Lotus Rhizome Research Articles

Functionality modulation of starch from lotus rhizome using single and dual physical modification

The effects of ultrasonication (US) assisted by pre- and post-treatment of heat-moisture treatment (HMT) on physicochemical, rheological, pasting, digestive, and thermal properties of lotus rhizome (LR) starch were investigated in this study. All treatments decreased the swelling power, amylose content, and peak viscosity except for the ultrasonicated sample when compared with native LR starch. All treatments showed similar diffraction patterns with different intensities. FTIR spectra characteristic peaks did not emerge or disappear after single and dual modifications. Storage modulus (G′) is greater than loss modulus (G″) for all LR starch gel samples demonstrating their elastic character. Moreover, ΔHgel (253.1–303.7 J/g) increased in all treatments. Dual modification (HMT & US) significantly enhanced resistant starch and reduced SDS in LR starches. These results could be beneficial for promoting ultrasound processing for potential uses in the food industry and starch production.

Formation mechanism of blue pigment in boiled lotus rhizome discs: Insight into the chelation of polyphenols and iron

Boiled lotus rhizome discs (BLRDs), as common processed products of lotus rhizome, have gained increasing attention from consumers and food manufacturers. However, the blue pigment formed during boiling affects its appearance and reduces the appetite of BLRDs. In this study, the effects of polyphenols and iron contents on blue pigment formation in BLRDs in different regions and months were investigated. Results revealed that blue variation was more serious in March and April of the second year in Wuhan, and polyphenols and iron contents in these two months were significantly higher than those in other months. Then, UPLC and UV–Vis analysis showed that polyphenols causing the formation of blue pigment in BLRDs were L-dopa, gallocatechin, catechin, epigallocatechin, chlorogenic acid and epicatechin, among which L-dopa (52.450 mg/100 g in fresh lotus rhizome (FLR)) and gallocatechin (36.210 mg/100 g in FLR) possessed the greatest effect. Moreover, the ESI-Q-TOF-MS analysis of L-dopa-iron chelate and gallocatechin-iron chelate suggested that the blue pigment of BLRDs was mainly in the form of bis-complexes under boiling conditions. The study on formation mechanism of blue pigment in BLRDs can provide a reference for lotus rhizome processing.

Functional Characterization of the Histone Acetyltransferase FcElp3 in Lotus Rhizome Rot-Causing Fungus Fusarium commune.

Fusarium commune is the main pathogen of lotus rhizome rot, which causes the wilt of many plants. Histone acetyltransferase plays a critical part in the growth and virulence of fungi. In the present study, we identified an FcElp3 in F. commune homologous to histone acetyltransferase Elp3. We further constructed a mutant strain of F. commune to determine the function of FcElp3 in fungal growth and pathogenicity. The results showed that the deletion of FcElp3 resulted in reduced mycelial growth and sporulation. Compared with the wild type, the ΔFcElp3 strain showed more tolerance to osmotic stress and cell wall stress responses but was highly sensitive to oxidative stress. The subcellular localization results indicated that FcElp3 was distributed in both the cytoplasm and nucleus. Western blotting showed that FcElp3 was important for acetylation of H3K14 and H4K8. RNA sequencing analysis showed significant transcriptional changes in the ΔFcElp3 mutant, with 3,098 genes upregulated and 5,770 genes downregulated. Peroxisome was the most significantly enriched metabolic pathway for downregulated genes. This led to a significant decrease in the expression of the core transcription factor Fcap1 involved in the oxidative stress response. Pathogenicity tests revealed that the ΔFcElp3 mutant's pathogenicity on lotus was significantly decreased. Together, these findings clearly demonstrated that FcElp3 was involved in fungal growth, development, stress response, and pathogenicity via the direct regulation of multiple target genes.

