جستجوی مقالات مرتبط با کلیدواژه "partial resistance" در نشریات گروه "گیاهپزشکی"

The emergence and rapid spread of virulent races of wheat rusts has driven a search for sources of resistance for durable resistance. Slow rusting resistance, a kind of race-nonspecific resistance, has been reported to be more durable. In this study in order to identify possible sources of durable stem rust resistance between elite wheat lines, slow rusting parameters including coefficient of infection (CI), final rust severity (FRS), apparent infection rate (r) and relative area under disease progress curve (rAUDPC) were evaluated in a set of forty six wheat lines along with susceptible control (mixture of McNair and the line CD-90-12) in 2015-2016 and 2016-2017 cropping seasons. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran). All lines were evaluated under natural infection conditions against race population having virulence to resistance genes including Sr25, Sr5, Sr6, Sr7a, Sr23, Sr28, Sr29, Sr30, Sr33, Sr34, Sr37, SrDP2, SrGT, SrPL, SrWLD, SrH and SrTmp < /em>. Results of evaluations for resistance parameters showed that the lines M-93-13, M-93-14, M-93-16 and M-93-20 had low level of CI, FRS, r and rAUDPC so were considered as lines having high levels of slow rusting resistance. The lines C-93-10, C-94-6, C-94-8, CD-94-6, M-93-3, M-93-12 and M-93-18 had moderate level of slow rusting and 25 lines with high values of CI, FRS, r and rAUDPC were grouped as lines having low level of slow rusting resistance. The remaining lines without slow rusting resistance were considered as susceptible group. The lines with high and moderate levels of slow rusting resistance can be used in breeding programs or releasing new resistant cultivars.

Basal stem rot caused by Sclerotinia sclerotiorum is considered the most important fungal disease of sunflower in Iran. Application of resistant genotypes is one of economic strategies for the disease management. Recently, in association mapping for resistance to sclerotinia rot disease in sunflower, a significant relationship has been observed between the lower Sclerotinia-induced necrosis and HaRIC_B gene expression. On the other hand, expression of defense genes is highly regulated by transcription factors. In this study, using real time PCR technique, the expression level of HaRIC_B gene and MYB-related transcription factor were studied in partial resistant (LC1064C/ 8*A) and susceptible (SDR19) lines of sunflower inoculated with the S. sclerotiorum isolate A37. In studying the expression pattern of HaRIC_B gene in two lines, it was seen that the expression pattern in the LC1064C/8*A line was increased regularly from one sampling time to another and the expression rate at any time was more in LC1064C/8*A line than SDR19. Comparison of HaRIC_B gene expression and MYB-related transcription factor revealed a reasonable relationship between the expression level of both genes, especially in the LC1064C/8*A ine. This finding highlight the possible major role of MYB-related transcription factor in stimulating HaRIC_B gene expression and consequently inducing resistance to Sclerotinia in sunflower which, of course, needs further investigation. By confirming the resistance of the LC1064C/8*A line to Sclerotinia at the molecular level, this line could potentially be used in the production of resistant hybrid cultivars in conventional plant breeding programs.

Background and Objectives Among biotic stresses, stem (black) rust, caused by Puccinia graminis f. sp. tritici is considered to be the most destructive disease of wheat in some countries and its damage reaches 100% in the years of epidemic on susceptible cultivars. Lack of durable resistance in wheat cultivars is the main reason for the black rust epidemics that can limit wheat production in some parts of the world. Today, it is possible to manage rusts with effective and new fungicides. However, growing resistant cultivars is the most effective, economical, and environmentally safe approach for disease management. Therefore, this study was performed in order to identify potential sources of partial resistance to black rust, which is a stable and non-race specific. Materials and Methods The partial resistance parameters including coefficient of infection (CI), final disease severity (FDS), apparent infection rate (r) and relative area under disease progression curve (rAUDPC) were assessed in a set of twenty six wheat genotypes along with susceptible control (Mixture of McNair and line; CD-90-12) during 2018-2019 cropping year. This study was conducted in field plots at Ardabil Agricultural Research Station (Iran). All genotypes were evaluated under natural infection conditions against race population having virulence to resistance genes; Sr25, Sr5, Sr6, Sr7a, Sr9e, Sr13, Sr23, Sr28, Sr29, Sr30, Sr33, Sr34, Sr37, SrDP2, SrGT, SrWLD, SrH and SrTmp. Seedling reaction was also appraised under greenhouse conditions against TKTTF (two isolates) and TTTTF pathotypes. Results The results showed that genotypes Gascogne, MV17 and Gonbad having low levels of CI, FRS, r and rAUDPC were considered as the group with desirable level of partial resistance. Nine cultivars/lines showed moderate values ​​of resistance parameters and were considered as genotypes with moderate level of partial resistance for stem rust. Six lines had low partial resistance and the rest of the lines were grouped in susceptible group without any partial resistance. Discussion Genotypes Zare, Gascogne, Gonbad, N-91-9, and N-91-15 due to susceptible reaction (at least against to one pathotype) at seedling and moderately resistant to moderately susceptible response at the adult plant stage are likely to have the more number of partial resistance genes. Genotypes with desirable and moderate levels of partial resistance identified from this study can be used to introduce candidate varieties or in wheat breeding programs to stem rust.

