Collar Rot Research Articles

Disease spectrum and its molecular characterisation in the lentil production system of lower-Indo Gangetic plains.

Lentil is a food legume grown in the Indo-Gangetic plains including lower Gangetic Bengal (LGB). Lentil productivity in this zone is severely impeded because of the prevalence of several biotic cues. Plausible reports regarding the status of disease scenario and the associated risk factors are missing. Therefore, judicious crop management strategies are lacking. An intensive survey of 267 farmers' fields was conducted over 3 years in major lentil-growing districts of LGB to evaluate the disease incidence and prevalence. Additional insights were generated, apprehending isolation and characterisation of associated pathogens through spore morphology and molecular markers as well as elucidating the role of biophysical factors in influencing disease development. Climate change has shifted the disease dimension of lentil and precipitated new disease complexes of great risk, which was reflected through geospatial mapping results in the present study. The prevalence of three major diseases, namely collar rot (Sclerotium rolfsii), lentil blight complex (LBC) incited by both Alternaria and Stemphylium, and lentil rust (Uromyces viciae-fabae), was ascertained through cultural and molecular studies and contextualised through pathogenicity appraisal. This study is the first to investigate the complex mixed infection of Alternaria alternata and Stemphylium botryosum, successfully isolating S. botyrosum in India, and confirming the pathogens through sequencing by using internal transcribed spacer (ITS) primers and Stemphylium-specific Glycerol-3-phosphate dehydrogenase 1 (gpd1) and gpd2 primers. Unlike late planting, early planting promoted collar rot infestation. LBC and rust incidence were magnified in late planting. Soil texture resulted in the spatial distribution of collar rot disease. The surveyed data also highlighted the potential role of resistant cultivars and cropping pattern intervention to ensure associational resistance towards addressing the disease bottleneck in lentil.

Germination and seedling growth of groundnut seeds infected with Macrophomina phaseolina isolates

Macrophomina phaseolina is a common contaminant of groundnut (Arachis hypogaea L.) seeds but not much information has been documented about its adverse impact on seed health and germination. This study was carried out to determine the incidence of M. phaseolina on groundnut (Arachis hypogaea) seeds displayed for sale in local markets, characterize the isolates and determine how the fungal presence would affect the germination and seedling growth, so as to provide information on seed handling practices and planning strategies for reducing crop loss due to the fungus. The fungus was isolated using the direct plating inoculation method and then grown for a period of 7 days on a potato dextrose agar (PDA) with temperature set at 28 oC. The DNA was extracted from pure cultures and PCR was performed using primer in pair: ITS4 and ITS5. The products got from the PCR were sequenced for identification of species on the National Centre for Biotechnology Information (NCBI) database. Phylogenetic tree was generated based on the ITS1-2 gene sequences of the isolates. The 18 M. phaseolina isolates adopted for use in this study were all obtained from apparently healthy seeds of different varieties of groundnut sourced from local markets in Delta and Edo States, Nigeria. The experiment on germination of groundnut seeds was set up in a completely randomized design in ten replicates. The individual M. phaseolina isolates inhibited germination and seedling growth in varying degrees. The virulence of the isolates ranged from moderately pathogenic (50%) to extremely pathogenic (75%). Out of the 18 isolates, 14 were found to cause 100% mortality. The inoculated plants exhibited the disease symptoms (damping off, root rot, collar rot, necrosis, wilting and chlorosis) while the control remained healthy. Seedling emergence, number of leaves, root length, and stem girth of infected plants decreased when compared to the control.

