<div>Background: Alternaria cyamopsidis (Rang. and Rao) causes Alternaria blight of clusterbean&nbsp;and it is one of the significant disease of clusterbean. Studies were conducted to compare the Cultural, morphological and pathogenic variability among ten isolates of Alternaria cyamopsidis from clusterbean, in five districts of Rajasthan viz., Bikaner, Barmer, Churu, Hanumangarh and Jaipur. 
 
Methods:&nbsp;During 2016-17 exhaustive survey was conducted in clusterbean growing areas of Rajasthan and collected diseased samples of clusterbean caused by Alternaria. All the samples were processed for isolation, purification&nbsp;and their pathogenicity was proved in cagehouse and laboratory and standard methods were adopted for cultural and morphological variability study. 
 
Result: All the isolates showed variation in their morphological characters, i.e., colony color and shape; conidial number, size, width, length, shape and septation on PDA. Out of ten isolates two isolate, viz., AlcyJp1 and AlcyJp2 showed maximum colony diameter 89.50 and 86.30 mm, respectively. All the isolates varied in their spore length and width and virulent on the tested variety of clusterbean for virulence. AlcyJp1 was the most virulent and produced maximum (65.50%) disease intensity, followed by AlcyJp2 isolate (61.22%).</div>

Cultural, Morphological and Pathogenic Variability in Alternaria cyamopsidis Causing Alternaria Blight of Clusterbean in Rajasthan

<div>Background: Fusarium wilt in lentil (Lens culinaris L.) infected by Fusarium oxysporum is considered as one of the major biotic factors for low productivity in lentil. The present study was conducted to determine nine Fusarium isolates (W1-W8 and W10) which were isolated from different lentil growing fields of West Bengal, India and were characterized for their physio-morphological, biochemical and molecular traits in vitro.&nbsp; 
 
Methods: Nine Fusarium infected lentil plant samples were collected from 9 different places of West Bengal. Pathogen was isolated from lentil samples using PDA media followed by cultural, morphological, pathogenic and molecular variability studies for all the isolates of Fusarium. Type of pigmentation, sporulation, conidia size of each isolate was recorded by observing culture plate after complete growth of the mycelium. Pathogenicity test were done to check the aggressiveness of all the 9 isolates of Fusarium in three varieties of lentil (Maitri, HUL-57 and BM-6). The isolated fungal DNA was amplified with specific primer pair, Forward primer ITS 1 and Reverse primer ITS 4. 
 
Result: Morphological assessment of 9 isolates showed distinct identification characters and variability. The mycelia of all the isolates were septate, profusely branched with differential pigmentation, texture and margin.All the Fusarium isolates produced micro-and macro-conidia in pure culture within seven days after inoculation and showed different morphological characters in pathogenicity test, variety Maitri showed better germination (100% in W2, W4, W6, W7, W8 and W10) and less disease severity against most of the strains (75% in W1) as compared to other two varieties against and hence variety Maitri taken into consideration for greenhouse and field trials. Furthermore, identification of molecular variability was performed by sequence analysis of rDNA-ITS region of each isolate and sequencing of rDNA-ITS region supported the morphological study and confirmed the associated fungi at species level.&nbsp;</div>

Morpho-molecular and Pathogenic Variability of Wilt of Lentil from Indo-Gangetic Plains of India

Background: Collar rot of chickpea infected by Sclerotium rolfsii is considered one of the major biotic factors for low productivity in chickpea. The present study was conducted to determine twenty nine isolates of collar rot were characterized for their Morphological, Pathogenic and Molecular variability. 
 
Methods: Twenty nine collar rot infected chickpea plant were collected from different places of Bundelkhand region of Uttar Pradesh. Pathogen was isolated from collar rot infected sample using PDA media followed by morphological, pathogenic and molecular variability studies from all isolates. Type of growth rate, mycelia colour, sclerotia size, sclerotial pattern, test weight of isolates was recorded by observing cultural plate after complete growth of mycelium. Pathogenicity test were done to check the aggressiveness of isolates in three varieties of chickpea. The isolated fungal DNA was amplified with specific primer pair, the quality and quantity of DNA was checked using gel electrophoresis and UV trasnliminator. 
 
