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Soil moisture fluctuation (SMF) stress due to erratic rainfall in rainfed lowland (RFL) rice ecosystems negatively affect production. Under such condition, root plasticity is one of the key traits that play important roles for plant adaptation. This study aimed to evaluate root plasticity expression and its functional roles in water uptake, dry matter production and yield under SMF using three chromosome segment substitution lines (CSSLs) with major genetic background of KDML105 and a common substituted segment in chromosome 8. The CSSLs showed greater shoot dry matter production than KDML105 under SMF, which was attributed to the maintenance of stomatal conductance resulting in higher grain yield. The root system development based on total root length of the CSSLs were significantly higher than that of KDML105 due to the promoted production of nodal and lateral roots. These results implied that the common substituted segments in chromosome 8 of the 3 CSSLs may be responsible for the expression of their root plasticity under SMF and contributed to the increase in water uptake and consequently dry matter production and yield. These CSSLs could be used as a good source of genetic material for drought resistance breeding programs targeting rainfed lowland condition with fluctuating soil moisture environments and for further genetic studies to elucidate mechanisms underlying root plasticity.  相似文献   
2.
Drought is a major abiotic constraint to rice production in rainfed lowland and insufficiently irrigated areas.The improvement of drought tolerant varieties is one of the strategies to reduce the negative effects of drought.Quantitative trait loci(QTLs) for primary and secondary traits related to drought tolerance(DT) on chromosomes 1,3,4,8 and 9 that determined from double haploid lines derived from a cross between CT9993 and IR62266 were introgressed and dissected into small pieces in the genetic background of Khao Dawk Mali 105(KDML105) to develop chromosome segment substitution line(CSSL) population.The CSSLs were evaluated at the reproductive stage for their agronomic performance and yield components under drought stress,and results were compared with irrigated condition.The flowering of CSSL lines was 6 to 7 d earlier than KDML105.The mean values of grain yields in the CSSLs were higher than KDML105 under drought and irrigated conditions.At irrigated condition,the grain yields of introgression lines carrying DT-QTLs from chromosomes 4 and 8 were higher than that of KDML105,whereas other traits showed little difference with KDML105.Analysis indicated that grain yield has positive correlation with plant height,tiller and panicle number per plant,and total grain weight per plant under drought stress while negatively correlated with days to flowering.As mentioned above,CSSLs showing good adaptation under drought stress can be used as genetic materials to improve drought tolerance in Thai rainfed lowland rice breeding program,and as materials to dissect genes underlying drought tolerance.  相似文献   
3.
‘Khao Dawk Mali 105’ (KDML105), a Thai aromatic rice cultivar, has been accepted in markets as a prime jasmine rice with premium prices. It has been extensively used as a parental line to develop new cultivars for rainfed lowland areas in Thailand because of its favorable quality and fragrance. However, this cultivar is highly susceptible to brown planthopper (BPH), a phloem sap-feeding insect pest of rice. The main objective of this study was to combine KDML105 essential grain quality traits with BPH resistance from the donor cultivar, ‘Rathu Heenati’. The linkage drag between Bph3 and Wxa alleles was successfully broken by phenotypic and marker-assisted selections. All introgression lines (ILs) developed in this study showed a broad spectrum resistance against BPH populations in Thailand and had KDML105 grain quality standards. Finally this study was revealed that the ILs can be directly developed into BPH resistant varieties or can be used as genetic resources of BPH resistance to improve rice varieties with the Wxb allele in rice breeding programs.  相似文献   
4.
