Crop Science

Hybrid crop breeding programs using a two-part strategy produced the most genetic gain, but a maximum avoidance of inbreeding crossing scheme was required to increase long-term genetic gain. The two-part strategy uses outbred parents to complete multiple generations per year to reduce the generation interval of hybrid crop breeding programs. The maximum avoidance of inbreeding crossing scheme manages genetic variance by maintaining uniform contributions and inbreeding coefficients across all crosses. This study performed stochastic simulations to quantify the potential of a two-part strategy in combination with two crossing schemes to increase the rate of genetic gain in hybrid crop breeding programs. The two crossing schemes were: (i) a circular crossing scheme, and (ii) a maximum avoidance of inbreeding crossing scheme. The results from this study show that the implementation of genomic selection increased the rate of genetic gain, and that the two-part hybrid crop breeding program generated the highest genetic gain. This study also shows that the maximum avoidance of inbreeding crossing scheme increased long-term genetic gain in two-part hybrid crop breeding programs completing multiple selection cycles per year, as a result of maintaining higher levels of genetic variance over time. The flexibility of the two-part strategy offers further opportunities to integrate new technologies to further increase genetic gain in hybrid crop breeding programs, such as the use of outbred training populations. However, the practical implementation of the two-part strategy will require the development of bespoke transition strategies to fundamentally change the data, logistics, and infrastructure that underpin hybrid crop breeding programs. Key messageHybrid crop breeding programs using a two-part strategy produced the most genetic gain by using outbred parents to complete multiple generations per year. However, a maximum avoidance of inbreeding crossing scheme was required to manage genetic variance and increase long-term genetic gain.

Breeding for less digestible starch in wheat can improve the health impact of bread and other wheat foods. Based on an established in vitro starch digestibility assay by Edwards et al. (2019) we developed a high-throughput assay to measure starch digestibility in hydrothermally processed samples for use in forward genetic approaches. Digestibility of purified starch from maize and wheat was measured using both methods and produced comparable results. Using the high-throughput assay, we estimated starch digestibility of 118 wheat landraces from the core Watkins collection and found wide variation across lines and elite UK varieties, (20% to 40% and 31% to 44% starch digested after 90 minutes respectively). Sieved flour fractions and purified starch for selected lines showed altered starch digestibility profiles compared with wholemeal flour, suggesting that matrix properties of flour rather than intrinsic properties of starch granules conferred the low starch digestibility observed.

High-quality malt is influenced by three primary factors: barley genotype, environmental conditions, and malting process. To effectively evaluate malting barley breeding material and assess how environmental changes influence malt quality, it is essential to have laboratory- scale malting methods that can produce malt approximating that produced by commercial malting operations. However, existing laboratory-scale malting procedures often demand large quantities of grain, rely on specialized equipment, and are costly. To overcome these challenges, we developed a small sample-scale benchtop malting method utilizing standard laboratory equipment and components available at hardware stores. We validated the method by conducting standard malt quality tests including diastatic power, -amylase activity, total malt protein, and wort composition (soluble protein, wort soluble/total malt protein, {beta}-glucan, free amino nitrogen, and malt extract). Our findings indicate that the benchtop malting method yields quality metrics comparable to those obtained from established small-scale and full-scale malting protocols. Furthermore, a key innovation of this system is the use of separate Erlenmeyer flasks for malting each sample. Unlike conventional shared malting systems, this design enables precise measurement and comparison of treatment effects across samples malted simultaneously. This reliable, low-cost, and efficient method provides a valuable tool for screening malt quality traits in breeding lines with limited sample sizes and for testing malting regimes aimed at improving malt quality and efficiency. Additionally, it offers an accessible solution for producing high-quality, research-scale malt in laboratories without dedicated quality assurance facilities.

