Recurrent Selection Program Research Articles

Combining ability for agronomic traits among commercial maize hybrids under low and high nitrogen inputs targeting the development of breeding populations.

Commercial hybrids are the main germplasm source for developing maize lines in breeding programs in Brazil; additionally, nitrogen (N) is one the major limiting maize production in Brazilian tropical areas. Here, we assessed the combining ability among ten commercial hybrids under contrasting N inputs and selected the best parental hybrids to develop breeding populations for optimal and N-stress environments. We evaluated the 45 F1 crosses for agronomic traits under contrasting N inputs and over two summer seasons. A mixed model approach was used to estimate the variance components of general combining ability (GCA) and specific combining ability (SCA) as well as to predict the GCA and SCA effects. N-stress caused a reduction in GY (33.25%) of F1 crosses averaged across seasons. We found presence of combining ability (GCA and SCA) x N input interaction for grain yield (GY), days to pollen and plant stature. The parental hybrids showed differences in GCA for cycle and plant stature but not for GY, irrespective of N inputs. Additionally, the variance components of SCA were not significant (P>0.10) for GY under LN, whereas SCA was the major component accounting for variation among F1 crosses under HN. Based on estimates of GCA effects for cycle and plant height, we selected the hybrids BAL188, BM3061, GNZ7210, BRS1060 and DKB390 as sources of favorable alleles for earlier maturing and shorter stature maize for both N conditions and suggested that hybrids GNZ7201 and DKB390, and AG1051 and NS70, which presented very small estimates of SCA for GY, must be recombined to develop two synthetic populations to begin a reciprocal recurrent selection program, mainly for non N-stress environments.

Genetic dissection of green pod yield in dolichos bean, an orphan vegetable legume, using new molecular markers.

In the era of genomic-assisted breeding for crop improvement, developing new molecular markers and validating them for use in breeding programs are the prelude. Dolichos bean is one of the most important vegetable legume crops owing to its nutrient-rich green pods used as vegetables. Limitations in genomic resources, including molecular markers, restrict the accelerated improvement of the crop. In the present investigation, a set of 430 new simple sequence repeat markers was developed from sequence information of a reference variety. These markers included di- and tri-nucleotide repeats. The markers were assayed on an association panel, which was evaluated for green pod yield over 5years. A multi-locus model, FarmCPU, was used to assess the marker-trait association analysis. A total of 106 marker-trait associations were identified using an efficient mixed-model approach. Tri-nucleotide repeats were more informative and predominantly associated with trait. Among these markers, 17 were associated with a high level of significance. Markers LP-D-68 and LP-D-14 were identified with a high level of significance in 5-year pooled data and explained 12.70% and 12% of the phenotypic variance, respectively. These markers associated with a high level of confidence have significant scope for use in marker-assisted selection programmes. Other associated markers may be utilized for improving parents through marker-assisted recurrent selection or genomic selection programs.

Origin of current intermediate wheatgrass germplasm being developed for Kernza grain production

Intermediate wheatgrass (IWG, Thinopyrum intermedium [Host] Barkworth & D. R. Dewey) has been developed as a perennial grain crop for human consumption along with providing environmental benefits and ecosystem services. Grain and products derived from IWG cultivars improved for food production have been marketed under the registered trademark, Kernza. Development of IWG as a perennial grain crop began in 1980s with a phenotypic recurrent selection program as the Rodale Institute (RI) and the Big Flats Plant Material Center (BFPMC) used IWG plant introductions (PI) from the National Plant Germplasm System (NPGS) to improve populations of IWG. Initial selections were provided to The Land Institute (TLI) where they were subsequently improved for grain production, yet the identity of the founder material of improved, food-grade IWG has not been publicly documented. Recently recovered original documents have been used to reconstruct the early breeding program to identify the most likely 20 PIs that form the founders of modern food-grade IWG. Molecular data using genotyping-by-sequencing in current elite breeding material, and remnant seed and plant material from the initial RI selections have provided supporting evidence for the historical records. The genetic origin for food-grade IWG is focused between the Black Sea and Caspian Sea in the Stavropol region of Russia, with smaller contributions likely from collections as distant as Kazakhstan in the east to Turkey in the west. This work connects the flow of germplasm and utility of NPGS PIs to present day IWG grain cultivars being developed in multiple breeding programs around the world.

