Early Detection of Phoma Lingam Infection in Oilseed Winter Rape Before Visible Symptoms Appear

A chlorophyll fluorescence technique enabled early detection of disturbances in the activity of the photosynthet-ic apparatus under Phoma lingam infection. The photosynthetic apparatus of leaves and cotyledons exhibited a negative response to P. lingam inoculation. The effect disappeared more rapidly in leaves, which were not inoculated directly, than in cotyledons, which were inoculated directly. Photosynthetic apparatus disturbances were detected in cotyledons and leaves as early as 24 h after inoculation. Photosynthetic apparatus activity can be affected by the level of hydrogen peroxide, which in cotyledons probably was an element of the hypersensitive response and in leaves could induce an increase in pathogenesis-related proteins, chitinase and β-1,3-glucanase.

The role of glucosinolates of Brassica genus in the crop system

Glucosinolates with Brassica genus as secondary metabolites have a lot of functions and effects. Glucosinolates form less than 2% of the overall sulphur content at the beginning of vegetation in different parts of the plants and during growth their content is decreasing and forms less than 0.1%. This low representation doubts their storage function. With its chemical composition, they are ranked among natural pesticides with active and passive resistance against diseases and pests. They show repellent effects and properties of natural biofumigators in soil after ploughing in their biomass as green fertilizing, or after ploughing in after harvest the leftovers of rape. The principle of these effects is decomposition products of glucosinolates – bioactive isothiocyanates. Very important from this point of view are turnip rape Rex and Brassica juncea, whose content of these compounds is the highest one and they are resistant against the attack of Ceutorrhynchus pleurostigma. The same effect showed also when attacked by Phoma lingam. With other winter Brassicas either hybrid or linea and summer rape is this defensive system suppressed because of their lowered content due to breeding interferences, leading to limitation of their anti-nutritional negative effects. It is possible to state the final result after finding out the production of the above matter, roots, and after evaluation of the sorbal characteristics of the soil and evaluation of the state of health of the following crop or vegetable. After this overall analysis, it will be possible to evaluate the biofumigation properties of accessible varieties of the Brassica genus.

Mapping the sirodesmin PL biosynthetic pathway — A remarkable intrinsic steric deuterium isotope effect on a 1H NMR chemical shift determines β-proton exchange in tyrosine

Sirodesmin PL is both an antibiotic and a phytotoxin produced by a fungal plant pathogen ( Leptosphaeria maculans, asexual stage Phoma lingam ) that causes blackleg disease on crucifers. To determine potential biosynthetic precursors of sirodesmin PL, deuterated compounds were synthesized and incubated with cultures of L. maculans. Incorporations of deuterium into sirodesmin PL (7) and its precursor phomamide (4) were determined using 1H and 13C NMR spectroscopy, LC-HRMS-ESI and HRMS-EI spectrometry. Spectroscopic analyses established that [3,3-2H2]l-tyrosine (1a), [3,3-2H2]O-prenyl-l-tyrosine (9a), [3,3,5′,5′,5′-2H5]O-prenyl-l-tyrosine (9b), and [5,5-2H2]phomamide (4a) were incorporated efficiently into sirodesmin PL (7). Interestingly, an unexpected “twist” revealed that one of the β-deuteria (pro-R) of [3,3-2H2]l-tyrosine (1a) was exchanged stereospecifically before incorporation into sirodesmin PL (7). As well, our studies revealed that O-prenyl-l-tyrosine is likely to be the first committed precursor en route to sirodesmin PL (7).