Information about the availability of soil mineral nitrogen (N) in organic greenhouse tomatoes after the application of mobile green manure (MGM), and its impact on plant nutrient status and yield is scarce. Considering this knowledge gap, the effects of legume biomass from faba beans that are cultivated outdoors (FAB), or from feed-grade alfalfa pellets at two different doses (AAL = 330 g m⁻²; AAH = 660 g m⁻²) that were applied as MGM on the nutrition and yield of an organic greenhouse crop of tomatoes were evaluated. All of the MGM treatments increased the mineral N concentrations in the soil throughout the cropping period, and the total N concentration in tomato leaves when compared to the untreated control. FAB and AAH treatments had a stronger impact than AAL in all of the measured parameters. In addition, AAL, AAH, and FAB treatments increased the yield compared to the control by 19%, 33%, and 36%, respectively. The application of MGM, either as faba bean fresh biomass or as alfalfa dry pellets, in organic greenhouse tomatoes significantly increased the plant available soil N, improved N nutrition, and enhanced the fruit yield. However, the N mineralization rates after the MGM application were excessive during the initial cropping stages, followed by a marked decrease thereafter. This may impose an N deficiency during the late cropping period.

In the present study, in addition to farmyard manure (FYM), cowpea was applied as green manure and faba bean as an intercrop in an organic greenhouse tomato crop, aiming to increase the levels of soil N. Three experiments (E1, E2, E3) were carried out, in which legumes were either noninoculated or inoculated with rhizobia alone or together with plant growth, promoting rhizobacteria. Inoculation of legumes with rhizobia considerably increased N₂ fixation in E1 but had no impact on N₂ fixation in E2 and E3. In E1, the application of cowpea decreased yield because it imposed a stronger nematode infection as the cowpea plants acted as a good host for Meloidogyne. However, in E2 and E3 the nematode infection was successfully controlled and the legumes significantly increased the tomato yield when inoculated in E2, irrespective of legume inoculation in E3. The total N concentration in the tomato plant tissues was significantly increased by legume application in E2 and E3, but not in E1. These results show that legumes applied as green manure can successfully complement N supply via FYM in organic greenhouse tomato, while legume inoculation with rhizobia can increase the amounts of nitrogen provided to the crop via green manure.

An organic greenhouse crop of tomato was established in February following cultivation of cowpea (CP) or common bean (CB) for green pod production, or faba bean (FB) for green manuring. The vegetative residues of CP and CB were incorporated to the soil together with farmyard manure (FYM), prior to establishing the tomato crop. The FB plants were incorporated to the soil at anthesis together with either FYM or composted olive-mill waste (CO). Green manuring with FB resulted in higher soil mineral N levels during the subsequent tomato crop and higher tomato fruit yield when combined with FYM, compared to compost. The level of soil mineral N was the main restrictive factor for yield in organic greenhouse tomato. FB for green manuring as preceding crop to tomato increased significantly the level of soil mineral N and tomato yield compared to CB or CP aiming to produce green pods. The lowest tomato yield was obtained when the preceding crop was CB cultivated for green pod production. The soil mineral N was significantly higher when FYM was applied as base dressing compared with CO, despite the higher total N concentration in CO, pointing to slower mineralization rates of CO during tomato cultivation.

Pepino mosaic virus (PepMV) (genus Potexvirus, family Flexiviridae) is a mechanically transmitted virus that has emerged as a significant problem of greenhouse tomato crops in Europe and around the world during the past 10 years (1). In spring of 2010, mosaic symptoms were observed on leaves of cherry tomato (Lycopersicon esculentum var. cerasiforme) greenhouse crops (hybrids Shiren, Tomito, and Rubino top) in the areas of Drymos and Vonitsa, located at Aitoloakarnania Prefecture, in Greece. A total of 63 tomato samples (55 from symptomatic and 8 from asymptomatic plants) were collected from 11 greenhouses where disease incidence ranged from 10 to 20%. All samples were tested by double-antibody sandwich (DAS)-ELISA using polyclonal antibodies from BIOREBA, AG (Reinach, Switzerland) for the presence of PepMV, Cucumber mosaic virus (CMV), and Tomato mosaic virus (ToMV). Leaf tissue from PepMV-, CMV-, and ToMV-infected samples and virus-free tomato plants were included in all tests as positive and negative controls, respectively. Results showed that 53 symptomatic samples collected from all greenhouses were infected with PepMV and two were co-infected with PepMV and CMV. Total RNA was extracted from all infected plants with a commercially available kit (Qiagen, Hilden, Germany) and amplified by conventional and real-time reverse transcription (RT)-PCR, using previously reported protocols (2). Positive and negative controls were also included in each assay. The 200-bp amplified PCR fragments of Triple Gene Block 3 (TGB3) obtained from five infected samples were purified and both strands were sequenced. Sequencing data were analyzed, deposited in the GenBank, and compared with other reported sequences. In addition, leaf tissue from five samples infected with only PepMV was used for mechanical inoculation of four plants of Nicotiana glutinosa, N. benthamiana, and tomato (L. esculentum FA 179 hybrid) plants. As negative controls, two plants from each species were used. Sequencing analysis showed that all five PepMV sequences were identical (GenBank Accession Nos. FR686904 to FR686908) and possessed 100% identity PepMVstrain CH2 (DQ000985). Inoculation results showed that the virus was successfully transmitted to N. benthamiana and tomato plants which developed mosaic symptoms, and tested positive by DAS-ELISA and RT-PCR. N. glutinosa plants did not develop any symptoms and were found to be free of PepMV when tested by DAS-ELISA and RT-PCR. To our knowledge, this is the first report of PepMV in Greece. Further studies on the disease prevalence and incidence and its economic impact on tomato production are required. PepMV is currently under quarantine status in the EU and therefore new protective measures should be recommended to prevent the spread of PepMV to other regions of Greece. References: (1) I. M. Hanssen and B. P. H. J. Thomma. Mol. Plant Pathol. 11:179, 2010. (2) K. S. Ling et al. J. Virol. Methods 144:65, 2007.

Manure is a common source of nitrogen (N) in organic farming. However, manure is not always easily available, while the maximum N amount added as animal manure in organic agriculture is restricted by EU regulations. The present study was designed to test whether green manuring with a warm-season legume and intercropping with a cold-season legume can substitute farm-yard manure or compost as N sources in organic greenhouse tomato crops. To test this hypothesis, a winter-spring (WS) tomato crop was installed in February following the incorporation of crop residues of an autumn-winter (AW) tomato crop intercropped with faba bean, which had been fertilized with cowpea residues as green manure. This treatment, henceforth termed legume treatment (LT), was compared with the use of compost or manure as an N fertilization source in both tomato crops. In addition, a combination of compost and LT was also used as a fourth treatment. The results showed that green manuring with legumes and particularly cowpea can contribute a significant amount of N to the following organic tomato crop, through the biological fixation process. Nevertheless, legumes as green manure, or compost, or their combination cannot efficiently replace farmyard manure as an N fertilization source. Compost exhibited a slow mineralization course.

ISHS XXX International Horticultural Congress IHC2018: II International Symposium on Organic Horticulture for Wellbeing of the Environment and Population Assessing the possibility to use legume plants as cover crops or intercrops in organic tomato production to optimize NUE