r. choukan

The new maize hybrid,Paya,is the result of the cross K47/2-2-1-2-2-1-1-1×K18.The single cross hybrid Paya produced an average grain yield of 11.47t/ha in preliminary yield trial in four locations in 2013,10.58t/ha in semi-final grain yield trail in seven locations in 2014,10.96 t/ha in final grain yield trials in 13 locations during 2015 -2016,and 11.33t/ha in final yield trail in 10 locations during 2017-2018 which were superior compared toKSC704as check,with an average grain yield of 9.34,9.46,10.72 and 11.04t/ha (in preliminary yield trial in2013semi-final grain yield trail in2014,final grain yield trails during 2015-2016 and2017-2018,respectively).In on-farm experiments carried out in eight regions,the new hybrid with an average grain yield of9.98t/ha compared to the check cultivar KSC704 with an average grain yield of 8.50t/ha,both with 14% grain moisture,showed 17.46% higher grain yield.Based on the results of the final forage yield trials in five locations,the new maize hybrid with an average yield of80.1t/ha,compared to KSC704 with an average yield of 75.9t/ha,revealed 4.2t/ha yield increase during2017and2018 years.The relative forage value (RFV) in the new maize hybrid (250.7) was higher than the check hybrid KSC704 (179.5).Also,based on the results of on-farm experiments in three regions,the new hybrid with an average forage yield of 85.93 t/ha,showed a 13.26% increase in forage yield compared to the check cultivar KSC704 with a forage yield of 75.87 t/ha.Although the new maize hybrid was superior to the KSC704 in terms of yield,stability,and rate of grain moisture reduction after physiological maturity; its most important advantage was its relative resistance and less infection to common smut disease (with9.16%infection) compared to the susceptible hybrid KSC704(with22.30%infection)as one of the main problems of maize farms in the country.More ever,the response of the new maize hybrid and the check cultivar KSC704 to Fusarium ear rot disease is semi-resistant.In general,the new maize hybrid,Paya,is suitable for cultivation in Karaj,Shiraz,Mashhad,Kermanshah,Moghan,Miandoab,Dezful,Kerman and Jiroft.

In order to study morphological traits, yield and yield components of 34 hybrids of corn, an experiment was carried out based on of randomized Complete Block Design with three replications under normal irrigation condition in Khorasan Razavi Agricultural Research and Natural Resources Center, Mashhad, Iran on 2009. Results of analysis of variance showed that there were significant differences between hybrids for all of traits. Results of hybrid means comparison showed that KSC500 hybrid was better than others in yield trait. Result of simple correlation between traits showed that ear diameter and kernel depth had the highest correlation with grain yield, respectively. In other to study relationship of traits in regression model with grain yield, path analysis showed that number of ear per plant had the highest direct and positive effect on grain yield. Principle component analysis was performed for corn hybrids. Seven components have been extracted, which describe 85% of traits variations. Also factor analysis (with Varimax rotation) was performed. Cluster analysis with Ward’s method, arranged hybrids into five different groups.

Twenty local and foreign maize (Zea mays L.) hybrids in five different maturity groups were evaluated in Mashhad, Iran for two years (2007-2009). Three planting dates (5th May, 20th May and 5th June) and hybrids were arranged in a randomized complete block design as split plot arrangements, with three replications. The planting dates were in main plots and hybrids in subplots. The results indicated that late maturing hybrids will have high risk in region. In 5 June planting, non of hybrids except early maturing group, failed to reach proper maturity. Results revealed that KSC 704 can be replaced by early hybrid, KSC 260 in 20 May and 5 June plantings, as well as medium-early hybrids such as KSC 400 in 5 May and 20 May plantings. Hybrid KSC 260 in 5th June sowing, produced 13.886 and 11.698 t.ha-1 grain with proper harvestable moisture in 2007 and 2008 respectively, while, late hybrid KSC 704 produced 13.007 and 16.243 t.ha-1 grain with very high moisture, without significant grain yield.

