Nitrogen is essential for plant growth and development. Improving the ability of plants to acquire and assimilate nitrogen more efficiently is a key agronomic parameter that will augment sustainability in agriculture. A transcription factor approach was pursued to address improvement of nitrogen use efficiency in two major commodity crops. To this end, the Zea mays Dof1 (ZmDof1) transcription factor was expressed in both wheat (Triticum aestivum) and sorghum (Sorghum bicolor) either constitutively, UBI4 promoter from sugarcane, or in a tissue specific fashion via the maize rbcS1 promoter. The primary transcription activation target of ZmDof1, phosphoenolpyruvate carboxylase (PEPC), is observed in transgenic wheat events. Expression ZmDof1 under control of the rbcs1 promoter translates to increase in biomass and yield components in wheat. However, constitutive expression of ZmDof1 led to the down-regulation of genes involved in photosynthesis and the functional apparatus of chloroplasts, and an outcome that negatively impacts photosynthesis, height, and biomass in wheat. Similar patterns were also observed in sorghum transgenic events harboring the constitutive expression cassette of ZmDof1. These results indicate that transcription factor strategies to boost agronomic phenotypic outcomes in crops need to consider expression patterns of the genetic elements to be introduced.

High-ambient-temperature stress, drought stress, root rot disease, and common bacterial blight [CBB; caused by Xanthomonas axonopodis pv. phaseoli (Smith) Dye] cause widespread yield reductions in common bean (Phaseolus vulgaris L.) worldwide. TARS-MST1 (Reg. No. GP-284, PI 661512) and SB-DT1 (Reg. No. GP-283, PI 661970) were developed by the USDA-ARS, the University of Nebraska Agricultural Research Division, and the University of Puerto Rico Agricultural Experiment Station. These black bean lines were selected for tolerance to multiple stresses, including tolerance to high ambient temperature and drought. Specifi cally, both lines showed signifi cantly higher yields under heat stress compared with the local check and had comparable yields to both heat-and drought-tolerant controls under those stress conditions. TARS-MST1 possesses resistance to CBB, and both lines are tolerant to root rot diseases. They incorporate exotic sources of stress tolerance, thus serving to diversify U.S. common bean germplasm. The lines were characterized for markers related to Bean common mosaic virus and CBB, and both lines carry the I gene, while TARS-MST1 was positive for the presence of two CBB SCAR markers, SU91 and SAP6. The use of this germplasm in breeding programs can serve to improve the yield and stress tolerance of common bean.

SummarySoya bean (Glycine max (L.) Merr.) is sought after for both its oil and protein components. Genetic approaches to add value to either component are ongoing efforts in soya bean breeding and molecular biology programmes. The former is the primary vegetable oil consumed in the world. Hence, its primary usage is in direct human consumption. As a means to increase its utility in feed applications, thereby expanding the market of soya bean coproducts, we investigated the simultaneous displacement of marine ingredients in aquafeeds with soya bean‐based protein and a high Omega‐3 fatty acid soya bean oil, enriched with alpha‐linolenic and stearidonic acids, in both steelhead trout (Oncorhynchus mykiss) and Kampachi (Seriola rivoliana). Communicated herein are aquafeed formulations with major reduction in marine ingredients that translates to more total Omega‐3 fatty acids in harvested flesh. Building off of these findings, subsequent efforts were directed towards a genetic strategy that would translate to a prototype design of an optimal identity‐preserved soya bean‐based feedstock for aquaculture, whereby a multigene stack approach for the targeted synthesis of two value‐added output traits, eicosapentaenoic acid and the ketocarotenoid, astaxanthin, were introduced into the crop. To this end, the systematic introduction of seven transgenic cassettes into soya bean, and the molecular and phenotypic evaluation of the derived novel events are described.

Rhizoctonia solani causes economically important root and hypocotyl diseases in common bean throughout the world. Root health is a vital factor in plant development and root diseases would negatively influence water and nutrient uptake as well as cause direct stand reduction and root rot damage to the crop. An efficient common bean screening method to evaluate damping-off and early root/ hypocotyl damage from R. solani was developed and used to identify dry bean lines with levels of resistance to this disease. Two sets of 163 and 111 lines previously evaluated for drought tolerance in Nebraska and Puerto Rico were evaluated for damping-off resistance and early root/hypocotyl damage under greenhouse conditions. Disease severity on plants was identified based on above-ground symptoms, seedling survival and root lesions using a rating scale of 1 (resistant) to 9 (susceptible). In the first set of lines representing commonly grown dry bean cultivars, germplasm and sources of damping-off resistance, the Rhizoctonia mean rating ranged from 1.7 to 3.9; Phaseolus vulgaris lines PI 310668 and PI 533249 had the highest damping-off resistance. In the second set of the best lines from a drought tolerance shuttle breeding program the Rhizoctonia mean rating was between 2.6 and 5.7. The availability of drought tolerant dry bean lines allowed the testing of the hypothesis that there was a correlation between selecting for drought tolerance and R. solani damping-off resistance. No correlation between mean disease rating and drought tolerance was found, but adapted dry bean lines such as NE14-08-176 released as SB-DT1, and NE14-08-225 were identified with moderate damping-off resistance and drought tolerance. Lines with both traits and other attributes will facilitate development of resistant bean cultivars to manage damping-off caused by R. solani.

Main conclusion -The expression of a barley alanine aminotransferase gene impacts agronomic outcomes in a C3 crop, wheat.The use of nitrogen-based fertilizers has become one of the major agronomic inputs in crop production systems. Strategies to enhance nitrogen assimilation and flux in planta are being pursued through the introduction of novel genetic alleles. Here an Agrobacterium-mediated approach was employed to introduce the alanine aminotransferase from barley (Hordeum vulgare), HvAlaAT, into wheat (Triticum aestivum) and sorghum (Sorghum bicolor), regulated by either constitutive or root preferred promoter elements. Plants harboring the transgenic HvAlaAT alleles displayed increased alanine aminotransferase (alt) activity. The enhanced alt activity impacted height, tillering and significantly boosted vegetative biomass relative to controls in wheat evaluated under hydroponic conditions, where the phenotypic outcome across these parameters varied relative to time of year study was conducted. Constitutive expression of HvAlaAT translated to elevation in wheat grain yield under field conditions. In sorghum, expression of HvAlaAT enhanced enzymatic activity, but no changes in phenotypic outcomes were observed. Taken together these results suggest that positive agronomic outcomes can be achieved through enhanced alt activity in a C3 crop, wheat. However, the variability observed across experiments under greenhouse conditions implies the phenotypic outcomes imparted by the HvAlaAT allele in wheat may be impacted by environment.