Evaluation and Utilization of a Chemical Male Gametocide in Sorghum

Sorghum bicolor (L.) is an ancient grain and forage crop, grown from the tropics to temperate regions of the world. It is a self-pollinated species that can be grown as either a pure line cultivar or hybrid, depending on the region of production. Existing methods of hybridization of sorghum are useful but have some limitations. Methods of inducing temporal male sterility could enhance several aspects of sorghum breeding. One potential application of temporal male sterility would be to scale up cross-pollination in order to implement a doubled haploid (DH) breeding system in sorghum. A chemical male gametocide that reliably renders plants male-sterile might be ideal for this purpose. Two studies were conducted to assess the utility of trifluoromethanesulfonamide (TFMSA) as a chemical gametocide of sorghum. The first study evaluated the amino acid composition of anther and glume tissues following application of TFMSA. To do so, anther and glume tissue were excised from florets of plants that had received an application of either 0 mg, 2 mg, 6 mg, or 20 mg. TFMSA. After excision of the tissues, the amino acids were extracted in Milli-Q® water; then -high-pressure liquid chromatography (HPLC) was used to quantify the amino acids. Fold changes were calculated to look for shifts among treated and untreated plant tissues. In the anther tissues, several amino acids experienced drastic shifts, the most notable being a >10x decrease of proline and a >20x increase of asparagine. Similar shifts were not observed in glume tissue. Consequently, one, or, both of these shifts may be associated with the induction of male sterility. The second study was conducted to evaluate the efficacy of TFMSA to induce male sterility in two field environments. Both environments were grown in College Station with planting dates that differed by 2 weeks. TFMSA was applied to three distinct genotypes using both hand application and backpack sprayer application in dosages ranging from 5 mg to 30 mg Multiple applications of the 10 mg and 15 mg dosages were also evaluated. Results indicated that once a minimum dosage threshold was exceeded, specific dosages and number of applications had little overall effect on male sterility. Use of a backpack sprayer showed sterility induction albeit at slightly lower levels of male sterility. The results indicate that TFMSA can be used as an effective and durable chemical male gametocide in sorghum

Impact of Spontaneous Haploid Genome Doubling in Maize Breeding

Doubled haploid (DH) technology has changed the maize-breeding landscape in recent years. Traditionally, DH production requires the use of chemical doubling agents to induce haploid genome doubling and, subsequently, male fertility. These chemicals can be harmful to humans and the plants themselves, and typically result in a doubling rate of 10%–30%. Spontaneous genome doubling and male fertility of maize haploids, without using chemical doubling agents, have been observed to a limited extent, for nearly 70 years. Rates of spontaneous haploid genome doubling (SHGD) have ranged from less than 5% to greater than 50%. Recently, there has been increased interest to forgo chemical treatment and instead utilize this natural method of doubling. Genetic-mapping studies comprising worldwide germplasm have been conducted. Of particular interest has been the detection of large-effect quantitative trait loci (QTL) affecting SHGD. Having a single large-effect QTL with an additive nature provides flexibility for the method of introgression, such as marker-assisted backcrossing, marker-assisted gene pyramiding, and systematic design. Moreover, it allows implementation of new methodologies, such as haploid-inducer mediated genome editing (HI-edit) and promotion of alleles by genome editing. We believe the use of SHGD can further enhance the impact of DH technology in maize

Mapping of QTL and Identification of Candidate Genes Conferring Spontaneous Haploid Genome Doubling in Maize (Zea mays L.)

In vivo doubled haploid (DH) technology is widely used in commercial maize (Zea mays L.) breeding. Haploid genome doubling is a critical step in DH breeding. In this study, inbred lines GF1 (0.65), GF3(0.29), and GF5 (0) with high, moderate, and poor spontaneous haploid genome doubling (SHGD), respectively, were selected to develop mapping populations for SHGD. Three QTL, qshgd1, qshgd2, and qshgd3, related to SHGD were identified by selective genotyping. With the exception of qshgd3, the source of haploid genome doubling alleles were derived from GF1. Furthermore, RNA-Seq was conducted to identify putative candidate genes between GF1 and GF5 within the qshgd1 region. A differentially expressed formin-like protein 5 transcript was identified within the qshgd1 region

Recent trends in soft-tissue infection imaging.

