Enzymatic Changes in Pomegranate Cultivars Infected with Phyto-Nematode Species with Emphasis on Role of Humic Acid Products in Controlling Root-Knot Nematode

Nitrated fly ash inhibits root-knot nematode and alleviates biotic stress in beetroot: A novel approach towards soil friendly nematode management

Malabar spinach (Basella alba L.) is a widely consumed leafy vegetable in Vietnamese daily meals. It has a short growth cycle but is susceptible to various diseases, of which the nematode Meloidogyne spp. is a significant factor causing yield reduction. This study focused on finding native plant growth-promoting rhizobacteria that can control root-knot nematodes and stimulate plant growth. The results isolated and selected Bacillus velezensis BHMT4.1, Staphylococcus carnosus CCMT2.1, and Pseudomonas fluorescens HMMT1.1, which showed promise in controlling Meloidogyne spp. in Malabar spinach and promoting plant growth. In the in vitro experiment, the B. velezensis BHMT4.1 strain caused the highest immobilization of J2 with 68.67%, followed closely by the P. fluorescens HMMT1.1 strain with 66.67%. The S. carnosus CCMT2.1 strain inhibited nematode egg hatching after 7days, achieving a rate of 42.67%, while B. velezensis HMMT1.1 reached 44%. In addition, the B. velezensis BHMT4.1 strain demonstrated the best ability to produce siderophores on CAS agar after 48h. The P. fluorescens HMMT1.1 strain exhibited the highest nitrogen fixation ability after 3days of culture on the NFb medium. In greenhouse trials, Malabar spinach was inoculated with the S. carnosus CCMT2.1, reducing the number of galls to 16.29% in comparison to the control, which stood at 91.88%. Additionally, the nematode density in the soil decreased to 45.20 individuals compared to the control of 66.66 individuals (nematodes/50g soil) after 28days. This study showed that native bacterial strains found in vegetable soil have the ability to enhance plant development and protect Malabar spinach from being attacked by Meloidogyne spp. The results suggest that these bacterial strains could be further developed into potential biopesticides to help reduce root-knot nematode damage. Additional field studies are necessary to assess how well these bacteria adapt to the rhizosphere ecosystem of vegetable plants.

Root knot nematode infection poses a serious threat to Okra cultivation in Nigeria. A field research was conducted at the Teaching and Research Farm of the Federal University of Agriculture, Makurdi, Benue State to offer valuable insights into combating root-knot nematode infections on okra using different fertilizer types. The experiment was designed using a factorial design with three (3) varieties of okra and two fertilizer treatments at different intervals. The seeds were planted two (2) seeds per hole on a spacing of 50cm after which normal agronomic practices were carried out on nematode infested soil. The results indicate that both SuperGro liquid fertilizer and Geese dung have potential in suppressing root-knot nematode infections on okra. Specifically, the application of Geese dung at either 2 or 4 weeks interval demonstrated a notable reduction in root gall index (RGI), suggesting its effectiveness in mitigating nematode damage. Furthermore, the application of Geese dung led to improved yield, manifested through increased fruit size and quantity. However, it's crucial to note that the application of SuperGro fertilizer at a 4-week interval resulted in a significantly higher Root Gall Index (RGI) compared to other treatments. The research highlights the potential of organic fertilizers like Geese dung as a sustainable and effective means of nematode control in okra cultivation. Nonetheless, future studies are warranted to identify the active ingredients in Geese dung responsible for nematode suppression, which could provide valuable insights for refining treatment protocols and enhancing agricultural practices.

