نشریه نهال و بذر
سال سی‌ام شماره 3 (پاییز 1393)

Charcoal rot caused by Macrophomina phaseolina (Tassi) Goid is a destructive fungal and soil-borne disease of sesame in Iran. To evaluate disease resistance in sesame germplasm، 26 isolates of the pathogen were prepared from infected plants collected from main sesame geowing areas of Iran. Pathogenicity test on cultivar Darab-14، carried out on water agar media in the plates، revealed a considerable pathogenicity in virulence of the isolates. To evaluate resistance of 75 entries of sesame germplasm، including improved cultivars، advanced lines and local genotypes، roots of seedlings were dipped into the hyphal suspension of mixed isolates for 5 minutes and maintained then at 32ᵒC in greenhouse. Reaction of each entry was recorded three days later، using a 1-5 scale. Calculated medians of scales showed that 14 genotypes were resistant and eight were moderately resistant. Using chi-square test، (Kruscal-Wallis method)، the statistical differences were sought. According to the calculations، genotypes Potak-e-Mousian، Mahalli Iranshahr and Safiabad line 3 had the highest level of resistance at the 95% confidence level. Although the rest of resistant genotypes showed the lower amounts of infection، a significant difference with the expected level of resistant and moderately resistant scores in the disease scale (score 1 and 2) was observed.

Identification and distinctness of quince cultivars and genotypes is more difficult than other pomoideae subfamily. This research was aimed at studying the vegetative and reproductive characteristics of endogenous quince germplasm for selection of key traits useful for distinctness and differentiation of genotypes. Thirty quince genotypes from Isfahan، Khorasan and Guilan provinces collected in central quince collection of Iran were evaluated from 2010 to 2012، based on UPOV descriptor. Totally 38 characteristics of descriptor were evaluated together with other 5 complementary characteristics of trunk cross-section area، seeds، fruits and time of leaf fall. The results demonstrated notable variation of characteristics in all tree parts، but also revealed necessity of several distinctive characteristics for identification of genotypes. Among these characteristics، fruit size and form، size of fruit eye، leaf shape and blooming time were more distinctive، all were in accordance with asterisked characteristics of UPOV descriptor. Based on this، leaf form and undulation، fruit size، neck form and length were fundamental distinctive characteristics. Additionally، valuable characteristics for quince breeding including spreading growth habit linked to the high productivity of trees، were found in some genotypes. Most superior genotypes demonstrating high fruit and tree values were in Isfahan germplasm، while Khorasan germplasm were in lower level for use as commercial cultivars. The highest yield was observed in two superior genotypes KVD1 and KVD2، respectively. It was concluded that endogenous promising new quince cultivars could be released from germplasm of Isfahan.

Wheat yellow rust caused Puccinia striiformis Westend f. sp. tritici is one of the most economically important diseases of wheat in Iran and wordwide. In order to determine the heritability، gene action and estimate of genetics parameters for yellow rust resistance components، six bread wheat cultivars and advance lines including Pishtaz، MV17، Moghan 3، SERI/KAUZ، KAUZ//KAUZ/PVZ as well as a susceptible cv. Bolani were crossed using half diallel 7  7 design. Evaluation of F1s and parents were carried out using a randomized complete blocks design with three replications. Plants were inoculated with 134E134A+ race using talk powder. Four resistance components latent period، infection type، pustule density and size were measured. Analysis of variance for combining ability using Griffing method showed that general combining ability (GCA) and specific combining ability (SCA) for four were significant which implies the additive and non-additive effects in genetic control of these components. Among parents cv. MV17 with high GCA for all four traits was identified as suitable parent to be used in breeding programs for enhancement of resistance to yellow rust. Bolani had the highest GCA next to MV17 but for susceptibility. Crosses of MV17 with Bolani، Pishtaz، Kauz//Kauz/PVZ had higher SCA (-) for infection type، number of pustules and pustule size، and the highest SCA (+) for latent period in enhancement of resistance which implies non-additive (dominance and epitasis) gene effects in these crosses. Graphic analysis of Vr and Wr indicated that latent period، infection type، pustule size، and number of pustules were recessive in some genotypes but dominant in some others. Broad and narrow sense heritabilities for all four traits were relatively high، therefore، selection based on these traits for enhancement of resistance to this race is useful.

