Study on combining ability, heterosis and genetic parameters of yield traits in rice

A study was conducted on heterosis, combining ability and genetic parameters of yield and yield components in rice. Five lines were crossed with two testers in line × tester manner to produce ten F1 hybrids. Results show that general combining ability (GCA) effect was only significant for total number of kernels per panicle, number of filled kernels and grain yield per plant, and specific combining ability (SCA) effect was significant for yield and all of its studied components (except for 100-kernel weight). Lines IR42 and Pouya showed a significant GCA for grain yield in opposite direction (20.9 and -13.7 g/plant, respectively). The two lines also showed highest significant GCA for number of filled kernels (22.7 and 23.3, respectively). In the total number of kernels, lines IR8 and IR42 and tester Usen showed the highest significant GCA (34.79, 27.97 and 12.56). In tiller number, only line IR36 and tester IR68897 had the highest significant GCA (3.51 and 0.84). Combination of IR68897×IR8 showed highest significant SCA for grain yield (9.7 g/plant), while in the case of number of filled kernels and tiller number, combinations IR68897×IR8 and Usen/IR36 showed a significant positive SCA (18.9 and 2.1, respectively), indicating that hybridization can be a choice for improving hybrids with better quantity of these traits. The highest general heritability (hbs) was obtained for tiller number (96.1%), indicating slight effects of the environment on the trait, while for other traits, a mild general heritability (~70%) was obtained, indicating considerable effect of environment on phenotypic expression of most yield traits. A low specific heritability (hn2) was obtained for all traits (18.2 to 26.3%), indicating that non-additive effects play an important role in genetic control of yield traits. Therefore, it seems that hybridization must be a choice for utilizing the putative heterosis in special crosses, and such a condition was observed for tiller number and grain yield in combinations of IR42×IR68897 and IR42×Usen.Key words: Rice, line × tester, combining ability, heritability, heterosis

The effect of drought stress on improved cotton varieties

Abstract Drought stress is one of the most important abiotic stresses influencing performance of crop plants. Therefore, the identification or development of tolerant genotypes is of high importance for incorporating in cotton production. In this study to evaluate the effect of drought stress on some cotton traits, 5 improved cotton varieties were studied in a split plot design with three replications in 2 years (2000)(2001) at 2 locations (Hashemabad and Anbaroloom); one with Mediterranean climate and the other with drought-stress condition. Treatments were irrigation as main plot in 3 levels (I 0 =without irrigation, I 1 =one time irrigation; that carried out 70 days after sowing, and I 2 =at least 3 times irrigation) and varieties as subplot in 5 levels (5 genotypes). In the basis of combined variance analysis significant differences were detected among varieties for yield, boll number, boll weight, length and number of sympodial and monopodial branches. Drought stress decreased yield, boll number, boll weight, and induced earliness. With increasing irrigation frequency, earliness lightly reduced in the former climate probably because of inducing vegetative growth and retarding in generative phase. In latter climate increased irrigation frequency had a positive effect on the yield. It seems that water deficiency has reduced yield via decreasing boll number. The number of formed bolls in stressful conditions was less than that of in non-stressful conditions. Stress tolerance index (STI) revealed that Siokra-324 and Tabladila were more tolerant and stable varieties

Identification of Genome-Wide Variations among Three Elite Restorer Lines for Hybrid-Rice

Rice restorer lines play an important role in three-line hybrid rice production. Previous research based on molecular tagging has suggested that the restorer lines used widely today have narrow genetic backgrounds. However, patterns of genetic variation at a genome-wide scale in these restorer lines remain largely unknown. The present study performed re-sequencing and genome-wide variation analysis of three important representative restorer lines, namely, IR24, MH63, and SH527, using the Solexa sequencing technology. With the genomic sequence of the Indica cultivar 9311 as the reference, the following genetic features were identified: 267,383 single-nucleotide polymorphisms (SNPs), 52,847 insertion/deletion polymorphisms (InDels), and 3,286 structural variations (SVs) in the genome of IR24; 288,764 SNPs, 59,658 InDels, and 3,226 SVs in MH63; and 259,862 SNPs, 55,500 InDels, and 3,127 SVs in SH527. Variations between samples were also determined by comparative analysis of authentic collections of SNPs, InDels, and SVs, and were functionally annotated. Furthermore, variations in several important genes were also surveyed by alignment analysis in these lines. Our results suggest that genetic variations among these lines, although far lower than those reported in the landrace population, are greater than expected, indicating a complicated genetic basis for the phenotypic diversity of the restorer lines. Identification of genome-wide variation and pattern analysis among the restorer lines will facilitate future genetic studies and the molecular improvement of hybrid rice