Effects of bio consortium for the management of collar rot (Sclerotium rolfsii) disease of chickpea in vivo condition

A experiment was conducted in 2019-20 Rabi cropping season to obtain information on the incidence of chickpea diseases. The investigation was entitled effects of bio consortium for the management of collar rot (sclerotiumrolfsii) disease of chickpea in vivo condition was conducted, Department of Plant pathology JNKVV. The experiment was laid out in Completely Randomized Design (CRD) concept comprising nine treatment combinations with three replications in net house condition.Effect of bio consortium against collar rot (Sclerotiumrolfsii) disease incidence on variety JG-12: Among the treatments minimum germination per cent 76.67 per cent was observed in T8. Maximum pre-emergence mortality 23.33 per cent was recorded in T8, Maximum disease incidence of 24.48 and 22.77 per cent was observed in T8 and minimum mortality 17.37% was recorded in T6. Effect of bio consortium on collar rot (Sclerotiumrolfsii) disease and phenotypic parameters on variety JG-12: Among the treatments minimum germination per cent 78.60 per cent was observed in T8, Maximum shoot height 24.33, 22.07, 20.07, 19.27, 16.37, 15.67, 14.23 and 13.30 cm were recorded in T6, Maximum root height 10.37 was recorded in T6, Maximum vigour index per cent of 3,274.21 was recorded in T6. Effect of bio consortium on collar rot (Sclerotiumrolfsii) disease incidence on variety JG-14: Among the treatments minimum germination per cent 77.78 per cent was observed in T8, Maximum pre-emergence mortality 22.22 per cent was recorded in T8, Maximum disease incidence of 24.27 per cent was observed in T8, minimum mortality 16.24 per cent was recorded in T6 (T. viride + T. harzianum + P. fluorescens).Effect of bio consortium on collar rot (Sclerotiumrolfsii) disease and phenotypic parameters on variety JG-14. Among the treatments minimum germination percent 80.68 per cent was observed in T8, Maximum shoot height 26.37 was recorded in T6, Maximum root length 11.53,was recorded in T6, Maximum vigour index percent of 3,658.07 was recorded in T6.

Studies on survey and surveillance for the management of Sclerotium rolfsii causing collar rot of chickpea

A survey was conducted in 2019-20 Rabi cropping season to obtain information on the distribution and incidence of chickpea diseases. The was investigation entitled Studies on Survey and surveillance for the management of Sclerotiumrolfsii causing collar rot of chickpea was conducted, Department of Plant pathology JNKVV, Jabalpur. Survey was conducted in the following six Block in Jabalpur – Jabalpur, Panagar, Sihora, Sahpura, Patan and Manjholi. Chickpea varieties were selected on the basis of disease susceptibility viz., JG – 12 and JG – 14 Variety. The disease was prevalent in all the blocks surveyed. The disease incidence recorded in six block was ranged between 7.5 to 34.5 per cent. The highest disease incidence (34.5%) collar rot was noticed in fields of Jamuwa village in Patan block. Whereas, least (7.5%) incidence of the disease was recorded at Bhedaghat village in Jabalpur block.

Evaluation of lablab bean [Lablab purpureus (L.) sweet] genotypes: unveiling superior pod yield, nutritional quality, and collar rot resistance.