CORE IDEASO_LINixtamalization moisture content can be selected early in breeding programs using NIR spectroscopy. C_LIO_LIYield does not significantly correlate with nixtamalization moisture content in diverse or elite populations. C_LIO_LIAdditive and dominance gene action impact nixtamalization moisture content in hybrid maize. C_LIO_LIGenomic prediction can be used to assess nixtamalization moisture content early in hybrid maize breeding. C_LI Nixtamalization moisture content, a measure of the quantity of water absorbed during the nixtamalization of a grain such as maize, has a large impact on the end-quality of masa-based products. An application to predict nixtamalization moisture content from raw inbred and hybrid maize grain was recently developed, but its utility in a breeding context has not been assessed. Important breeding considerations for nixtamalization moisture content were assessed in diverse maize hybrids, modern commercial hybrids, and historically high-acreage hybrids grown in up to three environments across two years. This study demonstrated that nixtamalization moisture content is heavily influenced by growing conditions, but sufficient genetic variance is present to allow breeders to make gains from selection. Contrary to prior theory, there was no substantial correlation between nixtamalization moisture content and yield suggesting breeders can select for both traits without negatively impacting either trait. Both additive and dominant genetic action was observed and genomic prediction was able to predict nixtamalization moisture content in hybrids with an average Spearmans rank correlation coefficient greater than 0.441 and a root mean square error below 0.006. The findings here suggest that nixtamalization moisture content can be selected for early in breeding cycles, allowing breeders to develop improved food-grade maize germplasm without negatively impacting important traits such as yield. PLAIN LANGUAGE SUMMARYPlant breeders need to understand the biological mechanisms underlying a trait of interest to maximize the efficiency of their efforts. Nixtamalization moisture content is a highly complex trait that is determined by both genetic and environmental factors. In this study, nixtamalization moisture content was assessed in a diverse set of hybrid and inbred maize to understand the biological mechanisms underlying nixtamalization moisture content. The relationship between nixtamalization moisture content and yield was assessed, the genetic architecture and mode of gene action underlying nixtamalization moisture content were evaluated, and the efficacy of genomic prediction in assessing nixtamalization moisture content was determined. The findings of this study will allow breeders to create optimized breeding strategies for nixtamalization moisture content, thus improving the raw materials that are used to produce globally consumed products such as tortillas and tortilla chips.

The presence or absence of awns - whether wheat heads are "bearded" or "smooth"- is the most visible phenotype distinguishing wheat cultivars. Previous studies suggest that awns may improve yields in heat or water-stressed environments, but the exact contribution of awns to yield differences remains unclear. Here we leverage historical phenotypic, genotypic, and climate data to estimate the yield effects of awns under different environmental conditions over a 12-year period in the Southeast US. Lines were classified as awned or awnless based on sequence data, and observed heading dates were used to associate grain fill periods of each line in each environment with climatic data and grain yield. In most environments, awn suppression was associated with higher yields, but awns were associated with better performance in heat-stressed environments more common at southern locations. Wheat breeders in environments where awns are only beneficial in some years may consider selection for awned lines to reduce year-to-year yield variability, and with an eye towards future climates.

Fusarium head blight (FHB) is an economically and environmentally concerning disease of wheat (Triticum aestivum L). A two-pronged approach of marker assisted selection (MAS) coupled with genomic selection (GS) has been suggested when breeding for FHB resistance. An historical dataset comprised of entries in the Southern Uniform Winter Wheat Scab Nursery (SUWWSN) from 2011-2021 was partitioned and used in genomic prediction. Two traits were curated from 2011-2021 in the SUWWSN: percent Fusarium damaged kernels (FDK) and Deoxynivalenol (DON) content. Heritability was estimated for each trait-by-environment combination. A consistent set of check lines was drawn from each year in the SUWWSN, and K-means clustering was performed across environments to assign environments into clusters. Two clusters were identified for FDK and three for DON. Cross-validation on SUWWSN data from 2011-2019 indicated no outperforming training population in comparison to the combined dataset. Forward validation for FDK on the SUWWSN 2020 and 2021 data indicated a predictive accuracy r {approx} 0.58 and r {approx} 0.53, respectively. Forward validation for DON indicated a predictive accuracy of r {approx} 0.57 and r {approx} 0.45, respectively. Forward validation using environments in cluster one for FDK indicated a predictive accuracy of r {approx} 0.65 and r {approx} 0.60, respectively. Forward validation using environments in cluster one for DON indicated a predictive accuracy of r {approx} 0.67 and r {approx} 0.60, respectively. These results indicated that selecting environments based on check performance may produce higher forward prediction accuracies. This work may be used as a model to create a public resource for genomic prediction of FHB resistance traits across public wheat breeding programs. CORE IDEASO_LIThe data from the Southern Uniform Winter Wheat Nursery may be used for genomic prediction. C_LIO_LICreating training populations based on like-check performance improves forward genomic predictive accuracies. C_LIO_LIFiltering out locations with low genomic, per-plot, narrow-sense heritability may improve predictive accuracies. C_LI

