Nutrient film technique (NFT) is a popular, ergonomic, hydroponic system, but is not often used in commercial aquaponic systems due to lower efficiency in overall nutrient removal. Experiments were conducted to assess if NFT lettuce production could be improved by exchanging aquaculture effluent more frequently, and if so, determine the optimal water exchange rate. The AE was taken from a biofloc-based nile tiapia production system. Treatments consisted of increasing hydraulic retention time (HRT (d)) viz: four-, eight-, twelve-, or sixteen-day water exchanges arranged in a randomized complete block design with five blocks. In one trial (trial 1) where iron (Fe) was not supplemented, there was one replication. There were three replications for the second trial with iron supplementation. The analysis of lettuce plant size index and chlorophyll index (SPAD units) in trial 1 was statistically different among the HRTs beginning 14 days after planting, exhibiting negative linear trends with increasing HRT. However, most foliar micronutrients were borderline sufficient, and all treatments showed foliar Fe deficiency. After iron supplementation (trial 2), lettuce plant chlorophyll and size index exhibited quadratic trends with increasing HRT on 14 and 21 DAP, respectively. In trial 2, plant fresh mass decreased linearly from 162.1 g/head to 147.1 g/head, with increasing HRT. Furthermore, iron supplementation eliminated Fe deficiencies in the plants albeit only up to 14 DAP. Our findings suggest that shorter hydraulic retention times provide a solution to using the NFT system in aquaponics especially with iron supplementation.

Assessment of pathogen diversity in agricultural fields is essential for informing management decisions and the development of resistant plant varieties. However, many population genomic studies have relied on culture-based approaches that do not provide quantitative assessment of pathogen populations at the field-level or the associated host microbiome. Here, we applied whole-genome shotgun sequencing of microbial DNA extracted directly from the washings of pooled leaf samples, collected from individual tomato and pepper fields in Alabama that displayed the classical symptoms of bacterial spot disease caused by Xanthomonas spp. Our results revealed that while the occurrence of both X. perforans and X. euvesicatoria within fields was limited, evidence of co-occurrence of up to three distinct X. perforans genotypes was obtained in 7 of 10 tomato fields sampled. These population dynamics were accompanied by the corresponding type 3 secreted effector repertoires associated with the co-occurring X. perforans genotypes, indicating that metapopulation structure within fields should be considered when assessing the adaptive potential of X. perforans. Finally, analysis of microbial community composition revealed that co-occurrence of the bacterial spot pathogens Pseudomonas cichorii and Xanthomonas spp. is common in Alabama fields and provided evidence for the non-random association of several other human and plant opportunists.

Bananas possess unique potential as a specialty crop, but require considerable inputs making their production cost prohibitive for smaller farm operations. Innovative production practices of interest are the incorporation of reflective mulches and cover crops in banana production systems. Reflective mulches and cover crop effects on banana phenology were documented under sub-tropical conditions of the Alabama Gulf Coast. Flower emergence of Musa AAB (Mysore subgroup) was 5 days earlier in plants grown on white mulch, but was delayed by 26 days on reflective silver mulch compared to the control. Banana bunches from plants on white or reflective silver mulch were 27% and 15% heavier and were produced on pseudostems that were 12% and 3% taller, respectively, compared to control bunches. Musa ABB 'Dwarf Orinoco' bananas were planted into experimental plots of crimson clover (Trifolium incarnatum), hairy vetch (Vicia villosia) or into natural cover that was 60% bahiagrass (Paspalum notatum) as the control. Banana leaf area was 24% greater in the crimson clover and 10% greater in the hairy vetch compared to the control. Banana pseudostems in crimson clover and hairy vetch were 20% and 8% taller, respectively, than those of the control. Use of mulches or cover crops provided slight gains in advancing productivity of sub-tropical banana cultivars in the Alabama Gulf Coast.

A series of experiments was conducted to evaluate variety selection and planting date for spring and fall season extension of tomato (Solanum lycopersicum L. (syn.: Lycoperisicon esculentum Mill.)) production in high tunnels in southeast Alabama. 'BHN 640', 'Florida 91', 'Sun Leaper', and 'Carolina Gold' were evaluated for early spring production in 2004. These varieties did not differ in total yield of marketable fruit; however, 'BHN 640' and 'Sun Leaper' produced higher early yields compared with the other varieties. 'BHN 640' and 'Florida 91' were evaluated for late-season extension in fall 2004. 'BHN 640' produced higher yields of large, medium, total marketable, and unmarketable fruit grades than 'Florida 91'. In a study conducted in early 2005, higher yields of marketable fruit were produced from the first planting date (31 January) compared with the final of four planting date (25 Mar.). In summary, results indicated that season extension of tomato production in high tunnels was possible, with harvests three weeks earlier in the spring and 12 weeks later in the fall compared with typical field harvest dates. These early yields can command prices from $3.30 to $4.40US per kg of fruit.