This article discusses the current techniques and future directions of infection imaging with particular attention to respiratory, central nervous system, abdominal, and postoperative infections. The agents currently in use localize to areas of infection and inflammation. An infection-specific imaging agent would greatly improve the utility of scintigraphy in imaging occult infections. The superior spatial resolution of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) and its lack of reliance on a functional immune system, gives this agent certain advantages over the other radiopharmaceuticals. In respiratory tract infection imaging, an important advancement would be the ability to quantitatively delineate lung inflammation, allowing one to monitor the therapeutic response in a variety of conditions. Current studies suggest PET should be considered the most accurate quantitative method. Scintigraphy has much to offer in localizing abdominal infection as well as inflammation. We may begin to see a gradual increase in the usage of (18)F-FDG-PET in detecting occult abdominal infections. Commonly used modalities for imaging inflammatory bowel disease are scintigraphy with (111)In-oxine/(99m)Tc-HMPAO labeled autologous white blood cells. The literature on central nervous system infection imaging is relatively scarce. Few clinical studies have been performed and numerous new agents have been developed for this use with varying results. Further studies are needed to more clearly delineate the future direction of this field. In evaluating the postoperative spine, (99m)Tc-ciprofloxacin single-photon emission computed tomography (SPECT) was reported to be \u3e80% sensitive in patients more than 6 months after surgery. FDG-PET has also been suggested for this purpose and may play a larger role than originally thought. It appears PET/computed tomography (CT) is gaining support, especially in imaging those with fever of unknown origin or nonfunctional immune systems. Although an infection-specific agent is lacking, the development of one would greatly advance our ability to detect, localize, and quantify infections. Overall, imaging such an agent via SPECT/CT or PET/CT will pave the way for greater clinical reliability in the localization of infection

Genetic analysis of doubled haploid and unilateral cross incompatibility systems for organic maize breeding

Recently, there has been increased interest in organic agriculture due to consumer concerns over pesticide usage and genetically modified organisms (GMOs). Production of organic field corn in the U.S. consisted of 213,934 acres in 2017 and is expected to increase. A challenge facing organic corn growers is maintaining genetic purity when nearby fields are growing GMO corn. Unilateral cross incompatibility (UCI) systems provide a potential solution to this problem. There are three systems of UCI in maize that prevent pollination by pollen that does not possess the same allele as the silks. Ga1-s UCI was crossed into 9 diverse maize inbreds from three major heterotic groups and the F1 hybrids tested for exclusion of exogenous ga1 pollen. We observed significant differences in exclusion capabilities between genotypes, indicating presence of modifier loci. Additionally, to improve the efficiency of line development and trait introgression in a maize breeding program, doubled haploid (DH) lines can be derived. In a typical DH system, chemicals such as colchicine are used for genome doubling but some genotypes have an ability to naturally double their genomes without colchicine, a trait called spontaneous haploid genome doubling (SHGD). There are many mechanisms of SHGD and they are controlled by varying numbers of genes. However, there is an inbred line that was identified as having greater than 40% SHGD rate and is controlled by a single large effect QTL located on chromosome 5. Using a line with a single large effect QTL as a donor will allow introgression of the QTL into non-SHGD backgrounds with marker-assisted backcrossing. Use of SHGD can improve the genome doubling rate as compared to colchicine which results in a genome doubling rate that is between 10-30%. Ga1 and SHGD both have the potential to drastically change organic corn breeding, protecting organic corn from pollen contamination and improving its breeding efficiency.</p

Genetic analysis of doubled haploid and unilateral cross incompatibility systems for organic maize breeding