Identifying dominant spoilage fungal species and preservative treatments for extending shelf life of whole lotus rhizomes at 4 °C

A preservative for whole lotus rhizome preservation was developed under 4 °C storage in this study. The study included the following steps: Firstly, isolation and identification of spoilage causing fungi of lotus rhizome, and four main spoilage causing fungi were identified, including Penicillium solitum, Geotrichum silvicola, Phytopythium helicoides, and Pseudeurotium zonatum. Secondly, selection of antifungal agent with good inhibitory ability against the above four spoilage causing fungi, finally 0.5 % potassium sorbate was selected considering edible security at the same time. Thirdly, the selection of suitable color fixative according to the indexes of root skin and flesh color differences, and sensory evaluation. The final color fixative composition: EDTA-2Na (8 g/L), ascorbic acid (8 g/L), and d-isoascorbic acid sodium (6 g/L). Finally, the antifungal agent and color fixatives were mixed to make the preservative. Soaked in preservative for 20min, drained and packed into PE bags, vacuumed and stored at 4 °C, the lotus rhizomes could maintain better color, got high sensory score, soluble solids content, and total acid content, and the microbial counts were always lower than the untreated group. The preservative could extend the shelf life of whole lotus rhizome to about 50 d at 4 °C.

Ultrasound-assisted extraction of polyphenols from lotus rhizome epidermis by alcohol/salt-based aqueous two-phase system: Optimization, extraction mechanism and antioxidant activities

In this study, ultrasonic-assisted (UA) alcohol/salt-based aqueous two-phase system (ATPS) method was constructed to extract lotus rhizome epidermis (LRE) polyphenols. The extraction conditions were optimized as salt concentration 26.75 %, ethanol concentration 25.45 %, ultrasonic power 487 W and liquid–solid ratio 35.33 mL/g by comparing response surface methodology (RSM) and artificial neural network (ANN) models. Then, l-dopa (2.35 ± 0.036 mg/g dw), gallocatechin (1.66 ± 0.0035 mg/g dw) and epigallocatechin (1.37 ± 0.0035 mg/g dw) were determined as major polyphenols in LRE by using UA-ATPS method. Moreover, study showed that ultrasound, van der Waals force, hydrogen bond and salting out could accelerate the mass transfer and extraction of polyphenols in LRE cells. The high-pressure cavity and collapse effect of ultrasound could also accelerate the extraction of polyphenols. In vitro antioxidant experiments showed that LRE polyphenols have good antioxidant ability. In sum, this study developed a green and efficient extraction method to enhance the profitability of LRE in food and medicine industries.

Structure, spectral properties and antioxidant activity of melanoidins extracted from high temperature sterilized lotus rhizome juice

Melanoidins are complex macromolecular compounds closely associated with the browning phenomenon in high-temperature sterilized lotus rhizome juice (HTSL). This study aimed to preliminarily investigate the structural properties of melanoidins extracted from HTSL. Results showed that the average molecular weight of HTSL melanoidins ranged from 1.48 to 41.40 kDa. Medium and high molecular weight melanoidins were the main contributors to the brown color of HTSL. Sugars, proteins, and phenolics were present in HTSL, among which sugar was the most abundant, with glucose being the predominant monosaccharide in acid degradation products of melanoidins. Through fluorescence and ultraviolet spectral analysis, we found that the melanoidins contained carboxyl and carbonyl compounds, as well as furan and pyran heterocyclic compounds. The infrared spectra and nuclear magnetic resonance spectra revealed a prominent sugar absorption peak, indicating that sugar was the main component of the melanoidins of HTSL. Furthermore, in vitro antioxidant experiments showed that the antioxidant activity of melanoidins was significantly positively correlated with phenolic compounds. Our results indicated that there were differences in the structural properties of melanoidins fractions with different molecular weights. MW-H fraction significantly impacted the color and antioxidant activity of HTSL.

Study on the formation mechanism of blackening in damaged lotus rhizome epidermis: Effects of polyphenols and iron.

Lotus rhizome is an important aquatic vegetable, but the blackening of lotus rhizome epidermis (LRE) seriously affects its appearance and quality, which makes lotus rhizome products unmarketable. In this study, the effects of polyphenols and iron on the LRE color were studied to explore the possible mechanism of LRE blackening. Results indicated that the measurable total phenols contents in the mud treatment (MT) group were significantly reduced, and the total iron contents were significantly increased compared with the bruised treatment group (p<0.05). The high-performance liquid chromatography results showed that the main polyphenols in LRE were dopa, gallocatechin, and catechin, as well as a small amount of catechol, epicatechin, proanthocyanidin B2, and proanthocyanidin C1. Moreover, the results of color difference and ultraviolet adsorption spectroscopy showed that there were obviously black or brown-gray of dopa (525nm), gallocatechin (504.5nm), and catechin (550 and 504.5nm) with FeCl2. The simulated system treatment of LRE further confirmed that the chromaticity effect of dopa and iron in bruised LRE was similar to that of the MT group, whereas 1% (w/w) ascorbic acid, 2% (w/w) EDTA-2Na, or 3% (w/w) citric acid could solely prohibit the blackening. This suggested that the dopa in LRE and FeCl2 in mud may mainly combine into [2(DOPA-2H+)+Fe3+]- through non-covalent interaction, which leads to the blackening of bruised LRE under neutral conditions. These results can guide the storage of lotus rhizomes and improve the development of the lotus rhizome industry.

