Kent Frank McCue

Biostimulants are agricultural inputs that enhance the ability of plants to absorb and utilize nutrients more efficiently through natural processes. There

This study aims to establish an Agrobacterium-mediated transformation system for use with the ‘MiniMax’soybean cultivar. MiniMax is a mutant soybean whose growth cycle is around 90 days, half that of most other soybean varieties, making it an optimal model cultivar to test genes of interest before investing in modification of elite lines. We describe an efficient protocol for Agrobacterium-mediated transformation using MiniMax seeds. It uses a modified ‘half seed’ regeneration protocol for transgenic soybean production, utilizing the rapid generation MiniMax variety to obtain T1 seeds in approximately 145 days. Addition of phloroglucinol (PG) to the regeneration protocol was key to obtaining high-efficiency rooting of the regenerated shoots. Transfer to soil was accomplished using an organic soil amendment containing nutrients and mycorrhiza for plants to thrive in the greenhouse. This combination of genotype and stimulants provides a transformation protocol to genetically engineer MiniMax seeds with a transgenic lab-to-greenhouse production efficiency of 4.0%. This is the first report of MiniMax soybean whole plant transformation and heritable T1 transmission. This protocol provides an ideal resource for enhancing the genetic transformation of any soybean cultivar.

A plant's growth and development are shaped by its genome and the capacity to negotiate its environment for access to light, water, and nutrients. There is a vital need to understand the interactions between the plant, its physical environment, and the fertilizers used in agriculture. In this study, a commercially available volcanic ash fertilizer, Azomite®, characterized as dacitic (rhyolitic) tuff breccia, was tested for its effect on promoting early seedling vigor. Early growth and photomorphogenesis processes are well studied in Arabidopsis. Seedling assays under different light conditions were used to dissect the underlying mechanisms involved. These assays are well established and can be translated to agriculturally important crop plants. The volcanic ash fertilizer was tested at different concentrations on seedlings grown on basic media lacking sucrose either in continuous darkness (Dc), continuous Red (Rc), Far‐Red (FRc), or White Light (WLc). Micronutrients in the volcanic ash significantly increased seedling growth under Rc and WLc, but not under Dc and FRc, indicating that photosynthetically active radiation was required for the observed growth increase. Furthermore, red‐light photoreceptor mutant, phyB‐9, lacked the growth response, and higher amount of fertilizer reduced growth in all conditions tested. These data suggest that light triggers the ability of the seedling to utilize micronutrients in volcanic ash in a dose‐dependent manner. The methods described here can be used to establish mechanisms of activity of various nutrient inputs and, coupled with whole‐genome expression profiling, can lead to better insights into optimizing nutrient field applications to improve crop production.

A plant’s growth and development are shaped by its genome and the capacity to negotiate its environment for access to light, water, and nutrients. There is a vital need to understand the interactions between the plant, its physical environment, and the fertilizers used in agriculture. In this study, a commercially available volcanic ash fertilizer, Azomite ^® , characterized as dacitic (rhyolitic) tuff breccia (DTB), was tested for its effect on promoting early seedling vigor. Early growth and photomorphogenesis processes are well studied in Arabidopsis. Seedling assays under different light conditions were used to dissect the underlying mechanisms involved. These assays are well established and can be translated to agriculturally important crop plants. The volcanic ash fertilizer was tested at different concentrations on seedlings grown on basic media lacking sucrose either in continuous darkness (Dc), continuous Red (Rc), Far-Red (FRc), or White Light (WLc). Micronutrients in the volcanic ash significantly increased seedling growth under Rc and WLc, but not under Dc and FRc, indicating that photosynthetically active radiation (PAR) was required for the observed growth increase. Furthermore, red-light photoreceptor mutant, phyB-9 lacked the growth response, and higher amount of fertilizer reduced growth in all conditions tested. These data suggest that light triggers the ability of the seedling to utilize micronutrients in volcanic ash in a dose-dependent manner. The methods described here can be used to establish mechanisms of activity of various nutrient inputs, and coupled with whole-genome expression profiling, can lead to better insights into optimizing nutrient field applications to improve crop production.

Various types of soil fertilizers are used routinely to increase crop yields globally. The effects of these treatments are assessed mainly by the benefits they provide in increased crop productivity.

One cellular response to toxic levels of metals is the induced synthesis of intracellular chelators. To that effect, animals and certain fungi produce small cysteine-rich proteins through the transcriptional activation of metallothionein genes (for reviews, see Hamer, 1986; Winge, this volume). In contrast, plants and some fungi respond by the metal-activated enzymatic synthesis of peptides derived from glutathione (for reviews, see Tomsett and Thurman, 1988; Rauser, 1990; Robinson, 1990; Steffens, 1990; Hayashi, this volume). These peptides have the general structure of (γGlu-Cys)_n-Gly (Kondo et al., 1984; Grill et al., 1985), where the γGlu-Cys repeating unit extends up to 11 (Grill et al., 1987). In members of the Fabales thus far examined, these peptides contain /3-alanine in place of glycine, consistent with the same carboxyl-end residue found in homoglutathione (Grill et al., 1986). First discovered in Schizosaccharomyces pombe (Murasugi et al., 1981), a variety of names have been used for these peptides: cadystins (Kondo et al., 1983), phytochelatins (Grill et al., 1985), poly(y-glutamylcysteinyl)glycine (Jackson et al., 1987), γ-glutamyl peptides (Reese et al., 1988), and (γEC)_nG (Delhaize et al., 1989). Although the chemical structure (γEC)_nG is a most accurate description, the ubiquity of these 340peptides in the plant kingdom (Gekeler et al., 1989) has popularized the term phytochelatins proposed by Zenk and colleagues; as in several recent reviews, we will use the term phytochelatins (PCs).

The intentional introduction of exotic species through classical biological control programs provides unique opportunities to examine the consequences of population movement and ecological processes for the genetic diversity and population structure of introduced species. The weevils Neochetina bruchi and N. eichhorniae (Coleoptera: Curculionidae) have been introduced globally to control the invasive floating aquatic weed, Eichhornia crassipes, with variable outcomes. Here, we use the importation history and data from polymorphic microsatellite markers to examine the effects of introduction processes on population genetic diversity and structure. We report the first confirmation of hybridization between these species, which could have important consequences for the biological control program. For both species, there were more rare alleles in weevils from the native range than in weevils from the introduced range. N. eichhorniae also had higher allelic richness in the native range than in the introduced range. Neither the number of individuals initially introduced nor the number of introduction steps appeared to consistently affect genetic diversity. We found evidence of genetic drift, inbreeding, and admixture in several populations as well as significant population structure. Analyses estimated two populations and 11 sub‐clusters for N. bruchi and four populations and 23 sub‐clusters for N. eichhorniae, indicating divergence of populations during and after introduction. Genetic differentiation and allocation of introduced populations to source populations generally supported the documented importation history and clarified pathways in cases where multiple introductions occurred. In populations with multiple introductions, genetic admixture may have buffered against the negative effects of serial bottlenecks on genetic diversity. The genetic data combined with the introduction history from this biological control study system provide insight on the accuracy of predicting introduction pathways from genetic data and the consequences of these pathways for the genetic variation and structure of introduced species.