RECURRENT SELECTION FOR GENERAL AND SPECIFIC COMBINING ABILITY IN MAIZE

This study was aimed to identify efficiency of recurrent selection program to improve maize population. This program was applied to var. Buhooth 106 with var. 5012 Using RGCA with the inbred Zm7 for the production of RSCA. The recurrent selection program was implemented for four consecutive seasons (2020 - 2021) at the Fields Station of the College of Agriculture - University of Anbar. In the spring season 2020, 100 top crosses were obtained from both varieties and progeny. During the fall season 2020, an experiment was carried out to compare the top crosses of each variety RGCA and RSCA using a 10 × 10 partially balanced lattice design.. Six genotypes from each genetic population as well as Buhooth 106 and 5012 and Zm7 inbreds). The genotype-S1-2 RSCA achieved the lowest female flowering period for females 61.50 days, the highest number of rows per ear 17.80 rows, and the highest grain yield 177.82 g. The genotype-S1-3 RSCA achieved the highest leaf area 0.593 m2 and the highest number of kernels per row 43.11 kernel. The broad sense heritability of the traits of the number of rows and the number of kernels in the row and the yield of the plant reached 53.23%, 73.85% and 41.94%, respectively, and high genetic advance for kernels per row and grain yield of 4.79 and 15.52 respectively.

Viability of simultaneously selecting for grain yield and seed physiological quality in maize

ABSTRACT: Currently, the demand is not only for more productive corn hybrids, but also for those with high physiological seed quality. Seed quality is considered the sum of genetic, physical, physiological and sanitary attributes that directly interfere in plant vigor. The objective of this study was to evaluate the physiological parameters of the seeds of parents and maize inter varietal hybrids obtained in a reciprocal recurrent selection program through physiological and image analysis techniques and either to study the feasibility of simultaneously selecting for seed physiological quality and grain yield. Two experiments were performed, one in the field and the other in the laboratory. The evaluated traits in the field were days of female flowering, days of male flowering, insertion of the 1st ear, plant height and grain yield. For the physiological quality, the attributes of germination at four days, germination at seven days, vigor by the cold test, emergence speed index, and the ratio of the root length to shoot length were obtained using GroundEye®. Heterosis was measured for the agronomic and physiological traits. Through the contrast between the inter varietal crosse hybrids and reciprocals we measured the maternal effect. The magnitudes of heterosis allowed us to infer that as greater as the number of selection and recombination cycles, on average, greater heterosis for the traits grain yield and seed germination. The correlated response indicated that, high yield intervarietal hybrids have better seed physiological quality.

Genome-wide association analysis of plant architecture traits using doubled haploid lines derived from different cycles of the Iowa Stiff Stalk Synthetic maize population.

Selection in the Iowa Stiff Stalk Synthetic (BSSS) maize population for high yield, grain moisture, and root and stalk lodging has indirectly modified plant architecture traits that are important for adaptation to high plant density. In this study, we developed doubled haploid (DH) lines from the BSSS maize population in the earliest cycle of recurrent selection (BSSS), cycle 17 of reciprocal recurrent selection, [BSSS(R)17] and the cross between the two cycles [BSSS/BSSS(R)C17]. We aimed to determine the phenotypic variation and changes in agronomic traits that have occurred through the recurrent selection program in this population and to identify genes or regions in the genome associated with the plant architecture changes observed in the different cycles of selection. We conducted a per se evaluation of DH lines focusing on high heritability traits important for adaptation to high planting density and grain yield. Trends for reducing flowering time, anthesis-silking interval, ear height, and the number of primary tassel branches in BSSS(R)17 DH lines compared to BSSS and BSSS/BSSS(R)C17 DH lines were observed. Additionally, the BSSS(R)C17 DH lines showed more upright flag leaf angles. Using the entire panel of DH lines increased the number of SNP markers identified within candidate genes associated with plant architecture traits. The genomic regions identified for plant architecture traits in this study may help to elucidate the genetic basis of these traits and facilitate future work about marker-assisted selection or map-based cloning in maize breeding programs.