ContextCold plasma is an ionised gas composed of reactive nitrogen and oxygen species, with demonstrated potential for improving wheat seed vigour. AimTo assess wheat seed vigour and grain quality after Blown-Arc plasma treatment. MethodsWheat seeds were treated with Blown-Arc plasma for 60 or 180 s from a distance of 21 cm in a closed environment to assess in vitro germination, seed quality, seedling emergence, and crop yield in the field. Key ResultsSeeds treated with Blown-Arc plasma showed significantly faster initial in vitro germination (day 4), although total germination by day 8 was similar to untreated controls. In the field, the treated seed showed no significant difference in seedling emergence in 2020, but in 2021 seed treated for 180 s produced a significantly lower number of seedlings, possibly due to differences in the soil microbial environment. The wheat grown from 180 s Blown-Arc plasma-treated seed produced more heads per plant; however, overall yield was unchanged. The treatment had no adverse effect on grain quality parameters, all remaining within acceptable Australian standards. ConclusionsBlown-Arc plasma did not alter seedling emergence, yield, or grain quality properties of the crop produced from treated wheat seeds. ImplicationsBlown-arc plasma is a safe treatment that can potentially increase wheat seed germination without affecting grain quality or yield. Faster germination of seeds when sown under adequate moisture may promote healthy root systems and plant growth. Further research is needed to determine how these benefits translate under variable field conditions in Australian wheat-growing regions.

The sterile pollen technique, which involves applying X-ray irradiated pollen to female plants, has shown promising results in reducing seed production in dioecious Palmer amaranth (Amaranthus palmeri S. Wats.). However, field-scale implementation of this method requires a carrier for pollen delivery, as applying pure pollen on a large scale is not practical. Additionally, variability in flowering time within and among individual plants may impact the techniques effectiveness. Mass pollination may also lead to a female-biased sex ratio in the progeny, a phenomenon known as certation. Therefore, in this study, we aimed to: (1) identify a suitable dry (inert) diluent and the most effective pollen-to-diluent ratio for large-scale application, and (2) determine the most effective combination of initiation time, frequency, and number of sterile pollen applications, and 3) test for evidence of certation in A. palmeri. Plants were grown in the greenhouse in summer 2021. Sterilized pollen irradiated at 300 Gy was mixed with talc or wheat powder flour, respectively, at six v/v ratios (pollen%/powder%) of 0/100 (powder alone), 5/95, 10/90, 25/75, 50/50, or 100/0 (pure irradiated pollen). An equal amount of the pollen-diluent powder mixture was then brushed onto the standardized lengths of inflorescence of receptive female plants. Flower and seed number on each inflorescence was counted and used to calculate seed set in each treatment. The findings showed that a minimum of 25% irradiated pollen in the mixture, either with talc powder or wheat flour, can effectively reduce seed set in A. palmeri. Building on this, a second round of greenhouse experiments was conducted in fall 2021, where female plants were pollinated with a 25% irradiated pollen and talc powder mixture using a powder duster. Pollination treatments were initiated at different times after anthesis (7, 14, and 21 days), and the number of applications varied (once, twice, or three times) with intervals of one, two, or three weeks between applications. The greatest reduction in seed output was achieved when sterile pollen application began seven days after anthesis and was repeated three times at 7-day intervals. Evidence of certation was also observed in A. palmeri, with the progeny of mass-pollinated females showing a higher female ratio (58%) compared to the open-pollinated population (47%). Mass pollination also led to a slight, though not statistically significant, reduction in plant size traits such as height and number of branches, providing an additional potential benefit of the sterile pollen technique.