Result: A morphological evaluation of isolates showed notable differences in identification characteristics, including colony size and sclerotial properties like count, test weight, dimensions and form on PDA media. Among the all isolates SRC 25 and SRC 28 considered as most virulent causes highest disease incidence in all selected chickpea variety under greenhouse experiments. RAPD analysis revealed distinct banding patterns, with PIC values between 0.59 and 0.89. The highest genetic similarity was observed between SRC-11 and SRC-29.

Morpho-pathogenic and Molecular Variability of Chickpea Collar Rot in Bundelkhand Region of Uttar Pradesh, India

Background: Macrophomina phaseolina (Tassi) Goid is a necrotrophic soil-inhabiting fungus that causes disease in several economic plants worldwide and has now become a serious threat to soybean cultivation in central India. 
 
Methods: The random surveys were done during 2018 and 2019 to determine the present status of charcoal rot (M. phaseolina) in key soybean growing districts of Madhya Pradesh. Sixteen isolates of pathogen were characterized based on morpho-cultural and pathogenic variability by using cut stem inoculation techniques at J.N.K.V.V., Jabalpur.&nbsp; 
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Result: Charcoal rot was prevalent in all surveyed sixteen districts of Madhya Pradesh. Out of six, Kymore plateau and Satpura hills (44.5%), Satpura plateau (42.5%), Central Narmada Valley (42.0%) and Vindhyan plateau agroclimatic zones (35.0%) were identified as favouable zones for charcoal rot. Malwa plateau (16.25%) and Northern hill region (24.5%) had low incidences of charcoal rot. Among varieties, JS 95-60, JS 93-05 and JS 20-29 were highly affected, whereas, JS 20-34, JS 20-98 and JS 20-69 were least affected. Incidence of charcoal rot was comparatively higher in the fields that had Maize-Chickpea (26.32%), Maize-Wheat, Soybean- Pea and Soybean - Chickpea cropping patterns in the previous year and lowest in Rice-Chickpea (12.00%) and Rice - Wheat (12.45%) cropping patterns. The incidence of charcoal rot was partially higher in the fields with light soil (21.3%) than in heavy soil (19.0%). Isolates investigation revealed that isolates from Jabalpur, Hoshangabad, Chhindwara and Sagar were fast-growing variables and highly aggressive in developing necrotic lesions on the cut stem of soybean. This investigation could be instrumental in forewarning sensitive areas of charcoal rot, varietal options and crop rotation to be followed to minimize the incidence of charcoal rot. Moreover, identified variable aggressive isolates could be utilized in genotype resistance screening programs.

Distribution of Charcoal Rot of Soybean, its Influencing Factors and Pathogenic Variabilities in Different Regions of Madhya Pradesh

<div style="text-align: justify;">Twelve Fusarium oxysporum f. sp. ciceri isolates were isolated from chickpea infected samples collected across different states of India. Pathogenic variability of twelve isolates was observed on seven chickpea cultivars viz., JG 62, Annigeri-1, Chaffa, CPS-1, K 850, L 550 and DCP 92-3. Among the twelve isolates APFOC-1 showed lowest wilt incidence 71.43 per cent and the isolate MPFOC-9 showed 100 per cent wilt incidence in all cultivars. The variability in morphological characters like size, shape, color of conidia and size, shape, color of chlamydospore were observed in all the isolates. &nbsp;The size of macroconidia varied from 9.23X2.53 &igrave;m (WBFOC-12) to 19.3X5.52 &igrave;m (MHFOC-8) with 2-4 septation. The size of microconidia varied from 4.4X2.93 &igrave;m (MPFOC-9) to 8.26X4.2 &igrave;m (MHFOC-8) with 0-1 septation. Macroconidia were sickle shaped and blunt ends with hyaline color. Microconidia were round to oval with hyaline color. Size of chlamydospore varied from 2.67 (UPFOC-11) to 8.24 (JKFOC-5). Chlamydospores did not show much variation with respect to shape and color. Based on the total number of spores observed per microscopic field, the twelve isolates categorized into four groups viz., poor sporulants, moderate sporulants, good sporulants and very good sporulants.</div>

