Significance of Sowing Dates and Meteorological Parameters on Severity of Stem Gall of Coriander Caused by Protomyces macrosporus

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.

Mixed Transcriptome Analysis Revealed the Possible Interaction Mechanisms between Zizania latifolia and Ustilago esculenta Inducing Jiaobai Stem-Gall Formation

The smut fungus Ustilago esculenta infects Zizania latifolia and induces stem expansion to form a unique vegetable named Jiaobai. Although previous studies have demonstrated that hormonal control is essential for triggering stem swelling, the role of hormones synthesized by Z. latifolia and U. esculenta and the underlying molecular mechanism are not yet clear. To study the mechanism that triggers swollen stem formation, we analyzed the gene expression pattern of both interacting organisms during the initial trigger of culm gall formation, at which time the infective hyphae also propagated extensively and penetrated host stem cells. Transcriptional analysis indicated that abundant genes involving fungal pathogenicity and plant resistance were reprogrammed to maintain the subtle balance between the parasite and host. In addition, the expression of genes involved in auxin biosynthesis of U. esculenta obviously decreased during stem swelling, while a large number of genes related to the synthesis, metabolism and signal transduction of hormones of the host plant were stimulated and showed specific expression patterns, particularly, the expression of ZlYUCCA9 (a flavin monooxygenase, the key enzyme in indole-3-acetic acid (IAA) biosynthesis pathway) increased significantly. Simultaneously, the content of IAA increased significantly, while the contents of cytokinin and gibberellin showed the opposite trend. We speculated that auxin produced by the host plant, rather than the fungus, triggers stem swelling. Furthermore, from the differently expressed genes, two candidate Cys2-His2 (C2H2) zinc finger proteins, GME3058_g and GME5963_g, were identified from U. esculenta, which may conduct fungus growth and infection at the initial stage of stem-gall formation.

Economic Assessment of ICAR-NRCSS Coriander Variety (ACr-1) using Economic Surplus Model

Coriander, the major seed spice is grown in the Rajasthan, suffers from various fungal diseases, of which the stem gall being the most destructive and versatile disease causing up to 50 percent yield loss. ICAR-NRCSS Ajmer released a stem gall resistant variety named Ajmer Coriander-1 (ACr-1). Economic Surplus Model was used to examine the economic impact of ACr-1 in Rajasthan. The study found that the ACr-1 variety developed by the ICAR-NRCSS performed well as the net social benefit was `11105.83 million with 15 percent adoption of the variety during six years (2013-14 to 2018-19). The impact assessment study of the stem gall resistant variety (ACr-1) released by ICAR-NRCSS has earned positive social impact, and net returns to the coriander farmers can be further increased with wider adoption of this variety.

In-vitro evaluation of six bio-product against coriander stem gall disease

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.