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Abstract Nematodes of the genus Meloidogyne (RKN) are very destructive pests that have a wide host range on horticultural and eld crops causing yield losses of up to 45-60 per cent. The most important nematode pests of potatoes in Egypt are Meloidogyne species (principally Meloidogyne incognita and M. javanica) which infest roots and tubers, causing root injury that severely reduces yields and may accelerate the ”early dying disease.” Root-knot nematode galling of tubers is a serious quality defect. Several control measures were employed to control root-knot nematodes in infested areas. The traditional method of nematode control is based mainly on chemical nematicides. However, the potential negative impact on environment and ineffectiveness after prolonged use have led to a total ban or restricted use of most chemical nematicides and an urgent need for safe and more effective alternatives. Biocontrol as an integral part of management is an attractive option for plant parasitic nematodes that should be pursued besides the cultural practices of crop rotation and organic amendments. Using of biological pesticides, either of bacterial or fungi origin, and the addition of organic material to the soil can be an effective alternatives to the environmentally unsafe chemical treatments that are used to control plant parasitic nematodes. Therefore, the present study analyzed the suppressive effects of some commercial formulations of biological pesticides, either of bacterial or fungal origin, on the soil populations of the second-stage juveniles of root-knot nematode, Meloidogyne spp., in potato fields. Also, we evaluated the efficacy of the addition of some organic materials to the soil, either alone or combined with the tested biological products on the occurrence of nematode density. Four cultivars of potato were planted during 2016/2017 season. We hypothesized that the addition of organic materials, either alone or mixed with selected biopesticides, could provide faster and better nematode suppression attacking potato. The present study was carried out on potato, Solanum tuberosum L., infesting with damaging populations of root-knot nematodes, Meliodogyne spp., under field conditions at Meeleg valley, Shebin El-Kom, Menoufia, during 2016/2017 season. Four cultivars of potato were planted, viz. Spunta The products we tested were: Dipel® (a biological pesticide containing the naturally occurring microorganism, Bacillus thuringiensis subspecies kurstaki (Btk)); NemaFree® (a biological pesticide containing bacteria, Serratia sp.); Mycorrhizeen® (a biological pesticide containing fungus, Arbuscular mycorrhizal); and NemaStop® (a plant-based biological product combined with fatty acids with claims of nematode suppression). Additionally, we tested some biofertilizers (Nitrobein® and Phosphorin®), organic compost, and poultry manure. Treatments were compared to untreated control plots and plots treated with the labeled rate of Counter® l5 G. Each experimental product was applied at rates corresponding to the manufacturer’s recommendations. There were three replications of each treatment. Therefore, the main purposes of the present study was to: Evaluate the sensitivity of some varieties (cultivars) of potatoes commonly grown in Egypt to the infection of nematodes. Evaluate the effectiveness of certain commercial formulations of biological pesticides of bacteria, fungi, or plant origins as alternatives to the conventional nematicides, especially against the most abundant nematode genera, RKN, Meloidogyne spp. Evaluate the effectiveness of selected natural organic products, i.e. poultry manure, organic compost, yeast, and organic biofertilizers, in controlling the population density of nematodes, in comparison with Counter 15G (Terbufos), as one of the most commonly conventional nematicides used. Evaluate the effectiveness of several mixtures of selected biocides, with different organic materials, in reducing the population density of root-knot nematodes. Determine the effects of different treatments on improving the tuber yield productivity of potatoes. Determine the effect of different treatments on the activity levels of catalase and peroxidase enzymes as important antioxidants, and estimating the nature of the relationship between them. Herein, we summarize the results of each part of the present study: 1. Survey of Plant-Parasitic Nematode Genera Associated with Potato Cultivars In the first part of our study, the data of incidence nematode population infesting different cultivars of potato showed the presence of different nematode genera. There were eight nematode genera associated with potato soils, viz. The root-knot nematode, Meloidogyne spp. (Meloidogynidae) was considered as the most widely distributed genera with the four potato cultivars followed by: root lesion, nematode , Pratylenchus (Pratylenchidae), spiral nematode, Helicotylenchus, stunt nematodes, Tylenchorhychus (Tylenchorhynchidae), stubby-root nematodes, Trichodorus (Trichodoridae), dagger nematode, Xiphinema (Longidoridae), needle nematodes, Longidorus (Longidoridae), ring nematode, Criconemoides (Criconematidae). the most sensitive to be infested by nematodes. 2. Effects of Different Treatments on Root-Knot Nematodes Infecting Potato under Field Applications 2.1. The Efficacy of selected Formulations of Biological Pesticides in Management of Root-Knot Nematode The data showed that most of the selected biocides significantly reduced the population densities of root-knot nematodes. The NemaFree treatment reduced the number of nematodes by 84.7% (estimated using the Henderson & Tilton ’formula), followed by NemaStop (82.6%) and Dipel® (82.2%) compared to the traditional nematicide used, Counter treatment which reduced the population density by 91.2%, after one month of treatment. The effectiveness of these biopesticides in reducing the number of nematodes extended up to 105 days of treatment, indicating reduction percentages by 90.2, 75.9, 83.2, 84.1%, respectively. In general, the overall means of reduction percentages of nematode juveniles showed that the most effective treatments were: Nemafree, Dipel®, Nemastop, and Counter, where reduction (%) ranged from 89.5 to 85.1% 2.2. Efficacy of selected organic-Soil Amendments in Nematode Management The results showed that application of organic compost resulted in a significant effect in reducing the population density of nematode after one month of treatment by 54.5%, followed by Nitrobein (25.8%), Phosphorin (22.3%), Potassium silicate (22.5%). The overall means of reduction percentages of nematode juveniles along the period of experiment showed that the most effective treatments were: Compost (66.3%) followed by Poultry manure (47.1%) and Phosphorin (45.2%). 