The purpose of the research is studying the species composition and control measures against parasitic nematodes of wild and cultivated subtropical fruit plants of Central Asia.Materials and methods. We studied subtropical fruit crops in 198 farms and 1985 household plots located in various soil and climatic zones of over 20,675 hectares in Central Asia. The materials were collected in the autumn (September-October), spring (April-May) and summer (June-August) months in 1970–1990 by the route method. Study subjects were plant parasitic nematodes of 8 species of wild and cultivated subtropical fruit plants in the Central Asian republics. A modified Baermann funnel method was used to isolate plant nematodes from plants and soil near roots. In total, we collected and analyzed more than 5,400 plant and soil samples. To identify the species of plant parasitic nematodes, we used the Atlas of plant parasitic nematodes compiled at the Institute of Parasitology of the Russian Academy of Sciences, as well as morphometric indicators obtained according to the generally accepted De Mann formulae.Results and discussion. More than 129,000 specimens of plant parasites of 98 species were found in the studied wild and cultivated subtropical fruit crops and soil near their roots. In many farms of the Central Asian republics, we found southern root-knot nematodes, peanut root-knot nematodes, javanese root-knot nematodes, and cotton root-knot nematodes in mixed populations. In Uzbekistan, the prevalence in these crops was from 8 to 61.3%, in Tajikistan – from 78 to 98%, in Turkmenistan – from 6 to 98%, and in Kyrgyzstan – 33%. In addition to root-knot nematodes, representatives of ecto- and endoparasites of the genera Tylenchorhynchus, Merlinius, Quinisulcius, Rotylenchus, Helicotylenchus, Pratylenchus, Paratylenchus, Macroposthonia, Labocriconema and Xiphinema were parasitizing in the above subtropical cultures. Under production conditions, we tested Furadan at a dose of 40 kg/ha, Heterophos at a dose of 60 and 120 kg/ha, and Aldicarb at a dose of 40 kg/ha to control root-knot and other parasitic nematodes. Their efficacy ranged from 89 to 100%. We also used the soil solarization method developed by us, the efficacy of which was 95–98%.

The potential of bacterial antagonists of fungal pathogens to control the root-knot nematode Meloidogyne incognita was investigated under greenhouse conditions. Treatment of tomato seeds with several strains significantly reduced the numbers of galls and egg masses compared with the untreated control. Best performed Bacillus subtilis isolates Sb4-23, Mc5-Re2, and Mc2-Re2, which were further studied for their mode of action with regard to direct effects by bacterial metabolites or repellents, and plant mediated effects. Drenching of soil with culture supernatants significantly reduced the number of egg masses produced by M. incognita on tomato by up to 62% compared to the control without culture supernatant. Repellence of juveniles by the antagonists was shown in a linked twin-pot set-up, where a majority of juveniles penetrated roots on the side without inoculated antagonists. All tested biocontrol strains induced systemic resistance against M. incognita in tomato, as revealed in a split-root system where the bacteria and the nematodes were inoculated at spatially separated roots of the same plant. This reduced the production of egg masses by up to 51%, while inoculation of bacteria and nematodes in the same pot had only a minor additive effect on suppression of M. incognita compared to induced systemic resistance alone. Therefore, the plant mediated effect was the major reason for antagonism rather than direct mechanisms. In conclusion, the bacteria known for their antagonistic potential against fungal pathogens also suppressed M. incognita. Such “multi-purpose” bacteria might provide new options for control strategies, especially with respect to nematode-fungus disease complexes that cause synergistic yield losses.

Commercial products consisting of humic and fulvic acids are thought to boost plant growth and economic yield in cropland agriculture. The specific mechanism for their benefit is unknown, in part because little information is available on the chemical nature of these products. We examined the chemical nature of eight humic acid products, three fulvic acids and seven of their source materials, lignite and leonardite ores, and humic shales. All samples were from the United States and Canada. Analysis by 13C cross polarization/magic angle spinning nuclear magnetic resonance spectroscopy found that the humic acid products and the ores were dominated by large signals at aliphatic C (ca. 30 ppm) and aromatic C (ca. 130 ppm). These products were distinguished from one another by their relative proportions of aromatics and aliphatics and relative percentages of smaller signals for carboxyl C (approximately 175 ppm) and ketones/aldehydes C (ca. 200 ppm). These samples were also extracted for their concentrations of seven carbohydrates through anion exchange chromatography and pulsed amperometric detection. All ores and humic acid products had low concentrations of carbohydrates. The ores and products made without alkali extraction had slightly greater concentrations of carbohydrates than did extracted products, suggesting that alkali extraction for production of the humic acid products discriminated against carbohydrates. Results will also be discussed for sample concentrations of amino acids, two amino sugars, and lignin-derived phenols. Although these products share the same dominant chemical traits, they cannot be considered as chemically similar until the chemical mechanism for their effect on plant growth is identified and the corresponding compound(s) or functional group(s) is/are measured in these products and ores. Until then, field efficacy established for one product cannot be transferred to other products.