Pathogenic and morphological variability among Fusarium oxysporum f. sp. ciceri isolates causing wilt in chickpea

Background: Employing resistant germplasm is one of the most practical and cost efficient approach for disease management. Neverthless, use of these resistant cultivars turns to be fruitless due to persistence of diversity among pathogen populations across different agroecologies. These variations facilitate the pathogen to adapt and thrive in diverse environmental conditions. The variants within a population can alter the pace of disease progression and potentially trigger disease outbreaks in other host lines, which could undermine the cultivar stability. Furthermore, pathogenic variability studies indirectly aid in discriminating between resistant and susceptible accessions. 
 
Methods: Five distinct isolates of Lasiodiplodia theobromae, associated with mango dieback and derived from five different mango varieties and five different districts in Kerala, were inoculated on six differential mango cultivars. Pathogenic attributes including PDI, PDS, incubation days, lesion size, and virulence index were assessed. The coefficient of infection was determined to discern the landraces for their level of resistance/susceptibility towards mango dieback. 
 
Result: Different virulence patterns were discerned for the isolates. The range for various pathogenic parameters, including PDI, PDS, incubation days, lesion size, and virulence index across different isolates, was recorded as follows: 33.33-100 per cent. 13.33-73.33 per cent, 9-17.33 days, 0.28-0.95 cm and 2.78-4.19 respectively. The parameter, virulence index indicated that the isolates KoKBn, KPB, and WMnMa were more virulent. The coefficient of infection calculated based on PDI and PDS identified the varieties Neelam, Bennet Alphonso, and Banganapally as susceptible and the remaining varieties Priyur, Muvandan, and Imam Pasand as moderately susceptible. 
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Pathogenic Variability of Lasiodiplodia theobromae (Pat.) Griffon and Maubl. Causing Mango Dieback and Screening of Mango Germplasm for Disease Resistance

<div>Background:&nbsp;Lentil wilt is one of the most important diseases of lentil directly contributing to the yield losses of the crop. It is caused by Fusarium oxysporum f. sp. lentis which shows the great genetic and morphological diversity. 
 
Methods:&nbsp;Present investigation was conducted during 2017-2019 with 22 isolates of the pathogen, collected from lentil grown areas of Uttarakhand and Uttar Pradesh to explore genetic and morphological variability employing eight ISSR and five SSR primers. 
 
Result:&nbsp;The isolates showed huge morphological variability based on the color, pigmentation and shape of conidia. Study on molecular variability revealed the versatility in the genome of different isolates of pathogen. The diversity among the isolates of pathogens collected from Uttarakhand and Uttar Pradesh was also evident. Generated work on genetic and morphological variability and the population diversity among the different isolates of the pathogen impact on developing ideal disease management strategies.</div>

Genetic and Morphological Variability among the Isolates of Fusarium oxysporum f. sp. lentis causing Wilt of Lentil

