نشریه نهال و بذر
سال هجدهم شماره 4 (پاییز 1381)

Common bunt (Tilletia laevis) isolates, were collected from naturally infected wheat spikes (1560 samples) in the wheat growing areas of Khorasan province, during 1997. Seeds of three sets of spring and winter wheat differentials, containing known resistance Bt genes were inoculated with teliospores obtained from twenty single head selections of these samples (each spike = one isolate). Two local susceptible cultivars Sardari and Roshan were also included as local checks. The experiments were carried out under natural conditions. In the field, artificially inoculated seeds of each set of differentials were sown in the depth of 4cm at two lines one meter long. In pot tests, 8-10 inoculated seeds were planted in each pot and 6 pots were allocated to each differential cultivar. Based on the resistance or susceptibility reactions of differential cultivars to 20 samples of T. laevis, four races L1, L3, L8 and L20, were identified. These races are reported for the first time from Khorasan province. Race L8 is new for Iran, and race L20 has not been reported anywhere else.

Physiological factors that control the growth of wheat grains are not well known. To evaluate the grain weight potentials and post-flowering source limitation, this study was carried out in climatically conditions of Neyriz in 1995 growing season. The design of the experiment was split plot with four replications. The main plots included four planting dates (6th Nov., 22nd Nov., 7th Dec. and 22nd Dec.), and the sub plots included three wheat cultivars (Roshan, Falat and Ghods). Assimilate increase for grain growth was done through decreasing the number of spiklets. In each spike, four spike lets with numbers 3, 6, 9 and 12 were kept and others were left out. The results indicated that source limitation increased with delaying the planting practice, in such a manner that the grains produced in the delayed planting date faced with a limitation of about 44.2% whereas the limitation for the first planting date was 4.8%. On the other hand, comparison among cultivars showed that source limitation average for Roshan cultivar was less than Falat and Ghods. The source limitations for above-mentioned cultivars were 13.6%,20.6% and 22.9%, respectively.

To detennine number and effects of genes that control erucic acid in rapeseed Brassica napus, two zero erucic acid cultivars were crossed with four cultivars containing various levels of erucic acid content (4.56% to 46.5%) including reciprocals. The erucic acid content of F1"s and their reciprocals was intennediate of parents indicating embryonic control of erucic acid and absence of maternal effect in inheritance of erucic acid in B. napus. Erucic acid content of F2 seeds segregated in to 5 classes 44% with a ratio of 1: 4: 6: 4: 1. Backcrosses seeds (BC1) derived from the F1× (zero erucic acid parents), segregated into three classes (44% erucic acid) with a ratio of 1: 2: 1. The segregation patterns in F2 and BC1 indicated that erucic acid content in B. napus was governed by two independent genes interacting in an additive manner. Pooled data analysis also conformed above results. Contributing of alleles of genes was not same. Alleles E1 and E2 in this study were equal to Ea and Eb that reported already.

Differences in dry matter accumulation among crop cultivars can be attributed to differences in either the absorption of incident photosynthetic ally active radiation (PAR) and/or for the conversion of absorbed into dry matter. A field study was conducted in 1999 to quantify the effect of planting pattern on dry matter accumulation. The experiment was split plot design on randomized complete block basis with 3 replications. Main plots were allocated to planting patterns: rectangular, square and diamond, and the sub plots were consisted of three maize hybrids (KSC 704, KSC 301, KSC 108). The Results revealed that planting pattern had a significant effect an PAR and radiation use efficiency at different growth stages, especially after the beginning of the reproductive phase. Leaf area index and canopy light extinction coefficient were significantly affected by planting pattern and cultivars. Significant differences were found among source of variations in respect of PAR absorbtion. Higher dry matter accumulation in square planting pattern was due to higher incident PAR and RUE compared to the other treatments.

To determine virulence factors of Puccini recondite f. sp. trifici on wheat and their annual changes, trap nurseries were grown annually during a period between 1995 to 1999 in Sari, Kermanshah, Moghan, Zabol, Ahvaz, Shiraz and Ardebil, where leaf rust often occurs. Nurseries consisted of 28 near - isogenic lines, each containing a single Lr resistance gene. The nurseries were grown under natural infection and mist irrigation system, to provide suitable conditions for disease development. Susceptible check cultivar were included in the nurseries for even more development and distribution of leaf ruct on plants. At adult plant stage, infection types and disease severity on all entries were recorded at least for three times. Infection types O, R, MR and MS were considered as Avirulence and type S as Virulence for interpretation of presence or absence of virulence factors for resistance genes. According to the results, in 1995, there was virulence for genes Lr1, 2a, Ech, 2c, 2b, 3, 3Ka, bg, 9, 11, 12, 13, 15, 17, 18,21, 22b, B. In 1996 virulence appeared for Lr1, 2a,Ech, 2b, 3, 3bg, 3Ka, 9, 12, 13, 14b, 15, 16,17,18,21,22,23,24,30,34. In 1997 the disease appeared only on some cultivars in a few regions. In this year virulence observed only for Lr1, 2a, 2b, 2c, 3, 3Ka, 10, 11, 12, 13, 15, 30,34. In 1998 disease appeared only in few locations, and resistance gene Lr1, 2a, 2b, 2c, 3Ka, 10, 11, 12, 13, 15,21,30 were affected. In 1999 for Lr2b, B, 15 in Sari and for Lr1, 2a, 2b, 2c, 3, 3Ka, 9, 10, 14a, 16,24, 30 in Ahvaz virulence factors were observed.

