Дослідження впливу збудника плямистості перцю Xanthomonas vesicatoria на активність фотосинтетичного апарату

Abstract

В статті проаналізовано дані щодо дослідження впливу штучного інфікування штамами збудника бактеріальної плямистості перцю роду Xanthomonas на фотохімічну активність листків рослин перцю овочевого чотирьох сортів – Дружок, Лада, Світлячок та Світозар. Виявлено, що патогенна дія штамів збудника на фотосинтетичний апарат рослин перцю різних сортів обумовлена зниженням ефективності поглинання квантів світла у процесі фотосинтезу, завдяки скороченню вмісту фотохімічно активного хлорофілу в листках. Найбільш стійким до ураження досліджуваними патогенними штамами виявився сорт Лада, а більш вразливими – сорти Світозар і Світлячок.

В статье проанализированы данные исследования по влиянию искусственного инфицирования штаммами возбудителя бактериальной пятнистости перца рода Xanthomonas на фотохимическую активность листьев растений перца овощного четырех сортов - Дружок, Лада, Светлячок и Светозар. Выявлено, что патогенное действие штаммов возбудителя на фотосинтетический аппарат растений перца разных сортов обусловлено снижением эффективности поглощения и использования энергии квантов света в процессе фотосинтеза, за счет сокращения содержания фотохимически активного хлорофилла в листьях. Наиболее устойчивым к влиянию исследуемых патогенных бактериальных штаммов оказался сорт Лада, а наиболее уязвимыми - сорта Светозар и Светлячок.

Pepper vegetable plants of four varieties Druzhok, Lada, Svitliachok and Svitozar grown within the greenhouse environments were artificially infected with different strains Xanthomonas vesicatoria: 33 and 45 – extracted from pepper and 7862 - extracted from tomato. The phenological observation of the bacterial spot development showed the presence of characteristic features on all the plants of studied varieties which were infected with pathogenic strains extracted from pepper. The symptoms of the affection in the form of convex dark-green roundish patches of watery borders firstly appeared on the pepper products – on 3-4 days after the infection and much later on the stems and leaves – on 10-12 days. The infection features of in the form of spots on different plant organs were slightly different in shape and color - pale brown with yellowish border located on the leaves and elongated black ones placed on the stems. The plants being inoculated by strains extracted from tomato, symptoms of the infection were observed on the plants of pepper varieties Druzhok and Svitozar, while the leaves of plants Svitozar and Svitliachok varieties had mild symptoms of the infection. In parallel we investigated the photochemical activity of pepper leaves of the following varieties by means of the method of induction of chlorophyll fluorescence using a portable device «Floratest». It has been found the increased level of chlorophyll fluorescence in the infected plants according to the control, at the same time fluorescent indicators varied in size. As a result of the infection on the photosynthetic apparatus of pepper plants of different varieties, a significant increase of parameters F0, Fm and Ft was observed in leaves. It should be noted that the increase of the parameter Ft indicated a slowdown in the outflow of electrons and transmission reduction of processes of dark carbon fixation, which took place in leaves of most infected plants. The variety Svitliachok had moderate resistant to the infection of strain 33 and the variety Druzhok demostrated moderate resistance to strain 45. In most plants of the variety Lada, which appeared to be more resistant to affection, this parameter remained at the control under inoculation by strain 33 and slightly decreased under the action of strain 45. The observed changes of fluorescent parameters in pepper plants of the varieties Druzhok and Svitliachok under the action of 33 and 7862 strains and of variety Svitozar – under the infection of 45 and 7862 strains indicate an increase of inactive chlorophyll concentration, that does not transfer the excitation energy to reaction centres, and the reduced efficiency of absorption and utilization of quanta light energy during photosynthesis. We observed the increase of number of non-renewable Qb-complexes that do not participate in the linear electron transport, which confirms the stress for plants under the infection. The pathogenic effect of strains X.vesicatoria on the photosynthetic apparatus of different varieties of pepper plants caused a significant increase of chlorophyll fluorescence emission which corresponds to reduction of efficiency of absorption and utilization of energy light quanta in the photosynthesis process by means of the method of chlorophyll fluorescence induction. However, the regulatory system of the photosynthetic apparatus of pepper plants in their more resistant varieties react adaptively to increasing of the number of photochemical activity complexes of PS II, except the infection of pepper plants of the variety Svitozar by strain 7862, in the leaves of which the processes of degradation of light-harvesting complexes have begun. Calculations of Fv / Fm parameters corresponding to the quantum yield of photochemistry and the number of photochemically active complexes PSII showed its increasing under the artificial infection of most studied varieties of plants. This reaction of the regulatory system of the photosynthetic apparatus is adaptable to more resistant varieties of pepper. An increase of the number of photophysical complexes PS II occurs as follows (from high to low parameters): Lada (strain 45), Druzhok (strains 7862 and 33), Lada (strain 7862), Svitliachok (strain 33), Druzhok (strain 45) Svitozar (strain 45), Svitliachok (strain 7862), except the pepper plants of the variety Svitozar infected by strain 7862, the leaves of which have started their light-degradation complexes. The increased variable fluorescence for the infection of studied strains (except the variety Svitliachok inoculated by strain 7862) indicates the blocking of electron transfer in the «fast» phase - between QA and Qb. At the same time there was an increase of the induction coefficient, whose parameter correlates closely with RBPK activity - the main limiting enzyme Calvin cycle that occurred in the following order (from the largest to the smallest): Druzhok (strain 7862), Lada (strains 7862 and 45), Svitliachok ( strain 33), Druzhok (strains 45 and 33), Lada (strain 33) Svitozar (strain 7862), Svitliachok (strain 7862) Svitozar (strain 45). It is possible that such an increase of RBPK efficiency and, consequently, of the Calvin cycle is adaptive at regulatory support while increasing of relative quantities of non-renewable Qb-complexes. Such activation in a short period of time may be favorable, but more longer it can lead to the depletion of supporting homeostasis and disrupt the metabolism of plants, which ultimately reduces the yield and quality. According to the degree of resistance to pathogenic bacterial strains on the particular photophysical and photochemical parameters of the photosynthetic apparatus of pepper plants of four different varieties, the most resistant was the variety Lada and the most sensitive were varieties Svitozar and Svitliachok. The data of the research performed by means of the chlorophyll fluorescence induction method demonstrating the resistance of different varieties of pepper plants which were infected by bacterial spot are confirmed by the phenological observations.