Malnutrition continues to be a significant concern at unacceptably high levels globally. There is significant potential for addressing malnutrition of human population through the biofortification of climate-resilient vegetables using strategic breeding strategies. Lablab bean [Lablab purpureus (L.) Sweet], a underutilized nutrient-dense crop holds great potential in this aspect. Despite its advantageous nutritional profile, the production, research, and consumption of lablab bean are currently limited. Addressing these limitations and unlock the nutritional benefits of lablab beans needs to prioritized for fighting malnutrition in local inhabitants on a global scale. Twenty five genotypes of lablab bean collected through exploration survey in Eastern India and were evaluated in 2020-2021. Among them, the nine highly diverse well adapted genotypes were again evaluated at the experimental farm of ICAR-Research Complex for Eastern Region, Patna, Bihar, India in 2021-2022. Horticultural important traits of lablab bean were recorded by using the minimum descriptors developed by ICAR-NBPGR in New Delhi and biochemical analysis was done by using standard protocols. Genotypic and phenotypic correlation and path coefficient analysis was done used understand relationships, interdependencies, and causal pathways between different traits. The outcome was revalidated by using principal component analysis (PCA). Descriptive statistics revealed substantial heterogeneity across the traits of lablab bean evaluated. Vitamin A content showed nearly a five-fold variation, Fe ranged from 5.97 to 10.5 mg/100 g, and Vitamin C varied from 4.61 to 9.45 mg/100 g. Earliness and dwarf growth was observed in RCPD-1 (60 cm) and early flowering (41 days). RCPD-3 and RCPD-12 had high pod yield due to their high number of pods and pod weight. Pod yield was significantly correlated with number of pod per plant (NPP) (rg = 0.995) and with average pod weight (APW) (rg = 0.882). A significant positive correlation was also found between protein and Zn content (rg = 0.769). Path coefficient analysis revealed that average pod weight had the most direct positive effect on pod yield, followed by NPP and protein content. The reaction of lablab bean genotypes to collar rot disease was also evaluated and significant differences in disease intensity were observed among the genotypes, with the resistant check RCPD-15 exhibiting the lowest disease intensity. The study highlights the substantial heterogeneity in lablab bean traits, particularly in nutritional components such as vitamin A, iron, and vitamin C concentrations. Early flowering and dwarf growth habit are desirable qualities for lablab bean, and certain genotypes were found to exhibit these traits. Positive correlations, both phenotypic and genotypic, existed among different traits, suggesting the potential for simultaneous improvement. Path coefficient and PCA revealed genotypes with high yield and nutritional traits. Finally, resistant and moderately resistant lablab bean genotypes to collar rot disease were identified. These findings contribute to the selection and breeding strategies for improving lablab bean production and nutritional value.

Efficacy of a Combination Formulation of Imidacloprid 18.5 Hexaconazole 1.5 against Termites, White Grub and Collar Rot in Groundnut

Efficacy of a Combination Formulation of Imidacloprid 18.5 Hexaconazole 1.5 against Termites, White Grub and Collar Rot in Groundnut

Artificial infection with Fusarium solani f.sp. passiflorae in plants of passion fruit under controlled conditions

Controlled infection systems constitute a valuable tool in the study of pathosystems, as they enable the observation and measurement of specific characteristics with greater precision and ease compared to natural conditions. Additionally, they are useful for exploring and identifying sources of resistance in host populations. However, the plant's response to infection can vary depending on the inoculation method; invasive methods can damage plant parts, thus facilitating pathogen entry even in the presence of certain resistance mechanisms. The purpose of this study was to evaluate the reproducibility of an artificial infection protocol and an assessment scale for primary symptoms at the stem base/root collar, as well as secondary symptoms in leaves and roots of two Passiflora species. We evaluated the effects of inoculating planting substrates of sweet granadilla and purple passion fruit plants with three concentrations of F. solani f. sp. passiflorae (0.5 × 106, 1 × 106, and 2 × 106 conidia gram-1 of substrate), using non-inoculated plants as controls under controlled conditions. These treatments were tested in two separate experiments performed in 2017 and 2020. The study included symptom development readings integrated in a disease severity index (SI) for collar rot. Both experiments showed severity indices greater that 56%, indicating a high level of efficacy of the inoculation system for replicating disease symptoms in greenhouse settings. Our inoculation method reflects the conditions of natural infection of F. solani in sweet granadilla and purple passion fruit plants; it could be suitable for epidemiological and disease control studies, as well as for routine germplasm screening to identify sources of resistance.