Powdery mildew caused by Blumeria gamines f. sp. tritici (Erysiphe gamines f. sp. trifici) has become one of the most widespread and important diseases of wheat in several provinces of Iran including Mazandaran. The impact of environmental (temperature, relative humidity, rainfall and number of sunny days) on the incidence and severity of the disease and the alternative hosts of the causal agent were studied during 1996-1999 in Mazandaran province. Wheat cultivars Atrak, Milan, Tajan, Falat, Hirmand and Rasoul were grown in six locations in central Mazandaran. Stepwise regression analysis with cultivars as treatments and locations as replications was employed. The results revealed existence of a linear correlation between disease severity and mean air temperature in all cultivars. There was a linear increase in disease severity with rise in temperature until mid-May, when powdery mildew reached its peak in severity. The fungus appeared to oversummer and overwinter as cleistothecium. The cleistothecia were fully matured, with fully developed asci and ascospores in July- August and emptied in late September. Cleistothecia appear to play a role, in addition to conidia and hyphae, in persistence and dispersal of the fungus. Powdery mildew infection of Aegilops triuncialis, Phalaris minor and Lolium temolentum were observed and pathogenicity of B. graminis f. sp. trifici on these weed species was confirmed by artificial inoculation. This is the first report on infection of Aegilops triuncialis and Lolium temolentum by the wheat powdery mildew in Mazandaran.

At the recent years, many sunflower restorer lines (Rf-lines) have been derived from exotic sunflower hybrids in Seed and Plant Improvement Institute at Karaj. Twenty four of these new Rf-lines (Resistant to Plasmopara halstedii), were crossed with three testers at the Oilseed Crops Research Department. Sixty hybrid combinations were evaluated in replicated field trials to estimate the general combining ability (GCA), and the gene effects. Analysis of the general combining ability for the grain yield and seed oil content showed that R-43, R-72, R-82, R-217, R-231, R-256, R-103, R-87, R-55 and R-45 for grain yield and R-43, R-256, R-46, R-87 and R-45 for oil seed content had high GCA values. Evaluation of gene effects indicated the involvement of additive and nonadditive effects for plant height, growth duration, head diameter, 1000 seed weight, grain yield and merely additive effect for seed oil content.

The effect of Triterponic growth regulator on yield and some morphological and physiological characteristics of three potato cultivars Agria, Marfona and Draga was studied in the Agricultural Experimental Station, Karaj in 2000. Triterponic acid was sprayed at four levels of 0, 150, 300 and 450 gha-1. Each concentration , was divided into three parts and sprayed on plants in three growth stages begriming of flowering, maximum flowering and one week after the second spray. This experiment as split-plot was carried out in four replications in a randomized complete block design. Potato cultivars were as main factor and levels of spraying as sub-factor. Fifteen days after spraying, sampling were done three time for determination of chlorophy1 a and b, together with assessment of some other morphological and physiological characteristics. The results indicated that application of Triterponic acid in the concentration of 300 gha-1 had significant effects on yield and other characteristics of different cultivars especially in Marfona.

In order to assess and compare the quantitative forage yield of berseem Clover (Trifolium alexandrinum), six berseem clover cultivars (Tolidi-e-Karaj, Selected line, Mesri, Sacromont, Letto and Zemestangozar, a cold tolerant cultivar) were used. A field experiment was carried out at SPII experimental station in Karaj in 1998-1999 growing seasons. The design of the experiment was randomized complete block (RCBD) with four replications and six treatments. The results of the experiment showed that there were not significant differences among cultivars in dry matter yield. The results of combined analysis of variance showed significant differences between years and cultivars based on dry matter yield at the 1% level. Among the cultivars, Tolidi-e-Karaj and Letto with 7.16 and 7.15 tha-1 dry matter yield, respectively, showed superiority (7% - 8%). Based on the comparison of means and other morphological characters, Tolidi-e-Karaj cultivar could be recommended as suitable cultivar for Karaj environmental conditions.

In order to investigate the effects of drought and salinity on germination and seedling growth in cotton, two experiments were carried out with two commercial cotton cultivars, Sahel and Bakhtegan. Experimental design was factorial with completely randomized design using 3 replications. Drought and salinity treatments were 0, -1, -2, -4, -6, -8 and -10 bars and were regulated using PEG 6000, and sodium chloride respectively. Results of variance analysis and means comparison indicated that percentage and rate of seed germination and percentage of normal seedings. were increased by increasing of both salinity and drought levels. However, length of rootlets increased up to-2.drought bars. The results also indicated that Bakhtegan cv. Had better tolerance to salinity stress than Sahel cv., but in drought condition its tolerance and germination rate were less than Sahel. In general, the both cultivars had better performance in salinity stress than in drought stress.