rapid mini-prep DNA extraction method in rice (Oryza sativa)

DNA extraction is an important step in molecular assays and plays a vital role in obtaining highresolution results in gel-based systems, particularly in the case of cereals with high content of interfering components in the early steps of DNA extraction. Here a rapid mini-prep DNA extractionmethod, optimized for rice, which was achieved via some modifications in present DNA extraction methods, especially in first step of cell wall lyses and the use of cheap and frequent chemicals found in every laboratory is presented. Normal quality and quantity was obtained by the method. The PCR based assays also revealed the efficiency of the method. This method is applicable with both dry and fresh samples, does not require liquid nitrogen, and is easy, rapid and applicable in every laboratory

Performance of different greenhouse cucumber cultivars (Cucumis sativus L.) in southern Iran

A 2 year trial was conducted with 15 cucumber (Cucumis sativus L.) varieties from diverse origins in the greenhouse conditions (southern Iran) to study genetic variation and to identify genetically distant parents to be involved in a hybrid seed production as well as to identify the most effective components of grain yield. However, the potential of identifying genetically distant parents depends on genetic diversity of population. The varieties were cultivated in a randomized complete block design (RCBD) with 3 replications for 2 years (2004 - 2006 seasons). Characters such as, yield and number of fruits in surface unit (m2), yield in cold season, diameter and length of stem, length and diameter of fruit were evaluated analyzed for 2 years. Compound variance analysis showed that there were significant differences ( Cucumis sativus L.) varieties from diverse origins in the greenhouse conditions (southern Iran) to study genetic variation and to identify genetically distant parents to be involved in a hybrid seed production as well as to identify the most effective components of grain yield. However, the potential of identifying genetically distant parents depends on genetic diversity of population. The varieties were cultivated in a randomized complete block design (RCBD) with 3 replications for 2 years (2004 - 2006 seasons). Characters such as, yield and number of fruits in surface unit (m2), yield in cold season, diameter and length of stem, length and diameter of fruit were evaluated analyzed for 2 years. Compound variance analysis showed that there were significant differences (Cucumis sativus L.) varieties from diverse origins in the greenhouse conditions (southern Iran) to study genetic variation and to identify genetically distant parents to be involved in a hybrid seed production as well as to identify the most effective components of grain yield. However, the potential of identifying genetically distant parents depends on genetic diversity of population. The varieties were cultivated in a randomized complete block design (RCBD) with 3 replications for 2 years (2004 - 2006 seasons). Characters such as, yield and number of fruits in surface unit (m2), yield in cold season, diameter and length of stem, length and diameter of fruit were evaluated analyzed for 2 years. Compound variance analysis showed that there were significant differences ( = 0.01) in yield between varieties at 2 years and the highest yield (23.81 kg/m2) was obtained for E3215516 variety. Correlation analysis of varietal means showed that the highest correlation (0.932) was observed between number of fruits (NOF) and yield, and the least (0.01) between diameter of stem (DOS) and length of fruit (LOF). Based on factor analysis, 3 components were identified, explaining 77.5% of observed variation. Factor 1 (yield factor) accounting for about 45% of the variation, was strongly associated with yield, yield in cold season and number of fruits. Factor 2 (source factor) accounting for about 18% of the variation, consisted of stem related components including diameter of stem (DOS) and length of stem (LOS). Factor 3 (sink factor) accounting for about 15% of the total variation, associated with length and diameter of fruit (LOF and DOF). Using cluster analysis, the lines were classified into 2 distinct classes A and B. Class B contained lines from different origins