Characterization of hydrogel beads constructed from gelatinized lotus rhizome starch and sodium alginate by calcium cross-linking

The purpose of this study was to construct calcium cross-linked gelatinized lotus rhizome starch (LRS)/sodium alginate (SA) hydrogel beads of adjustable quality and to reduce the digestibility of gelatinized starch. LRS was mixed with SA, gelatinized by heating and subsequently cross-linked with Ca2+ to form hydrogel beads. The digestibility of the gelatinized LRS could be adjusted by changing the dose of SA in the hydrogel beads. When the LRS/SA ratio was 4/6, the rapidly digested starch (RDS) content in the beads was reduced by 26.9% compared with gelatinized LRS alone, whereas the slowly digested starch (SDS) and resistant starch (RS) contents increased by 12.3-fold and 2.3-fold, respectively. In addition, the water distribution in the Ca2+-crosslinked LRS/SA hydrogel bead samples also showed an SA dose dependence. With increasing SA concentration, the ability of the hydrogel beads to immobilize water increased. The diffusion of Ca2+ into the interpenetrating polymer network that was prepared with gelatinized LRS and SA gradually resulted in gelation dominated by ion bonds, leading to the heterogeneous microstructure of the hydrogel beads, which also involved intermolecular hydrogen bond interactions. Overall, the present study suggested a strategy for developing novel LRS hydrogel bead systems for quality control and gelatinized starch digestibility downregulation by adjusting the SA dose, which provided insights for the innovation of personalized and convenient starchy products in the food industry.

Transcriptomics and metabolomics analysis revealed the regulatory network of apical buds development in lotus (Nelumbo nucifera Gaertn.)

As a perennial ornamental plant, lotus will begin to become dormant in the face of adverse environmental conditions. The dormancy and apical buds development of lotus are of great significance in regulating the flowering period, storage and reproduction of the lotus rhizome, but the related regulatory mechanisms have not been reported. In this study, we sampled the lotus apical buds at 0 d, 12 d and 24 d after planting, and determined that the lotus could complete the dormancy releaseprocess at 12 days after planting. The monitoring of physiological indexes, hormone levels and transcriptome sequencing of 9 samples in three periods were carried out. It was found that the contents of carbohydrates and hormones changed significantly during apical buds development. Transcriptome analysis also showed that a large number of differentially expressed genes were enriched in hormone synthesis and signal transduction pathways, starch and sucrose metabolism pathways, and lipid metabolism pathways, these genes may be involved in the development of lotus apical buds. Subsequently, we analyzed the differential transcription factors during apical buds development and screened a key differential gene NnHSP18.2. NnHSP18.2 is a heat shock protein (HSP) family gene specifically expressed on apical buds, encoding a protein of 160 amino acids with a conserved α-crystallin domain (ACD) domain. Overexpression of NnHSP18.2 can inhibit Arabidopsis seed germination. These results are of great significance for exploring the molecular mechanism of lotus apical buds development and actively promoting the development of the lotus industry.

Changes in the pasting and rheological properties of wheat, corn, water caltrop and lotus rhizome starches by the addition of Annona montana mucilage

Annona montana mucilage (AMM) is a novel mucilage with unique but limited information. This study investigated the effects of AMM addition on the pasting and rheological properties of wheat starch (WS), corn starch (CS), water caltrop starch (WCS), and lotus rhizome starch (LRS). The addition of AMM generally increased the pasting temperature and peak viscosity, but reduced the setback value of all starches to varying degrees, and the initiation of viscosity-increase for cereal starch/AMM systems during pasting occurred at lower temperatures, accompanied with a distinctive two-stage swelling process as well as lower peak and final hot paste viscosity at 50 °C. AMM significantly increased the pseudoplasticity and entanglement of the systems to varying degrees (LRS > WS > WCS > CS). Under a constant shear rate of 50 s−1, the consistency level was found to fall in honey-like for cereal starch/AMM groups, and honey-like to extremely thick levels for WCS and LRS/AMM groups. Except for the WCS/AMM systems, the storage and loss modulus as well as tanδ increased with increasing AMM concentration. Short-term retrogradation of starch at 4 °C was pronouncedly retarded by the addition of AMM for WS, CS and WCS groups, but was less affected for LRS group.

