Hossein Sabouri

QTLs mapping of physiological traits related to salt tolerance in young rice seedlings

Oryza sativa L. F2 population and F2:3 derived from a cross between salt tolerance cv. Tarommahali and salt sensitive cv. Khazar were used in this study. A linkage map based on F2 population was constructed (74 SSR markers on 192 individuals), which covered a total of 1231.50 cM with an average two locus interval of 19.83 cM. Two QTLs related to Na+/K+ ratio were found on chromosome 3 and 6. qDM-3 and qDM-8 (for dry mass of shoot) are major QTLs with very large effects explained 20.90 and 17.72 % of the total phenotypic variance, respectively. Major locus for DM (qDM-3) was bracketed by RM1022 — RM6283 spread over 13.6 cM on chromosome 3. Major part of the variability for standard tolerance ranking (STR) was explained by the qSTR-6 flanked by RM3727 — RM340 on chromosome 6, which exhibited phenotypic variance of 17.25 % and peak likelihood ratio (LR) of 17.51. The length of this QTL is 8.8 cM and identification of any tightly linked markers in this region will serve as a candidate gene for fine-mapping. qSTR-3 overlapped with qNA-3 and qNAK-3. The qSTR-3 may contain a new major gene for salt stress tolerance at seedling stage in rice. Major QTLs identified in this paper, after fine-mapping, could be used for marker assisted selection.

QTL detection of rice grain quality traits by microsatellite markers using an indica rice (Oryza sativa L.) combination.

The gelatinization temperature (GT), gel consistency (GC) and amylose content (AC) are the three major rice traits that are directly related to cooking and eating quality (Little et al. 1958). GT is a physical trait responsible for cooking time and the capacity to absorb water during the processes cooking, and the temperature at which starch irreversibly loses its crystalline order during cooking. The GC is responsible for softness, and the AC is responsible for texture and appearance in rice. Hence, regulating AC in rice has been a major concern of rice breeders. To facilitate the development of new varieties with high cooking and eating qualities, it is necessary to understand the genetic bases of such traits. Lanceras et al. (2000) found four QTLs for AC on chromosomes three, four, six and seven. These QTLs accounted for 80% of phenotypic variation observeded in AC. Two QTLs on chromosome six, and one on chromosome seven were detected for GC, which accounted for 57% of phenotypic variation. Umemoto et al. (2002) confirmed this and demonstrated that the alk locus encodes the enzyme soluble starch synthase IIa. Bao et al. (2002) and Lanceras et al. (2000) found the effect of the wx region on GC. However, He et al. (1999) and Bao et al. (2002) showed that GC is controlled by two QTLs with minor effects. Zhou et al. (2003) improved the eating and cooking quality of Zhenshan 97 by introgressing the waxy gene region from Minghui 63 (wx-MH), a restorer line that had medium AC, soft GC and high GT. Li et al. (2004) identified four QTLs for AC, three for GT and five for GC using backcross-inbred lines. The four QTLs for AC were located on chromosomes three, four, five and six. The QTL on chromosome six covered the wx gene region and mainly contributed to the variance between

Mapping QTLs for Traits Related to Salinity Tolerance at Seedling Stage of Rice (Oryza sativa L.): An Agrigenomics Study of an Iranian Rice Population

Rice (Oryza sativa L.) is one of the most important food crops in the world, especially in Asian countries, and salinity is a major constraint to the sustainability and expansion of rice cultivation. Genetically improving salt tolerance of rice is a highly important objective of rice breeding programs. Traits such as salt tolerance are quantitatively inherited. Hence, mapping quantitative trait loci (QTL) with molecular markers can be very helpful to plant breeders in the field of agricultural genomics (AgriGenomics). In this investigation, QTL analysis of physiological traits related to salt tolerance was carried out using F2:4 population of rice derived from a cross between a salt-tolerant variety, Gharib (indica), and a salt-sensitive variety, Sepidroud (indica). A linkage map based on 148 F2 individuals was constructed with 131 SSR markers and 105 AFLP markers, covering 2475.7 cM of rice genome with an average distance of 10.48 cM between flanking markers. A total of 41 QTLs for twelve physiological traits under salinity stress were detected distributed on all rice chromosomes, some of them being reported for the first time. Also, overlapping of QTLs related to salt tolerance were observed in this study. Some of the identified QTLs on specific chromosomal regions explaining high phenotypic variance could be used for marker-assisted selection (MAS) programs. New QTLs retrieved in this study play an important role in growth of rice at seedling stage in an Iranian local population under high salinity conditions.