Penicillium expansum Link. is a major decay agent of fruits including peach and nectarine، in storage. In this research، relative resistance of fourteen commercial and local peach and nectarine cultivars to blue mold in cold storage and its correlation with physicochemical traits as potential resistance indicators were studied. For inoculation، the fungus conidial suspension was prepared and inoculated in wells in equatorial region of fruit. The fruits were then transferred to a cold storage room and lesions diameter was measured six weeks later. Pomological traits including cortex firmness، epidermal toughness، total soluble solids، titratable acidity and total acidity were also measured and their correlation with lesion diameter was studied. Based on the results، different susceptibility levels were observed in cultivars and mean lesion diameter varied from 3. 31 cm in Shams cultivar to 0. 58 cm in Sunglu cultivar. Clustering based on lesion diameter indicated that Shams was highly susceptible، Anjiri، MHF101، Independence، Rome Star، MHF100، MHF102، Nectared 9 and Nectared 4 were susceptible and GH Hall، Red Skin، Sunglu and Nectared 6 were relatively resistant. All cultivars varied in physicochemical traits. A negative correlation was observed between lesion diameter and titratable acidity and epidermal toughness but these relations were not strong enough to be used as decay resistance criteria.

Septoria tritici blotch (STB)، caused by Zymoseptoria tritici is a heterothallic ascomycete fungus and genetic variation in its population is high، therefor identification of new sources of resistance is always necessary to manage the disease. In this study the reaction of 51 pured landrace genotypes was evaluated under greenhouse condition at seedling stage against five Z. tritici isolates. The experiments were performed at Seed and Plant Improvement Institute in 2011. The results showed that the majority of the genotypes were susceptible to all isolates tested. Out of 255 reactions، 15 isolate-specific resistances were identified. Furthermore، genotype no. 14 and 41 originated from Markazi and Fars provinces، respectively، showed the greatest number of isolate specific resistances. These genotypes can be effectively used in the wheat breeding programs in Iran to control the disease.

For estimation and graphical analysis of genetic parameters related to plant height، yield and yield components in lentil، six parental genotypes along with 30 F2 generations derived from compete diallel crosses between them (totally 36 genotypes) were grown in a randomized complete block design with three replications at research farm of Shahre Kord University in 2012. From each experimental plot، fourty F2 and ten parental plants were randomly selected and desired characteristics were measured. Estimation of average degree of dominance and results of graphical analysis showed that gene action was of complete dominance type for plant height. However، incomplete dominance type of gene action was observed for number of pods per plant، number of seeds per plant، 100 seed weight، seed yield and number of seeds per pod. The highest amount of narrow-sense heritability (77%) was observed for 100 seed weight and number of seeds per plant and the lowest (32%) for plant height. Proportion of genes with positive and negative effects (H2/4H1) differed from 0. 25 in all traits which indicated that the frequency of positive and negative genes is not equal in the parents.

Sunflower as an annual crop is being cultivated for nut and oil usages. Having different morphological and physiological traits، the yield of different cultivars and genotypes are varied. The selection of favorable genotypes using morphological markers for the aim of increasing yield have been effective and achieved to the trade benefit of sunflower. In present work، morphological characteristics effective on the yield of 22 genotypes of oil sunflowers، were studied in a randomized complete block design in four replications. The comparison of treatment means showed that cultivar Record had the highest yield of seed and oil. Simple correlation between characteristics coefficients confirmed the direct relationship of seed yield with oil yield and the number of seeds per cap. Stepwise regression analysis followed by path analysis exhibited the number of seeds and weight of thousand seeds as important traits effective on seed and oil yield، and revealed their direct and indirect effects. In factor analysis based on maximum likelihood، five factors were extracted. Cluster analysis categorized the genotypes to five groups based on the yield mean of the studied traits using Ward method.