In order to study the reaction of fifteen maize hybrids to different levels of drought stress, and evaluate drought tolerance indices, an experiment was conducted in split plot arrangement using randomized compelet block design with four replications in Gharakhil(Ghaemshahr) Agricultural Station, in 2006. The main plots consisted of drought stress levels and sub-plots included maize hybrids. Six drought tolerance indices were calculated for grain yield. Under normal, mild and severe stress conditions, hybrid OSGT14 produced 9.445, 9.270 and 8.352 tha-1, respectively, while under most severe stress, hybred SPGT12 produced the highest grain yield(7.455 tha-1). Based on the highest correlation observed between grain yield and different indices, MP, GMP, Harm and STI, were suitable indices. Biplot analysis determined hybrids OSGT14, KSC710GT and KSC-mog 84- 062, in group A, as tolerant hybrids and suitable for normal and stress conditions, and hybrids BGT10, KSC 708 GT, BGT15 and KSC712GT as susceptible hybrids. Cluster analysis based on different indices, divided hybrids under mild and severe stress conditions, into five, and under most severe stress into six groups. Indices MP, GMP, Harm and STI, identified hybrids OSGT14 and KSC710GT as tolerant, and BGT15 and KSC708GT as susceptible hybrids to drought stress, while, indices TOL and SSI showed KSC 720 and KSC700 as tolerant and KSC712GT and BGT10 as susceptible hybrids to drought stress.

A field experiment was conducted to study the effects of planting date and pattern on grain yield of new corn hybrid (KSC 700) in Islamabad Agricultural Research Station for two years (2004-05). A randomized complete block design in split split plot arrangement with three replications was used in this study. Three planting dates (25 April 5 May and 15 May), three row distances (55, 65 and 75 cm) and three plant densities ( 65000, 75000 and 85000 plants/ha) were assigned to main plots, subplots and sub-subplots, respectively. The results showed that the best planting dates were 25 April and 5 May and the best row spacing was 65cm. Grain yield of 65 cm treatment was higher than those of the other row distances (55 and 75 cm). The best plant density was 75000 plants/ha. The highest grain yields were obtained in treatment combinations of 65 cm row spacing and 75000 plants/ha with 13388 and 12838 tha-1, in planting dates 25 April and 5 May, respectively. Therefore, planting of late maturing hybrids in early May with 70000-75000 plants/ha in 65 cm row spacing can be recommended for moderate regions of Kermanshah province.

In order to study the genetic control of common smut in maize, eight inbred lines (two resistant, K1264/1 and K47/2-2-1-21-2, two moderately-resistant K74/1 and K47/2-2-1-4-1, two susceptible K19/1 and K19, and two very susceptibles K3304/1-2 and K47/2-2-1-3-3-1-1, were crossed in diallel in 2005 and evaluated in 2006 under artificial inoculation. All diallel crosses and parents were inoculated with a suspension of 106 sporidia per ml, 7-10 days after silking using tip injection method. At physiological maturity, disease severity was evaluated in each ear. Diallel analysis revealed the role of genes with additive and non-additive effects in genetic control of resistance. Lines K1264/1 and K74/1 with the highest negative GCA, had the least disease severity, while, K3304/1-2 with the highest positive GCA, had the highest infection .Cytoplasmic effect was also revealed for heritance of resistance to common smut. Ressesive alleles revealed to act as increasing and dominant alleles as decreasing factors of the disease severity. Wr/Vr graph showed K47/2-2-1-3-3-1-1 as holding the highest number of ressecive alleles, while, K1264/1 and K74/1 holding the highest dominant alleles..

In order to study the genetic control of different traits in maize, a diallel mating was used with 14 inbred lines. Parents and their F1 generations were evaluated in a RCB design with three replications at research farm of Seed and Plant Improvement Institute in Karaj in 2006. Hayman and Jinks method was used for data analysis. The results indicated over dominance genes effect for plant height, ear height, number of kernel per row, number of kernel per ear, 100-seed weight, and kernel moisture percent and for yield Gene effects for ear length, ear diameter, number of row per ear, corn cob percent and kernel weight per ear were partial dominance. The increasing alleles for 100-seed weight, corn cob percent and kernel moisture percent were ressecive and for other traits were dominant. The parents which had the highest number of dominant and ressecive genes for different traits were as follow: For yield lines no. 12 and 14, for plant height lines no. 12 and 9, for ear height lines no. 7 and 13, for ear length lines no. 3 and 6, for ear diameter lines no. 8 and 14, for number kernel per row lines no. 7 and 6, for number of row per ear lines no. 13 and 1, for number kernel per ear lines no. 8 and 1, for 100-seed weight lines no. 8 and 2, for cob percent lines no. 10 and 9, for kernel weight per ear lines no. 12 and 2 and for moisture percent lines no. 12 and 11.

