Characterization of Soil Suppressiveness to Root-Knot Nematodes in Organic Horticulture in Plastic Greenhouse

Abstract

The fluctuation of Meloidogyne population density and the percentage of fungal egg parasitism were determined from July 2011 to July 2013 in two commercial organic vegetable production sites (M10.23 and M10.55) in plastic greenhouses, located in northeastern Spain, in order to know the level of soil suppressiveness. Fungal parasites were identified by molecular methods. In parallel, pot tests characterized the level of soil suppressiveness and the fungal species growing from the eggs. In addition, the egg parasitic ability of 10 fungal isolates per site was also assessed. The genetic profiles of fungal and bacterial populations from M10.23 and M10.55 soils were obtained by Denaturing Gradient Gel Electrophoresis (DGGE), and compared with a non-suppressive soil (M10.33). In M10.23, Meloidogyne population in soil decreased progressively throughout the rotation zucchini, tomato, and radish or spinach. The percentage of egg parasitism was 54.7% in zucchini crop, the only one in which eggs were detected. Pochonia chlamydosporia was the only fungal species isolated. In M10.55, nematode densities peaked at the end of the spring-summer crops (tomato, zucchini, and cucumber), but disease severity was lower than expected (0.2–6.3). The percentage of fungal egg parasitism ranged from 3 to 84.5% in these crops. The results in pot tests confirmed the suppressiveness of the M10.23 and M10.55 soils against Meloidogyne. The number of eggs per plant and the reproduction factor of the population were reduced (P < 0.05) in both non-sterilized soils compared to the sterilized ones after one nematode generation. P. chlamydosporia was the only fungus isolated from Meloidogyne eggs. In in vitro tests, P. chlamydosporia isolates were able to parasitize Meloidogyne eggs from 50 to 97% irrespective of the site. DGGE fingerprints revealed a high diversity in the microbial populations analyzed. Furthermore, both bacterial and fungal genetic patterns differentiated suppressive from non-suppressive soils, but the former showed a higher degree of similarity between both suppressive soils than the later.

Population dynamics of Meloidogyne incognita on cucumber grafted onto the Cucurbita hybrid RS841 or ungrafted and yield losses under protected cultivation

“…Dasher II was grafted onto Cucurbita maxima x C. moschata hybrid RS841 by tongue approach, because it is easy to apply, successful, and provides a uniform growth rate (Davis et al 2008 ). The squash hybrid RS841 has been proven to develop a longer root system than cucumber and to improve crop yield (Maršić and Jakše 2010 (Giné et al 2016 ). Plants were irrigated as needed through a drip irrigation system and weekly fertilized with a solution consisting of NPK (15-5-30) at 31 kg ha and iron chelate and micronutrients at 0.9 kg ha .…”

Management of Root Knot Nematode on Tomato through Grafting Root Stock of Solanum sisymbriifolium

“…Root-knot nematodes are common and destructive plant parasitic nematodes which have wide host range and can significant yield loss in many crops (Giné et al 2016). They are polyphagous and reported in many crops such as tomato, brinjal, okra, potato, chilly, radish, carrot, onion, cabbage, cauliflower, lettuce, chickpea, broad bean, cowpea, cucumber, pumpkin and various gourds from plains to high hills of the country Shrestha 1969, PPD 2009).…”

“…In tomato, root-knot nematodes are major biotic factor which is responsible for low yield (Giné et al 2016). It has been reported that on an average of 30 percent tomato fruits was reduced due to the nematodes in plastic tunnels at Hemja of Kaski district (PPD 2008).…”

Commercial Formulates of Trichoderma Induce Systemic Plant Resistance to Meloidogyne incognita in Tomato and the Effect Is Additive to That of the Mi-1.2 Resistance Gene

“…The site M10.55 was a sandy clay loam soil (68% sand, 0% silt, and 32% clay), pH 8.1, 2.5 organic matter (w/w), and 1,069 µS cm −1 electric conductivity. Both soils were previously characterized as suppressive to Meloidogyne, with P. chlamydosporia as the only fungal species recovered from RKN-parasitized eggs (Giné et al, 2016). Each soil was mixed with steam-sterilized sand at a ratio of 1:1 (dry w/dry w), to avoid soil compaction and to improve plant growth, and served as substrate for cropping tomato plants in 3-l pots.…”

“…might limit growth of other soil microorganisms by predation or resource competition, including nematode antagonistic fungi such as Pochonia (Metacordyceps) chlamydosporia. This fungal species is frequently isolated from RKN eggs produced in vegetable crop roots cultivated in northeastern Spain (Giné et al, 2012) and has been reported as the main biotic factor responsible for soil suppressiveness to RKN in this area (Giné et al, 2016). In addition, it has been reported that some P. chlamydosporia strains can induce systemic resistance in tomato plants (Ghahremani et al, 2019).…”