Effects of soil physico-chemical parameters on Sclerotium rolfsii suppressiveness

The relationship of soil physico-chemical parameters with disease suppressiveness property of soil is not well understood phenomenon. In this regard, the surveys were conducted on the occurrence of collar rot disease caused by Sclerotium rolfsii in two districts (North 24 Parganas and Nadia) of West Bengal Gangetic new alluvial region of India from February to March, 2016. Soil samples were screened through the disease conduciveness and suppressiveness. The physicochemical properties of soils showed that the clay loam soil dominated in new the alluvial region of West Bengal. It was found that soil suppressiveness against S. rolfsii significantly positively correlated with soil aggregate ratio (AR). PCA explained the closeness of the parameters with soil suppressive index (SI) and aggregate stability (AS). Mostly the exponential relationship has been observed among the selected physico-chemical parameters. From this study we found AR, AS and bulk density were most determining parameters for S. rolfsii soil suppressiveness. Such indicators of soil health would be very beneficial for forecasting potential risks and providing guidance on appropriate farming techniques for specific geographic areas or microclimates. However, further investigation is required to fully comprehend the impact of physical and chemical properties on soil suppressiveness.

A Novel biopolymer-based T. harzianum, (Th4d) - a viable alternative to chemical seed treatment for management of collar rot of groundnut

Groundnut (Arachis hypogaea L.) is an economically important edible oil seed crop of the world. Collar rot caused by Aspergillus niger is one of the most serious, destructive diseases in groundnut. A field experiment on the effect of seed treatment with biopolymer-based T. harzianum, Th4d blend in groundnut on disease incidence and seed yield of groundnut was taken up at IIOR, Hyderabad during 2020 and 2021. Chitosan-based T. harzianum, Th4d blend recorded pooled mean of significantly high germination percent (90.0%), pod yield (3047 kg/ha) and reduced collar rot incidence (67.7%) whereas chemical seed treatment with carboxin + thiram recorded germination of 78%, 45.1% reduction in disease and 2064 kg/ha pod yield.

GG HPS-2: A high yielding and large seeded Virginia bunch groundnut (Arachishypogaea L.) variety for Gujarat state

A Virginia bunch large seeded groundnut variety GG HPS 2 was developed from the cross JVB HPS 2 and GG 20. It recorded a higher mean pod yield (2835 kg/ha) and kernel yield (1945 kg/ha) as compared to the checks.GG HPS 2 recorded an average 100 kernel weight of 66.71 g, shelling out-turn of 68.61% and oil content of 48.82%. GG HPS 2 showed restistance reaction to tikka (leaf spot) and rust reaction, whereas it showed comparableresistance to stem rot, collar rot, damages due to leaf defoliators and thrips under field conditions with check varieties. Based on the superior performance, it has been released for kharif groundnut growing areas of the Gujarat State.

Evaluation of soybean genotypes against collar rot disease caused by Sclerotium rolfsii Sacc.

Collar rot caused by S. rolfsii is one of the economical diseases of soybean that can cause up to 30-40% yield loss in India. A total of 18 soybean genotypes were screened artificially during 2021 at ICAR-IISR, Indore, to study the virulence among the fungal isolates as well as to identify the resistance sources. Based on pathogenicity, Indore isolate (SRI) was found to be more virulent than Assam isolate (SRA). On the basis of percent emergence (PE) and the disease indices - root weight of inoculation (RWI) and ratio of root weight (RRW), genotypes JS 335, JS 20-34 and MACS 1620 were resistant against SRI whereas RSC 10-52 and JS 335 were found to be potential donors for resistance against SRA.

GG-35: A high yielding Spanish bunch groundnut, Arachis hypogaea L.variety for Gujarat State

A Spanish bunch groundnut genotype GG 35 was developed on the basis of mean pod yield from the state level trials. It has recorded the highest pod yield of 3177 kg/ha as compared to the checks viz., GG 7 (2452 kg/ha), GJG 9 (2471 kg/ha) and TG 37A (2758 kg/ha). GG 35 had recorded average 100 kernel weight of 42.79 g, average 100 pod weight of 101.93 g and average shelling out-turn of 71.36%. The reaction against tikka, rust, stem rot and collar rot, the variety was comparable to the check varieties under field conditions whereas, the damages due to thrips was not observed in the released variety as well as check varieties. Based on the superior performance, GG 35 has been released for general cultivation in the kharif bunch groundnut growing areas of Gujarat state.

