm collections of East and Southern Africa using morphological traits and high-density SNP markers.

Abstract: Knowledge of genetic diversity in plant germplasm and the relationship between genetic factors and phenotypic expression is vital for crop improvement. This study's objectives were to understand the extent of genetic diversity and population structure in 60 common bean genotypes from East and Southern Africa. The common bean genotypes exhibited significant (p<0.05) levels of variability for traits such as days to flowering (DTF), days to maturity (DTM), number of pods per plant (NPP), number of seeds per pod (NSP), and grain yield per hectare in kilograms (GYD). About 47.82 per cent of the variation among the genotypes was explained by seven principal components (PC) associated with the following agronomic traits: NPP, NFF (nodes to first flower), DTF, GH (growth habit) and GYD. The SNP markers revealed mean gene diversity and polymorphic information content values of 0.38 and 0.25, respectively, which suggested the presence of considerable genetic variation among the assessed genotypes. Analysis of molecular variance showed that 51% of the genetic variation were between the gene pools, while 49% of the variation were within the gene pools. The genotypes were delineated into two distinct groups through the population structure, cluster and phylogenetic analyses. Genetically divergent genotypes such as DRK57, MW3915, NUA59, and VTTT924/4-4 with high yield and agronomic potential were identified, which may be useful for common bean improvement.

Genetic variation and diversity for grain iron, zinc, protein and agronomic traits in advanced breeding lines of pearl millet [Pennisetum glaucum (L.) R. Br.] for biofortification breeding

Abstract: Genetic improvements of iron (Fe) and zinc (Zn) content in pearl millet [Pennisetum glaucum (L) R Br] may reduce the problems of anemia and stunted growth among millet dependent staple food consumers The availability of variation in diverse-breeding lines is essential to improve grain micronutrients in high-yielding cultivars This study aimed to determine the extent of variability, heritability and diversity for grain Fe, Zn and protein, along with key agronomic traits, in 281 advanced breeding lines bred at ICRISAT and evaluated across two seasons (environments) A pooled analysis of variance displayed significant variation for all these traits Highest variability was recorded for Fe (35–116 mg kg−1), Zn (21–80 mg kg−1), and protein (6–18%), and a three-fold variation was observed for panicle length, panicle girth and 1000-grain-weight (TGW) Diversity analysis showed 10 clusters Cluster-III had maximum lines (25%) and Cluster-V showed the highest mean values for Fe, Zn, protein and TGW These results highlight the success of breeding program that aimed both the maintenance and creation of genetic variability and diversity A significant positive correlation among Fe, Zn, protein and TGW indicated the potential for simultaneous improvement Grain yield had a non-significant association with Fe and Zn, while protein showed a negative correlation These results suggest that significant variability exists in elite-breeding lines, thus highlighting an opportunity to breed for biofortified varieties without compromising on the grain yield The lines with high Fe, Zn and protein content can be used as hybrid parents and may also help in further genetic investigations

Marker-assisted selection for grain number and yield-related traits of rice (Oryza sativa L.).

Abstract: Continuous rise in the human population has resulted in an upsurge in food demand, which in turn demand grain yield enhancement of cereal crops, including rice. Rice yield is estimated via the number of tillers, grain number per panicles, and the number of spikes present per panicle. Marker-assisted selection (MAS) serve as one of the best ways to introduce QTLs/gene associated with yield in the rice plant. MAS has also been employed effectively in dissecting several other complex agricultural traits, for instance, drought, cold tolerance, salinity, etc. in rice plants. Thus, in this review, authors attempted to collect information about various genes/QTLs associated with high yield, including grain number, in rice and how different scheme of MAS can be employed to introduce them in rice (Oryza sativa L.) plant, which in turn will enhance rice yield. Information obtained to date suggest that, numerous QTLs, e.g., Gn1a, Dep1, associated with grain number and yield-related traits, have been identified either via mapping or cloning approaches. These QTLs have been successfully introduced into rice plants using various schemes of MAS for grain yield enhancement in rice. However, sometimes, MAS does not perform well in breeding, which might be due to lack of resources, skilled labors, reliable markers, and high costs associated with MAS. Thus, by overcoming these problems, we can enhance the application of MAS in plant breeding, which, in turn, may help us in increasing yield, which subsequently may help in bridging the gap between demand and supply of food for the continuously growing population.