Recently, there has been increased interest in organic agriculture due to consumer concerns over pesticide usage and genetically modified organisms (GMOs). Production of organic field corn in the U.S. consisted of 213,934 acres in 2017 and is expected to increase. A challenge facing organic corn growers is maintaining genetic purity when nearby fields are growing GMO corn. Unilateral cross incompatibility (UCI) systems provide a potential solution to this problem. There are three systems of UCI in maize that prevent pollination by pollen that does not possess the same allele as the silks. Ga1-s UCI was crossed into 9 diverse maize inbreds from three major heterotic groups and the F1 hybrids tested for exclusion of exogenous ga1 pollen. We observed significant differences in exclusion capabilities between genotypes, indicating presence of modifier loci. Additionally, to improve the efficiency of line development and trait introgression in a maize breeding program, doubled haploid (DH) lines can be derived. In a typical DH system, chemicals such as colchicine are used for genome doubling but some genotypes have an ability to naturally double their genomes without colchicine, a trait called spontaneous haploid genome doubling (SHGD). There are many mechanisms of SHGD and they are controlled by varying numbers of genes. However, there is an inbred line that was identified as having greater than 40% SHGD rate and is controlled by a single large effect QTL located on chromosome 5. Using a line with a single large effect QTL as a donor will allow introgression of the QTL into non-SHGD backgrounds with marker-assisted backcrossing. Use of SHGD can improve the genome doubling rate as compared to colchicine which results in a genome doubling rate that is between 10-30%. Ga1 and SHGD both have the potential to drastically change organic corn breeding, protecting organic corn from pollen contamination and improving its breeding efficiency

Evaluation and Utilization of a Chemical Male Gametocide in Sorghum

Sorghum bicolor (L.) is an ancient grain and forage crop, grown from the tropics to temperate regions of the world. It is a self-pollinated species that can be grown as either a pure line cultivar or hybrid, depending on the region of production. Existing methods of hybridization of sorghum are useful but have some limitations. Methods of inducing temporal male sterility could enhance several aspects of sorghum breeding. One potential application of temporal male sterility would be to scale up cross-pollination in order to implement a doubled haploid (DH) breeding system in sorghum. A chemical male gametocide that reliably renders plants male-sterile might be ideal for this purpose. Two studies were conducted to assess the utility of trifluoromethanesulfonamide (TFMSA) as a chemical gametocide of sorghum. The first study evaluated the amino acid composition of anther and glume tissues following application of TFMSA. To do so, anther and glume tissue were excised from florets of plants that had received an application of either 0 mg, 2 mg, 6 mg, or 20 mg. TFMSA. After excision of the tissues, the amino acids were extracted in Milli-Q® water; then -high-pressure liquid chromatography (HPLC) was used to quantify the amino acids. Fold changes were calculated to look for shifts among treated and untreated plant tissues. In the anther tissues, several amino acids experienced drastic shifts, the most notable being a >10x decrease of proline and a >20x increase of asparagine. Similar shifts were not observed in glume tissue. Consequently, one, or, both of these shifts may be associated with the induction of male sterility. The second study was conducted to evaluate the efficacy of TFMSA to induce male sterility in two field environments. Both environments were grown in College Station with planting dates that differed by 2 weeks. TFMSA was applied to three distinct genotypes using both hand application and backpack sprayer application in dosages ranging from 5 mg to 30 mg Multiple applications of the 10 mg and 15 mg dosages were also evaluated. Results indicated that once a minimum dosage threshold was exceeded, specific dosages and number of applications had little overall effect on male sterility. Use of a backpack sprayer showed sterility induction albeit at slightly lower levels of male sterility. The results indicate that TFMSA can be used as an effective and durable chemical male gametocide in sorghum

