RESUMO
Panicle traits are the most important agronomic characters which directly relate to yield in rice. Panicle length (PL) being one of the major components of rice panicle structure is controlled by quantitative trait loci (QTLs). In our research, conducted at Research Farm of SKUAST-J, crosses of parental lines K343 and DHMAS were made for generating F2 mapping population, which were then transplanted into the field using augmented design-I. The F2 population was used for phenotypic evaluation, development of linkage map and identification of QTLs on the chromosomes by using SSR markers. A total of 450 SSR markers were used for screening both the parents of which 53 highly polymorphic markers were selected and used for genotyping of 233 genotypes of F2population. Linkage map was generated using MAPMAKER/EXP3.0 software, seven linkage groups were found distributed on 11 chromosomes of rice. QTLs were detected using QTL Cartographer (v2.5) software. Based on 1000 permutation tests, a logarithm of odds (LOD) threshold value 2.0 and 3.0 was set. Composite interval mapping was used to map QTLs in populations derived from bi-parental crosses. The phenotypic data, genotypic data and the genetic linkage map generated identified total three QTLs of which one was identified for PL qPL2, located at 85.01 cM position with 2.1 LOD value and in between the marker intervals RM324–RM208, this QTL explained the phenotype variation by 4.36%. The other two QTLs were identified for spikelet density (SD) qSD3.1 and qSD3.2, located at 28.91 and 39.51 cM, respectively, both with a flanking marker RM6832 on chromosome 3. The LOD value and phenotypic variation explained for qSD3.1 and qSD3.2 was 3.00 and 3.25; 9.70 and 12.34% respectively. The reported QTLs identified in the study suggested a less diversity in the parents used and also the rejection of not so useful markers from the used set of markers for PL and SD.
RESUMO
Increasing scarcity of irrigation water is a major threat to sustainable production of cotton (Gossypium hirsutum L.). Identifying genomic regions contributing to abiotic stress tolerance will help develop cotton cultivars suitable for water-limited regions through molecular marker-assisted breeding. A molecular mapping F2 population was derived from an intraspecific cross of the drought sensitive G. hirsutum cv. FH-901 and drought tolerant G. hirsutum cv. RH-510. Field data were recorded on physiological traits (osmotic potential and osmotic adjustment); yield and its component traits (seedcotton yield, number of bolls/plant and boll weight); and plant architecture traits (plant height and number of nodes per plant) for F2, F2:3 and F2:4 generations under well-watered versus water-limited growth conditions. The two parents were surveyed for polymorphism using 6500 SSR primer pairs. Joinmap3.0 software was used to construct linkage map with 64 polymorphic markers and it resulted into 35 markers mapped on 12 linkage groups. QTL analysis was performed by composite interval mapping (CIM) using QTL Cartographer2.5 software. In total, 7 QTLs (osmotic potential 2, osmotic adjustment 1, seedcotton yield 1, number of bolls/plant 1, boll weight 1 and plant height 1) were identified. There were three QTLs (qtlOP-2, qtlOA-1, and qtlPH-1) detected only in water-limited conditions. Two QTLs (qtlSC-1 and qtlBW-1) were detected for relative values. Two QTLs (qtlOP-1 and qtlBN-1) were detected for well-watered treatment. Significant QTLs detected in this study can be employed in MAS for molecular breeding programs aiming at developing drought tolerant cotton cultivars.