Iranian Journal of Crop Sciences
Year:2009 | Volume:10 | Issue:4 (40)|Papers Count:9

Study of the action of genes involved in controlling grain yield, plant height, ear height, ear length, ear diameter, grain/ear row, row no./ear, grain no./ear, 100 grain weight, cob percent, grain weight/ear, in maize, a diallel cross with 14 inbred lines was carried out. Parents and their F1's were tested using randomized complete block (RCB) design with three replications in Research station of Seed and Plant Improvement Institute, Karaj in 2006 cropping season. Significant (p<0.01) differences were observed among genotypes for all traits, therefore Griffing’s method 2, model 1 was used for subsequent diallel analysis. Variances due to general combining ability (GCA) and specific combining ability (SCA) were significant (P < 0.01), for all traits. Results indicated that for ear diameter, number of grain row per ear, 100 grain weight and additive gene effects were more important than non additive gene effects, but for grain yield, plant height, ear height, number of grain per row and number of grain per ear, non-additive gene effects were more important. For ear length, cob percent and grain weight per ear, both additive and non additive gene effects were important. High broad sense heritability observed for all traits (>60%), the estimate of narrow sense heritability for yield was 25%, high value belonged to the number of grain row per ear (71%) and low value obtained for ear height (18%). Parents with high GCA for grain yield were K19/1, K166B and K3615/2 inbred lines. For other traits, GCA effect was significant in about 50% of the inbred lines. SCA effect was significant in few crosses for all the traits. The highest heterosis for grain yield was observed in A679 × K3493/1 cross.

In order to determine the effect of defoliation intensity at different reproductive stages in sunflower (Helianthus annus L.) on seed and oil yields, and determining the most sensitive reproductive stages to defoliation, a field experiment was conducted at Tarbiat Modares University Research field using a split plot arrangement in a RCBD with four replications in 2007 cropping season. Main plots consisted of defoliation at four reproductive stages including: star shape of inflorescence stage (R1), pollination stage (R5), seed setting initiation (R6), and end of grain filling (R7), while five defoliation intensities (0% as an undefoliated control, 25%, 50%, 75% and level removed 100%) were arranged in sub-plots. The results indicated that defoliation time and intensities had significant effects on all traits. The interaction of two factors significantly (P<0.01) reduced the grain yield, thousand seeds weight, unfilled seed and oil content. The most variation resulted from defoliation effect on number of filled seed per area and1000 seed weight, at R1 and R5 stages, consequently reduced grain and oil yields. On the bases of these results it could be concluded that sunflower crop that lost 100% of its leaves would be economically unprofitable and it is more logic to be replaced with a suitable crop adapted to the region.

In order to estimate the gene action and heritability of 8 important agronomic traits, 6 genotypes of rice were studied in a 6×6 half-diallel cross. Parents and their progenies were grown in a randomized complete block design with three replications in Field Research Station of the University of Guilan, Rasht, Iran, in 2006 cropping season. Eight traits including pre-anthesis phase, post anthesis phase, flag leaf area, panicle length, number of grain per panicle, 1000 grain weight and grain yield were evaluated. Analysis of variance of data showed significant differences (p<0.01) between genotypes for all studied traits. Results from graphical analysis based on Hayman method showed that non-additive effect for all traits, except pre-anthesis phase and panicle length, were important than the additive effect. Pre-anthesis phase and panicle length were controlled by partial dominance effect (with higher additive effect) and the other traits were controlled by over-dominance gene effect in selected genotypes. For panicle length, the parents had more recessive allele frequencies, while for other traits the frequencies of dominant alleles were greater in parents. Narrow-sense heritability varied from 0.165 to 0.794 for duration of post-anthesis phase and panicle length, respectively. It can be concluded that both hybridization and selection approaches can be used to improve panicle length and duration of pre-anthesis phase, however, for the other traits including grain yield heterosis and hybrid development are recommended.

In order to study effects of limited irrigation and plant density on morphological characteristics and seed yield of a dwarf sunflower hybrid CMS26 × R103, a field experiment was conducted in a spilt plot arrangement using randomized complete block design with three replications in Seed and Plant Improvement Institute Karaj in 2005 cropping season. Limited irrigation levels included: irrigation after 50, 100, 150 and 200 millimeter evaporation from class A pan and plant density levels were 6, 8, 10 and 12 plant m-2 that were assigned to main and sub plots, respectively. Limited irrigation had significant effect on plant height, head diameter, seed yield, productivity index, seed oil content and oil seed yield, but there was no significant effect on leaf number. Plant density affected on all characteristics, except of plant height, seed oil content and productivity index. The highest seed yield of 2726 kg.ha-1 was obtained from irrigation after 50 mm evaporation from class A pan. The highest seed yields under different irrigation levels were also obtained from 12 plant m-2. Results indicated that under irrigation after 50, 100 and 150 millimeter evaporation from class A pan, maximum seed yield was obtained from 12 plant m-2, however in irrigation after 200 millimeter evaporation from class A pan and 12 plant m-2 yield increase was not significant, due mainly to stress severity.