Exploring of Walnut Genetic Resources in Kazakhstan and Evaluation of Promising Selections

Abstract: Kazakhstan has very rich walnut genetic resources; however there is no ongoing walnut breeding program. Kazakhstan government has several projects in cooperation with Russia, USA, Bulgaria, Czech Republic and Poland for plant breeding purposes. In the present research walnut genetic resources originated from Jabagil, Tulkibas, Sayram, Lenger, and Botanical Garden of International Hodja Ahmet Yesevi Turkish-Kazakh University of Kazakhstan were evaluated during 2015-2018. In the pre-selection stage, 47 genotypes were selected according to their lateral bearing, disease and pest tolerance. In the next step, 10 genotypes with high nut quality and high yield were selected. These genotypes were grafted onto seedling walnut rootstocks in Turkey. All of the grafted genotypes had fruit at the first year. Among 47 genotypes, we recorded nut weight between 6.21-15.18 g, kernel weight 2.36-6.64 g, kernel percentage 33.55-70.96% and average nut length 2.61-4.19 cm and nut diameter between 2.65 to 3.39 cm. The selected genotypes have been found to have very low fruit quality compared to commercial walnut varieties in the world. However, these genotypes have been evaluated as a good genetic resource for lateral bearing which can be used in breeding programs.

Genetic structure and molecular diversity of Brazilian grapevine germplasm: Management and use in breeding programs.

Abstract: The management of germplasm banks is complex, especially when many accessions are involved. Microsatellite markers are an efficient tool for assessing the genetic diversity of germplasm collections, optimizing their use in breeding programs. This study genetically characterizes a large collection of 410 grapevine accessions maintained at the Agronomic Institute of Campinas (IAC) (Brazil). The accessions were genotyped with 17 highly polymorphic microsatellite markers. Genetic data were analyzed to determine the genetic structure of the germplasm, quantify its allelic diversity, suggest the composition of a core collection, and discover cases of synonymy, duplication, and misnaming. A total of 304 alleles were obtained, and 334 unique genotypes were identified. The molecular profiles of 145 accessions were confirmed according to the literature and databases, and the molecular profiles of more than 100 genotypes were reported for the first time. The analysis of the genetic structure revealed different levels of stratification. The primary division was between accessions related to Vitis vinifera and V. labrusca, followed by their separation from wild grapevine. A core collection of 120 genotypes captured 100% of all detected alleles. The accessions selected for the core collection may be used in future phenotyping efforts, in genome association studies, and for conservation purposes. Genetic divergence among accessions has practical applications in grape breeding programs, as the choice of relatively divergent parents will maximize the frequency of progeny with superior characteristics. Together, our results can enhance the management of grapevine germplasm and guide the efficient exploitation of genetic diversity to facilitate the development of new grape cultivars for fresh fruits, wine, and rootstock.

Genetic Progress of Seed Yield and Nitrogen Use Efficiency of Brazilian carioca Common Bean Cultivars Using Bayesian Approaches.

