Evaluation of Sulfentrazone Alone or in Combination with Other PRE and POST Herbicides for Weed Control in Tomato (Solanum lycopersicum) and Strawberry (Fragaria ×ananassa)

Sulfentrazone was recently registered for use in tomato and strawberry in Florida. Field experiments were conducted at the Gulf Coast Research and Education Center in Wimauma, FL, to evaluate PRE sulfentrazone applications when applied on flat soil 30 days before bed formation (PRE-f), on the bed top immediately before laying plastic mulch (PRE-t), applied PRE-t as a tank mix with other PRE herbicides, or PRE-t followed by POST halosulfuron or rimusulfuron (POST). Sulfentrazone did not damage the tomato and strawberry crop and had no effect on strawberry and tomato fruit yield. It was as effective as the industry standards but none of the evaluated herbicide treatments provided adequate weed control. POST halosulfuron in tomato resulted in significantly greater nutsedge control at 11 (14%) and 13 (27%) weeks after initial treatment (WAIT) compared with other treatments in Fall 2019 and Spring 2020, respectively. However, in tomato, tank-mixing sulfentrazone with S-metolachlor or metribuzin did not enhance nutsedge control. Weed control did not improve with increased rates or with the use of PRE-f followed by (fb) PRE-t applications in tomato. PRE-t sulfentrazone fb POST halosulfuron was an efficient nutsedge management option in tomato. Sulfentrazone alone did not effectively control weeds in tomato or strawberry. Increased rates of sulfentrazone with the use of PRE-f fb PRE-t sulfentrazone applications did reduce (34%) total weed density in strawberry.

The Enhanced Expression of Cruzipain-Like Molecules in the Phytoflagellate Phytomonas serpens Recovered From the Invertebrate and Plant Hosts

Phytomonas serpens is a protozoan parasite that alternates its life cycle between two hosts: an invertebrate vector and the tomato fruit. This phytoflagellate is able to synthesize proteins displaying similarity to the cysteine peptidase named cruzipain, an important virulence factor from Trypanosoma cruzi, the etiologic agent of Chagas disease. Herein, the growth of P. serpens in complex medium (BHI) supplemented with natural tomato extract (NTE) resulted in the increased expression of cysteine peptidases, as verified by the hydrolysis of the fluorogenic substrate Z-Phe-Arg-AMC and by gelatin-SDS-PAGE. Phytoflagellates showed no changes in morphology, morphometry and viability, but the proliferation was slightly reduced when cultivated in the presence of NTE. The enhanced proteolytic activity was accompanied by a significant increase in the expression of cruzipain-like molecules, as verified by flow cytometry using anti-cruzipain antibodies. In parallel, parasites incubated under chemically defined conditions (PBS supplemented with glucose) and added of different concentration of NTE revealed an augmentation in the production of cruzipain-like molecules in a typically dose-dependent way. Similarly, P. serpens recovered from the infection of mature tomatoes showed an increase in the expression of molecules homologous to cruzipain; however, cells showed a smaller size compared to parasites grown in BHI medium. Furthermore, phytoflagellates incubated with dissected salivary glands from Oncopeltus fasciatus or recovered from the hemolymph of infected insects also showed a strong enhance in the expression of cruzipain-like molecules that is more relevant in the hemolymph. Collectively, our results showed that cysteine peptidases displaying similarities to cruzipain are more expressed during the life cycle of the phytoflagellate P. serpens both in the invertebrate and plant hosts.