The root-lesion nematode, Pratylenchus penetrans (de Man, 1880) Filipjev, 1936, is a common pathogen of potato in the United States east of the Rocky Mountains and frequently interacts with Verticillium dahliae to aggravate early dying disease (4). West of the Rocky Mountains, P. penetrans is associated with numerous crops including mint, tree, and small fruits but is rarely recovered from potato fields. Pratylenchus neglectus is a common plant-parasitic nematode on potato in the west, but causes little loss in yield and does not usually interact with V. dahliae (1). Management of P. neglectus is generally unnecessary; although a population of P. neglectus from Ontario, Canada appears to be more pathogenic and does interact with V. dahliae (1). During May 2003 (6 weeks after planting), large areas of stunted plants were observed in field inspections and in aerial photographs of two fields (50.6 ha) of cv. Ranger Russet in Benton County, Washington. Lower roots and stolons had numerous, dark lesions that are typical of P. penetrans damage and were severely stunted, while long, white roots had formed abnormally near the soil surface. In early May 2003, lesion nematodes (65 nematodes per 250 g of dry soil and 810 nematodes per g of fresh root weight) recovered from these potato fields were identified as P. penetrans on the basis of morphological characters (2,3). The crop responded to oxamyl (four applications at 1.1 kg of a.i. per ha between early May and mid-July), but the grower estimated that yields were 1.62 tons/ha (4 tons/acre) less than in comparable unaffected fields. To our knoweldge, this is the first report of severe damage to potato from P. penetrans in the Colombia Basin potato-production area. Soil fumigation with Telone II (1,3-dichloropropene) is commonly used in the Columbia Basin to control root-knot (Meloidogyne chitwoodi and M. hapla) and stubby-root (Paratrichodorus allius) nematodes, and metam sodium is used to control V. dahliae. However, since the only nematode recovered from preplant samples was assumed to be P. neglectus, and because cv. Ranger Russet is relatively tolerant to V. dahliae, no fumigant was used in these fields. An increase in mint production in this area may be responsible for introducing P. penetrans into previously uninfested fields since mint is propagated vegetatively and lesion nematodes are commonly associated with mint and could be easily spread in planting material and adhering soil. Identification of P. penetrans in stunted corn from two nearby fields during 2004 suggests that this nematode may be a new and emerging problem in this area. The Columbia Basin is one of the largest potato-producing regions in the United States, and widespread introduction of P. penetrans could add substantial cost to potato production in this area.

Humic acids (HA) are organic macromolecules of high structural complexity and are primarily obtained from non-renewable carbon sources such as peat and coal. HA is widely used in agriculture but is known to have therapeutic properties, which are still poorly explored. Previous studies have shown the potential of biotechnological processes in the production of HA in submerged fermentation (SF) and solid-state fermentation (SSF) using pre-treated fibers of oil palm of empty fruit bunch (EFB) for the cultivation of Trichoderma strains. EFB is an agro-industrial residue that is readily available at a low cost. The present study aimed to study the production of HA by Trichoderma reesei in the SSF of raw fibers of EFBs from two different palm oil producers. Profiles of HA production, cellular protein, pH, glucose, moisture, and oxygen transfer were obtained during SSF by EFB with and without lipids, as well as, images by electron microscopy of fibers. Results showed efficient HA production in the raw fibers of the EFBs. HA production followed the cellular protein (6g HA per 100g of fibers) evolution of the fermentations in the absence of lipids, while the composition of lipids greatly affected its production. The best HA production (350mg HA per 100g of fibers) was obtained from EFB that was richer in lignocellulosics and the residual lipids were similar to the fractions of palm and kernel oils, while EFB with lower lignocellulosic presented a production 110mg HA per 100g of fibers.

Advances and challenges in humic acid production technologies from natural carbonaceous material wastes

Review: Biotic and abiotic approaches to artificial humic acids production

The goal of this research was to examine the prospects for humic acid products and in particular a humic acid product produced from animal manure/digestate. Based on a literature review it is concluded that humic acids are used worldwide as biostimulants and overall positive effects on crop growth are reported, but variation in results is high. Stakeholders explained during interviews that in the Netherlands the use of Humic acid products are mostly related to niche markets. For conventional agriculture in the Netherland the value of humic acids has not been proven yet, this can be explained by the high fertility of the Dutch soils, and high yields that are already obtained without adding humic acids. Also field experiments were done. In several field experiments with potatoes and onions the specific humic acid product was tested. Adding the humic acids (on soil and as foliar spraying) did not benefit crop growth, but also did not harm the crops. No effect was found on the development of diseases.