Tomatoes are the most abundantly produced greenhouse vegetable crop in the United States. The use of composted substrates has increased in recent years for the greenhouse production of many vegetables, bedding plants, and nursery crops. `Blitz' tomatoes were grown during the spring and fall growing seasons in six substrate blends of pine bark ( PB), a traditional production substrate in the southeastern US, and cotton gin compost (CGC), an agricultural by-product, to assess the potential use of CGC as a viable replacement for PB for the production of greenhouse tomatoes. Treatments ranged from 100% PB to 100% CGC. Plants grown in substrates containing CGC produced similar total yields during both seasons compared to plants grown in 100% PB. In both seasons marketable yields were similar across all treatments. Similarly, cull fruit was not different across treatments. Substrates containing 60% or more CGC had significantly higher electrical conductivity (salt) levels both initially and throughout both growing seasons than did 20 and 40% CGC and 100% PB substrates. Water holding capacity increased as the percent CGC increased in each substrate, indicating the need for adjusted irrigation volume for substrates containing CGC compared to the 100% PB. Results indicate that CGC has potential to be used as an amendment to PB in greenhouse tomato production.

Lettuce is a cool season vegetable often produced in greenhouses and other protective structures to meet market demands. Greenhouses are being increasingly adopted in warm climate zones where excessive heat often leads to physiological disorders of lettuce, such as tipburn and premature bolting. Greenhouse lettuce growers in warm climates need cultivar recommendations that can help improve production without ignoring marketability. In the current study, eighteen lettuce cultivars were grown in deep water culture and evaluated for growth, bolting, and tipburn in a greenhouse in Auburn, AL, starting on 30 June and 19 August 2016. Based on the severity of bolting and tipburn, nine cultivars were then selected and evaluated on 17 November 2016 for sensory attributes and marketability by 50 untrained consumer panelists. Cultivars ‘Adriana’, ‘Aerostar’, ‘Monte Carlo’, ‘Nevada’, ‘Parris Island’, ‘Salvius’, ‘Skyphos’, and ‘Sparx’ were selected as having higher heat tolerance than cultivars ‘Bambi’, ‘Buttercrunch’ ‘Coastal Star’, ‘Flashy Trout Back’, ‘Green Forest’, ‘Green Towers’, ‘Jericho’, ‘Magenta’, and ‘Truchas’. Higher crispness, lower bitterness, higher overall texture, and higher overall flavor each correlated to higher marketability, regardless of cultivar, but the strongest predictor of marketability was overall flavor. Overall flavor and overall texture were more strongly correlated to marketability than bitterness and crispness, respectively, suggesting that broader sensory categories may better capture human sensory perceptions of lettuce than narrower categories. Cultivars ‘Aerostar’, ‘Monte Carlo’, ‘Nevada’, ‘Parris Island’, ‘Rex’, ‘Salvius’, and ‘Sparx’ performed well in a hot greenhouse and were preferred by consumers. This step-wise experiment could be an adaptable tool for determining highest performing cultivars under any given production constraint, without ignoring marketability.

Xanthomonas perforans is the predominant pathogen responsible for bacterial leaf spot of tomato and X. euvesicatoria for that of pepper in the southeast United States. Previous studies have indicated significant changes in the X. perforans population collected from Florida tomato fields over the span of 2 decades, including a shift in race and diversification into three phylogenetic groups driven by genome-wide homologous-recombination events derived from X. euvesicatoria In our sampling of Xanthomonas strains associated with bacterial spot disease in Alabama, we were readily able to isolate X. perforans from symptomatic pepper plants grown in several Alabama counties, indicating a recent shift in the host range of the pathogen. To investigate the diversity of these pepper-pathogenic strains and their relation to populations associated with tomatoes grown in the southeast United States, we sequenced the genomes of eight X. perforans strains isolated from tomatoes and peppers grown in Alabama and compared them with previously published genome data available from GenBank. Surprisingly, reconstruction of the X. perforans core genome revealed the presence of two novel genetic groups in Alabama that each harbored a different transcription activation-like effector (TALE). While one TALE, AvrHah1, was associated with an emergent lineage pathogenic to both tomato and pepper, the other was identified as a new class within the AvrBs3 family, here designated PthXp1, and was associated with enhanced symptom development on tomato. Examination of patterns of homologous recombination across the larger X. euvesicatoria species complex revealed a dynamic pattern of gene flow, with multiple donors of Xanthomonas spp. associated with diverse hosts of isolation.IMPORTANCE Bacterial leaf spot of tomato and pepper is an endemic plant disease with a global distribution. In this study, we investigated the evolutionary processes leading to the emergence of novel X. perforans lineages identified in Alabama. While one lineage was isolated from symptomatic tomato and pepper plants, confirming the host range expansion of X. perforans, the other lineage was isolated from tomato and acquired a novel transcription activation-like effector, here designated PthXp1. Functional analysis of PthXp1 indicated that it does not induce Bs4-mediated resistance in tomato and contributes to virulence, providing an adaptive advantage to strains on tomato. Our findings also show that different phylogenetic groups of the pathogen have experienced independent recombination events originating from multiple Xanthomonas species. This suggests a continuous gene flux between related xanthomonads associated with diverse plant hosts that results in the emergence of novel pathogen lineages and associated phenotypes, including host range.