Submergence tolerance and jasmine-like cooking quality are desirable for rice varieties grown in rainfed and irrigated lowland ecosystems in the Mekong region of Southeast Asia. Hybridization between varieties IR57514 and Kao Dawk Mali 105 (KDML105) was initiated with the goal of producing an ideotype that combines submergence tolerance and jasmine-like cooking quality. Through the single seed descent (SSD) method, a large population of recombinant inbred lines (RILs) was developed, and we demonstrated the potential of using marker-assisted selection (MAS) in the identification of the ideotype from the offspring. Four markers, R10783Indel, Waxy, Aromarker and GT11, were used to select the favored alleles of the Sub1, Wx, badh2 and SSIIa loci, respectively. The ideotype was classified into two groups: ideotype1 (ID1), carrying the Sub1IR, badh2KD, WxKD and SSIIaKD alleles and consisting of 66 RILs and ideotype2 (ID2), carrying the Sub1IR, badh2KD, WxKD and SSIIaIR alleles and consisting of 31 RILs. Submergence tolerance, cooking quality, grain quality and agronomic characteristics of the IDs were evaluated and compared with those of the parents. All of the ID1 lines exhibited submergence tolerance and jasmine-like cooking quality and displayed a low amylose content, a fragrance and a high alkali spreading value, whereas the ID2s showed the same characteristics as ID1, except for a low alkali spreading value, which was inherited from IR57514. A wide range of agronomic characteristics was observed in both of the ID groups, and some of the IDs were superior in the yield component, as compared to their parents. This study provides further support that the precision of markers used in MAS can enhance the development of ideotypes in rice.  相似文献   
5.
Chlorophyll-deficiency mutants are useful as genetic markers and as materials for studying the photosynthesis process. We characterized the inheritance of the gene controlling an opaque leaf (OL) trait in mungbean (Vigna radiata (L.) Wilczek). An F2 population was developed from the cross between the OL mutant and ‘Berken’, an Australian mungbean cultivar, to study inheritance and molecular tagging. The population was advanced by selfing to produce F5 lines from which two normal lines and two OL lines were randomly chosen to study chlorophyll content, seed growth and development, and seed cell morphology. The chlorophyll content in opaque leaf was lower than normal and thus was expected to have lower photosynthetic activity. This resulted in yellowish and shrinking pods and seeds within 15 days after flowering, while those from normal plants extended their growth up to 18 days. The cotyledon transfer cells of the OL plants deformed at 12 days and deteriorated at 14 days after flowering. The OL trait was controlled by a single recessive ol gene which was independent from the genes controlling petiole color and growth habit. We used 193 AFLP primer combinations to tag this gene and found that the marker AGG/ATA was linked with the ol gene at a distance of 3.4 cM.  相似文献   
6.
Several components contribute to rice grain quality, and among these, fragrance and taste qualities are the most important to consumers. Manawthukha, an elite non-fragrant cultivar with high amylose content (AC), intermediate gel consistency (GC) and gelatinisation temperature (GT), occupies the largest number of acres in Myanmar. To improve fragrance and intermediate AC in Manawthukha, Basmati370 was used as a donor parent to introgress the Basmati alleles of genes conferring fragrance and intermediate AC into Manawthukha by Marker Assisted Backcrossing (MAB). Four backcrosses and one selfing were conducted to transfer positive alleles of badh2 and Wx from Basmati into Manawthukha. Twelve BC4F2 selected lines that carried the homozygous Basmati alleles were planted in multi-location trials (four in Myanmar and one in Thailand) and examined for their agronomic performance and cooking quality. The seeds of the improved lines and their parents, harvested from Kamphaeng Saen, Kuaukse, Kyauktada and Latpatan, were investigated for fragrance and AC. All improved lines had fragrance and intermediate AC similar to the donor parent Basmati, whereas their agronomic performances were the same as the original Manawthukha. All improved lines had medium plant heights, high tiller numbers, dense panicles, non-lodging phenotypes and high yielding potentials. Simultaneous improvement of fragrance and intermediate AC indicated that badh2 and Wx genes had major effects on the fragrance and AC, respectively. We show here the success of improving fragrance and intermediate AC by MAB and the high efficiency of selection in early generations. In the present study, MAB accelerated the development of superior qualities in the genetic background of Manawthukha. The improved Manawthukha should be immediately useful for Myanmar farmers and will help farmers to increase their incomes.  相似文献   
7.