Physicochemical, in vitro antidiabetic and sensory characteristics of leavened functional bread made with Lasia spinosa and Nelumbo nucifera rhizome flours composited with wheat flour

Bread is considered one of the most popular bakery products consumed in several world regions including Sri Lanka. The potential of utilization of two rhizome flours (Lasia spinosa and Nelumbo nucifera) was evaluated in bread formulation with four different substitution levels (20, 40, 60, and 80%). After the incorporation of L. spinosa and N. nucifera flours, the alterations in compositional, functional, in vitro anti diabetic activity, in vitro starch digestibility and sensory attributes were observed. The results revealed that the total dietary fiber, resistant starch and ash contents were higher while protein, fat and starch contents were lower in the rhizome flour incorporated breads. The functional properties showed that the water absorption index and water solubility increased with increasing of rhizome or proportion. The results showed that 20% rhizome flour incorporated bread had the highest sensory score compared to other percentage ratios and contained a higher level of dietary fiber, resistant starch, antidiabetic activity, and low rate of starch digestibility compared to control bread. The mixture of Lasia spinosa and Nelumbo nucifera rhizome flours could be incorporated up to 20% substitution level with wheat flour to formulate functional bread with more nutritious and functional along with sensory acceptability.Graphical

Phytochemical Properties and Nutritional Benefits of Lotus Rhizome (Nelumbo nucifera): A Comprehensive Review

Phytochemical Properties and Nutritional Benefits of Lotus Rhizome (Nelumbo nucifera): A Comprehensive Review

Physicochemical Properties of Granular and Gelatinized Lotus Rhizome Starch with Varied Proximate Compositions and Structural Characteristics.

As a traditional and popular dietary supplement, lotus rhizome starch (LRS) has health benefits for its many nutritional components and is especially suitable for teenagers and seniors. In this paper, the approximate composition, apparent amylose content (AAC), and structural characteristics of five LRS samples from different regions were investigated, and their correlations with the physicochemical properties of granular and gelatinized LRS were revealed. LRS exhibited rod-shaped and ellipsoidal starch granules, with AAC ranging from 26.6% to 31.7%. LRS-3, from Fuzhou, Jiangxi Province, exhibited a deeper hydrogel color and contained more ash, with 302.6 mg/kg iron, and it could reach the pasting temperature of 62.6 °C. In comparison, LRS-5, from Baoshan, Yunnan Province, exhibited smoother granule surface, less fragmentation, and higher AAC, resulting in better swelling power and freeze-thaw stability. The resistant starch contents of LRS-3 and LRS-5 were the lowest (15.3%) and highest (69.7%), respectively. The enzymatic digestion performance of LRS was positively correlated with ash content and short- and long-term ordered structures but negatively correlated with AAC. Furthermore, the color and network firmness of gelatinized LRS was negatively correlated with its ash content, and the retrograde trend and freeze-thaw stability were more closely correlated with AAC and structural characteristics. These results revealed the physicochemical properties of LRS from different regions and suggested their advantages in appropriate applications as a hydrogel matrix.

Antioxidant and Antibacterial activity of Lotus tea in Thua Thien Hue province from Vietnam

In this study, we determined the antioxidant and antibacterial activity in different types of lotus tea (Nelumbo nucifera Gaernt.) in Thua Thien Hue province, Vietnam. The results showed that in four types of lotus tea, the catalase enzyme activity was 0.92-1.35 U/mg protein, the peroxidase enzyme activity was 0.97-2.67 U/mg protein, ascorbic acid content was 0.088-0.135%, the IC50 value was 4.98-6.03 mg/mL and all four kinds of lotus tea inhibited bacteria to a variable extent with low sensitivity. The inhibition zone’s mean diameter increased from 0.23 cm to 0.77 cm. The flower lotus tea gave the highest results on most of the research criteria and the lowest was lotus rhizome tea. From obtained results, tea produced from lotus plants grown in Thua Thien Hue province, Vietnam has a high potential for antioxidant and antibacterial properties.