Use of Selection Indices Based on Multivariate Analysis for Improving Grain Yield in Rice

In order to study selection indices for improving rice grain yield, a cross was made between an Iranian traditional rice (Oryza sativa L.) variety, Tarommahalli and an improved indica rice variety, Khazar in 2006. The traits of the parents (30 plants), F1 (30 plants) and F2 generations (492 individuals) were evaluated at the Rice Research Institute of Iran (RRII) during 2007. Heritabilities of the number of panicles per plant, plant height, days to heading and panicle exsertion were greater than that of grain yield. The selection indices were developed using the results of multivariate analysis. To evaluate selection strategies to maximize grain yield, 14 selection indices were calculated based on two methods (optimum and base) and combinations of 12 traits with various economic weights. Results of selection indices showed that selection for grain weight, number of panicles per plant and panicle length by using their phenotypic and/or genotypic direct effects (path coefficient) as economic weights should serve as an effective selection criterion for using either the optimum or base index.

Mapping of QTLs for Germination Characteristics under Non-stress and Drought Stress in Rice

Identification of genetic factors controlling traits associated with seed germination under drought stress conditions, leads to identification and development of drought tolerant varieties. Present study by using a population of F2:4 derived from a cross between a drought tolerant variety, Gharib (indica) and a drought sensitive variety, Sepidroud (indica), is to identify and compare QTLs associated with germination traits under drought stress and non-stress conditions. Through QTL analysis, using composite interval mapping, regarding traits such as germination rate (GR), germination percentage (GP), radicle length (RL), plumule length (PL), coleorhiza length (COL) and coleoptile length (CL), totally 13 QTLs were detected under pole drought stress (−8 MPa poly ethylene glycol 6000) and 9 QTLs under non-stress conditions. Of the QTLs identified under non-stress conditions, QTLs associated with COL (qCOL-5) and GR (qGR-1) explained 21.28% and 19.73% of the total phenotypic variations, respectively. Under drought stress conditions, QTLs associated with COL (qCOL-3) and PL (qPL-5) explained 18.34% and 18.22% of the total phenotypic variations, respectively. A few drought-tolerance-related QTLs identified in previous studies are near the QTLs detected in this study, and several QTLs in this study are novel alleles. The major QTLs like qGR-1, qGP-4, qRL-12 and qCL-4 identified in both conditions for traits GR, GP, RL and CL, respectively, should be considered as the important and stable trait-controlling QTLs in rice seed germination. Those major or minor QTLs could be used to significantly improve drought tolerance by marker-assisted selection in rice.

Evaluation of rice cultivars in weeds control different periods under non-stress and stress conditions

In order to evolution the effect of different periods of weed control on yield and agronomic characteristics and determine the drought tolerant variety under two separate conditions, flooding and drought, two experiment were conducted as a spilt-plot based on Randomized Completed Blocked Design with three replications at the Research Farm of Gonbad Kavus University, during spring 2010. The different levels of weed control were as the main plot treatment and the rice cultivars Shiroudi, Domsiah (native cultivar), IR70358-84-1-1, IR70358-84-1-2, WAB56-125, IR83752-B-B-12-3 and KORAL were as the sub plots. Results showed that differences among flooding and drought conditions, different levels of weed control and cultivars both flooding and drought conditions had significant effect. Grain yield in drought condition rate to flooding condition decreased 49.42%. Both flooding and drought conditions with weed control to tillering maximum stage compared to other control conditions, for all of traits the most profitable. Shiroudi cultivar perspective grain yield, harvest index, filled grain number and the number of fertile tillers was highest rate. At both flooding and drought conditions, Shiroudi (weed control to tillering maximum stage, weed control of tillering maximum to maturity and un-weeded) was the most profitable. Shiroudi cultivar can as the tolerant variety recommended and with weed control to maximum tillering stage. In this cultivar, the maximum amount of characters can be achieved.

Genetic analysis seedling vigour under osmotic stress in rice by QTL mapping

Seed vigour is one of the most important parameters for establishing rice seed that affects high yielding production, especially under stress condition in rice (Oryza sativa L.). Improvement of rice yields under abiotic stress through breeding requires a good understanding of genetic factors controlling important traits such as seedling vigour and related traits. To understand the genetic background of the relationships among these traits in indicia rice, we genetically analyzed F2:3 population derived from a cross between Tarommahalli × Khazar, under osmotic stress caused by sorbitol. In this investigation, a simple sequence repeat (SSR) linkage map of 1231.50 cM of rice was constructed by using 74 markers and quantitative trait loci (QTL) analysis was accomplished for eight traits including germination percent, seed germination rate, radicle length, plumule length, coleoptile length, radicle dry matter, plumule dry matter, and coleoptile dry matter. A total of 32 QTLs were identified for the eight traits. Among them, one QTL for percent of germination (qGP-8) was located in RM6208-8264 on chromosome 8 showed large effect (28.99%) on the trait. These results suggest the potential for increase productivity by transferring osmotic stress tolerance gene from Tarommahalli to other rice lines and identification of QTLs with large effects could be considered for use in marker assisted selection (MAS).