Walnut tree is one of the most important orchard and jungle trees in Iran. It's world cultivation is growing up due to its plentiful uses. Meanwhile, some pests and diseases are known as the major reasons of restriction in walnut cultivation. Among walnut diseases, anthracnose is the most destructive in Iran. In this study, the main area of walnut cultivation in Zanjan were surveyed, walnut's infected organs (sprouts, leaves and fruits) were sampled and the disease agent was isolated and identified using ordinary plant pathological methods. The results showed that Ophiognomonia leptostyla (Fr.) Sogonov contribute to the walnut anthracnose disease, and it is permanently scattered in all Zanjan walnut orchards. It's damage varies between15% to 67% in different regions. Our study on Telemorph and Anamorph phases of the fungus showed that there are no significant differences between isolates collected from Zanjan and those from other provinces in vicinity. Meantime, the results showed that the majority of the collected isolates were Heterothal. Study on partial resistance of three Iranian local genotypes (Z53, Z63 and 60) and six exotic cultivars (Sere, Lara, Franket, Pedro, RDM and B21) showed that local genotypes were more susceptible to walnut anthracnose in comparison to exotic varieties. Although none of the varieties and genotypes was totally resistant, in comparison to introduced interior superior genotypes, exotic varieties of Persian walnut were by far in better condition against anthracnose.

Rice sheath blight disease caused by Rhizoctonia solani AG1- IA is the second economically important disease of the crop in most rice- growing regions of the world، including Northern of Iran. The disease is mainly controlled through application of fungicides. The present study was performed to identify the candidate cultivar (cultivars) as source of resistance to the pathogen in rice field conditions in Northern Iran. Thirty seven vs twenty three rice cultivars respectively from Iranian Local (IL) and Iranian Improved (II) cultivars along with ten Foreign Resistant (FR) cultivars were field grown at the Rice Research Institute of Iran. They were inoculated with the mycelial mass of a virulent isolate (G309) of pathogen، 45 days after being transplanted. To supply favorable humidity for disease development، the plants were kept wet until the evaluation time through 2-5 times of daily water spraying، while applying a overhead water sprayer system available on the field. Assessment of cultivars، reaction was done by recording the Sheath Blight Severity as appeared on the sheath (SSS)، number of Lesions on the Sheath (LS)، Relative Lesion Height (RLH)، percentage of Infected Tiller (IT)، number of Dead and Green Leaves (DL and GL)، Number of tillers (Nt)، Tiller Angle (TA)، Stem Width (SW)، and Plant Height (PH). Results indicated that، the group of FR cultivars significantly differed from groups (IL) and (II) cultivars by exhibiting less SSS، LS، DL vs more GL. Cluster analysis of the cultivars as based on RLH، SSS and DL، using UPGMA method revealed 4 groups. One of the grpups comprised of: Jasmine 85، Teqing، Pecos and Tetep was observed as resistant، whereas، another one containing Swarna (Foreign susceptible)، Moosatarom، Hassansaraei، Jamshidjo، Khazar، Shiroodi، D4 (IL and II)، and Fujiminori was recorded as susceptible. Analysis of the relationship between plant traits and disease response indicated that RLH and SSS were not significantly correlated with the assessed morphological characteristics as regarded FR cultivars، whereas a positive significant correlation was observed between SSS and TA (r = 0. 20، P. value= 0. 033)، and a negative one between RLH and PH (r = -0. 29، P. value= 0. 002) as detected on local cultivars.