Iranian Journal of Crop Sciences
Year:2013 | Volume:15 | Issue:2 (58)|Papers Count:7

Dissection of genetic architechture of salinity tolerance in different rice cultivars is a prerequisite of a breeding program for salinity stress. Therefore, to dissect genetics of salinity tolerance, 6 diverse rice genotypes such as Tarom mahalli, Gharib, Shahpasand, Dorfak, Sepidroud and IR28 were tested in a full diallel genetic design, 6×6, during 2007-08 at Rice Research Institute of Iran in Rasht, Iran. All cross combinations together with their parentss, totally 36 genotypes, were set in Randomized Complete Block Design with two replications.The plant materials were evaluated for salinity tolerance index, plant dry matter, sodium and potassium concentrations, Na+/K+ ratio at seedling stage and tiller number, grain weight, filled-grain, plant height and days to 50% flowering at reproductive stage in saline conditions with EC 10 and 12 ds/m, respectively. Analysis of variance for traits of interest among parents showed that they were significantly different for salinity tolerance index, plant dry matter, sodium uptake (%), tiller number, filled-grain.panicle-1, plant height and days to 50% flowering. Therefore, analysis of variance for combining ability was performed for this group of traits. Results of dissection of genetic variance to general, specific and cytoplasmic effects showed that for all these traits those components were highly significant. It’s revealed that both additive and non-additive components of genetic variance were important. Estimation of genetic parameters showed that both additive and dominance variances as well as maternal effect were important in controlling of the traits of interest. We also found that broad sense heritability (h2b) was rather high and ranged from 0.25 to 0.75 for different traits. According to results, cultivar Tarom was good combiner for increasing salinity tolerance index, lower sodium concentration and short duration for days to 50% flowering and Shahpasand was the second suitable parent and combiner for salinity tolerance index, but was the best parent for sodium uptake. Therefore, the mechanism of tolerance to salinity could be related to storage of high amount of sodium in the cell vacuoles.

The objective of this study was to determine the microsatellite (SSR) and AFLP markers linked to plant height and maturity time in the 188 F2: 3 families derived from the cross between two Iranian rice cultivars, Binam and Kadous for using in marker assisted selection method and pyramiding of genes (QTLs) for decreasing of plant height and maturity time in progenies. Among SSR and AFLP markers that used in this research, 61 SSR and 74 AFLP markers had adequate polymorphism between the parents that were used to construct linkage map of the population. The average distance of adjacent markers was 14.06 cM and covers 1786.4 cM of the rice genome. Using the Composite interval mapping (CIM) method, 5 QTLs were mapped for plant height on the chromosomes 3, 7, 9, 10 and 11, and 2 QTLs for maturity time on the chromosomes 6 and 7.These QTLs totally controlled 62.82 % and 23.96 % of the phenotypic variance of 2 traits, respectively. Among these mapped QTLs, qPH-3 (between P36-M42-3_RM232) and qPH-10 (between RM147_P77-M62-4) for plant height andqMD-6 (between RM314_P51-M74-4) for maturity timewith distance from nearest markers, respectively equal 5.5, 19.7 and 0.8 cM, controlled 17.16 %, 15.47 % and 15.71 % of the phenotypic variance, respectively. These QTLs were identified as effective and relatively major QTLs for plant height and maturity times. Results showed that these three QTLs can be used for pyramiding of genes and their linkage markers can be used in marker assisted selection programs for selection of dwarf and early lines in these segregating populations.