A genomic analysis of the University of Nebraska Replicated Recurrent Selection program.

The inbred-hybrid system of maize breeding closely resembles a reciprocal full-sib (RFS) selection program. Studying changes in genetic variation as a result of RFS selection can help illuminate long-standing questions regarding the relative roles of selection and genetic drift and help understand the nature of adaptation occurring in selection programs. The University of Nebraska-Lincoln Replicated Recurrent Selection (UNL-RpRS) program underwent eight cycles of replicated RFS and S1-progeny selection, making it a powerful system to study genomic changes accompanying selection for inter-population performance. The objectives of this study were to identify regions of the genome under selection after eight cycles of selection and evaluate the effect eight cycles of selection for inter-population full-sib performance had in expanding genome-wide and localized population structure. We address these questions with a large set of individuals sampled from the UNL-RpRS program with dense genotyping-by-sequence data. We found evidence of parallel selection signatures in the UNL-RpRS program, with a region on chromosome 7 being implicated in three of the four selection systems studied. Regions that displayed selection signatures across independently run selection programs represent regions likely to be capitalizing on standing genetic variation and support a soft sweep model of adaptation. We did not find selection to be a strong force in diverging populations undergoing RFS. This could be due to the nature of adaptation occurring in these populations, underlying gene action, or a result of unstable genetic topographies.

Realized genomic selection across generations in a reciprocal recurrent selection breeding program of Eucalyptus hybrids.

Genomic selection (GS) experiments in forest trees have largely reported estimates of predictive abilities from cross-validation among individuals in the same breeding generation. In such conditions, no effects of recombination, selection, drift, and environmental changes are accounted for. Here, we assessed the effectively realized predictive ability (RPA) for volume growth at harvest age by GS across generations in an operational reciprocal recurrent selection (RRS) program of hybrid Eucalyptus. Genomic best linear unbiased prediction with additive (GBLUP_G), additive plus dominance (GBLUP_G+D), and additive single-step (HBLUP) models were trained with different combinations of growth data of hybrids and pure species individuals (N = 17,462) of the G1 generation, 1,944 of which were genotyped with ~16,000 SNPs from SNP arrays. The hybrid G2 progeny trial (HPT267) was the GS target, with 1,400 selection candidates, 197 of which were genotyped still at the seedling stage, and genomically predicted for their breeding and genotypic values at the operational harvest age (6 years). Seedlings were then grown to harvest and measured, and their pedigree-based breeding and genotypic values were compared to their originally predicted genomic counterparts. Genomic RPAs ≥0.80 were obtained as the genetic relatedness between G1 and G2 increased, especially when the direct parents of selection candidates were used in training. GBLUP_G+D reached RPAs ≥0.70 only when hybrid or pure species data of G1 were included in training. HBLUP was only marginally better than GBLUP. Correlations ≥0.80 were obtained between pedigree and genomic individual ranks. Rank coincidence of the top 2.5% selections was the highest for GBLUP_G (45% to 60%) compared to GBLUP_G+D. To advance the pure species RRS populations, GS models were best when trained on pure species than hybrid data, and HBLUP yielded ~20% higher predictive abilities than GBLUP, but was not better than ABLUP for ungenotyped trees. We demonstrate that genomic data effectively enable accurate ranking of eucalypt hybrid seedlings for their yet-to-be observed volume growth at harvest age. Our results support a two-stage GS approach involving family selection by average genomic breeding value, followed by within-top-families individual GS, significantly increasing selection intensity, optimizing genotyping costs, and accelerating RRS breeding.

Molecular characterization of doubled haploid lines derived from different cycles of the Iowa Stiff Stalk Synthetic (BSSS) maize population.

