Agro-morphological characterization and assessment of variability, heritability, genetic advance and divergence in bacterial blight resistant rice genotypes

AbstractGenetic based knowledge of different growth traits including morphological, physiological and developmental plays fundamental role in the improvement of rice. Genetic divergence allows superior recombinants which are essential in any crop development project. Forty-one rice genotypes including bacterial blight (BB) resistant and susceptible checks were assessed for 13 morphological traits. Among the genotypes, almost all the traits exhibited highly significant variation. The higher extent of genotypic (GCV) as well as phenotypic coefficients of variation (PCV) were noticed for number of tillers hill−1, total number of spikelets panicle−1, number of filled grains panicle−1, and yield hill−1. High heritability together with high genetic advance was observed for total number of spikelets panicle−1, number of filled grains panicle−1, and yield hill−1 indicating dominant role of additive gene action in the expression of these traits. Number of filled grains panicle−1 exhibited positive correlation with most of the traits. Yield hill−1 showed a good number of highly significant positive correlations with number of filled grain panicle−1, total number of spikelets panicle−1, 1000 grain weight hill−1, number of panicle hill−1, and panicle length. The UPGMA dendrogram divided all the genotypes in to six major clusters. The PCA showed 13 morphological traits generated about 71% of total variation among all the genotypes under this study. On the basis of 13 morphological traits, genotypes such as IRBB2, IRBB4, IRBB13, IRBB21, and MR263 could be hybridized with genotypes MR84, MR159, MRQ50, MRQ74, PH9 and IR8 in order to develop suitable BB resistant rice genotypes

Analysis of the genetic diversity of physic nut, Jatropha curcas L. accessions using RAPD markers.

A sum of 48 accessions of physic nut, Jatropha curcas L. were analyzed to determine the genetic diversity and association between geographical origin using RAPD-PCR markers. Eight primers generated a total of 92 fragments with an average of 11.5 amplicons per primer. Polymorphism percentages of J. curcas accessions for Selangor, Kelantan, and Terengganu states were 80.4, 50.0, and 58.7%, respectively, with an average of 63.04%. Jaccard’s genetic similarity co-efficient indicated the high level of genetic variation among the accessions which ranged between 0.06 and 0.81. According to UPGMA dendrogram, 48 J. curcas accessions were grouped into four major clusters at coefficient level 0.3 and accessions from same and near states or regions were found to be grouped together according to their geographical origin. Coefficient of genetic differentiation (Gst) value of J. curcas revealed that it is an outcrossing species

Genetic Divergence of Bermudagrass (Cynodon spp.) Population Using ISSR Markers

Bermudagrass is a widely distributed turf grasses use in Malaysia. Nevertheless, the genetic variation on molecular level of bermudagrass was insufficient. In this study, a sum of 15 cultivars were collected from different accessions in Malaysia and being analyzed using Inter-simple Sequence Repeat Markers (ISSR). A total of 172 fragments were generated from 15 selected ISSR primers. There are 164 polymorphic bands with 95.3% of polymorphism. Fragment size ranged from 120 to 1867bp. The cultivars were clustered into 5 major groups at coefficient level of 0.5 through arithmetic average (UPGMA) cluster analysis of Jaccard’s similarity coefficient. The genetic similarity coefficient was range from 0.25 to 0.61 with an average of 0.43. Satiri and Melaka cultivars were clustered separately from their own hybrid and common clusters, respectively. These findings indicated that ISSR marker is an effective molecular method use to study genetic variation of bermudagrass and could be used for varietal development program

Mapping of QTLs conferring resistance in rice to brown planthopper, Nilaparvata lugens