The choice of a suitable breeding procedure depends on knowledge of the genetic system controlling the character to be selected. The objective of this study was to determine genetic parameters for yield and it’s associated traits, using analysis of generation means (P1, P2, F1, F2, BC1 and BC2) derived from crossing K3218 with K74/1 and K3653/5 inbred lines of corn. All generations were planted in a randomized complete block design with three replications in 2005. The significant differences among six generations were observed for all the studied traits of both crosses. Generation means analysis indicated that dominance genetic effects were more important than additive and epistatic effects in the inheritance of majority of studied traits. Average broadsense heritabilities were between 41% and 70% and between 33% and 83% and the range of narrowsense heritabilities were between 0% and 57% and between 1% and 73% for all traits in K3218 × K74/1 and K3218 × K3653/5 crosses respectively.

 Ten diallel combinations of five maize tester lines were evaluated for grain yield and some related traits using randomized complete block design with two replications in Karaj and Gorgan during year 2004. Combined analysis of variance over two locations revealed significant differences among crosses for all the traits. Diallel analysis indicated presence of additive and non-additive gene action for grain yield, plant height, ear row number, kernel width and number of kernels per ear, as well as, additive effects for tassel length and tassel main axis length above the branches, ear length, kernel number per ear row and kernel thickness. MO17 and B73 were identified as efficient testers in screening maize germplasm, and K1264/1 and KL17/2-5 as non-efficient ones. 

Information on germplasm diversity and relationships among elite materials is fundamentally important in crop improvement programs and especially will increase the efficiency of procedures used in hybrid breeding programs. In order to assess the possibility of grouping the maize inbred lines in maize breeding program, 52 inbreeds were evaluated for 40 morphological traits using randomized complete block design in three replications for two years(2002- 3) in experimental field of the Seed and Plant Improvement Institute, Karaj, Iran. According to the analysis of variance, constancy and broad-sense heritability, 25 traits were selected for grouping the lines. Cluster analysis. based on standardized morphological data assigned the lines in four groups. According to step wise discrirnnant analysis, among the 25 traits, the most important ones were ear conicalness index, pedancul length out of flag leaf, kernel rows, length and area of flag leaf. The first seven principle components(PC) accounted for 83.5% of total variance. In the first PC, pedancul and ear shape were the most important, while, the second PC, described variations in ear diameter and kernel shape. The cluster analysis distinguished four clusters with seven PC clusters. The grouping of lines using these PCs, was in good agreement with morphological data. Some lines located in different groups, comparing the first groups. Concerning the independence of each PC, this grouping can be considered as a primary grouping for maize inbred lines.

To study the effects of plant density and source limitation on grain yield, yield components and dry matter and nitrogen remobilization in corn (Zea mays L.), a field experiment was conducted at Seed and Plant Improvement Institute in 1998. A strip plot design based on randomaized complete blocks with 4 replications was used. In this study maize hybrids (KSC704 and KSC711) were sown in vertical plots. Density (65, 70, 75, 80, 85, 90 thousand plant ha-1) and topping levels, T1 (control) and T2 (Removing tassel and all leaves above the ear) were assigned as factorial to horizontal plots. Results revealed that toppng at two weeks after anthesis did not have any adverse effect on grain yield. Therefore, a considerable quantity of forage could be harvested without any reduction in grain yield. The highest yield of green fodder (5.45 tha-1) was obtained from 90 thousand plant ha-1. Although topping caused an increase in 1000 kernel weight by 7 percent compared to control, but there was no significant difference in their grain yield. Remobilization of dry matter and nitrogen from different parts of th shoot (leaves and stem) to the grain responded differently and among them stem contributed more. Maximum remobilization of dry matter from stem (58%) was recorded in 80 thousand . plant ha-1 which had significantand positive correlation with grain yield.