Abstract: Common bean (Phaseolus vulgaris L.) is one of the most important crops worldwide and is considered an essential source of proteins, fibers, and minerals in the daily diet of several countries. Nitrogen (N) is considered the most important nutrient for common bean crop. On the other hand, the reduction of chemical fertilizers is a global challenge, and the development of cultivars with more N use efficiency (NUsE) is considered one of the main strategies to reduce the amount of N fertilizers. Genetic progress of NUsE has been reported in several crops; however, there was still no quantity in common bean. In this study, our goal was to analyze the genetic progress of seed yield (SY) and NUsE-related traits of 40 carioca common bean cultivars release from 1970 to 2017 in eight environments under low (zero) or high N (40 kg ha-1) in top-dressing. Genetic progress, principal component analysis, correlations among traits, and cultivar stability were analyzed using Bayesian approaches. The lowest values of the deviance information criterion (DIC) for the full model tested indicated the presence of the genotype × N × environment interaction for all evaluated traits. Nitrogen utilization efficiency (NUtE) and nitrogen uptake efficiency (NUpE) were the traits that most contributed to discriminate cultivars. The genetic progress of SY under high N (0.53% year-1, 95% HPD = 0.39; 0.65% year-1) was similar to that obtained in low N conditions (0.48% year-1, 95% HPD = 0.31; 0.64% year-1). These results indicate that modern cultivars do not demand more N fertilizers to be more productive. In addition, we observed a high genetic variability for NUsE-related traits, but there was no genetic progress for these variables. SY showed negative correlation with seed protein content (Prot) in both N conditions, and there was no reduction in Prot in modern cultivars. Both modern and old cultivars showed adaptability and stability under contrasting N conditions. Our study contributed to improve our knowledge about the genetic progress of common bean breeding program in Brazil in the last 47 years, and our data will help researchers to face the challenge of increase NUsE and Prot in the next few years.

Genetic Advancement in Dry Pea (Pisum sativum L.): Retrospect and Prospect

Abstract: Dry pea or field pea is one of the most important and highly productive cool season pulse crops grown worldwide. There are several biotic and abiotic stresses which are the key constraints in achieving potential production of dry pea. Among biotic stresses, fungal diseases such as powdery mildew, rust, root rots, wilt, common root rot and ascochyta blight are the most common and severely affecting the crop at different growth stages. In case of abiotic stresses, high temperature, drought and frost are frequently occurring and reduce quantity and quality of produces. Hence, genetic improvement for aforesaid traits is important globally and needs to be addressed using conventional and molecular breeding approaches together to accelerate the breeding programme. Genetic improvement of pea began with domestication and has been aid on by decades of research through incorporation of novel traits from wild germplasm and landraces as well as pyramiding multiple constructive alleles in well-adapted genetic backgrounds. Sincere efforts have been made during recent past in terms of improving plant type and tolerance/resistant to important biotic and abiotic stresses around the world. Several major and minor genes/QTLs have been dissected controlling the important biotic and abiotic stresses. The introgression of genes for these resistant sources is possible using marker-assisted selection to speed up dry pea breeding programme more efficiently and precisely due to the availability of comprehensive genetic maps and reliable DNA markers. This book chapter briefly elaborates about the research accomplishment made so far for improvement of major traits and future perspectives to enhance dry pea productivity through genetic improvement.

Genetic analysis and fine mapping of the gall midge resistance gene Gm5 in rice (Oryza sativa L.).

Abstract: The rice gall midge resistance gene, Gm5, confers remarkable antibiosis and is located in the same region on chromosome 12 in three different rice varieties. Fine mapping narrowed this region to a 49-kb segment and identified two candidate genes showing remarkable response to GM infestation. The Asian rice gall midge (GM; Orseolia oryzae; Diptera: Cecidomyiidae) invades rice shoots and forms galls, adversely affecting plant growth and yield production. Thus, the development of resistant varieties through the identification, mapping, and application of GM resistance genes is considered the most efficient strategy for managing this insect. Here, a GM resistance survey of F2 populations derived from intercrosses between resistant rice varieties ‘ARC5984,’ ‘570011,’ and ‘ARC5833’ indicated that the resistance gene Gm5 was located on the same chromosomal region in the three varieties. For the initial mapping, three independent F2 mapping populations were developed for the three resistant varieties, and the Gm5 gene was consistently mapped to the same chromosomal region near marker 12M22.6. Fine mapping, which was conducted using the BC1F2 and BC2F2 populations derived from the 9311/ARC5984 cross, narrowed the Gm5 gene region to a 49-kb segment flanked by the markers Z57 and Z64. In the final mapped region, we detected 10 candidate genes, of which six were analyzed for their relative expression. Consequently, two of these genes, Os12g36830 and Os12g36880, showed significantly higher expression in GM-resistant plants than in GM-susceptible plants at 24 and 72 h after GM infestation. Finally, the PCR amplification of markers 12M22.5 and 12M22.6 yielded clear single bands, and these markers were effectively applied for the marker-assisted selection (MAS) of the Gm5 gene. With the developed MAS markers, the fine mapping of this resistance gene will facilitate its map-based cloning and incorporation into insect-resistant rice varieties through breeding.

