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The present study was aimed to evaluate the effect of different biocontrol agents, botanicals and fungicides on crop yield and stem gall disease of coriander (Coriandrum sativum L.), caused by Protomyces macrosporus Unger. The effectiveness of plant leaf extracts, fungicides and bioagents were evaluated against the test fungus under in vitro conditions by using poisoned food technique and further evaluated under field conditions for disease management and crop yield improvement. Among the biocontrol agents and botanicals evaluated, Pseudomonas fluorescens and datura leaf extract were most effective in in inhibiting the pathogenic growth; whereas amongst fungicides, metalaxyl + mancozeb @ 0.2% and copper oxychloride @ 0.2% were significantly superior with 100% pathogenic growth inhibition under in vitro conditions. Under field conditions, seed treatment and foliar spray of metalaxyl + mancozeb and copper oxychloride @ 0.2% proved most effective in managing the disease as well as improved crop yield (1493.06 and 1284.72 kg ha-1, respectively) in comparison to the control (729.17 kg ha-1).

Background: Coriander (Coriandrum sativum L.) belongs to family Apiaceae is generally grown in winter season as a main crop in India. Stem gall of coriander caused by Protomyces macrosporus L. is a serious disease damaging all aerial plant parts. Under favourable ecological conditions, the disease may lead losses to the extent of 100 per cent therefore it is necessary to investigate the epidemiology of the disease to devise suitable remedial measures Methods: The field experiment was conducted during Kharif season of 2018 with two varieties to study the effect of different meteorological parameters on stem gall of coriander at different sowing dates (1st week of November to 1st week of December). The stem gall severity was recorded at weekly intervals from the start of its incidence. Result: The disease severity was lowest (5.42%) in the variety DH-36 sown in 3rd week of November and maximum disease severity (11.88%) was observed in variety DH-228 sown in 1st week of December. The quantitative relationship between the disease severity and weather variables at different dates of sowing for two varieties was obtained by performing correlation analysis. The temperature (maximum and minimum) and sunshine hours had positive correlation with per cent disease intensity, while relative humidity (morning and evening) and remaining weather parameters were non-significant at each dates of sowing but correlated with the disease intensity.

Stem gall of coriander caused by Protomyces macrosporus Unger. is a highly devastating seed and soil borne pathogen in coriander and has emerged as one of the major disease causing substantial quantitative and qualitative losses. In the present studies, efficacy of six bio-products, namely, Neemazal, cow urine, butter milk, fresh milk, beejamrit and jeevamrit was screened against mycelial growth inhibition of P. macrosporus under in vitro conditions. Extracts of these bio-products were evaluated at three different concentrations (i.e 10, 20 and 30%) by poison food technique. Results revealed that that among the various bio-products evaluated against test pathogen, irrespective of concentration tested, all the bio-products resulted in significant inhibition in mycelial growth of test pathogen with neemazal giving the complete inhibition [100.00 % (90.00)] followed by fresh milk [30.66 % (28.44)] and butter milk [26.55 % (25.99)], though these treatments were statistically different from one another. Different concentrations (10 to 30 %) of bio-products, irrespective of the treatments showed that 30 per cent concentration of all bio-products was most efficacious in inhibiting the mycelial growth of the test pathogen giving 69.95 per cent (36.77) growth inhibition. This was followed 20 and 10 per cent concentration of bio-products resulting in 55.58 per cent (32.49) and 45.53 per cent (16.30) growth inhibition, respectively. The result regarding evaluation of bio-products under in vitro conditions against the P. macrosporus showed that Neemazal treatment was most effective at all concentrations and completely inhibited the test fungus followed by 30 per cent fresh milk resulting in the mycelial growth inhibition of 51.60 per cent.

This investigation was carried out to examine the effect of some biocontrol agents (Trichoderma viride, T. harzianum, Azotobacter chroococcum, Pseudomonas putida) and botanicals (Melia azedarach, Eucalyptus globulus, Calotropis procera) both alone and in combination on growth, yield and stem gall disease of coriander (Coriandrum sativum L.) caused by Protomyces macrosporus Unger in a pot experiment. Plants inoculated with P. macrosporus caused significant reduction in growth and yield attributes as compared to untreated control. Stem gall intensity was recorded 59% in plants treated with pathogen alone. The results revealed that, application of biocontrol agents / botanicals both alone and in combination caused significant reduction in stem gall intensity (20.33–84.82%) as compared to control. Among the tested biocontrol agents, T. viride was found superior in enhancing the growth and yield as well as reduction in stem gall intensity (44.37%). Application of biocontrol agents in soil supplemented with botanicals was found more beneficial in enhancing plant growth and yield attributes as well as reducing stem gall intensity (52.54–84.82%). Among various combinations tested T. viride + Melia azedarach and T. viride + E. globulus caused greater increase in plant growth and yield characters both in pathogen inoculated as well as uninoculated plants. Keywords: Biocontrol agents, Botanicals, Protomyces macrosporus, Stem gall, Coriander