Maize (Zea mays L.) is one of the world's most important crops, but its productivity is at high risk as climate change increases the risk of water stress. Therefore, the development of mitigation strategies to combat water stress in agriculture is fundamental to ensure food security. Humic acids are known to have a positive effect on drought tolerance, but data on their efficacy under waterlogging are lacking. This study aimed to elucidate the effect of a new humic acid product, a by-product of Ukrainian bentonite mining, on maize growth and nutrient status under waterlogging. Maize was grown for 9 weeks and three water stress treatments, which were applied for 14 days: waterlogging, alternating waterlogging and drought, and drought. On the day of stress application, the humic acid product (1% v/v) was applied to the leaves. Soil Plant Analysis Development (SPAD) values were recorded during the stress treatments. Plants were harvested after stressing ceased and fresh weight and P and Zn status were analyzed. Drought reduced shoot fresh weight, while it was unaffected under waterlogging. This is in contrast to SPAD readings, which showed a significant decrease over time under submergence, but not under drought. Under alternating stress, although SPAD values declined under waterlogging but stabilized when switched to drought, no growth reduction was apparent. Application of the humic acid product was ineffective in all cases. Although anthocyanin discoloration occurred under waterlogging stress, P deficiency, which is usually the main factor driving anthocyanin formation, was not the reason. Interestingly, Zn concentration decreased under waterlogging but not under the other stresses, which was alleviated by humic acid application. However, no effect of foliar-applied humic acids was observed under alternating and drought stress. It can be concluded that the tested humic acid product has the potential to improve the Zn status of maize under waterlogging.

The aim of this research was to study the production of humic acids (HA) by Trichoderma reesei from empty fruit bunches (EFBs) of palm oil processing, with a focus on the effects of lignocellulosic content and residual lipids. EFBs from two different soils and palm oil producers were previously characterized about their lignocellulosic composition. Submerged fermentations were inoculated with T. reesei spores and set up with or without residual lipids. The results showed that the soil and the processing for removal of the palm fresh fruits were crucial to EFB quality. Thus, EFBs were classified as type 1 (higher lignocellulosic and fatty acids composition similar to the palm oil and palm kernel oil) and type 2 (lower lignocellulosic content and fatty acids composition similar to palm oil). Despite the different profiles, the fungal growth was similar for both EFB types. HA production was associated with fungal growth, and it was higher without lipids for both EFBs. The highest HA productivity was obtained from type 1 EFB (approximately 90mgL-1 at 48h). Therefore, the lignocellulosic composition and the nature of the residual lipids in EFBs play an important role in HA production by submerged fermentation.

The novelty of this study was to produce humic acids by submerged fermentation of empty fruit bunch (EFB) with Trichoderma viride and to investigate the effects of the cellulosic substrates and the organic sources of nitrogen on the biotechnological production of these acids. The results obtained indicate the potential application of EFB, a waste of oil palm processing, for humic acids production. Because EFB contains cellulose, hemicellulose and lignin, fermentations were also performed using these polymers as carbon sources, separately or in combination. After 120 h of fermentation, significant production of humic acids was observed only in cultures containing either EFB or a mixture of the three polymers. Use of either potato peptone or yeast extract as a nitrogen source yielded nearly identical patterns of fungal growth and production of humic acids. The data obtained from microscopic imaging of T. viride growth and sporulation in EFB, coupled with the determined rates of production of humic acids indicated that the production of these acids is related to T. viride sporulation.

Humic acids may play an important role in the environmental chlorine budget. The enzymatically mediated incorporation of chlorine into humic acids has been previously shown. The present study reports the enzymatically mediated incorporation of 4-chlorophenol into humic acids. The stability of the 4-chlorophenol - humic acid product as well as the possible enzymatically mediated polymerization of 4-chlorophenol as a concurrent reaction to the incorporation are reported. The possible extent of the reaction in the environment is discussed.