Background and ObjectivesPericarp retention during nixtamalization directly influences masa quality, affecting texture, machinability, and nutritional content of staple foods such as tortillas and chips. Despite its industrial relevance, the underlying kernel traits that govern pericarp retention remain poorly characterized. This study aimed to assess an existing staining method to quantify pericarp retention based on visual evaluation, and identify the compositional and morphological characteristics of maize kernels that most strongly predict pericarp retention during nixtamalization. FindingsStain-based scoring of pericarp retention showed moderate correlation with directly measured pericarp mass, achieving a Pearsons correlation coefficient of 0.77 in the rapid cook test and 0.56 in the benchtop cook test. Pearson correlation coefficients of 18 compositional and morphological traits range from -0.294 to 0.538. Ground kernel ash content and initial pericarp quantity were the most correlated and predictive variables associated with pericarp retention. ConclusionsStain-based methods lack the resolution necessary for quantitative pericarp assessment. Initial pericarp quantity and ground kernel ash content are likely key determinants of nixtamalization pericarp retention. Significance and NoveltyThis study provides a first assessment on the impacts of morphological and compositional variation for pericarp retention, which can be built upon to develop improved varieties and cooking methods for product optimization.

Hybrid breeding is a method of selecting parental lines and determining crosses that are likely to yield the best hybrids. Genomic prediction (GP), a tool that uses genome wide markers, can be employed to predict the performance of untested hybrids based on general combining ability (GCA) of their parents. We investigated the potential of GP for GCA prediction in a commercial canola breeding program. We used female tester data, where many female lines are crossed with few male lines, to predict economically important traits in canola. Multi-year and location data for grain yield, oil, protein, days to flowering, days to maturity, total glucosinate and saturated fat were available for prediction. Three different cross-validation strategies were implemented to determine the predictive ability (PA) of each trait. In the first cross-validation scheme (CV1), a prediction model was validated using five-fold cross validation strategy. In the second cross-validation scheme (CV2), an unseen year was predicted using the previous years data as a training set. In the third cross-validation scheme (CV3), Inbred pe se performance was added to the training set to exploit the covariance between traits of inbred and hybrid trials. The highest PA was observed for CV1 while the lowest PA was seen for CV2. In CV1, PA ranged from 0.34 to 0.62. The highest PA was observed for protein (0.62) while the lowest PA was observed for days to maturity (0.34). For CV2, PA ranged from 0.16 to 0.46, while for CV3 PA ranged from 0.27 to 0.71. The highest PA for CV2 (0.46) and CV3 (0.71) was observed for total glucosinate while the lowest PA (0.16 CV2 and 0.27 -CV3) was for days to maturity. The current study demonstrates the potential of using marker information to select parents with the highest GCA to create the best hybrid combinations.

For popcorn, obtaining and identifying haploids are still challenging steps. We aimed to induce and screen haploids in popcorn using the Navajo phenotype, seedling vigor and ploidy level. We used the Krasnodar Haploid Inducer (KHI) in crosses with 20 popcorn source germplasms and five maize controls. The field trial design was completely randomized, with three replications. We assessed the efficacy of induction and of identification of haploids based on haploidy induction rate (HIR) and false positive and negative rates (FPR and FNR). Additionally, we also measured the penetrance of the Navajo marker gene (R1-nj). All putative haploids classified by R1-nj were germinated together with a diploid sample and evaluated for false positives and negatives based on vigor. Seedlings from 14 females were submitted to flow cytometry to determine the ploidy level. The HIR and penetrance were analyzed by fitting a generalized linear model with a logit link function. The HIR of the KHI, adjusted by cytometry, ranged from 0.0 to 1.2%, with a mean of 0.34%. The average FPR from screening based on the Navajo phenotype were 26.2% and 76.4%, by the vigor and ploidy, respectively. The FNR was zero. The penetrance of R1-nj ranged from 30.8 to 98.6%. The average number of seeds per ear in temperate germplasm (76) was lower than that obtained in tropical germplasm (98). There is induction of haploids in germplasm of tropical and temperate origin. We recommend the selection of haploids associating the Navajo phenotype with a direct method of confirming the ploidy level, such as flow cytometry. We also show that haploid screening based on Navajo phenotype and seedling vigor reduces misclassification. The origin and genetic background of the source germplasm influence the R1-nj penetrance. Because the known inducers are maize, developing doubled-haploid technology for popcorn hybrid breeding requires overcoming the unilateral cross-incompatibility.