Impact of Spontaneous Haploid Genome Doubling in Maize Breeding

Doubled haploid (DH) technology has changed the maize-breeding landscape in recent years. Traditionally, DH production requires the use of chemical doubling agents to induce haploid genome doubling and, subsequently, male fertility. These chemicals can be harmful to humans and the plants themselves, and typically result in a doubling rate of 10%–30%. Spontaneous genome doubling and male fertility of maize haploids, without using chemical doubling agents, have been observed to a limited extent, for nearly 70 years. Rates of spontaneous haploid genome doubling (SHGD) have ranged from less than 5% to greater than 50%. Recently, there has been increased interest to forgo chemical treatment and instead utilize this natural method of doubling. Genetic-mapping studies comprising worldwide germplasm have been conducted. Of particular interest has been the detection of large-effect quantitative trait loci (QTL) affecting SHGD. Having a single large-effect QTL with an additive nature provides flexibility for the method of introgression, such as marker-assisted backcrossing, marker-assisted gene pyramiding, and systematic design. Moreover, it allows implementation of new methodologies, such as haploid-inducer mediated genome editing (HI-edit) and promotion of alleles by genome editing. We believe the use of SHGD can further enhance the impact of DH technology in maize.This article is published as Boerman, Nicholas A., Ursula K. Frei, and Thomas Lübberstedt. "Impact of Spontaneous Haploid Genome Doubling in Maize Breeding." Plants 9, no. 3 (2020): 369. doi: 10.3390/plants9030369.</p

Estimating reliability for evaluating nitrate accumulation in sorghum (Sorghum bicolor L. Moench) inbred A‐lines

Abstract Sorghum is an important forage crop in many cropping systems. Nitrate can accumulate in the vegetative plant tissue to levels high enough that result in fatality when fed to ruminant livestock when grown under high nitrate conditions. If variation among inbred lines can be documented for nitrate concentration, it may be possible to reduce nitrate accumulation within forage sorghum hybrids by selecting inbred lines having lower nitrate accumulation. The goal of this study was to evaluate a diverse set of male‐sterile sorghum inbred lines grown under high nitrate conditions, to observe if genotypic variation exists among lines used to produce forage sorghum hybrids. Forty replicates of 20 sorghum A‐lines were grown in a greenhouse and received either 272 kg ha−1 or 408 kg ha−1 of actual nitrogen per plant through applications of ammonium nitrate. Variance components were extracted from linear regression models and reliability was estimated on an entry‐mean basis. Leaf and stem reliability estimates were 0.95 and 0.93, respectively. These reliability estimates indicate the genetic variance comprised most of the phenotypic variance, and that our measurements were consistent. Significant differences were also observed between genotypes for both leaf and stem tissue. Therefore, sufficient genetic variance exists for developing male sterile sorghum inbred lines having leaf nitrate concentrations below the potentially lethal toxicity threshold of 10,000 μg g−1

Is it feasible to improve stand persistence of eastern gamagrass (Tripsacum dactyloides L.) through breeding?

Abstract Eastern gamagrass is a warm‐season perennial grass that has excellent forage nutritional quality and a broad range of adaptations. Despite the favorable forage qualities, agronomic issues persist; most important for grazing systems is stand persistence from preferential grazing when growing in mixed species communities. Stand persistence when monoculture stands are grazed has been previously studied, and it has been observed that stands decline under high stocking rates or low grazing height. The objective of our study was to evaluate if an improvement of stand persistence under defoliation to a low‐cut height is feasible through the breeding of improved lines. A persistence trial was conducted using a completely random design and eight replications to evaluate the stand persistence of two commercial cultivars, two experimental lines, and an ecotype selection. Defoliation occurred by grazing and mowing to a height of 8 cm three‐to‐four times over the course of five growing seasons. Stand counts of live plants were taken following the final defoliation of the season. Mixed linear regression modeling indicates significant differences between genotypes developed in years where no grazing occurred. An ecotype selection from Northwest Oklahoma exhibited significantly greater persistence than the cultivar Pete and the other experimental lines. These results suggest that different alleles exist for critical persistence genes, indicating it may be feasible to improve the trait through breeding and selection