Systemic resistance induced by plant growth-promoting rhizobacteria in Bhut Jolokia (Capsicum chinense Jacq.) suppressed the collar rot disease

Collar rot disease caused by Rhizoctonia solani is a major constraint to the commercial cultivation of Bhut Jolokia (Capsicum chinense Jacq.) in North-East India. However, the management of the disease is not addressed comprehensively in this plant. Some plant growth-promoting rhizobacteria (PGPR) could control plant diseases by triggering induction of resistance systemically, and emerge as a highly promising approach to reduce the use of chemical fungicides. Therefore, five selected PGPRs were tested for plant growth promotion and induced systemic resistance (ISR) for controlling the disease. Induced systemic resistance was determined in vivo condition. Confocal laser scanning microscopic observation was done to see any harmful effects on cells in the induced plant. The PGPRs could significantly improve plant growth as well as suppress the disease and boost defense-related enzymes activity in the induced plants. Bacillus megaterium JPR68 triggered the maximum ISR in the plant. Expression of the defense-related genes was analyzed which were highly expressed in ISR plants. Microscopic observation revealed that no internal changes occurred in PGPR treated plant cells similar to the untreated plant, and indicated no harmful effect of the bacteria in the host cell. The study demonstrates the possible application of B. megaterium JPR68 as a biocontrol agent for sustainable management of the disease. To our knowledge, this is the first report of ISR against any fungal disease in Bhut Jolokia.

Optimal treatment against Athelia rolfsii rot in processing tomatoes using pesticide and rootstock against key stages of the disease

The soilborne fungus Athelia rolfsii (synonym Sclerotium rolfsii) causes stem or collar rot in tomato (Lycopersicon esculentum Mill.). We aimed to develop an optimal treatment for A. rolfsii in processing tomatoes in Israel through an understanding of the key developmental stages of the plant that are susceptible to disease development. We tested two approaches: best timing for pesticide application, and grafting onto a tolerant rootstock. The fungus attacked processing tomatoes at two stages: (i) immediately after planting, when the root neck is attacked and the young plant wilts, and (ii) in the last month of growth, when the humidity under the foliage increases, temperatures are high, and the root neck, shoot and fruit, which are lying on the ground, are susceptible to pathogen attack. The number of infected plants was significantly reduced after incorporating azoxystrobin at 2.5 and 5 L a. i./ha in the soil preplanting, and applying the combination fungicide Nativo (a.i. tebuconazole and trifloxystrobin) at 0.75 kg/ha in the drip-irrigation system (chemigation) once, 60–90 days after planting. This treatment enhanced total yield by up to 35.2% and marketable yield by up to 33.7% relative to untreated plots. Grafting to a resistant rootstock significantly reduced plant wilting in the first weeks of growth to less than 1% of the plants, and enhanced fruit yield up to four fold. In soil with a history of infestation, A. rolfsii infection should be treated during the plants’ susceptible stages: preventive azoxystrobin treatment preplanting, and a single treatment of Nativo later on to prevent infection and decay, especially for late harvest; grafting to a resistant rootstock can also reduce infection in the early stages of growth and enhance yield. In this study, we show for the first time that A. rolfsii infection in processing tomato can be dramatically decreased with minimal pesticide application against key stages of the disease and rootstocks.

Exploring the Potential Biocontrol Isolates of Trichoderma asperellum for Management of Collar Rot Disease in Tomato