Xanthomonas perforans is the predominant pathogen responsible for bacterial leaf spot of tomato and X. euvesicatoria of pepper in the southeast United States. Previous studies have indicated significant changes in the X. perforans population collected from Florida tomato fields over the span of two decades including a shift in race, diversification into three genetic groups, and host range expansion to pepper. Recombination originating from X. euvesicatoria was identified as the primary factor driving the diversification of X. perforans in Florida. The aim of this study was to genetically characterize X. perforans strains that were isolated from tomato and pepper plants grown in Alabama and compare them to the previously published genomes available from GenBank. Surprisingly, a maximum likelihood phylogeny coupled with a Bayesian analysis of population structure revealed the presence of two novel genetic groups in Alabama, which each harbored a different transcription activation-like effector (TALE). While one TALE, avrHah1 , was associated with adaptation of X. perforans to pepper, the other was identified as a new class within the avrBs3 family, designated here as pthXp1 . Examination of patterns of homologous recombination between X. perforans and other closely related Xanthomonas spp. indicated that the lineages identified here emerged in part through recent recombination events originating from xanthomonads associated with diverse hosts of isolation. Our results also suggest that the evolution of pathogenicity to pepper has likely emerged independently within X. perforans and in one lineage, was associated with the recombination-mediated remodeling of the Xps type II secretion and TonB transduction systems. Importance The emergence of novel pathogen lineages has important implications in the sustainability of genetic resistance as a disease management tool in agricultural ecosystems. In this study, we identified two novel lineages of X. perforans in Alabama. While one lineage was isolated from symptomatic pepper plants, confirming the host range expansion of X. perforans , the other lineage was isolated from tomato and acquired a novel transcription activation-like effector, pthXp1 . Unlike AvrBs4, PthXp1overcomes Bs4-mediated resistance in tomato, indicating the evolution of this novel lineage towards fitness on this host. Our findings also show that different phylogenetic groups of the pathogen have experienced independent recombination events originating from multiple Xanthomonas species. This suggests a continuous gene flux between related xanthomonads associated with diverse plant hosts which results in the emergence of novel pathogen lineages and associated phenotypes, including host range expansion.

The development of more cold-tolerant short-cycle banana cultivars has made subtropical production possible, but fruiting may be unreliable in colder margins, such as the coastal region of Alabama, as a result of cold winter temperatures and other suboptimal growing conditions. Thus, the objectives of this study were to determine plant growth parameters that predict flowering, and to evaluate vegetative and reproductive growth of Cavendish and non-Cavendish banana cultivars. Pseudostem circumference and the height-to-circumference ratio (HCR) for tall cultivars and HCR for medium cultivars exhibited linear or quadratic relationships when regressed to the number of days from planting to inflorescence emergence (DPE), and hence were the best predictors of inflorescence emergence. The banana cultivars Double, Grand Nain, Cardaba, Ice Cream, and Goldfinger demonstrated cropping potential by producing mature bunches in the cooler environment of the subtropics and currently offer the best possibilities for banana production in Alabama.

Bananas have wide adaptability but environmental conditions will affect growth responses and plant vigour. The present study was initiated to determine the potential for banana fruit production in the coastal region of Alabama by comparing phenological parameter responses as a measure of plant vigour of five medium height cultivars: 'Cardaba', 'Gold Finger', 'Ice Cream', 'Raja Puri', and 'Veinte Cohol'. At 150 days after planting (DAP), 'Viente Cohol' and 'Ice Cream' produced significantly more leaves (38.8 and 38.3 leaves/plant, respectively) than 'Cardaba' and 'Raja Puri'. At 150 DAP, 'Cardaba' and 'Ice Cream' had a higher number of leaves present (NLP) than 'Raja Puri' indicating the plant's ability to maintain more leaves at a given time for the accumulation of dry matter. 'Gold Finger' exhibited the lowest height to circumference ratio value (HCR) of 3.28, indicating a stronger pseudostem to withstand lodging due to high winds or heavy crop load. 'Ice Cream' and 'Gold Finger' exhibited the greatest plant vigour and/or pseudostem strength overall and potential for fruit crop production in the region.

Studies have shown that conversion to conservation tillage from conventional tillage does not increase total soil organic carbon (SOC) significantly in the short term (<5yrs). While no-till increases total SOC in the medium to long term, it was hypothesized that the inclusion of high biomass cover crops and organic mulches may increase total SOC in the short term. The use of invasive, perennial leguminous species as mulch may sustainably increase SOC during limited-input fall vegetable production. The objective of this study, conducted in Alabama (USA), was to quantify total SOC changes due to organic mulches and forage soybean (Glycine max (L.) Merr. cv. Derry) as a summer cover crop after conversion to no-till during limited-input fall collard (Brassica oleracea L.) production. Forage soybean as a summer cover crop did not increase SOC. No-till without mulch (control treatment) significantly increased SOC at 0-5cm from 6.3 to 14.0gkg(-1) soil in 3yrs, whereas inclusion of cut-and-carry mulches increased SOC to 22.6gkg(-1) soil. Treatments did not affect collard yield, which averaged 17,863kgha(-1) yr(-1). This represents a novel, limited-input system that may help control on-farm invasive species while sustainably increasing SOC in the short term.