The purpose of the present study was to identify QTLs for lodging in durum wheat (Triticum turgidum L. var durum) using a doubled haploid population. The population included a set of 155 lines that were developed from the cross (Kyle*2/Biodur)/Kofa using maize pollen method. The Kofa parent shows more resistance than Kyle*2/Biodur, to lodging. Phnotypic data of resistance to lodging of the doubled haploid population lines and the parents was scored in 2000-2001 cropping seasons in Regina and Indian Head, Saskatchewan, Canada. There was highly significant differenc between the population lines for this trait. Parents were tested with 517 wheat microsatellite (Simple Sequence Repeat) markers. The primers that were polymorphic in the parents were tested on the whole population to prepare the genotypic data. The genetic linkage map of the 53 polymorphic loci covered about 970 cM and converged into 14 linkage groups. Eleven markers remained unlinked. Linkage between the markers and the lodging genes done based on single marker analysis, simple interval mapping and composit interval mapping using least square means. Three linkage marker groups were associated with lodging trait. The first QTL is located on the chromosome 4BL and its effects were highly significant (P<0.0001) in four environments and explained 20% of lodging phenotypic variation. The other two loci were located on the 2AL, also have highly significant effects on the trait at least at one environment and explained 4-8 percents of lodging phenotypic variation, depending on environments.

This study was conducted to determine freezing damages on sugar beet seedling (at cotyledon, two and four leaves stages) in seven sugar beet cultivars (Shirin, Rasol, Gadook, 276, 428, 7233 and BR1) in Karaj in 2002 cropping season In first experiment, sugar beet seedlings at the four mentioned stages were transferred to the growth chamber and exposed to zero, -2 and –4°C for two periods of 4 and 8 hours. Second experiment, was carried out in the field to compare the results of greenhouse and field. Leaf samples were taken at three growth stages of sugar beet seedlings, transferred to growth chambers, and exposed to freezing temperatures.Assessment of freezing damages was performed using visual (survived or dead) and leaf chlorophyll florescence measurements. The results showed that freezing damage was 0.5, 8 and 85%, for low temperatures of zero, -2, and -4°C, respectively. Freezing damage on the detached leaves from field and the seedlings grown in growth chamber showed similar results. Chlorophyll fluorescence measurements as index for freezing damage showed that an increase of freezing stress caused a decrease in the amount of Fm (maximum chlorophyll fluorescence) and Fv/Fm (photochemical efficiency of photosystem II). Sugar beet cultivars were more susceptible at two leaves stage as compared to four- leaves stage. The threshold of freezing damage had no significant differences among sugar beet cultivars, however, BR1 and Gadook cultivars showed the lowest and highest susceptibility to freezing, respectively. Results also showed that threshold of freezing damage on sugar beet seedling in concerned cultivars was -2°C and the lower the temperature the more damages occur in the field.

In order to study the effect of drought stress on grain yield and determining maize hybrids with tolerance to drought stress, a field experiment was conducted in Moghan Agricultural Research field station in 2004 cropping seasons, using a split block arrangement in randomized complete block design with three replications. The experimental Factors were four irrigation regimes as factor A including: (I1: normal irrigation, I2: water stress at vegetative, I3: water stress at flowering and I4: water stress at grain filling stages) and 7 commercial maize hybrids as factor B including: SC704 . SC703, SC700, SC720, SC647, SC724, TWC600. Based on grain yield of hybrids in normal and stress conditions, stress susceptibility index (SSI), tolerance (TOL), mean productivity (MP), mean geometric productivity (GMP), stress tolerance index (STI) and Harmonic Mean (MHAR) were calculated. The results showed that, in addition to significant correlation between these indices and grain yield there were also significant relationships between different indices. Since stress tolerance index (STI) was more efficient index in identifying group A from other groups, it was chosen as the most suitable index for selecting tolerant genotypes to drought stress. Therefore, in three-dimension plot only STI index with grain yield in normal and drought stress conditions were used. The plot also identified SC704 and SC647 as tolerant hybrids under drought stress conditions.