First report of tomato fruit blotch virus infecting tomatoes in Brazil

Recently, a new blunervirus was reported in tomatoes showing fruit chlorotic lesions. This virus, named tomato fruit blotch virus (ToFBV), was found associated with the tomato fruit blotch disease in Italy and Australia, even though Koch’s postulates were not fulfilled and no viral particles were seen in leaf dips observed with an electron microscope (Ciuffo et al. 2020). In December 2019, symptoms of circular or irregular chlorotic blotches were observed in tomato fruits in an organic farm in Distrito Federal, Brazil. Five different tomato cultivars (2100 plants of cv. Sweet grape, 1700 of Giacomo, 560 of Grazianni, 160 of Tropical, and 160 of DRC 5640) were being grown in two greenhouses and all of them presented the symptoms in at least one fruit, particularly in older fruits. No virus-like symptoms were observed in young and middle leaves, but older leaves could not be examined because they were removed as a routine activity of the farm; and also due to the moderate infestation of the tomato russet mite Aculops lycopersici, associated with leaf and stem necrosis. No viral particles were observed in an electron microscope analysis of symptomatic fruit tissues, and sap inoculation and grafting of stems did not produce any symptom in indicator plants. Two young and asymptomatic plants with the first fruits still in development were removed from another greenhouse of the farm and transported to our greenhouse, but the typical blotch symptoms neither appeared in the fruits nor the necrosis symptoms in the leaves. Serological tests performed for all collected leaf and fruit samples using antibodies produced in-house against common tomato-infecting tospoviruses and potyviruses were negative, as well as a polymerase chain reaction (PCR) detection test for begomoviruses (Rojas et al. 1993). Total RNA from newly collected samples consisting of one symptomatic fruit sample and five asymptomatic leaf samples from distinct plants were individually extracted using RNeasy Plant Mini Kit (Qiagen, Hilden, Germany) and pooled for next generation sequencing (NGS). The library was constructed using TruSeq Stranded Total RNA with Ribo-Zero Plant (Illumina, San Diego, USA) and sequenced at Macrogen, Inc. (Seoul, South Korea) in an Illumina Novaseq6000 platform. The 4,621,977,958 reads obtained were trimmed using Trimommatic 0.35 (Bolger et al. 2014) and contigs were assembled using Velvet (Zerbino and Birney 2008). Following tblastx analysis on Geneious 9.1.8 (Biomatters Ltd.) and BLAST on the NCBI platform (Altschul et al. 1990), seven contigs matching tomato chlorosis virus (ToCV) and five contigs matching ToFBV were identified. Sequences for each of the four genome components of ToFBV (MK517477-MK517480) already present in databases were used as reference using the Map to Reference function in Geneious. A total of 338,402, 78,039, 555,302 and 461,474 reads mapped to virus genome components 1 to 4, respectively, with >99% coverage for each. Four final consensus sequences were used for BLAST analyses on NCBI and presented 97 to 99.7 % nucleotide identity with those used for mapping. These sequences were deposited in GenBank as isolate MAL under accession numbers MW546267 (RNA 1, 5770 nt), MW546268 (RNA 2, 3612 nt), MW546269 (RNA 3, 2826 nt) and MW546270 (RNA 4, 1950 nt). The primer pair Bluner1F (5’-ATTCCTGTTCCTTCGGATAAACTCGT-3’) and Bluner1R (5’-CACACGTGCAGGAAATGGAAAGA-3’) directed to RNA 1 was used to specifically detect the virus. Three leaf samples and two fruit samples, each from a different plant with typical symptoms, were tested positive for ToFBV and negative using ToCV-specific primers in RT-PCR (Dovas et al. 2002). This confirmed that although some plants pooled in the HTS library were infected with ToCV, the chlorotic blotch symptom was clearly associated with the presence of ToFBV. Furthermore, the ~0.5 kbp amplicon for ToFBV-specific primers from one randomly selected sample was sequenced with both primers and the resulting sequence shared 100% nt identity with the RNA 1 of ToFBV isolate Fondi2018 from Italy (MK517477). Then, the virus was detected in the tissue from the surface of another fruit, but not from its internal part, suggesting a superficial infection. The findings presented here are of high phytosanitary significance, given the strong symptoms associated with tomato fruit blotch disease and the identification of ToFBV in the tomato samples from Brazil.

Additional Blue LED during Cultivation Induces Cold Tolerance in Tomato Fruit but Only to an Optimum

Tomato is a chilling-sensitive fruit. The aim of this study is to examine the role of preharvest blue LED lighting (BL) to induce cold tolerance in ‘Foundation’ tomatoes. Blue and red supplemental LED light was applied to achieve either 0, 12 or 24% additional BL (0B, 12B and 24B). Mature green (MG) or red (R) tomatoes were harvested and cold stored at 4 °C for 0, 5, 10, 15 and 20 d, and then stored for 20 d at 20 °C (shelf life). Chilling injury (CI) indices, color and firmness, hydrogen peroxide, malondialdehyde, ascorbic acid and catalase activity were characterized. At harvest, R tomatoes cultivated at 12B were firmer and showed less coloration compared to fruit of other treatments. These fruits also showed higher loss of red color during cold storage and lower CI symptoms during shelf-life. MG tomatoes cultivated at 12B showed delayed coloring (non-chilled) and decreased weight loss (long cold stored) during shelf life compared to fruit in the other treatments. No effects of light treatments, both for MG and R tomatoes, were observed for the selected antioxidant capacity indicators. Improved cold tolerance for R tomatoes cultivated at 12B points to lycopene having higher scavenging activity at lower concentrations to mitigate chilling injury.

The Response of Tomato Fruit Cuticle Membranes Against Heat and Light

Two important biophysical properties, the thermal and UV-Vis screening capacity, of isolated tomato fruit cuticle membranes (CM) have been studied by differential scanning calorimetry (DSC) and UV-Vis spectrometry, respectively. A first order melting, corresponding to waxes, and a second order glass transition (Tg) thermal events have been observed. The glass transition was less defined and displaced toward higher temperatures along the fruit ripening. In immature and mature green fruits, the CM was always in the viscous and more fluid state but, in ripe fruits, daily and seasonal temperature fluctuations may cause the transition between the glassy and viscous states altering the mass transfer between the epidermal plant cells and the environment. CM dewaxing reduced the Tg value, as derived from the role of waxes as fillers. Tg reduction was more intense after polysaccharide removal due to their highly interwoven distribution within the cutin matrix that restricts the chain mobility. Such effect was amplified by the presence of phenolic compounds in ripe cuticle membranes. The structural rigidity induced by phenolics in tomato CMs was directly reflected in their mechanical elastic modulus. The heat capacity (Cprev) of cuticle membranes was found to depend on the developmental stage of the fruits and was higher in immature and green stages. The average Cprev value was above the one of air, which confers heat regulation capacity to CM. Cuticle membranes screened the UV-B light by 99% irrespectively the developmental stage of the fruit. As intra and epicuticular waxes contributed very little to the UV screening, this protection capacity is attributed to the absorption by cinnamic acid derivatives. However, the blocking capacity toward UV-A is mainly due to the CM thickness increment during growth and to the absorption by flavone chalconaringenin accumulated during ripening. The build-up of phenolic compounds was found to be an efficient mechanism to regulate both the thermal and UV screening properties of cuticle membranes.