Molecular characterization of a given set of maize germplasm could be useful for understanding the use of the assembled germplasm for further improvement in a breeding program, such as analyzing genetic diversity, selecting a parental line, assigning heterotic groups, creating a core set of germplasm and/or performing association analysis for traits of interest. In this study, we used single nucleotide polymorphism (SNP) markers to assess the genetic variability in a set of doubled haploid (DH) lines derived from the unselected Iowa Stiff Stalk Synthetic (BSSS) maize population, denoted as C0 (BSSS(R)C0), the seventeenth cycle of reciprocal recurrent selection in BSSS (BSSS(R)C17), denoted as C17 and the cross between BSSS(R)C0 and BSSS(R)C17 denoted as C0/C17. With the aim to explore if we have potentially lost diversity from C0 to C17 derived DH lines and observe whether useful genetic variation in C0 was left behind during the selection process since C0 could be a reservoir of genetic diversity that could be untapped using DH technology. Additionally, we quantify the contribution of the BSSS progenitors in each set of DH lines. The molecular characterization analysis confirmed the apparent separation and the loss of genetic variability from C0 to C17 through the recurrent selection process. Which was observed by the degree of differentiation between the C0_DHL versus C17_DHL groups by Wright's F-statistics (FST). Similarly for the population structure based on principal component analysis (PCA) revealed a clear separation among groups of DH lines. Some of the progenitors had a higher genetic contribution in C0 compared with C0/C17 and C17 derived DH lines. Although genetic drift can explain most of the genetic structure genome-wide, phenotypic data provide evidence that selection has altered favorable allele frequencies in the BSSS maize population through the reciprocal recurrent selection program.

Effect of three cycles of recurrent selection for yield in four Spanish landraces of maize

Landraces of maize (Zea mays L.) have a variability not found in the elite hybrids due to the bottleneck during selection. There is a renewed interest in using that variability, incorporating alleles for specific traits, or widening the general variability of elite germplasm. In Europe, there is also an interest in the direct use of local landraces by farmer’s associations seeking agriculture that preserves crop diversity. Pre-breeding programs are aimed to reduce the yield gap among landraces and improved materials. In the Misión Biológica de Galicia we have carried out three cycles of a S1 recurrent selection program for yield on four local landraces from Northwestern Spain with the objective of obtaining improved populations that might be cultivated by farmers and that could be used as sources of superior inbred lines. One hundred plants were selfed in each landrace and the S1 families were evaluated in a 10 × 10 simple lattice. The 20 S1 families with the highest grain yields were randomly intercrossed to form the selected population of each landrace. After three cycles of selection, each population and its cycles of selection were evaluated in three locations for two years. All the populations had a consistent yield gain in the first cycle of selection. However, the response in later cycles differed among the populations: one population had a continuous increase of 21% per cycle while two populations had a reduced yield in the last cycles. Our results highlight the need to include secondary traits to avoid unintentional indirect effects. We conclude that, in pre-breeding programs, it could be worthy to use large effective numbers to prevent inbreeding depression, particularly when the objective is the direct use of improved landraces. Another conclusion is that recurrent selection does not seem to be as efficient on European germplasm as it is on Corn Belt varieties. Finally, obtaining valuable new germplasm requires a sustained, long-term effort.

Graphical analysis of multi-environmental trials for wheat grain yield based on GGE-biplot analysis under diverse sowing dates

BackgroundInformation on the nature and extent of genetic and genotype × environment (GE) interaction is extremely rare in wheat varieties under different sowing dates. In the present study, the GGE biplot method was conducted to investigate genotype × environment interaction effects and evaluate the adaptability and yield stability of 13 wheat varieties across eight sowing dates, in order to facilitate comparison among varieties and sowing dates and identify suitable varieties for the future breeding studies.ResultsConsiderable genotypic variation was observed among genotypes for all of the evaluated traits, demonstrating that selection for these traits would be successful. Low broad sense heritability obtained for grain yield showed that, both genetic and non-genetic gene actions played a role in the control of this trait, and suggested that indirect selection based on its components which had high heritability and high correlation with yield, would be more effective to improve grain yield in this germplasm. Hence, selection based on an index may be more useful for improvement of this trait in recurrent selection programs. The results of the stability analysis showed that the environmental effect was a major source of variation, which captured 72.21% of total variation, whereas G and GE explained 6.94% and 18.33%, respectively. The partitioning of GGE through GGE biplot analysis showed that, the first two PCs accounted for 54.64% and 35.15% of the GGE sum of squares respectively, capturing a total of 89.79% variation. According to the GGE biplot, among the studied varieties, the performance of Gascogen was the least stable, whereas Sirvan, Roshan, and Pishtaz had superior performance under all sowing dates, suggesting that they have a broad adaptation to the diverse sowing dates. These varieties may be recommended for genetic improvement of wheat with a high degree of adaptation.ConclusionThe results obtained in this study demonstrated the efficiency of the GGE biplot technique for selecting high yielding and stable varieties across sowing dates.