Mechanism for gel formation of pectin from mealy and crisp lotus rhizome induced by Na+ and D-glucono-d-lactone

Lotus rhizome residue, a cell wall material produced during the production of lotus rhizome starch, has long been underutilized. This study aims to extract pectin-rich polysaccharides from the cell wall of lotus rhizome and investigate their gelation mechanism in order to improve their industrial applicability. The results indicated that both CP and MP (pectin extracted from crisp and mealy lotus rhizome) exhibited a highly linear low methoxyl pectin structure, with the primary linkage mode being →4)-GalpA-(1→. The pectin chains in MP were found to be more flexible than those in CP. Then the impact of Na+, D-glucono-d-lactone (GDL), urea, sodium dodecyl sulfate (SDS), either individually or in combination, on the rheological characteristics of gels was evaluated. The results indicated that gels induced by GDL exhibited favorable thermoreversible properties, whereas the thermoreversibility of Na+-induced gels is poor. In addition to hydrogen bonding and ionic interactions, hydrophobic interactions also play a significant role in the formation of pectin gels. This study offers theoretical guidance and methodologies to improve the utilization rate of lotus rhizome starch processing by-products, while also provides novel insights into the correlation between LMP structure and gelation mechanism.

Non-enzymatic browning of lotus rhizome juice during sterilization mediated by 1,2-dicarboxyl and heterocyclic compounds.

Lotus rhizome juice (LRJ) is prone to Maillard reaction (MR) and caramelization, which tend to cause quality decline and lower consumer acceptance of the product. 1,2-dicarbonyl compounds (DCs) and heterocyclic compounds have attracted increasing attention as key intermediates responsible for the formation of brown pigments during MR and caramelization. However, little is known about the effects of these two types of compounds on brown pigments in LRJ during sterilization. This study quantified the changes in brown intensity (A420), DCs, and heterocyclic compounds before and after spiking, and identified the precursors and intermediates for brown pigment formation as well as the formation pathways of the intermediates. The spiking experiments suggested that spiking with fructose resulted in more 3-deoxyglucosone (3-DG) and 2,3-Dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), while that with lysine led to more glucosone (GS) and 2,3-butanedione (2,3-BD) in LRJ. The addition of glucose, asparagine, and glutamine significantly promoted the formation of 5-hydroxymethylfurfural (HMF), while that of glucose, lysine, and asparagine resulted in more norfuraneol. Spiking with reducing sugars and amino acids promoted both glyoxal (GO) and methylglyoxal (MGO), and the effect of glucose on GO was particularly significant. Correlation analysis showed that A420 had the highest correlation with 3-DG in the fructose- and lysine-spiked group, and with HMF in the glucose-, asparagine-, and glutamine-spiked groups. This study revealed that fructose, glucose, asparagine, glutamine, and lysine were essential precursors of MR and caramelization in LRJ during sterilization. 3-DG and DDMP were mainly produced by caramelization with fructose as the primary precursor, whereas GS and 2,3-BD were primarily formed via MR under the catalysis of lysine. MR and caramelization were the main formation pathways of HMF (catalyzed by asparagine and glutamine) and norfuraneol (catalyzed by lysine and asparagine), with glucose as the critical precursor. MGO was mainly produced by MR or caramelization, while caramelization was the main formation pathway of GO with glucose as the precursor. Additionally, for brown pigment formation from fructose and lysine, 3-DG was identified as the most crucial intermediate, while for that from glucose, asparagine, and glutamine, HMF was found to be the most important intermediate. This article is protected by copyright. All rights reserved.

Combined analysis of microRNA and mRNA profiles provides insights into the pathogenic resistant mechanisms of the lotus rhizome rot.