To study the effect of planting time on the flag leaf anatomy (stomata number, stomata diameter and surface, large and small vascular bundles surface, xylem, and phloem) of rice genotypes in Khuzestan climate a field experiment was conducted as split plot arrangements in randomized complete blocks design with three replications, in Shavoor agricultural research station 70 km north of Ahvaz, Iran, in 2010-2011. The main plots was planting time in three levels (15 March, 14 April and 26 May 2011) and the sub-plots comprised of rice genotypes; Gerde Zanjan and 3 local genotypes namely Hoveizeh, Hamar, and Gerde Ramhormoz (tolerant to heat), 4 foreign genotyes (Dollar, N22, CR547-1-2-3 and IR1567-228-3-3) and two breeding lines; No.7 and 13.Results revealed that, for all the evaluated traits, there was a significant effect of planting time, genotype and the interaction of genotype × planting time. Hamar genotype in 26 May and IR1567-228-3-3 in 15 March had the highest and least numbers of stomata with averages of 1366 and 786, respectively. Maximum and minimum stomata diameter and surface were observed for genotype N22 in 26 May (diameter 30.3 μm and surface 484.5mm2) and Gerde Ramhormoz in 14 April (diameter 13.6 mm and surface 97.7 μm²), respectively. The highest large vascular bundles surface was recorded for line No.13 in second planting time with average of 1348.5 mm2 and the lowest large vascular bundles surface belonged to Dollar with average of 5267.6 mm2 in 26 May planting time. Maximum and minimum small vascular bundles surface belonged to Hoveizeh in 15 March with average of 2011.5 mm2 and Dollar in 14 April with average of 321.2 mm2, respectively. IR1567-228-3-3 (2089.7 kg.ha-1) in had the highest grain yield in 15 March and Hoveizeh (4898.1 kg.ha-1) in 14 April and Hamar genotypes (4804.4 kg.ha-1) in 26 May planting times had the highest grain yields.

To investigate the effect of timing, intensity and position of leaf removal from below and above the ear of maize hybrid SC 704, a field experiment was conductedin 2008 and 2009 in the research filed of the faculty of agriculture of the Shiraz University, Shiraz, Iran. The experimental treatments included: removal of two and four leaves from above and below of the ear 10, 20 and 30 days after mid-silking stage and control (no leaf removal) which were evaluated in randomized complete block design with four replications. Results showed that in both seasons the highest stem dry weight was obtained from control treatment and the lowest stem dry weight was achieved from removal of four leaves below the earin10 days after mid-silking stage. The highestgrain numberrow-1was achieved from the removal of two leaves above the ear in 20 days after mid-silking, while the lowest grain grain number row-1was obtained from the removal of four leaves below the ear in10 days after midsilking.In the first year, the heavier1000 grain weight were obtained from both four leaves removal above the ear in 20 days after mid-silking as well as two leaves removal above the ear in 30 days after mid-silking treatment. In the second year, four leaves removal above the ear in 20 days after mid-silking resulted inthe heaviest1000 grain weight. Also, the highest grain yield in the first (12505.5 kg.ha-1) and second seasons (17352.6 kg.ha-1) wereachieved from four leaves removal above the ear 20 days after mid-silking. However, the lowest grain yields for the first (9000.50 kg.ha-1) and second (13992.8 kg.ha-1), were obtained from four leaves removal below the ear in10 days after mid-silking. Therefore, removal of two or four leaves above the ear enhanced grain number.ear-1, mean grain weight and led to higher grain yield in maize hybrid SC704.

To investigate the possibility of tank-mix application of two herbicides; nicosulfuron+rimsulfuron (Ultima) and bromoxynil+MCPA (Bromicide MA) for controlling of narrow and broadleaf weeds in maize an experiment was carried out in 2010 in Karaj, Jiroft, and Moghan Agricultural Research Centers of Iran. The experiment was conducted as factorial arrangement inrandomized complete block design with two-factors and four replications.The first factor was nicofulfuron+rimsulfuron dosage at four levels; 0, 125, 150 and 175 g.ha-1 and the second factor wasbromoxynil+MCPA at 0, 0.5, 1.0 and 1.5 l.ha-1. A hand weeded control was also added to treatments.Results showed that the best combination of tank-mix application of the above mentioned herbicides, considering weed control efficiency, maize grainyield increase (%) and minimal environmental risk, was 0.5 to 1.0 l.ha-1 of bromoxynil+MCPA and 125 to 150 g.ha-1 of nicosulfuron+foramsulfuron. These treatments had the best control of weeds and could be used for weed management in maize. The nicosulfuron+rimsulfuronis an ALS-inhibitor herbicide and combination of the two aforementioned herbicides would delay broad leaf weed resistance to both herbicides in maize.