Coriander (Coriandrum sativum L.) is an important highly nutritive crop belonging to family Apiaceae. To meet increasing global demand and consumption, coriander productivity must be enhanced. However, biotic stresses such as diseases have impeded coriander cultivation both in the tropics and subtropics. Of them, stem gall of coriander, incited by the fungus Protomyces macrosporus Unger, is one of the most common, widespread and serious diseases throughout the world and causes significant yield losses. Symptomatology, biology, and etiology of stem gall and its control through fungicides, bio-product and bio-control have not been widely studied, and substantial information is still required on the inoculum potential, growth models and epidemiological parameters of stem gall, the influence of changing the climate, impact of extensive use of fungicides and disease resistance. These critical factors may influence the development and emergence of stem gall. Because of the increasing demands of coriander in the world, control of stem gall is gaining importance. The present review deals briefly with different aspects of stem gall disease with major emphasis on its ecology, pathology, epidemiology, and management. Some new approaches such as biological control, integrated management strategies, and some other aspects are also discussed.

Stem gall (Protomyces macrosporus Unger), a serious disease that affects leaves, petioles, stems and fruits of coriander (Coriandrum sativum L.) causing heavy loss in yield. Genetic improvement of coriander for stem gall disease is indispensable. Coriander cultivars of stem gall resistance (ACr-1) and susceptible (CS-6) leaf samples were utilized and transcriptome sequenced using Illumina NextSeq500 platform. After trimming low-quality reads and adapter sequences, a total of 49,163,108 and 43,746,120 high-quality reads were retained and further assembly resulted validated transcripts of 59,933 and 56,861. We have predicted 52,506 and 48,858 coding sequences (CDS) of which 50,506 and 46,945 were annotated using NCBI nr database. Gene ontology analysis annotated 19,099 and 17,625 terms; pathway analysis obtained 24 different functional pathway categories; signal transduction, transport, catabolism, translation and carbohydrate metabolism pathways etc. were dominated. Differentially expressed genes analysis predicted 13,123 CDS commonly expressed of which 431 and 400 genes were significantly upregulated and downregulated, respectively, in which R genes, stress inducible transcription factors such as ERF, NAC, bZIP, MYB, DREB and WRKY and antifungal related genes were predicted. The real-time PCR analysis of HSP20 gene expression in resistance showed upregulation by 10-fold over susceptible sample and 18s used as a housekeeping gene for normalization. The present results provide an insights into various aspects underlying the development of resistance to stem gall in coriander.

Coriander is a widely grown crop and suffers from various fungal, bacterial and viral diseases, of which stem gall caused by Protomyces macrosporus in predominant and destructive and of common occurrence. The disease appears in the form of tumour like swellings of leaf veins, leaf stalks, peduncles, stems and on fruits. Out of the seven fungicides tested in vitro, propiconazole, copper oxychloride and mancozeb were found the most effective and significantly superior among all the treatments with 100 per cent mycelial growth inhibition of the pathogen at 100 and 2000 ppm concentrations. Seed treatment of propiconazole and mancozeb was the most effective in managing the disease and also gave higher yield than the other treatments under field conditions. Foliar spray of hexaconazole and propiconazole resulted in 86.27 and 80.27 per cent disease reduction. The highest yield was obtained with hexaconazole giving 152.00 g followed by propiconazole with 143.33 g per 2 m2.

Twenty-seven varieties of coriander were evaluated for their resistance against stem gall disease caused by Protomyces macrosporus. Out of 27 varieties screened only four varieties viz., UD-125, UD-317, UD-749 and Rlr- 480 having less than 10% stem gall intensity were graded as resistant. The mean yield of healthy seeds was found between 1.33 to 1.97 g/plant and of diseased seeds was between 0.13 to 0.68 g/plant. Average seed yield loss (%) ranged between 6.04 to 27.87%. Minimum yield loss was recorded in UD-125 and maximum in American green.

Seventy accessions of coriander (Coriandrum sativum L.) were screened for resistance against stem gall, a severe disease caused by Protomyces macrosporus Unger., with the goal to select the resistant cultivars. The accessions PH-7, Pant Haritima, COR-17 and COR-2 were highly resistant. These may be used as the parents to breed high yielding accessions resistant to stem gall disease.

An outline classification of the Protomycetales enables clarification of the difference between the Protomycetaceae and the Ustilaginaceae . Light, electron transmission and scanning electron microscopy of Burenia inundata on Apium nodiflorum and of Protomyces macrosporus on Anthriscus sylvestris show the emerging vesicle of B. inundata and the relationship of P. macrosporus to host vascular tissue. The very early development of P. macrosporus galls on A. sylvestris in discussed and illustrated.

The archiascomycetous fungus Protomyces pachydermus has two group I introns within the nuclear small subunit (nSSU) rRNA gene. One of these introns has an internal open reading frame (ORF) that encodes a predicted protein of 228 amino acid residues. On the other hand, Protomyces macrosporus has two group I introns that insert at the same positions as P. pachydermus, which have no ORF. Each alignment was constructed with Protomyces group I introns located in the same position and other introns retrieved by the BLAST Search. Each phylogenetic tree based on the alignment shows that Protomyces introns are monophyletic but the relationships among fungal introns do not reflect on the fungal phylogeny. Therefore, it is suggested that two different horizontal transfers of group I introns occurred at the early stage of Protomyces species diversification.

