The response of eight maize hybrids against five different salinity levels namely 0, 60, 120, 180 and 240 mM) were studied at germination and early seedling stage. This investigation was performed as factorial experiment under completely randomized design (CRD) with three replications for each salinity level. Analysis of variance (ANOVA) showed that there were significant differences (P < 0.05) between salinity stress levels, hybrids and interaction effects for all investigated traits. Supplementary analysis showed that there were significant differences (P < 0.05) between hybrids for germination percentage, germination rate, mean germination time and seed vigor in all salinity levels. But, there were no significant differences found between studied hybrids at salinity level of 240 mM for the length of radicle, the length of plumule and the length of whole seedling. Results also indicated that maximum reduction in germination percentage (77.4%), germination rate (32.4%), length of radicle (79.5%) and plumule (78%), seedling length (78.1%) and seed vigor (95%) were obtained in highest level of salinity (240 mM). Results further depicted that hybrid K166B×K47/2-2-21-2-1-1-1 was the most tolerant hybrid than other hybrids under salinity stress.
This experiment was set up to understand genetic diversity in maize hybrids under heat stress condition. 30 morphological traits of 28 hybrids were studied in a randomized complete block design with three replications in 2010 at two planting dates, 6th July (to coincide heat stress with the pollination and grain filling periods) and 27 th July (normal) in Shoushtar City in the southern part of Iran. The results showed that the traits of grain filling period, plant growth period, rows per ear and grains per ear in the both conditions had positive and significant correlation with grain yield. Under heat stress condition however, the highest coefficient of phenotypic variation was obtained for grain yield, grains per ear, grains per row and ASI, and in normal condition for grain abortion percentage and ASI. Cluster analysis by Ward ' s minimum variance, clustered hybrids in to three groups for both conditions. Hybrids K18×K166B and K18×K47/2-2-1-21-2-1-1-1 in the second cluster from the heat stress condition and hybrids K18×K166B, K166A×K3640/5, K166A×K47/2-2-1-21-2-1-1-1 and K166A×K19 in second cluster from the normal condition were found to be the most suitable because they had higher values for grain yield and other desirable traits and lower grain abortion percentage, ASI and grain protein percentage. Therefore, in accordance with the cluster analysis these aforementioned hybrids would be the most suitable for cultivation under the studied conditions.
In order to find the best drought tolerant inbred lines, experiment was performed at the Agricultural College of Islamic Azad University, Shoushtar Branch, Iran during 2010. Experiment treatments were compared in a split-plot design by a randomized complete block design with 3 replications. Main factors included non-stress, drought stress in 6 to 7 leaves (vegetative) stage, drought stress in pollination stage and drought stress in grain filling stage. Sub factors were 7 inbred lines. Five stress tolerance indices, including mean productivity (MP), stress tolerance (TOL), stress susceptibility (SSI), stress tolerance index (STI) and geometric mean productivity (GMP) were used in this study. Drought stress in grain filling stage had the minimum grain yield that showed severe effects of drought stress at this stage of growth. Data analysis revealed that the MP, GMP and STI indices were the more accurate criteria for selection of drought tolerant and high yielding inbred lines. The positive and significant correlation of STI and grain yield under all conditions revealed that this index is more applicable and efficient for selection of parental inbred lines in producing hybrids tolerant to drought in vegetative, pollination and grain filling stages and high yielding under non-stress and stress conditions. Based on the STI, GMP and MP indices, K166B proved to be the most drought tolerant line. Biplot analysis allowed us to distinguish groups of tolerant and sensitive inbred lines. Based on the results of this study, the inbred line K166B can be recommended in future breeding programs for production of drought tolerant hybrids.
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