2.3. Effectiveness of Treatment with selected Biopesticides in Combinations with Organic-Soil Amendments The treatment of tested biopesticides in combination with organicor biofertilizers showed significant increase in the effectiveness of these components when applied alone. For example, the results showed that the best mixture proposed was: [Compost + NemaStop+ Dipel®], which reduced the population density of nematodes by 94.4% after one month of treatment, followed by mixtures: [Poultry manure+ NemaStop + Dipel®] and [Poultry manure+ NemaStop] with reduction percentages by 93.6% and 90.6%. respectively. It is worth noting that the effectiveness of these mixtures extended until the 105-day of treatment, causing a decrease in the number of nematode juveniles by 95.3, 90.6, 92.4%, respectively. The overall means of reduction percentages of nematode juveniles along the whole period of experiment showed that the most effective treatments were mixtures of: Compost+Nemastop+ Dipel® (96.05%), Poultry manure+ Nemastop+ Dipel® (93.8%), Poultry manure+ Nemastop (93.8%) and Potassium silicate + Nemastop (92.9%). 3. Effects of Treatments on Potato Productivity The results of treatment with tested biological pesticides showed an overall increase in the average plant productivity of tubers weight, as compared with that in the untreated control. Mycorrhizeen® significantly increased the mean total weight of tubers / plant by 47.8%, followed by Nemafree (41.8%) and NemaStop (38.7%), in comparison with Counter -treatment which increased the potato productivity by 45.7% than that of the control. The results also showed that the addition of organic products (both bio-fertilizer and organic compost) led to a significant increase in the average productivity of the tubers per plant, compared to the control. Where, soil amendments with either Poultry manure, Phosphorin®, or Organic compost resulted in an increase in potato tuber weights by 41.4, 41.1 and 31.2%, respectively. While the effect of Potassium silicate fertilizer and Nitrobein seemed to be the least effective, although it increased crop productivity by 19.7% and 20.9%, respectively. Our results also revealed that soil treatment with selected biological products in combination with organic- and bio-fertilizes significantly increased the average plant productivity of tubers by weight. The most significant mixtures in increasing yield productivity were the following mixtures, in order: [Compost+NemaStop] > [Poultry manure+ Nemastop] > [Poultry manure+ Nemastop+ Dipel®], which increased the average plant productivity of tubers by weight: 61.6, 53.8 and 51.8%, respectively. 4. Improvement of Antioxidant Enzymes in Potato by Application of Biological Pesticides and Organic Bioactive Products The levels of enzymatic -antioxidants, Catalase and Peroxidase, were estimated in potato leaves from different treatments and compared with these of the control treatment. The importance of these estimates is due to the vital importance of both enzymes as antioxidants which they play an important role in protecting the body’s tissues from oxidative stress caused by the increase of cracks / free radicals that contain the oxygen element which may be happened as a result of nematode attack. Therefore, the results of the chemical evaluation of the activity of these two enzymes showed the following: (1) Catalase activity Our data showed that NemaStop®, NemaFree®, Mycorrhizeen®, Dipel® resulted in a significant increase in the activity of this enzyme along the experimental period until the 105- day of the treatment, compared to the untreated control. It is worth noting that there is a significant decrease in the level of activity of this enzyme in plant tissues treated with the traditional nematicide, Counter . The addition of Potassium silicate and Poultry manure had also significantly increased the level of this enzyme. The integrated effect of adding organic biofertilizers to selected biocide increased the levels of enzyme activity. The most significant mixtures were the following mixtures: Summary [Nemastop + Nitrobin], [Nemastop + Phosphorin], [Nemastop + Compost] and [Nemastop + Potassium silicate]. (2) Peroxidase activity The results showed, in general, that the effects of different treatments on the levels of Peroxidase were less affected than that reported on Catalase activity. For example, treatment with bacterial biocide, Dipel®, resulted in a slight increase (17%) in the activity of peroxidase than that of the control. Similarly, the enzymatic activity was slightly increased after 60 days of soil treatments with tested biofertilizer Phosphorin (18.4%), Compost (18.8), Nitrobin (17.2%) and Poultry manure (15.8%) as compared to that of the control. The addition of organic biofertilizers to selected biopesticide in mixtures: i.e. [Nemastop+ Phosphorin], [Nemastop + Poultry manure], [Nemastop + Dipel®+ Compost], resulted in slight increases (~ 14.3- 17.2%) in enzyme activity levels as compared to that of the control. from all aforementioned results, it is concluded that using the biological pesticides, Dipel®, NemaFree®, and NeemStop®, resulted in reducing the J2-stage of root-knot nematode in potato fields. The nematicidal activity of biological pesticides increased if mixed with some bio-organic fertilizers. The best proposed mixture was: [Dipel®+ NemaStop + Organic compost], followed by [Dipel®+ Nemastop + Poultry manure], [Nemastop + Poultry manure]. Consequently, the average productivity of tuber yield per plant increased. The study confirmed the importance of using biological Summary biopesticides: Nemastop, Nemafree, Mycorrhizeen, Dipel®, especially if applied in mixtures with certain organic substances to increase the activity levels of antioxidant enzymes, Catalase and Peroxidase, which protect plant tissues from excessive oxidation due to attacking plants with nematodes. |