Brown planthopper (BPH), Nilaparvata lugens Stål (Hemiptera: Delphacide), is a destructive insect pest of rice, Oryza sativa L. (Poaceae), in rice-producing areas worldwide. Host plant resistance is a major aspect of managing this pest. In this study, a mapping population consisting of 150 F3 lines, derived from a cross of MR276 and Rathu Heenati, was used to detect and analyse quantitative trait loci (QTLs) for the resistance to BPH. Composite Interval Mapping (CIM) was used for QTL detection. In total 10 QTLs controlling BPH resistance were mapped on chromosomes 1, 3, 6, 7, 9, 10, and 12. Four QTLs – qBph-1-1, qBph-3-1, qBph-6-1, and qBph-7-1 – were mapped on chromosomes 1, 3, 6, and 7 in the standard seedbox screening test, explaining 41% of the phenotypic variance. Two QTLs, qBph-6-1 and qBph-9-1, were detected on chromosomes 6 and 9 in the honeydew test, accounting for 32% of the total phenotypic variance. Moreover, four QTLs – qBph-3-1, qBph-6-1, qBph-10-1, and qBph-12-1 – were identified on chromosomes 3, 6, 10, and 12 expressing antixenosis to BPH and explaining 41% of the phenotypic variance. QTL qBph-3-1 was located in the chromosomal region between markers RM231 and RM3872 on chromosome 3, and QTL qBph-6-1 was located in the region between RM588 and RM204 on chromosome 6, indicating that these regions have a major effect in controlling the resistance to BPH in the population studied. The molecular markers linked to QTLs that are identified will be useful in the development of varieties resistant to BPH. Our study contributes to the development of genetic material for breeding programmes and marker-assisted selection (MAS) in rice to improve BPH resistance

Improvement of drought tolerance in rice (Oryza sativa L.): genetics, genomic tools, and the WRKY gene family

Drought tolerance is an important quantitative trait with multipart phenotypes that are often further complicated by plant phenology. Different types of environmental stresses, such as high irradiance, high temperatures, nutrient deficiencies, and toxicities, may challenge crops simultaneously; therefore, breeding for drought tolerance is very complicated. Interdisciplinary researchers have been attempting to dissect and comprehend the mechanisms of plant tolerance to drought stress using various methods; however, the limited success of molecular breeding and physiological approaches suggests that we rethink our strategies. Recent genetic techniques and genomics tools coupled with advances in breeding methodologies and precise phenotyping will likely reveal candidate genes and metabolic pathways underlying drought tolerance in crops. The WRKY transcription factors are involved in different biological processes in plant development. This zinc (Zn) finger protein family, particularly members that respond to and mediate stress responses, is exclusively found in plants. A total of 89 WRKY genes in japonica and 97 WRKY genes in O. nivara (OnWRKY) have been identified and mapped onto individual chromosomes. To increase the drought tolerance of rice ( Oryza sativa L.), research programs should address the problem using a multidisciplinary strategy, including the interaction of plant phenology and multiple stresses, and the combination of drought tolerance traits with different genetic and genomics approaches, such as microarrays, quantitative trait loci (QTLs), WRKY gene family members with roles in drought tolerance, and transgenic crops. This review discusses the newest advances in plant physiology for the exact phenotyping of plant responses to drought to update methods of analysing drought tolerance in rice. Finally, based on the physiological/morphological and molecular mechanisms found in resistant parent lines, a strategy is suggested to select a particular environment and adapt suitable germplasm to that environment

Diversity of physic nut (Jatropha curcas) in Malaysia: application of DIVA-geographic information system and cluster analysis-GIS-A geographic information system for the analysis of biodiversity; GPS-Global positioning system

Abstract A sum of 59 accessions of physic nut, Jatropha curas were collected from different locations of Selangor, Kelantan and Terengganu states of Malaysia to assess genetic diversity using multivariate analysis and DIVA-geographic information system (GIS). Six quantitative characters, seed length, seed width, fruit length, fruit width, 100 seed weight and oil content were recorded. Based on 6 quantitative characters, 59 accessions were grouped into three clusters at a coefficient level of 3.7. Highly positive correlations were found between fruit length and fruit width, fruit length and seed length, fruit width and seed length, fruit length and seed width, fruit width and seed width and seed length and seed width. DIVA-GIS showed the highest diversity index for 100 seed weight in the J. curcas accessions which were collected from the central parts of Selangor state. On the other hand, the highest diversity index for oil content was observed in the accessions of northern parts and costal region of Terengganu state, followed by the central parts of Selangor state in Malaysia