Characteristics of powdery mildew and its importance for wheat grown in Poland.

Abstract: Powdery mildew of grasses and cereals (Blumeria graminis) is a fungal plant disease which is caused by species of fungi from the Erysiphaceae order. B. graminis is a biotrophic parasite, biologically diverse parasite with a high degree of specialization in certain host species and with numerous physiological breeds adapted to different varieties of a particular host species. In Poland, powdery mildew of cereals and grasses is recorded every year, and its greatest intensity is in south-eastern and south-western regions. The degree of infestation by B. graminis varies every year. This means that the disease occurs every year, in greater or lesser severity. Therefore, it requires monitoring (harmfulness thresholds) and chemical control practically in every vegetation season. Nowadays, an important role is played by immunological breeding. In breeding programs, resistance genes from wild crop forms, primitive and indigenous varieties are an effective tool. The introduction of effective resistance genes into cultivated varieties is a common procedure used in breeding program. The aim of this study was to describe the fungal disease of plants from the group of powdery mildews caused by B. graminis as an overview.

Genetic analysis of agronomic traits in elite sugarcane (Saccharum spp.) germplasm.

Abstract: Sugarcane (Saccharum spp.) is an important economic crop, supplying up to 80% of the table sugar and ~60% of bio-ethanol worldwide. Due to population growth and dwindling fossil-fuel reserves, the demand for sugar and bio-ethanol requires significant improvement in sugarcane production. Breeding sugarcane cultivars with high-performance agronomic traits is undoubtedly the most efficient way to achieve this goal. Therefore, evaluating agronomic traits and dissecting underlying loci are critically important for this aim steps in providing genetic resources and molecular markers for selection. In this study, we assembled a diversity panel of 236 elite sugarcane germplasms originally collected from 12 countries. We evaluated 28 agronomic traits in the diversity panel with three replicates. The diversity panel was genotyped using amplified fragment length polymorphism markers, and a total of 1,359 markers were generated. Through the genome-wide association study, we identified three markers significantly associated with three traits evaluated at a stringent threshold (P < 0.05 after Bonferroni correction). The genotypes of the three associated markers grouped respective trait values into two distinct groups, supporting the reliability of these markers for breeding selection. Our study provides putative molecular markers linked to agronomic traits for breeding robust sugarcane cultivars. Additionally, this study emphasized the importance of sugarcane germplasm introduced from other countries and suggested that the use of these germplasms in breeding programs depends on local industrial needs.

Twenty-two-year papaya breeding program: from breeding strategy establishment to cultivar development

Abstract: The papaya crop occupies 32 thousand hectares of planted area in Brazil, with a total annual production of 1.6 million tons (12.5% of the world supply). The country stands out in this scenario as the second biggest producer of the fruit worldwide, only after India. The narrow genetic base of the crop once limited its variability, but the use of classical and molecular plant breeding techniques has enabled the development of a number of higher-yielding cultivars with different levels of resistance to fungal diseases. However, many studies still ought to be undertaken to investigate the papaya crop, given the constant search for higher-yielding cultivars with quality and flavor attributes and the wide range of pathogens affecting the crop, which has not yet shown fully resistant genotypes. Advances in the genomics of papaya provide tools that may improve cultivar production and development systems. This article describes studies conducted by the genetics and breeding group at UENF, in a partnership with Caliman Agricola S.A., using conventional breeding, diallel cross, and topcross, among other techniques, for the development of 21 hybrids, which were registered at MAPA, in addition to studies with DNA-based markers for sex determination and for the generation of resistant and productive cultivars. This review focuses on the 22 years of conventional breeding for the most recent molecular progress in papaya growing. The information reported here is extremely useful for breeders to develop resistant, productive, and high-quality varieties through assisted selection.