Bio-control agents are the best alternative to chemicals for the successful management of plant diseases. Among them, Trichoderma is commonly used as a biological control agent in plant disease management due to its ability to suppress soil-borne plant pathogens. In the present study, 20 Trichoderma asperellum isolates were collected from different geographical locations and confirmed using morphological characteristics and molecular phylogenetic inferences based on combined ITS and β-tubulin sequences. All twenty isolates were screened for their antagonism against the collar rot pathogen under in vitro and in planta conditions. The isolates were evaluated through dual culture and volatile methods in an in vitro study. Isolate A10 inhibited the test pathogen Agroathelia rolfsii at 94.66% in a dual culture assay and 70.95% in a volatile assay, followed by the isolates A11 and A17, which recorded 82.64% and 81.19% in dual culture assay and 63.75% and 68.27% in the volatile assay respectively. An in planta study was conducted under greenhouse conditions in tomato var. pusa ruby by pre- and post-inoculation of T. asperellum isolates in the A. rolfsii infected soil to evaluate their antagonistic potential against the disease. The A10 isolate was found effective under both pre- and post-inoculation conditions, with a disease inhibition percent of 86.17 and 80.60, respectively, followed by the isolates A11 and A17, which exhibited inhibition of 77.80% and 75.00% in pre-inoculation and 72.22% and 69.44% in post-inoculation, respectively. Further, biochemical analysis was conducted to determine the specific activity of hydrolytic enzymes produced by T. asperellum during interaction with A. rolfsii. We found that isolate A10 produces more hydrolytic enzymes with the specific activity of 174.68 IU/mg of β-1,3 glucanase, 183.48 IU/mg of β-1, 4 glucanase, 106.06 IU/mg of protease, followed by isolate A17, A11 respectively. In GC-MS analysis, we observed maximum anti-microbial volatile organic compounds from the isolate A10, including 2H-Pyran-2-one (17.39%), which was found to be most abundant, followed by dienolactone (8.43%), α-pyrone (2.19%), and harziandione (0.24%) respective retention time of 33.48, 33.85, 33.39, and 64.23 min, respectively, compared to other isolates. In the TLC assay, we observed that a greater number of bands were produced by the A10 and A17 isolates in the Hexane: Ethyl Acetate (1:1) solvent system than in the 9:1 solvent system, which represents the presence of major metabolites in the ethyl acetate extract.

First Report of Root Rot Caused by Phytophthora lacustris on alder (Alnus lusitanica) in Spain.

Alder decline caused by Phytophthora species is considered one of Europe´s most important diseases of natural ecosystems. In Spain, P. x alni, P. uniformis, P. x multiformis and P. plurivora have been detected in association with root and collar rot in riparian alder populations (Pintos et al. 2010, 2012, 2017; Haque et al. 2014). During the active growth periods 2020-2021, a field survey of the newly designed species Alnus lusitanica (Vít et al. 2017) was carried out at the most symptomatic areas along the Miño-Sil river basin in Galicia and León (NW-Spain). Samples of bark, root, rizosphere soil of declining trees, and river water were collected. Symptoms, similar to those caused by other Phytophthora species, included low leaf density of the canopy, generally with smaller and chlorotic leaves, and branches with dry tips. In some cases, the presence of cankers on the trunk were observed (Figure 1). Necrotic lesions were transferred onto V8-PARPH, a Phytophthora selective medium. Soil and water were baited with carnation petals. Three isolates of one Phytophthora species was recovered: two from the roots of trees, and one from river water at three different sites. The isolates were transferred to V8 agar and incubated a 22ºC in the dark. Colonies had petaloid patterns, and their optimum growth temperature ranged from 25 to 30 °C. In soil extract, non-caducous, non-papillate and ovoid sporangia were produced. Sporangia averaged 41.0×29.4 μm with a length/breadth ratio of 1.39. Internal proliferation occurred (Figure 2). No sexual structures were observed . Genomic DNA was extracted from mycelium obtained from pure cultures of three Phytophthora isolates. The ITS region of the ribosomal DNA template was performed by nested PCR using DC6 (Cooke et al. 2000) and ITS4 (White et al. 1990) in the first round, and ITS6 (Cooke et al. 2000) and ITS4 in the second. The mitochondrial gene cox1 was amplified with primers CoxF4N and CoxR4N (Kroon et al. 2004). BLASTn analyses showed 100% identity to the type of P. lacustris (AF266793, 156 matching bp) for ITS, and 100% identity to the ex-type of P. lacustris (MH136916, 596 matching bp) for the cox1 sequence. Phylogenetic analysis indicated that our isolates were localized in the same evolutionary branch as P. lacustris based on consense sequences of ITS and cox1 sequences. The ITS and cox1 sequences generated in this study were deposited in GenBank with accession number OP588369 and OP548051, and one isolate isolated from root (CECT 21212) was submitted to the Spanish Type Culture Collection (Paterna, Valencia). Pathogenicity tests with isolate CECT 21212 were conducted on ten 3-year-old alders (A. lusitanica) growing in free draining 5 L pots. One shallow cut was made into the cambium at the root collar level. A colonized 5-mm mycelial agar plug, from a 7-day-old culture was inserted into every wound (mycelial surface face-down) and sealed with Parafilm®. Five control plants were inoculated with a sterile agar plug. Plants were kept in a controlled chamber at 25 ºC and 80% humidity. After a 3-week incubation period, inoculated plants showed dieback symptoms and necrosis of the inner bark tissue (Figure 3). Lesion lengths ranged from 2 to 8 cm. Control plants remained symptomless. P. lacustris was recovered from all inoculated plants, but not from the control ones. To our knowledge, this is the first report of P. lacustris causing root rot on alders in Spain. This new detection represents an increased threat to riparian alders by the presence of an additional Phytophthora species associated with alder decline, since P. lacustris can readily adapt to a wide variety of climatic conditions with the ability to infect different hosts (Nechwatal et al. 2013).

