تجزیه و تحلیل مقاومت به بیماری بلایت فوزاریومی سنبله در لاین‌های گندم امیدبخش اقلیم گرم و مرطوب شمال کشور

بیماری بلایت فوزاریومی سنبله، عمدتاً ناشی از گونه قارچی fusarium graminearum، یکی از مهم ترین بیماری های گندم به‌ویژه در اقلیم گرم و مرطوب شمال کشور است. در تحقیق حاضر، با هدف شناسایی و گزینش لاین‌های مقاوم به بیماری، تعداد 20 لاین گندم امیدبخش مربوط به این اقلیم به‌همراه گندم رقم فلات به‌عنوان شاهد حساس به بیماری، طی سال زراعی 94-1393 در دو منطقه گرگان و مغان و سال زراعی 1394-95 در منطقه مغان بررسی شدند. همچنین، به‌منظور شناسایی مقاومت نوع ii در این لاین‌ها، واکنش آن‌ها در برابر بیماری در شرایط گلخانه (کرج) نیز بررسی شد. تجزیه واریانس مرکب داده های مربوط به میزان وقوع، شدت و شاخص بیماری و میزان آلودگی دانه به‌دست آمده از سه محیط آزمایشی مزرعه نشان داد که برای هر چهار صفت مذکور تفاوت معنی داری بین لاین‌های آزمایشی وجود داشت. ارزیابی واکنش لاین‌های آزمایشی نشان داد که شاهد تجاری مروارید به‌همراه پنج لاین n-93-6، n-93-12، n-93-15، n-93-18 و n-93-19 با داشتن میانگین وقوع، شدت و شاخص بیماری و آلودگی دانه پایین تر در مزرعه و شدت بیماری کمتر در گلخانه، از مقاومت بالاتری نسبت به بیماری برخوردارند. به‌نظر می‌رسد که وجود مقاومت نوع i در این لاین‌ها موجب کاهش بیماری در آن‌ها شده باشد. در این بررسی، نتایج اندازه گیری پارامترهای مختلف ژنتیکی تفاوت های زیادی را بین صفات مختلف نشان داد. از نظر مقایسه ضرایب تنوع ژنتیکی و فنوتیپی بین صفات مختلف، سه صفت، دانه آلوده به فوزاریوم (fdk)، میزان وقوع بیماری و شاخص بیماری در مقایسه با دو صفت دیگر یعنی شدت بیماری در شرایط مزرعه و گلخانه دارای بیشترین ضریب تنوع و از بین آن‌ها صفت fdk دارای بالاترین نسبت ضریب تنوع ژنتیکی به ضریب تنوع فنوتیپی بود. درنهایت یافته‌های پژوهش حاضر نشان داد که دو صفت fdk و شدت بیماری در مزرعه دارای وراثت‌پذیری عمومی بالا (به‌ترتیب 68 و 60 درصد) و بقیه صفات دارای وراثت‌پذیری پایین‌تری بودند.

analysis of fusarium head blight (fhb) resistance in elite wheat lines from the north warm and humid zone of iran