Marker-Assisted Recurrent Selection for Pyramiding Leaf Rust and Coffee Berry Disease Resistance Alleles in Coffea arabica L.

In this study, marker-assisted recurrent selection was evaluated for pyramiding resistance gene alleles against coffee leaf rust (CLR) and coffee berry diseases (CBD) in Coffea arabica. A total of 144 genotypes corresponding to 12 hybrid populations from crosses between eight parent plants with desired morphological and agronomic traits were evaluated. Molecular data were used for cross-certification, diversity study and resistance allele marker-assisted selection (MAS) against the causal agent of coffee leaf rust (Hemileia vastatrix) and coffee berry disease (Colletotrichum kahawae). In addition, nine morphological and agronomic traits were evaluated to determine the components of variance, select superior hybrids, and estimate genetic gain. From the genotypes evaluated, 134 were confirmed as hybrids. The genetic diversity between and within populations was 75.5% and 24.5%, respectively, and the cluster analysis revealed three primary groups. Pyramiding of CLR and CBD resistance genes was conducted in 11 genotypes using MAS. A selection intensity of 30% resulted in a gain of over 50% compared to the original population. Selected hybrids with increased gain also showed greater genetic divergence in addition to the pyramided resistance alleles. The strategies used were, therefore, efficient to select superior coffee hybrids for recurrent selection programs and could be used as a source of resistance in various crosses.

Simultaneous effect of water deficit and mating systems in fennel (Foeniculum vulgare mill.): Genetics of phytochemical compositions and drought tolerance

Limited information is available on the impact of deliberate selfing compared with open-pollination and its interaction with water deficit on productivity and phytochemical constituents of essential oil in fennel (Foeniculum vulgare Mill.) and also the genetic analysis of traits. During this research, 21 selfed (S1) and 42 open-pollinated (OP) progenies of fennel developed in 2017–18 were evaluated in the field under well-watered and water deficit conditions in two years (2019 and 2020) for phytochemical and productivity traits. GC–MS analysis revealed that among the eight different compounds in the essential oil, trans-anethole, fenchone, estragole, and limonene were found to be the main constituents. Water deficit greatly decreased grain yield and essential oil content, α-pinene, trans-anethole, and anisaldehyde; while significantly increased β-myrcene, limonene, γ-terpinene, fenchone, and estragole, in both populations. Compared with open-pollination, selfing reduced the mean performance of seed and essential oil yield, β-myrcene, and limonene under normal and water deficit conditions, and α-pinene under normal condition, demonstrating the effects of inbreeding on these traits. The relationship between γ-terpinene and anisaldehyde was positive in the S1 population; while in the OP population, there was significant and negative association between these two constituents. The genetic analysis of traits indicated that additive gene action played an important role in controlling most of the traits, but that both additive and non-additive gene effects played a role in the genetic control of grain yield; indicating that selection based on an index may be more useful for improvement of grain yield in recurrent selection programs.

Identification of Fusarium wilt resistance loci in two major genetic backgrounds for oil palm breeding

Fusarium wilt (FW) caused by Fusarium oxysporum f. sp. elaeidis is the main disease of oil palm in Africa and is a latent threat to other producing regions. A long-term work based on a genetic survey of FW resistance using field observations and pre-nursery screening tests with inoculation resulted in FW resistant planting material whose resistance has not been overcome in 40 years. The genetic determinism of FW resistance has never been studied. Such information would eventually enable marker assisted selection (MAS) to ensure continuous improvement of planting material, through multi-trait selection (yield and disease or multiple diseases) and diversification of the genetic base. In this study, we used a pedigree-based QTL mapping approach that took advantage of the extensive pre-nursery FW resistance data recorded in the framework of a reciprocal recurrent selection program in Benin Republic. Eight QTL regions were mapped in two major genetic backgrounds and favorable QTL alleles were identified in the current breeding populations. The QTL pattern was specific to the population studied in terms of number, location and genetic variance explained, highlighting the different genetic architecture of FW resistance depending on the genetic background. To investigate a putative trade-off between FW resistance and yield, FW resistance QTL genotypes were predicted in a population that was formerly evaluated for yield in the field. The effects on yield of a FW QTL were offset in the commercial planting material thanks to different effects on different yield components in both heterotic groups. These results shed light on FW resistance in oil palm and provide valuable information for the implementation of MAS in the breeding program. Considering that pre-nursery screening tests are widely used, the approach presented here could be implemented in other breeding programs to provide further insights into FW resistance, especially in the context of wider genetic diversity.