Rice blast disease, caused by the filamentous fungus Pyricularia oryzae, is one of the most destructive diseases in rice worldwide. Breeding of resistant rice cultivars remains a cost-effective and environment-friendly means for controlling blast disease, but the resistance tends to break down over time because of the pathogen's rapid adaptation. In this study, AVRPiz-t gene sequences of 46 rice blast isolates were evaluated using a Southern blot analysis. The AVRPiz-t gene was present in 24 of 46 (52.2%) rice blast isolates. The pathogenicity assay showed that all blast isolates were avirulent against Japanese rice cv. Toride 1, which carries several rice blast resistance genes including Piz-t, Pii, Pi37, and Pi-ta. Screening for the Piz-t gene in Thai rice germplasm revealed that less than 20% of rice varieties harbour the Piz-t gene. Therefore, the Toride 1 rice variety could serve as an effective donor of rice blast resistance to be used in rice breeding programmes in Thailand. This study provides evidence for co-evolution between the rice blast resistance gene Piz-t and the rice blast fungal avirulence gene AVRPiz-t. Understanding this relationship will facilitate the sustainable development of breeding for rice blast resistance in the future.  相似文献   
8.
Paw San Hmwe(PSM) rice has been cultivated in many areas of Myanmar for a long time. Strong aroma,good taste and its elongation during cooking are the key characteristics of PSM rice. Thirty-one PSM accessions were genotypically characterized,and their physical grain and cooking quality traits were studied. We used specific gene markers associated with aroma,apparent amylose content(AAC) and alkali spreading value to determine the alleles carried by different PSM accessions. The results revealed that six PSM accessions(PSM10,PSM12,PSM13,PSM21,PSM22 and PSM30) had a 3-bp insertion in Os2 AP gene. Gel consistency(GC) allele was predominant among the PSM accessions for gelatinization temperature(GT),however,the phenotype observed was between low and intermediate GT because of the combination of the GC allele with the presence of low GT allele at heterozygous state from the other loci of the SSIIa gene. Intermediate to high AAC was observed among the PSM accessions corresponding to the haplotype identified for the single nucleotide polymorphism G/T and the(CT)n repeat in the Wx gene. The characterization and grouping data of PSM accessions posted benefits to Myanmar seed banks,and our results will help in maintaining the integrity of PSM rice variety.  相似文献   
9.
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10.
Key genomic regions associated with blast resistance against a broad spectrum of isolates could be identified in backcross introgression lines developed by conventional breeding program. In this article, eighty three BC3F2 backcross introgression lines (BILs) derived from a cross between IR68835-98-2-B-2-1-1 (a broad spectrum blast resistance variety) and KDML105 (a susceptible variety) were developed by phenotypic selection against a mixture of six virulent blast isolates (MXL) that are widely spread out in the rainfed lowland of the North and Northeast of Thailand. The resistance spectrum of the BILs was assessed by inoculating with 12 different Magnaporthe oryzae isolates that showed differential responses on the parental cultivars and the MXL that was used for phenotypic selection. All BILs showed highly resistant reactions (low disease score) to the MXL and to two blast isolates THL48 and THL149. Four markers, i.e., RM246, RM241, RM303 and RM164 completely favoring the IR68835 allele (shifting of allele frequencies from KDML105 to IR68835) were identified on chromosomes 1, 4 and 5, respectively. Therefore, these markers could be linked to the resistance genes functioning against the MXL, THL48 and THL149. Furthermore, significant shifting of alleles was identified at six markers located on chromosomes 2, 4, 8, 9 and 12. Seven DNA markers linked to specific resistance genes were identified, in which allele from IR68835 at 6 markers, i.e., RM6, RM205, RM211, RM252, RM273 and RM342 reduced disease score (DS), against blast isolates THL16, THL329, THL458, THL831, THL868 and THL96036 while allele from KDML105 at RM208 (Pi-kd on chromosomes 2) reduce DS against THL84, THL191, THL557 and THL1108. In this study, the use of DNA markers enabled the identification of specific resistance genes in the backcross breeding materials developed from routine rice breeding program through the conventional phenotypic selection. In this experiment, the usefulness of breeding materials from conventional breeding program in identifying genes corresponding to the selection was illustrated. Linked markers and their genomic location provide necessary information for further use of marker-assisted selection to improve blast resistance in rice breeding program.  相似文献   
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