introduction fusarium head blight (fhb), primarily inflicted by fusarium graminearum, is a devastating wheat disease, particularly in regions where flowering coincides with warm and humid conditions. in addition to reducing crop yield, fhb poses significant threats to human and animal health as well as food safety due to the production of different types of mycotoxins in infected grains. in iran, fhb is among the most significant wheat diseases in the north warm and humid regions, including golestan and mazandaran provinces as well as in the warm areas of moghan in ardabil province. however, under favorable weather conditions, the fhb disease can spread to other parts of iran and potentially lead to epidemics. to this end, several methods, including agronomic, chemical, biological, and the use of resistant cultivars are employed for the fhb disease management. among such methods, the use of resistant cultivars is considered the most practical, most economical, and environmentally sound method for sustainable control of the fhb disease. the first step in developing fhb disease-resistant wheat cultivars is to evaluate existing cultivars or breeding lines for their resistance to the fhb disease and to identify the most resistant genotypes. to this end, the response of 20 elite wheat lines from the north warm and humid zone of iran along with the susceptible check cultivar falat was evaluated for fhb disease resistance under field conditions in gorgan, golestan province and moghan, ardabil province, iran in 2014-15 and in moghan in 2015-16. in order to identify type ii resistance in these lines, their response to the disease was also evaluated in the greenhouse in karaj, iran. based on the results of this study, wheat lines with sufficient resistance to fhb were identified for use in breeding programs and potential release in the northern regions of iran. materials and methods wheat genotypes in all the relevant field and greenhouse experiments were manually inoculated. the wheat lines were evaluated under field conditions in gorgan and moghan in 2014-2015 cropping season and in moghan in 2015-2016 cropping season as a randomized complete block design (rcbd) with three replications. in this regard, wheat lines were sown on a 1.5-meter row in late fall (december) and the usual agricultural practices were performed until heading stage. as soon as each wheat line reached 50% flowering, it was inoculated by spraying with a suspension of spores of the pathogen (at 5×104 spores per milliliter of suspension) and it was repeated two days later. to enhance the disease development, mist irrigation was established in the nurseries. about three weeks after the first inoculation, disease incidence and severity were recorded for each line, and disease index was calculated by dividing the product of disease incidence and severity by 100. fusarium-damaged kernels (fdk) were also quantified by determining the ratio of the infected seeds to healthy seeds after grain harvest. to investigate the reaction of the wheat lines under greenhouse conditions (karaj), an rcbd with three replications was also used. to do this, in mid-autumn 2015, eight to 10 seeds from each wheat line were sown in plastic pots (15 cm × 15 cm), containing a mixture of field soil (70%) and peat moss (30%). to promote seed germination, the pots were placed in a greenhouse at 25-30 ° c for one week. to promote tillering and the development of more and stronger spikes, the pots containing the seedlings were placed outdoors for two months under relatively cool conditions. they were then transferred to a greenhouse maintained at 25–30 °c. as soon as each spike from each wheat line reached 50% of flowering, plants were point-inoculated with 10 μl of the suspension of fungal spores (5×104 spores per ml of suspension). three weeks post inoculation, the percentage of disease progress (disease severity) was quantified by determining the ratio of infected spikelets to total spikelets in each spike. the sas software was used for the analysis of data recorded from the field and greenhouse expiriments. results and discussion combined analysis of variance of data for several datasets including disease incidence, disease severity, disease index, and fdk from three environments showed significant differences among the genotypes. evaluation of the wheat genotypes revealed that the commercial wheat cultivar morvarid, along with five lines, including n-93-6, n-93-12, n-93-15, n-93-18, and n-93-19 exhibited lower mean values for disease incidence, disease severity, disease index, and fdk under field conditions, as well as reduced disease severity in the greenhouse. these genotypes were therefore identified as more resistant to fhb. it seems that type i resistance in these wheat lines might have reduced the incidence of fhb disease. the results of present study demonstrated significant variation among traits based on the assessment of genetic parameters, including trait minimum, maximum, and mean values; environmental, genetic, and phenotypic variances; environmental, genetic, and phenotypic coefficients of variation; and broad-sense heritability. in terms of comparing the genetic and phenotypic coefficients of variation between different traits, fdk, disease incidence, and disease index had the highest coefficients of variation compared to the other traits including disease severity under field and greenhouse conditions. in addition, fdk had the highest ratio of genetic to phenotypic coefficient of variation. finally, fdk and disease severity under field conditions had the highest values of broad-sense heritability,68 and 60 percent, respectively.conclusion in the present study, high genetic and phenotypic coefficient of variations were observed for fdk, disease incidence, and disease index traits. considering that the ratio of genetic coefficient of variation to phenotypic coefficient of variation for fdk was very high, it seems that this trait was mainly under genetic control. despite the low genetic and phenotypic coefficients of variation observed for disease severity under field conditions, the high ratio between them indicates that the trait is largely governed by genetic factors. the high broad-sense heritability estimates for fdk and disease severity traits under field conditions provide further evidence of strong genetic control over these traits. in contrast, the relatively low ratio of genetic to phenotypic coefficients of variation for disease incidence and disease index traits may suggest a lesser contribution of genetic factors and a greater influence of environmental conditions on their performance.