<div style="text-align: justify;">Environment is an important aspect of plant ecology and global environmental change is of major concern that is caused by natural and human activities which alter greenhouse gas concentrations in the atmosphere. The increase in concentration of greenhouse gases is foreseen to continue to raise average global temperature. Elevated concentration of carbon dioxide with increased temperature influences the plant-disease interactions. The environment has an influence over the development as well as temporal and spatial dissemination of plant diseases. The result of change in environment can either be favorable, non favorable or impartial, as these changes can either lessen, expand or have no influence on diseases as each disease may be attributed differently to these variations in accordance to an area or time of year. Variation in environmental conditions is said to be influencing plants in natural ecosystems all around the world and change in climate directly impacts crops, along with their synergy in accordance with the microbial population. The important elements governing magnification and spread of plant diseases are temperature, moisture, light and carbon dioxide concentration. Environment change causes a significant impact on germination, reproduction, sporulation, spore dispersal, along with perforation by pathogens as a vulnerable host will not be invaded by a pernicious pathogen if the environmental conditions are not facilitative for disease. The environment influences all life stages of host as well as that of a pathogen and as a result induces an opposition to various pathosystems. Resistance mechanisms of plants, including effector-triggered immunity (ETI), pattern-triggered immunity (PTI) and defence network of hormones, are particularly influenced by environmental elements. Pathogenic virulence mechanisms like fabrication of virulence proteins and toxins, and also spore germination and survival are governed by factors such as atmospheric carbon dioxide, temperature and humidity. A large number of in-vitro experiments to understand interactions between plants and pathogens rely on predetermined pathosystems by making use of ascertained environmental conditions which take into consideration relatively small part of vital plant&ndash;pathogen&ndash;environment interactions occurring in natural ecosystem. Thus, there is a need to research effectiveness of disease management strategies that is, to assess current management strategies to understand multifaceted nature of environment-pathogen interactions for production of crops that are irrepressible to environment change.</div>

Environment-Pathogen Interaction in Plant Diseases

Background: Collar rot of groundnut (Arachis hypogaea L.) caused by Aspergillus niger is a significant constraint in groundnut cultivation and responsible for huge economic losses in India including Rajasthan. 
 
Methods: By surveying of eight major groundnut growing districts of Rajasthan, India, one representative Aspergillus niger isolate from each district was established (ANBK-01= Bikaner, ANCH-02= Churu, ANDA-03= Dausa, ANJP-04= Jaipur, ANJL-05= Jalore, ANJD-06= Jodhpur, ANNG-07= Nagaur and ANSK-08= Sikar) for studying variability in the pathogen as well as to know the response of groundnut varieties to the highly virulent isolate. The colony and spore characteristics were observed for cultural and morphological variability. For resistance response to the disease, ten varieties (M-13, RG-633-9, RG-382, Girnar-2, RG-604, RG-578, Gajraj 10, RG-510, RG-632-1 and RG-644) were evaluated in the field for two consecutive years against a highly virulent Aspergillus niger (ANJP-04) isolate.&nbsp; 
 
Result: Our investigations cleared that all the isolates were showed cultural and morphological variability such as shape, colour and size of colony and size of conidia, conidiophores and columella. Isolate (ANJP-04) collected from Khejroli village of Chomu tehsil in Jaipur district showed maximum mycelial growth, conidia diameter, length and diameter of conidiophores and length and diameter of columella, early sporulation and found most virulent as it produced higher disease incidence (54.43%). Ten released varieties of groundnut in the field conditions, revealed that none of the variety was found completely free from the disease whereas RG-644, M-13 and RG-510 were found resistant while RG-604, Girnar-2, Gajraj-10 and RG-632-1 were found moderately resistant and rest were found susceptible to highly susceptible to the disease. Conclusively, it can be finalized that famers may cultivate these resistant varieties in areas where collar rot is a severe constraint. The conclusion of this study can also be utilized to screen varieties/genotypes of groundnut against highly virulent isolate for sustainability of breeding material to the disease effectively.

Variability and Virulence Analysis of Aspergillus niger Isolates Causing Collar Rot of Groundnut

<div>A vector is an organism capable of transmitting pathogens from one host to another. Among the plant pathogen transmitting agencies, insect vectors are most important and various plant pathogens in crops are transmitted by insects. Insect vectors are much more hazardous because small population of vector can spread the pathogen in whole of the field or to new areas. These are difficult to manage and hence multi-pronged strategy should be adopted. To effectively manage insect vectors of plant pathogens there is a need to look into the careful timing of application of chemicals, integrated treatment with vector sampling, estimation of threshold level of vectors, assessing infection of pathogen at varying period of the year and combining insecticides with other means of control such as resistant cultivars, natural enemies, inclusion of plant products, cultural practices, biotechnology tools etc. An integration of control measures will be more effective and ecologically sound than any single method to control insect vectors of plant pathogens. The control of insect vectors with the use of various tactics should be used to reduce the severity and to delay appearance of disease.</div>