First Report of Fusarium oxysporum Causing Leaf Wilt on Dinteranthus vanzylii (Green Stone Plant) in China.

Dinteranthus vanzylii is a low-growing species in the family Aizoaceae, native to southern Africa, with a pair of thick grey leaves covered with dark red spots and stripes. This stone-like succulent grows near the ground, which may protect it from water evaporation and herbivores. Dinteranthus vanzylii has become popular in China due to its attractive appearance and easy indoor cultivation. In September 2021, 7% of D. vanzylii (approximately 140 pots) showed leaf wilt symptoms in a commercial greenhouse located in Ningde (119°35'39.696″E, 27°23'30.556″N), Fujian Province, China. The diseased plants were shrivelling and eventually underwent necrosis. Their leaf tissues were rotting and carpeted with white mycelium. The leaf tissues of 10 symptomatic plants were cut into 0.5 cm2 pieces, surface-sterilized and placed on PDA medium. According to the colony morphology after 7 days of culture, 20 fungal isolates with abundant whitish aerial mycelium were divided into two types: 8 isolates produced lilac pigment whereas 12 did not. Both produced unicellular ovoid microconidia, sickled-shaped macroconidia with 3 - 4 septa and single or paired smooth, thick-walled chlamydospores on carnation leaf agar (CLA). Molecular identification based on DNA sequences from EF1-α (O'Donnell et al. 1998), RPB1 and RPB2 (O'Donnell et al. 2010) revealed 100% identity among isolates within each group; however, there were several base differences between two types. Sequences of representative isolates KMDV1 and KMDV2 were deposited in GenBank (acc. nos.: OP910243, OP910244, OR030448, OR030449, OR030450 and OR030451), which showed 99.10% - 99.74% identity with different F. oxysporum strains (GenBank acc. nos.: KU738441, LN828039, MN457050, MN457049, ON316742 and ON316741). Phylogenetic tree inferred from the concatenated EF1-α, RPB1 and RPB2 revealed that these isolates clustered with F. oxysporum. Thus, these isolates were identified as F. oxysporum. Using a root-drenching method, 10 one-year-old healthy D. vanzylii were inoculated in conidial suspensions (1*106 conidia/mL) of isolates KMDV1 and KMDV2 for 60 min, respectively. They were transplanted into pots with sterilized soil and incubated in a plant-growth chamber at 25°C and 60% relative humidity. Control plants were treated with sterilized water. The pathogenicity test was repeated three times. All plants inoculated with each isolate developed leaf wilt symptoms after 15 days and were dead after 20 - 30 days. However, no symptoms were observed in the control plants. Fusarium oxysporum was reisolated and confirmed based on morphology and EF1-α sequence analysis. No pathogens were isolated from the control plants. This is the first report of F. oxysporum causing leaf wilt disease on D. vanzylii in China. To date, several diseases have been reported on members of the Aizoaceae. For instance, collar and stem rot on Lampranthus sp. caused by Pythium aphanidermatum (Garibaldi et al. 2009), wilt on Lampranthus sp. and Tetragonia tetragonioides caused by Verticillium dahliae (Garibaldi et al. 2010; Garibaldi et al. 2013), and leaf spot on Sesuvium portulacastrum caused by Gibbago trianthemae (Chen et al., 2022). Our research could provide insight into fungal diseases on members of the Aizoaceae and contribute to their cultivation and management.