The genus Amaranthus is composed of numerous annual herbs, several of which are primary driver weeds within annual production agricultural systems. In particular, Amaranthus tuberculatus, a dioecious species, is noteworthy for rapid growth rates, high fecundity, and an expanding geographic distribution. Interspecific hybridization within and between the subgenera Amaranthus and Acnidia is reported both in controlled environment and field studies, however a gap in knowledge exists with the subgenus Albersia. Interspecific hybridization may contribute to genetic diversity, and may contribute to the current range expansion of A. tuberculatus. Recently, a herbicide resistance survey of A. tuberculatus across five Midwestern states reported alleles of PPX2 similar to sequences of Amaranthus albus, a monoecious species. Here, we seek to generate empirical data for the hybridization potential of A. albus and A. tuberculatus through replicated, controlled crosses in a greenhouse. Of 65,000 progeny screened from A. albus grown with A. tuberculatus males, three were confirmed as hybrids. Hybrids were dioecious, possessed phenotypic traits of both species, and had limited to no fertility. DNA content analysis of backcross progeny suggested a polyploid state may be required for hybrid formation. Screening of 120 progeny of A. tuberculatus females grown with A. albus identified no hybrids, though a skew to female progeny was observed. The female skew may be due to apomixis or auto-pollination, the spontaneous generation of male flowers on otherwise female plants. Our results indicate that introgression between A. albus and A. tuberculatus will occur less frequently than what has often been reported from hybridization studies with different pairs of Amaranthus species.

Computer simulations of breeding strategies are an essential resource for tree breeders because they allow exploratory analyses into potential long-term impacts on genetic gain and inbreeding consequences without bearing the cost, time, or resource requirements of field experiments. Previous work has modeled the potential long-term implications on inbreeding and genetic gain using random mating and phenotypic selection. Reduction in sequencing costs has enabled the use of DNA marker-based relationship matrices in addition to or in place of pedigree-based allele sharing estimates; this has been shown to provide a significant increase in the accuracy of progeny breeding value prediction. A potential pitfall of genomic selection using genetic relationship matrices is increased coancestry among selections, leading to the accumulation of deleterious alleles and inbreeding depression. We used simulation to compare the relative genetic gain and risk of inbreeding depression within a breeding program similar to loblolly pine, utilizing pedigree-based or marker-based relationships over ten generations. We saw a faster rate of purging deleterious alleles when using a genomic relationship matrix based on markers that track identity-by-descent of segments of the genome. Additionally, we observed an increase in the rate of genetic gain when using a genomic relationship matrix instead of a pedigree-based relationship matrix. While the genetic variance of populations decreased more rapidly when using genomic-based relationship matrices as opposed to pedigree-based, there appeared to be no long-term consequences on the accumulation of deleterious alleles within the simulated breeding strategy.