Strategies for the recurrent selection program in tobacco breeding for green leaf yield

In conducting a recurrent selection (RS) program in tobacco (Nicotiana tabacum L.), inbred and noninbred progenies as well as double-haploid (DH) progenies can be used. There is also the possibility of recombining the selected progenies using half-sib (HS) or full-sib (FS) progenies. To choose the best RS strategy, the breeder's equation can be used. When using inbred progenies with an allelic frequency other than 50%, one of the genetic variance components is the genetic covariance between additive effects and homozygous dominance effects (D1). This component may present negative values and is part of the numerator in the equation for gain from selection (GS). Thus, the objective of this study was to estimate the genetic variance components in a tobacco population and compare the different strategies to conduct RS. From an RS population, HS, FS, and S1:2 inbred progenies were evaluated in different experiments. The dominance variance was null. In this condition, the estimate of D1 is not significant, meaning that D1 does not influence the GS in the RS program. With the obtained estimates, the GS was estimated for the seven different strategies for conducting the RS program. The use of DH lines in tobacco RS represents the best strategy. Other strategies allow expressive GS, such as the alternate use of inbred and FS progenies, for evaluation and FS progenies for recombination.

Genetic Trends Estimation in IRRIs Rice Drought Breeding Program and Identification of High Yielding Drought-Tolerant Lines

Estimating genetic trends using historical data is an important parameter to check the success of the breeding programs. The estimated genetic trends can act as a guideline to target the appropriate breeding strategies and optimize the breeding program for improved genetic gains. In this study, 17 years of historical data from IRRI’s rice drought breeding program was used to estimate the genetic trends and assess the breeding program's success. We also identified top-performing lines based on grain yield breeding values as an elite panel for implementing future population improvement-based breeding schemes. A two-stage approach of pedigree-based mixed model analysis was used to analyze the data and extract the breeding values and estimate the genetic trends for grain yield under non-stress, drought, and in combined data of non-stress and drought. Lower grain yield values were observed in all the drought trials. Heritability for grain yield estimates ranged between 0.20 and 0.94 under the drought trials and 0.43–0.83 under non-stress trials. Under non-stress conditions, the genetic gain of 0.21% (10.22 kg/ha/year) for genotypes and 0.17% (7.90 kg/ha/year) for checks was observed. The genetic trend under drought conditions exhibited a positive trend with the genetic gain of 0.13% (2.29 kg/ha/year) for genotypes and 0.55% (9.52 kg/ha/year) for checks. For combined analysis showed a genetic gain of 0.27% (8.32 kg/ha/year) for genotypes and 0.60% (13.69 kg/ha/year) for checks was observed. For elite panel selection, 200 promising lines were selected based on higher breeding values for grain yield and prediction accuracy of > 0.40. The breeding values of the 200 genotypes formulating the core panel ranged between 2366.17 and 4622.59 (kg/ha). A positive genetic rate was observed under all the three conditions; however, the rate of increase was lower than the required rate of 1.5% genetic gain. We propose a recurrent selection breeding strategy within the elite population with the integration of modern tools and technologies to boost the genetic gains in IRRI’s drought breeding program. The elite breeding panel identified in this study forms an easily available and highly enriched genetic resource for future recurrent selection programs to boost the genetic gains.