Publisher Summary This chapter studies the genus Protomyces. In the determination of the asexual reproduction, it is seen that cell division is by budding on a narrow base near the poles of the cell. The cells are ovoid to elongate, and elongate cells may be asymmetrical. Pseudohyphae and true hyphae are not formed in culture. In sexual reproduction it is found that the ascosporic state is confined to the tissue of infected plants. Heavy walled spherical structures, variously termed ascogenous cells, synasci, and “chlamydospores,” are formed in infected tissue. The ascogenous cells germinate to form a vesicle (ascus) that in turn produces 50–200 spherical or ellipsoidal ascospores. Ascospore release is through a slit in the vesicle. Ascospores germinate to form asaprophytic, yeast-like budding stage. Reinfection of the host seems only to occur by hyphae, which results following conjugation of compatible yeast cells. Where examined, species are heterothallic. The chapter also discusses physiology/biochemistry and phylogenetic placement of the genus in which sugars are not fermented, nitrate is assimilated by most species, carotenoid pigments are usually produced by yeast phase cells in culture, and formation of extracellular starch-like compounds is strong, weak, or variable. The major ubiquinone is coenzyme Q-10 and the diazonium blue B reaction is negative. The type species taken is Protomyces macrosporus.

Publisher Summary This chapter focuses on Protomyces genus and its member species. The cells of this genus are ovoidal to elongate, and elongate cells may be asymmetrical. Asexual reproduction occurs through budding on a narrow base near the poles of the cell. The ascosporic state is confined to the tissue of infected plants. The ascospore release may occur directly through a slit in the ascogenous cell, or an ascus-like vesicle containing the ascospores may emerge through a slit in the ascogenous cell. The ascospores form a yeastlike budding stage and the infection of the host seems to occur only through hyphae. The member species of this genus include Protomyces gravidus, Protomyces inouyei, Protomyces inundatus, Protomyces lactucaedebilis, Protomyces macrosporus, and Protomyces pachydermus. The cells of Protomyces gravidus, after 3 days of growth on 5% malt extract agar at 20° C, appear as ellipsoidal to elongate, and may be tapered or curved. In the case of Protomyces inouyei, after 3 days of growth on 5% malt extract agar at 20° C, the cells appear as ellipsoidal to elongate, and may be tapered, curved, or of unusual shapes. The cells occur singly in pairs and in small clusters and the growth is butyrous and salmon colored.

Field trials on the efficacy of certain fungicides applied as spray treatment, seed treatment, or combined seed and soil treatment against stem gall ( Protomyces macrosporus Unger) of coriander were conducted at the Institute of Agriculture and Animal Science, Rampur, during the winter seasons of 1981–1982 and 1982–1983. Four sprayings with thiram, captafol or carboxin, when given at fortnightly intervals from the time of disease manifestation, were far more effective than seed treatment or combined seed and soil treatment in controlling stem gall and increasing the yield of coriander.

The fruits of coriander (Coriandrum sativum L.) collected from stem gall infected plants indicate comparable viability and germinability of seeds on testing with triphenyl tetrazolium chloride (TTC) and germination, respectively. Systemic invasion by the pathogen considerably reduces germinability of the seed from these plants. The seedlings raised in the latter test, however, show infection on the stem due to incipient carriage of the pathogen through the integuments, thus adding to the primary inoculum potential of the disease.

Protomyces macrosporus Unger inciting the stem gall disease of coriander (Coriandrum sativum L.) is perpetuated through the resting chlamydospores released in the soil after the monsoon rains from the crop debris and/or the fruit galls in uncleaned seed lot planted in the season. The pathogen also survives in the soil through the heat-resistant desiccated endo- and blastospores and possibly through the chlamydospores hibernating in an intensively cultivated field.

Observations are presented on the cytology of chlamydospore germination and sporogenesis in Protomyces macrosporus Unger. A resting chlamydospore contains 50 or more diploid nuclei. The chlamydospore on germination produces a thinwalled vesicle and the nuclei become arranged along the periphery of the vesicle. Meiotic division of these nuclei results in the formation of quartets. Radial septation takes place enclosing a nucleus in each cell, which develops into a uninucleate haploid spore. Two chromosomes appear to be the haploid number (n=2) in the complerhent of the species. Taxonomic aspects of the genus Protomyces in the fam. Protomycetaceae are discussed in light of these observations.

Susceptibility of coriander (Coriandrum sativum L.) to stem gall disease incited by Protomyces macrosporus Unger is mainly influenced by the inoculum potential, microclimate comprising of soil and air around the host plant, and susceptible host period amongst other factors. Occurrence of concurrent influence of all the environmental factors for a severe disease outbreak is probably thwarted by the shortfall of some factor(s) for an early maturing crop escaping the pathogenic infection.

Die Keimruhe der Chlamydosporen vonProtomyces macrosporus Unger, welcher aufCoriandrum sativum L. Stamm-Gallen erzeugt, kann durch kunstliches Aufweichen der Exospore gebrochen werden. Der Pilz ist auf Kartoffel-Dextrose-Agar kultivierbar.