In vitro evaluation of fungicides and bio-control agents against sunflower collar rot (Sclerotium rolfsii)

The efficacy of different fungicides against Sclerotium rolfsii was tested using poison food technique under in vitro conditions and through seed treatment in screen house. Efficacy of fungicides in vitro against S. rolfsii showed that carboxin, vitavax power and hexaconazole completely inhibited mycelial growth up to 100 per cent at 100 ppm concentration. Thiram inhibited 95.8 per cent and propiconazole inhibited 98.1 per cent at 1000 ppm. Captan inhibited 80.6 per cent at 1000 ppm while, carbendazim only inhibited 18.5 per cent at 1000 ppm. Pencycuron have failed to show antifungal activity against S. rolfsii even at 1000 ppm. Evaluation of bio-agents against S. rolfsii in vitro revealed that Trichoderma harzianum showed maximum antifungal activity with 70.1 per cent inhibition of mycelial growth followed by T. viride (63.1%) and Bacillus spp. (53.7%). Seed treatment with fungicides and soil treatment with bio-agents significantly reduced the disease incidence of collar rot. Maximum collar rot control wasfound by carboxin (73.9%) followed by vitavax power (69.9%) and thiram (69.4%) by seed treatment under screen house conditions. For the bio-agents, T. harzianum showed maximum control of the disease (40.8%) followed by Bacillus spp. (36.9%) and T. viride (34.6%) in comparison to control.

Integrated Approaches for Managing Collar Rot Disease and Increasing Soybean Yield

Integrated Approaches for Managing Collar Rot Disease and Increasing Soybean Yield

GJG-9: A high yielding and stem rot tolerant Spanish bunch groundnut (Arachis hypogaea L.) variety for Gujarat state

A Spanish bunch groundnut genotype GJG-9 was identified based on the mean pod yield from the state level trials. It has recorded higher pod yield of 1632 kg/ha as compared to the checks viz., GG-2 (1255 kg/ha), GG-5 (1355 kg/ha) and GG-7 (1413 kg/ha). The genotype was also tested in Spanish bunch trials of AICRPG and performed better than GG-2 by 9.95% and 12.20% during kharif, 2007 and 2008, respectively with a mean increase of 11.00%. But, it was comparable with GG-7 and TG-37A. Average kernel yield of GJG-9 was 1183 kg/ha as against the checks viz., GG-2 (935 kg/ha), GG-5 (997 kg/ha) and GG-7 (1026 kg/ha). GJG-9 had recorded an average 100 kernel weight of 36.89 g, average 100 pod weight of 96.70 g and average shelling out-turn of 72.49%. The reaction against tikka, rust and collar rot, the variety was comparable to the check varieties under field conditions. However, GJG-9 was found tolerant to the stem rot as compared to the check varieties. Whereas, the damage due to thrips and jassids of GJG-9 was comparable to the check varieties. Based on the superior performance, GJG-9 has been released in 2010 for general cultivation in the kharif bunch groundnut growing areas of Gujarat State.