Comparison between doubled haploid lines and lines obtained via the bulk method in tobacco

This study aimed to compare recombinant inbred lines (RIL) obtained via the bulk method with doubled haploid lines (DHL). For comparison, 190 DHL and 194 RIL were evaluated simultaneously at two different locations. Phenotypic and genetic parameters were estimated for the traits green leaf yield (GLY) and alkaloid content (ALK). The results of the RIL and DHL evaluations were similar for ALK. Conversely, estimates of genetic variation and heritability in the DHL were higher than those in the RIL for GLY. However, the mean estimate of the RIL was 13.3% higher than that of the DHL and thus, the annual gain with selection was higher for the RIL. The use of DHL in a recurrent selection program will be efficient in comparison to RIL if a large number of lines are obtained, which must undergo a preliminary selection before the most intensive evaluation to identify the lines to be recombined.

Eucalyptus breeding programs: a proposal for the use of inbred progênies

Background: This review aims to discuss alternatives for obtaining new clones of eucalyptus ( Eucalyptus spp.) with greater efficiency than current methods, as well as the feasibility of obtaining hybrid seeds. The commercial-scale use of eucalyptus hybrid seeds may reduce implantation costs and bring other advantages for forest exploitation. The proposal focuses on using inbred progenies (S 1, S 2...S g) to improve the species. Self-fertilization releases a greater proportion of undesirable alleles hidden in heterozygotes, increasing selection success. Results: From the best individuals of the inbred progenies, full-sibling (FS) progenies will be developed, allowing the selection of new clones and conduct recurrent selection programs. The hybrid seeds must be obtained, also from the FS evaluations, in each selfing generation (S g x S g). Simultaneously with the conduction of inbreeding generations, information must be gathered aiming to implement the strategy for obtaining hybrid seeds, such as verifying the feasibility of generating double haploid lines and looking for alternatives to facilitate the large-scale production of hybrid seeds. Conclusion: this review of research results can serve as an initial basis for obtaining new clones of eucalyptus with greater efficiency than current methods, as well as the feasibility of obtaining hybrid seeds.

Maize breeding for sustainable agricultural systems

In the present work, a recurrent selection program was initiated, between and within half-sib families in landrace maize, with the objective of obtaining, at the end of the process, a productive maize variety for agroecological cultivation systems adapted to the northeast region. A base population composed of 10 landrace varieties donated by farmers the region. In the base population, 60 half-sib families were selected. These were grown for selection among families, in Capistrano/CE, at Fazenda Repouso das Águas, in the agricultural year 2017/2018, in randomized blocks with three replications. It was used as a witness for a variety of BRS-Caatingueiro. The selection within the families was carried out in the agricultural year 2018/2019 at the Fazenda Experimental Piroás located in the municipality of Redenção/CE. 15 characteristics were evaluated in the selection among and 10 in the within families. In the selection between, the average production and productivity was 5.033,90 kg.ha-1 and 4.316,04 kg.ha-1, respectively. The superiority in relation to the witness was 8.67%. In the selection within, the average production and productivity was 4.448,413 kg.ha-1 and 3.998,41 kg.ha-1, respectively.

Reciprocal Recurrent Genomic Selection Is Impacted by Genotype-by-Environment Interactions.

Reciprocal recurrent genomic selection is a breeding strategy aimed at improving the hybrid performance of two base populations. It promises to significantly advance hybrid breeding in wheat. Against this backdrop, the main objective of this study was to empirically investigate the potential and limitations of reciprocal recurrent genomic selection. Genome-wide predictive equations were developed using genomic and phenotypic data from a comprehensive population of 1,604 single crosses between 120 female and 15 male wheat lines. Twenty superior female lines were selected for initiation of the reciprocal recurrent genomic selection program. Focusing on the female pool, one cycle was performed with genomic selection steps at the F2 (60 out of 629 plants) and the F5 stage (49 out of 382 plants). Selection gain for grain yield was evaluated at six locations. Analyses of the phenotypic data showed pronounced genotype-by-environment interactions with two environments that formed an outgroup compared to the environments used for the genome-wide prediction equations. Removing these two environments for further analysis resulted in a selection gain of 1.0 dt ha−1 compared to the hybrids of the original 20 parental lines. This underscores the potential of reciprocal recurrent genomic selection to promote hybrid wheat breeding, but also highlights the need to develop robust genome-wide predictive equations.