Lotus rhizome rot caused by Fusarium oxysporum is a common vascular fungal disease in plants that significantly impacts the yield. However, only a few studies have studied the mechanism of Nelumbo nucifera responding to lotus rhizome rot. Here, we investigated the pathogenic genes and miRNAs in lotus rhizome rot to uncover the pathogenic resistant mechanisms by transcriptome and small RNA sequencing of lotus roots after inoculation with Fusarium oxysporum. GO and KEGG functional enrichment analysis showed that differential miRNAs were mostly enriched in starch and sucrose metabolism, biosynthesis of secondary metabolites, glutathione metabolism, brassinosteroid biosynthesis and flavonoid biosynthesis pathways. Twenty-seven upregulated miRNAs, 19 downregulated miRNAs and their target genes were identified. Correlation analysis found that miRNAs negatively regulate target genes, which were also enriched in starch and sucrose metabolism and glutathione metabolism pathways. Their expression was measured by reverse transcription quantitative PCR (qRT-PCR), and the results were consistent with the transcriptome analysis, thus verifying the reliability of transcriptome data. We selected three miRNAs (miRNA858-y, miRNA171-z and a novel miRNA novel-m0005-5p) to test the relationship between miRNAs and their target genes. The activity of the GUS testing assay indicated that miRNA could decrease the GUS activity by inhibiting the expression of their target genes. Collectively, this study provides a comprehensive analysis of transcriptome and small RNA sequencing of lotus root after inoculation with Fusarium oxysporum, and we identified candidate miRNAs and their target genes for breeding strategies of Nelumbo nucifera.

Analysis of pectin-cellulose interaction in cell wall of lotus rhizome with assistance of ball-milling and galactosidase

The current study sought to depict the structural feature of polysaccharides extracted from Na2CO3 unextractable fraction (LUN) of lotus rhizome using galactosidase with assistance of ball milling. The extracted polysaccharides were a complex of cellulose microfibrils and the RG-I structural domain of pectin, and the top three monosaccharides were glucose, galactose and galactose uronic acid, which allowed to tune the properties of the enzyme-hydrolyzed polysaccharide from LUN after 15 and 45 min of ball milling. The data of XRD revealed that pectin has a masking effect on the diffraction peaks of cellulose components. The removing of the polysaccharides could increase the degree of crystallinity and the pectin-cellulose interaction mainly occured through the galactan side chain was speculated. Textural characterization by SEM exhibited a cross-linked rod-like structure, which is similar to the structure of cellulose microfibrils. The morphological analysis of AFM revealed that L15-P (enzyme-hydrolyzed polysaccharide from LUN after 15 min of ball milling) contained relatively ordered and uniform network structures. Overall, the present study provides an important insight into cell wall of lotus rhizome matrix polysaccharide.

Effects of Slow-Release Fertilizer on Lotus Rhizome Yield and Starch Quality under Different Fertilization Periods

Slow-release fertilizer is an environmentally friendly fertilizer that is widely used in crop cultivation instead of traditional nitrogen fertilizer. However, the optimal application time of slow-release fertilizer and its effect on starch accumulation and rhizome quality of lotus remains unclear. In this study, two slow-release fertilizer applications (sulfur-coated compound fertilizer, SCU, and resin-coated urea, RCU) were fertilized under three fertilization periods (the erect leaf stage, SCU1 and RCU1; the erect leaf completely covering the water stage, SCU2 and RCU2; and the swelling stage of lotus rhizomes, SCU3 and RCU3) to study the effects of different application periods. Compared with CK (0 kg∙ha-1 nitrogen fertilizer), leaf relative chlorophyll content (SPAD) and net photosynthetic rate (Pn) remained at higher levels under SCU1 and RCU1. Further studies showed that SCU1 and RCU1 increased yield, amylose content, amylopectin and total starch, and the number of starch particles in lotus, and also significantly reduced peak viscosity, final viscosity and setback viscosity of lotus rhizome starch. To account for these changes, we measured the activity of key enzymes in starch synthesis and the relative expression levels of related genes. Through analysis, we found that these parameters increased significantly under SCU and RCU treatment, especially under SCU1 and RCU1 treatment. The results of this study showed that the one-time application at the erect leaf stage (SCU1 and RCU1) could improve the physicochemical properties of starch by regulating the key enzymes and related genes of starch synthesis, thus improving the nutritional quality of lotus rhizome. These results provide a technical choice for the one-time application of slow-release fertilizer in lotus rhizome production and cultivation.

Identification and characterization of Fusarium commune, a causal agent of lotus rhizome rot

Identification and characterization of Fusarium commune, a causal agent of lotus rhizome rot