The response of Sclerotinia sclerotiorum , the causal agent of stem rot of oilseed rape ( Brassica napus ), to toxic volatiles produced by the glucosinolate-myrosinase system was studied. Mycelium plugs were exposed to inoculated leaf discs of oilseed rape cultivars and two related species, black mustard ( Brassica nigra ) and white mustard ( Sinapis alba ). Growth of exposed colonies was inhibited by more than 87% compared with controls. Despite inhibition of exposed fungal colonies, the fungus continued to grow in infected tissue. Repeated exposure of the fungus to hydrated mustard powder (which contains both glucosinolates and myrosinase) or synthetic isothiocyanates (ITCs) resulted in growth inhibition decreasing from initial levels of up to 80% to insignificant levels after 2-3 days, suggesting that S. sclerotiorum has the ability to adapt to volatiles during the infection progress. This adaptation was studied by investigating induction of glutathione S-transferase-like genes identified from the S. sclerotiorum genome. Three genes, with locus numbers SS1G_07195.1, SS1G_01918.1 and SS1G_10295.1, appeared to be up-regulated following exposure of S. sclerotiorum to mustard powder or allyl ITC. A fourth gene, SS1G_07319.1, appeared to be down-regulated. In addition, glutathione S-transferase catalytic activity in crude mycelium extracts was doubled following 48 h of exposure to mustard powder volatiles. This adaptation could allow S. sclerotiorum to parasitize tissues of Brassica species despite the production of toxic metabolites.

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The glucosinolate-myrosinase defence system, specific to Brassicales plants, produces toxic volatile compounds during mechanical injury or pathogen attack. The reaction of this system to oxalic acid, known as a pathogenicity factor of Sclerotinia sclerotiorum, is not fully understood. The hydrolysis of glucosinolates was studied at varying conditions in the presence of oxalic acid in the substrate. In a bioassay, colonies of the pathogen were exposed to volatiles from hydrated mustard powder used as a myrosinase and glucosinolate source. The glucosinolate-myrosinase (GSL-M) system was activated in the presence of oxalic acid at a concentration and pH similar to that expected in vivo. Volatile production was inhibited only when the pH fell to 3 or below. It is unlikely that oxalic acid plays a significant role in disarming the GSL-M system during infection of Brassica hosts.

In order to identifying of high yielding compatible sunflower hybrids for different regions of Iran, a set of 10 exotic hybrids from Serbia, Turkey, and Italy and four Iranian hybrids were evaluated for agronomic traits; days to flowering and maturity, plant height, head and stem diameter, 1000-achenes weight, achene number per head, oil content and achene, and oil yield. The experiments were conducted as completely randomized block design with four replications in Alborz, Mazandaran, Khuzestan, and West Azerbaijan Provinces for two years (2017–2018). According to the results growing period of the hybrids were variable from 86 days for Dukat to 98 days for Fantaziya. The hybrids Slatki and Dukat had the highest (70 g) and lowest (56 g) 1000-achenes weight. The highest oil content was observed in 08TR003 (45.6%). Among the locations, Miandoab had the highest achene yield (3110 kg/ha). In Sari; the hybrids Barzegar, Fantaziya, and Slatki (3080, 2893, and 2853 kg/ha respectively), In Dezful; Barzegar, Cartago, and Oscar (3234, 3409, and 3226 kg/ha respectively), in Karaj; Oscar, Shams, and Fantaziya (3138, 3081, and 3050 kg/ha respectively), and in Miandob Shams, Fantaziya, and Slatki (4093, 4038, and 3895 kg/ha respectively) had the highest achene yield. Considering overall mean Fantaziya, Shams, and Oskar had the highest achene yield (3286, 3145, and 3087 kg/ha respectively), as well as Fantaziya followed by Barzegar and Shams had the highest oil yield (1396, 1335, and 1330 kg/ha respectively). Considering phenotypic variability among the exotic hybrids Fantaziya, Oskar, Slatki, Novak, 08TR003, and Meteor with lower coefficient of variation and higher achene yield considered as the stable higher yielding hybrids in four test locations of Iran. Through identifying high-yielding and compatible hybrids, the results of this study can assists in increasing of sunflower yield and production in Iran.

Natural compounds play an important role in shaping living plant responses. The resistance of plants is dependent on the formation and production of antimicrobial compounds of secondary metabolites. Glucosinolates (GSLs) are the main source of phytoanticipin in Brassicaceae and other plant families. The biological activity of glucosinolates are dependent on the release of various toxic compounds due to hydrolysis by myrosinase, isothiocyanate (ITC) is glucosinolate-breakdown products that inhibit the growth of microorganisms. In this review, we aim to understand how fungal pathogens overcome the glucosinolate-myrosinaseisothiocyanate system. The pathogens overwhelm the plant's defense system in various ways and disable each component of the system. Many plant pathogens may not cause tissue damage or activation of the glucosinolatemyrosinase-isothiocyanate system, others degrade or transforms the intact GSLs to less or non-toxic products, or inhibit the hydrolysis of GSLs catalyzed by myrosinase, or formed special mechanisms to detoxify toxic GSLs degradation products.

Edited by E BalazsKeywords: Cucumis melo L. Zucchini yellow mosaic virus IRAP REMAP Mixed linear model Melon (Cucumis melo L.) is one of the most important commercial vegetable crops grown in Iran. Very few studies on the genetic structure and diversity of melon landraces of Iran are available in the literature. In addition, it is susceptible to a number of diseases causing reduction in both productivity and quality of the crop. In this study we applied inter retrotransposon amplified polymorphism (IRAP), retrotransposon-microsatellite amplified polymorphism (REMAP) and inter simple sequence repeat (ISSR) molecular markers to investigate genetic diversity and its association with populations resistant to ZYMV in 11 Iranian melon populations and 12 commercial lines. Significant differences (P ≤ 0.01) were detected among populations for reaction to ZYMV infection. No symptoms observed on inbred line PI414723, while variety Charentais T showed the highest value of virus infection (1.87). Based on five IRAP, 15 REMAP and 20 ISSR primers, a total of 656 reproducible and scorable loci were generated, among them 75.41% were polymorphic. Population structure analysis using STRUCTURE software identified K = 10 as the reliable value for the number of clusters. Associations between molecular markers and populations resistant to ZYMV were tested using mixed linear model (MLM) approach that accounts for population structure. Highly significant associations were found for seven REMAP and four ISSR markers affecting ZYMV resistance (P ≤ 0.01). This study provides evidence that using natural germplasms, the diversity can be enhanced for marker-trait associations that can be validated in segregating populations and exploited through marker-assisted selection.

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