Use of the morphogenic genes Baby Boom (Bbm) and Wuschel2 (Wus2), along with new ternary constructs, has increased the genotype range and the type of explants that can be used for maize transformation. In addition, altering the ectopic expression pattern for Bbm/Wus2 has resulted in rapid maize transformation methods that are faster and applicable to a broader range of inbreds. However, expression of Bbm/Wus2 can compromise the quality of regenerated plants, leading to sterility. We reasoned excising morphogenic genes after transformation but before regeneration would increase production of fertile T0 plants. We developed a method that uses an inducible site-specific recombinase (Cre) to excise morphogenic genes. The use of developmentally regulated promoters, such as Ole, Glb1, End2 and Ltp2, to drive Cre enabled excision of morphogenic genes in early embryo development and produced excised events at a rate of 25%-100%. A different strategy utilizing an excision-activated selectable marker produced excised events at a rate of 53.3%-68.4%; however, the transformation frequency was lower (12.9%-49.9%). The use of inducible heat shock promoters (e.g. Hsp17.7, Hsp26) to express Cre, along with improvements in tissue culture conditions and construct design, resulted in high frequencies of T0 transformation (29%-69%), excision (50%-97%), usable quality events (3.6%-14%), and few escapes (non-transgenic; 14%-17%) in three elite maize inbreds. Transgenic events produced by this method are free of morphogenic and marker genes.

Field pennycress (Thlaspi arvense L.), is a new oilseed winter annual crop being investigated as a source of biofuel in the United States. The purpose of this study is to assess long term survivability and dormancy of both wild-type pennycress and gene-edited golden pennycress seed. Seeds from one wild type and three gene-edited golden types that carried an edit to TT8 gene were buried at 2 cm and 15 cm depths under well-drained and poorly-drained field conditions. The seeds were exhumed at 2, 4, 6, 12, 18, and 24 months after burial and germinated to determine the viability of the seed over time. All golden seeded gene-edited lines decreased to 0% germination by 6 months while the wild black seeded variety ARV1 retained almost 60% germination after 2 years. A significant difference was seen in the ARV1 survival in the well- drained field but not in the poorly-drained field. However, there was no significant difference in seed viability for burial depth in the well-drained field but there was significant difference for burial depth in the poorly-drained field. These results indicate that gold seeded varieties carrying the edit to TT8 through gene-editing have dramatically decreased the survivability of the seed in the seedbank. Reduced survivability will greatly assist in the adoption of golden pennycress as a new viable off-season crop in the Midwest without concerns of adding to the seedbank or serving as weed pressure in primary crops.

Evaluating genetic gains over time is essential for assessing the success of breeding programs and refining strategies for ongoing improvement. Hard red spring (HRS) wheat is an important wheat class in the US and is primarily grown in the Northern Great Plains. Despite a long history of breeding efforts in this region, long-term quantification of genetic gains for key traits has remained limited. This study analyzes over sixty years of data from the USDA-coordinated Hard Red Spring Wheat Uniform Regional Nursery (HRSWURN) to evaluate genetic advancements in agronomic traits across multiple phases. A significant positive genetic gain of 0.61% per annum was observed for grain yield in HRS wheat released in the Northern US region, which is lower than the expected gains needed to meet future wheat demand. The change was 0.07% for test weight, -0.04% for days to heading, and -0.16% for plant height. Notably, sustained yield improvements have not affected grain protein levels since they were first measured in 1995, indicating that ongoing selection has effectively balanced grain yield and protein despite their negative correlation (r = -0.31). Assessment of genetic gains over 20-year phases suggested slowing rates of genetic gains for grain yield but did not indicate any plateaus. The realized genetic gains were generally higher for individual breeding programs when breeding for target environments, with the public breeding program in Minnesota observing gains of approximately 1% per annum. These findings highlight the significant impact of long-term breeding efforts and offer valuable insights for refining future breeding strategies.

Acrylamide is a neurotoxin and probable carcinogen formed as a processing contaminant during baking and production of different foodstuffs, including bread products. The amino acid asparagine is the limiting substrate in the Maillard reaction that produces acrylamide, so developing wheat varieties with low free asparagine concentrations in the grain is a promising approach to reduce dietary acrylamide exposure. A candidate gene approach was used to identify chemically-induced genetic variation in ASPARAGINE SYNTHETASE 2 (ASN2) genes that exhibit a grain-specific expression profile. In field trials, durum and common wheat lines carrying asn-a2 null alleles exhibited reductions in free asparagine concentration in their grains of between 9 and 34% compared to wild-type sister lines. These plants showed no significant differences in spikelet number, grain size and weight, germination or baking quality traits. These non-transgenic variants can be deployed without restriction in elite wheat germplasm to reduce acrylamide-forming potential with no negative impacts on quality or agronomic performance. Core ideasO_LIThree wheat ASPARAGINE SYNTHETASE 2 knockout alleles were characterized in field experiments. C_LIO_LIMutant alleles conferred significant reductions in grain free asparagine concentration. C_LIO_LIThe alleles did not affect quality or agronomic traits. C_LIO_LIThese non-transgenic alleles can be deployed without restriction in wheat breeding programs. C_LI

