اثر استرینtr6 trichoderma harzianum در القای مقاومت علیه سفیدبالک گلخانه (hem.: aleyodidae) trialeurodes vaporariorum، در گیاه گوجه‌فرنگی

یکی از مکانیسم‌ های عمل قارچ‌ های جنس trichoderma spp.، تحریک سامانه دفاعی در گیاهان است. در این مطالعه، اثر استرینtr6  trichoderma harzianum بر ترجیح میزبانی و تخم‌ گذاری سفیدبالک گلخانهtrialeurodes vaporariorum westwood در شرایط آزمایشگاهی بررسی شد. در این راستا چهار آزمایش شامل سنجش فنول کل، بررسی اثر زمان در بروز مقاومت، انتخاب آزاد و بدون انتخاب در شرایط دمایی 2±25 درجه سلسیوس، رطوبت نسبی6070 درصد و دوره نوری 8:16 ساعت (روشنایی:تاریکی) انجام شد. نتایج نشان داد بیش‌ترین غلظت فنول کل در گیاه مربوط به زمان‌ های3 و 4 روز بعد از تلقیح قارچ بود که به ‌ترتیب برابر با 0.003±0.3503و 3323.001±0.0 میلی ‌گرم بر گرم بود و کم‌ترین تعداد افراد بالغ پشت برگ از روی گیاهانی که 2 و 4 روز از زمان تلقیح آن ها می‌ گذشت، جمع‌ آوری شد که به‌ترتیب میانگین آن ‌ها برابر با 0.86±2.2 و0.63±2.0بود. هم‌چنین در گیاهان تیمارشده به ‌وسیله قارچ تریکودرما، کاهش معنی‌داری در میانگین تعداد حشرات بالغ درپشت برگ (0.66±3.4)، تخم‌های گذاشته شده (1.51±7.4) و میزان قطرات عسلک تولیدشده (0.28±1.0) نسبت به گیاهان شاهد، مشاهده شد. یافته ‌های این پژوهش نشان داد که تیمار گیاه با استرین tr6 t. harzianum سبب القای مقاومت نسبت به گیاه‌خواری سفیدبالک، کاهش ترجیح میزبانی و تخم‌گذاری شد و کاربرد آن می تواند یک گزینه امیدوارکننده در برنامه مدیریت تلفیقی این آفت در گلخانه باشد.

Effect of Trichoderma harzianum Tr6 in inducing resistance in tomato against Trialeurodes vaporariorum (Hem.: Aleyodidae)

Background and ObjectivesThe greenhouse whiteflies, Trialeurodes vaporariorum (Westwood), are one of the major pests of vegetable and ornamental crops in greenhouses in the world. They damage crops through direct feeding, inserting their stylet into leaf veins, and extracting nourishment from the phloem sap. As a byproduct of feeding, honeydew is excreted, which is an indirect but yet another substantial source of damage. The third most harmful characteristic is the ability of adults to transmit various plant viruses. Induced resistance is a nonchemical control method that has no negative impact on the environment and human health and can be a desirable approach in plant protection and pest control. Trichoderma spp. has spread in many ecosystems and its various species such as Trichoderma harzianum Rifai have been successful as nonpathogenic symbionts in controlling plant pathogens via different mechanisms. Some of these mechanisms include enzymatic degradation, secretion of antibiotics, and increasing root absorption capacity. Recent findings suggest that T. harzianum is also a potent inducer of Induced Systemic Resistance (ISR) and can stimulate the immune system in plants against plant diseases and pests. In this study, the efficacy of T. harzianum Tr6 was investigated on host preference and egg production of T. vaporariorum.Material and Methods To evaluate the effect of T. harzianum Tr6, four tests were carried out: 1) Total phenol assay using Folin–Ciocalteu reagent, 2) The effect of time on induced resistance, 3) Free choice, and 4) Non choice. These tests were conducted on tomato plants (Falat cultivar) at 25±2°C, relative humidity of 6070%, and a photoperiod of 8 h/16 h (day/night). Also, these experiments were performed on onedayold adults in plots with four or six leaves in shelves equipped with organza mesh. ResultsAccording to the phenol assay, the highest amount of total plant phenol was observed three and four days after inoculation by Tr6 strain respectively 0.3503±0.001 and 0.3323±0.001mg/g. Therefore, for the next three tests, plants that were inoculated after three days were used as treated samples, and plants watered with distilled water were used as control ones. In these experiments, the lowest number of adults on the back of the leaves after 24 hours was observed two and four days upon inoculation respectively 2.2±  0.86 and 2.0±  0.63. On the other hand, plants inoculated by Tr6 displayed a significant decrease in adults on the back of the leaves (3.4± 0.66), egglaying (7.4± 1.51), and honeydew droplets (1± 0.28) compared to control plants.Conclusion The most important factor in controlling the whitefly population is reducing the reproduction rate. Induced resistance can repel insects from plants and limit their nutrition, and thus, reduce their reproduction. This study implied that the inoculation of tomato by T. harzianum Tr6 strain could induce resistance to whitefly and reduce host preference and egg production, as well as honeydew secretion. Therefore, this strain can be a promising option in preventing the outbreak of this multigenerational pest.