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola is one of the most important diseases theating wheat crop worldwide. Use of resistant cultivars is the most effective and economically way to control the disease. To evaluate and identify sources of resistance to STB among wheat genotypes at seedling stage، infected leaf samples were collected from different ares of Khuzestan province during 2010-2011 cropping season. After purification and preparation of several isolates of the pathogen، four most virulent isolates were selected and inoculated on primary leaves of seedlings of 219 wheat cultivars and advance lines together with four check cultivars selected from breeding materials of Seed and Plant Improvement Institute، Karaj، Iran. Resistance of genotypes were evaluated based on reaction types of seedlings on day 21 after inoculation، pecentage of necrotic areas and pycnidial coverage. Based on the results، eight cultivars Arina، Riband، M3، Arya، Shotordandan، Karkheh، Soison and Chamran were resistant to all four isolates. Line Sep-49 was resistant to two isolates 90014 and 90018 but susceptible to isolates 91001 and 91002. Lines Sep-58 and Sep-59 were also susceptible to isolate 91002 but resistant to other three isolates. The remaining genotypes were susceptible to all four isolates.

Iran has rich cherry germplasm resources and increasing the fruit quality of these trees is the goal of their breeding programs. In this study، fruit physicochemical and qualitative characteristics of 8 selected sour cherry genotypes which were collected from different regions of Iran، were investigated during 2011 and 2012. The results showed that genotype had significant effect on the studied characteristics and there were differences among genotypes in terms of different characteristics. PCA analysis indicated that the studied characters located in three components that explained 84% of the total variability observed. According to the cluster analysis، genotypes were divided into three clusters that some Iranian superior sour cherry genotypes were separated from foreign cultivars. Standing of Iranian and foreign genotypes in a same cluster is an indication of high fruit physicochemical and qualitative characteristics of these genotypes. It can be claimed that these genotypes are superior in terms of properties such as high weight، firmness، red color، total sugar، TA and flavor and panel test that has resulted in a better position in ranking than improved genotypes. According to the results، genotypes KaThLaSSGe21، Hamedan، KaTaJo2Ge9، KrRIV4C20 and KaThLa3Ge23 had better fruit physicochemical and qualitative characteristics than other genotypes، so they can be considered as promising genotypes for further evaluations of sour cherry breeding programs and new cultivar release programs.

Identification of self-incompatibility alleles in almond (Prunus dulcis) is a very useful tool for orchard design and for choosing parents in breeding programmes. In order to identify the new S-RNases in some Iranian almond cultivars، each allele fragment was amplified and PCR products were purified. The vector PCR-Blunt-II-TOPO was used for cloning. Constructs were transformed into chemically competent Escherichia coli TOP 10 cells and positive transformants were identified. Plasmids were isolated from positive colonies and sequenced by SECUGEN using M13 primers and then a consensus sequence was obtained for each allele with SeqManII software. The results identified eight alleles in the Iranian almond cultivars including Tejari (S36)، Holouei (S37)، Sefid (S38)، Yazd-17 (S39 and S40)، Mashhad 40 (S41)، G-R-16 (S42) and Mamaei (S43). Seven of these alleles have not previously been reported in Prunus species، while one of alleles (S40) was similar to that (S5) identified before in an accession of the wild species Prunus webbii. The similarity between self-incompatibility alleles in cultivated almond wild species of Prunus webbii points out the existence of a common ancestor with other Prunus species and also a possible introgression with P. webbii as a primary ancestors in almond evolution.

Septoria tritici blotch (STB)، caused by Mycosphaerella graminicola (anamorph، Zymoseptoria tritici) is considered as an important destructive disease of wheat worldwide as well as Iran. In order to study the virulence spectra of isolates collected from Fars province on the differential cultivars possessing Stb resistance genes، pathogenicity tests using seven isolates were conducted under controlled conditions in 2013 at Seed and Plant Improvement Institute in Karaj based on 0-5 scaling system. Out of 126 M. graminicola-wheat interactions، 41 specific resistances and 85 susceptible interactions were found. Except RM186 and RM177 that had similar virulence pattern، the remaining isolates exhibited distinct virulence patterns indicating that these isolates had genetic differences. Isolates RM9، RM175 and RM179 were the least virulent isolates that were pathogenic on 9 out of 18 differential cultivars. Isolates RM28 and RM159 were virulent on 16 differential cultivars and thus، were considered as the most virulent isolates. The results showed that among resistance genes، Stb16/Stb17 presented in M3 cultivar were effective against all isolates. None of the Stb5، Stb6، Stb7 and Stb8 genes was effective against isolates tested. These results can be used in wheat breeding programs for resistance to septoria tritici blotch disease in Fars province.