Crop wild relatives can serve as a source of variation for the genetic improvement of modern varieties. However, the realization of this genetic potential depends critically on the conservation of wild populations. In this study, five populations of Zea mays ssp. parviglumis, the closest relative of domesticated maize, were collected in Jalisco, Mexico and planted in a common garden. Eleven traits related to plant fitness were measured and evaluated in the context of genetic diversity and genetic load. Plants whose seed were sourced from larger, less disturbed populations had greater genetic diversity, lower genetic load, and possessed phenotypes associated with higher fitness, while plants sourced from smaller, heavily impacted populations had traits characteristic of lower fitness and increased genetic load. For example, plants from larger populations germinated more quickly, reached anthesis sooner, demonstrated a higher level of photosynthetic activity, and produced more above-ground biomass, suggesting a direct correlation between the fitness of a population, genetic diversity, and genetic load. These results emphasize the importance of preserving the habitat of populations of Zea mays ssp. parviglumis to limit inbreeding depression and maintain the genetic diversity and adaptive potential of this germplasm.

The domestication process of sugar kelp in the Northeast U.S. was initiated by selective breeding two years ago. In this study, we will demonstrate how obstacles for accelerated genetic gain can be assessed using simulation approaches that inform resource allocation decisions in our research. Thus far, we have used 140 wild sporophytes (SPs) that were sampled from the northern Gulf of Maine (GOM) to southern New England (SNE). From these SPs, we sampled gametophytes (GPs) and made and evaluated over 600 progeny SPs from crosses among the GPs. The biphasic life cycle of kelp gives a great advantage in selective breeding as we can potentially select both on the SPs and GPs. However, several obstacles exist, such as the amount of time it takes to complete a breeding cycle, the number of GPs that can be maintained in the lab, and whether positive selection can be conducted on farm tested SPs. Using the GOM population characteristics for heritability and effective population size, we simulated a founder population of 1000 individuals and evaluated the impact of overcoming these obstacles on genetic gain. Our results showed that key factors to improve current genetic gain rely mainly on our ability to induce reproduction of the best farm-tested SPs, and to accelerate the clonal vegetative growth of released GPs so that enough GP biomass is ready for making crosses by the next growing season. Overcoming these challenges could improve rates of genetic gain more than two-fold. Future research should focus on conditions favorable for inducing spring and early summer reproduction, and increasing the amount of GP tissue available in time to make fall crosses.

1Plant breeding programs must adapt genomic selection to an already complex system. Inbred or hybrid plant breeding programs must make crosses, produce inbred individuals, and phenotype inbred lines or their hybrid test-crosses to select and validate superior material for product release. These products are few, and while it is clear that population improvement is necessary for continued genetic gain, it may not be sufficient to generate superior products. Rapid-cycle recurrent truncation genomic selection has been proposed to increase genetic gain by reducing generation time. This strategy has been shown to increase short-term gains, but can quickly lead to loss of genetic variance through inbreeding as relationships drive prediction. The optimal contribution of each individual can be determined to maximize gain in the following generation while limiting inbreeding. While optimal contribution strategies can maintain genetic variance in later generations, they suffer from a lack of short-term gains in doing so. We present a hybrid approach that branches out yearly to push the genetic value of potential varietal materials while maintaining genetic variance in the recurrent population, such that a breeding program can achieve short-term success without exhausting long-term potential. Because branching increases the genetic distance between the phenotyping pipeline and the recurrent population, this method requires sacrificing some trial plots to phenotype materials directly out of the recurrent population. We envision the phenotypic pipeline not only for selection and validation, but as an information generator to build predictive models and develop new products.