Characterization of chromosomal segment substitution lines developed in the genetic background of rice variety K 343.

In this study, BC3F2 convergent population [(K343*3/RML22 × K343*3/DHMAS) × K343] was constructed by marker-assisted backcross breeding using K343 as the recurrent parent. DHMAS and RML22 were used as donor parents for the rice blast resistance genes Pi54 and Pi9, respectively. The population was first characterized using GGT 2.0 software, which showed 96.7% of the recurrent genome recovery covering 13953.6 cM, while DHMAS and RML22 showed 1.6% (235.5 cM) and 1.2% (177.1 cM) introgression respectively. The chromosomal segment substitution lines (CSSLs) were then identified using CSSL Finder software. A total of 36 CSSLs were identified, including 22 for DHMAS/K343 and 14 for RML22/K343. Introgression rates for donor substituted segments in DHMAS/K343 CSSLs ranged from 0.54% to 5.99%, with donor coverage of 44.5%, while in RML22/K343 CSSLs, introgression rates ranged from 0.54% to 4.75%, with donor coverage of 24.5%. The identified CSSLs would be a valuable genetic pool and could be used as genomic resources for the discovery and mapping of important genes and QTLs in rice genetic improvement.

Harnessing the potential of bulk segregant analysis sequencing and its related approaches in crop breeding.

Most plant traits are governed by polygenes including both major and minor genes. Linkage mapping and positional cloning have contributed greatly to mapping genomic loci controlling important traits in crop species. However, they are low-throughput, time-consuming, and have low resolution due to which their efficiency in crop breeding is reduced. In this regard, the bulk segregant analysis sequencing (BSA-seq) and its related approaches, viz., quantitative trait locus (QTL)-seq, bulk segregant RNA-Seq (BSR)-seq, and MutMap, have emerged as efficient methods to identify the genomic loci/QTLs controlling specific traits at high resolution, accuracy, reduced time span, and in a high-throughput manner. These approaches combine BSA with next-generation sequencing (NGS) and enable the rapid identification of genetic loci for qualitative and quantitative assessments. Many previous studies have shown the successful identification of the genetic loci for different plant traits using BSA-seq and its related approaches, as discussed in the text with details. However, the efficiency and accuracy of the BSA-seq depend upon factors like sequencing depth and coverage, which enhance the sequencing cost. Recently, the rapid reduction in the cost of NGS together with the expected cost reduction of third-generation sequencing in the future has further increased the accuracy and commercial applicability of these approaches in crop improvement programs. This review article provides an overview of BSA-seq and its related approaches in crop breeding together with their merits and challenges in trait mapping.

Marker association study of yield attributing traits in common bean (Phaseolus vulgaris L.).

Common bean is gaining acceptance as one of the most valuable major food consumed worldwide owing to innumerable nutritional and therapeutic benefits. Comparatively less productivity in underdeveloped countries encouraged us to proceed for QTL mining of yield traits in common bean. Heretofore, multiple yield associated markers have been detected all over the world; even so, the present work is looked on as the first report on identification of novel/new potent markers by exploiting the germplasm of Northern India. A panel of one hundred and thirty five genotypes was used for morphological studies and based on preliminary molecular evaluation; a set of ninety six diverse common bean genotypes (core set) was selected for association analysis. Molecular data generated by a total of ninety eight microsatellite markers (53 genomic and 45 genic SSRs) revealed high estimation of polymorphism among the genotypes that were observed to be divided into two major sub-populations and varying levels of admixtures based on population structure analyses. By employing both MLM and GLM analysis approaches, we identified 46 and 16 significant marker-trait associations (p ≤ 0.005) respectively, few of which have already been reported and hence validate our results. PVBR213 marker was found to be strongly associated with days to bud initiation trait when analyzed with both the approaches. Phenotypic variation of identified significant markers ranged from 3.1% to 32.7% where PVBR87, PVBR213, X96999 and X57022 explain more than 30% of phenotypic variation for 100 seed weight, days to bud initiation, pods per plant and pod length traits respectively. These findings introduce highly informative markers to aid marker-assisted selection program in common bean for high yield performance along with good agronomic merit.

Lignin degradation and nutrient cycling by white rot fungi under the influence of pesticides.

The production of enzymes involved in lignin degradation (laccase, ligninase), carbon cycling (ß-glucosidase), and phosphorous cycling (phosphomonoesterase) by white rot fungi (Pleurotus sajor-caju) was studied. In the presence of chlorpyrifos, carbofuran, and their mixture, laccase activity was highest on the 7th day, i.e., 192.5 ± 0.31 U ml- 1, 213.6 ± 0.31 U ml- 1, and 164.6 ± 0.31 U ml- 1, respectively, compared to the control which produced maximum laccase on the 14th day (126.9 ± 0.15 U ml- 1). Phosphomonoesterase activity in the presence of chlorpyrifos, carbofuran, and their mixture was 31.5 ± 0.25, 24.1 ± 0.15, and 29.2 ± 0.35 µg PNP min-1 ml-1, respectively, which was more than the control on the 21st day (11.63 ± 0.21 µg PNP min-1 ml-1). ß-Glucosidase production increased with the days of incubation in the presence of pesticides than in the control. ß-Glucosidase activity on the 21st day in the presence of chlorpyrifos, carbofuran, and their mixture was 32.4 ± 0.1, 24.2 ± 0.3, and 28.4 ± 0.25 µg PNP min-1 ml-1, respectively, as compared to control (15.3 ± 0.6 µg PNP min-1 ml-1). Thus, chlorpyrifos, carbofuran, and their mixture were found to have a positive effect on the production of laccase, ß-glucosidase, and phosphomonoesterase by P. sajor-caju, which can use these pesticides as a source of their nutrition, thereby improving the health of pesticide-polluted soils.

Linkage disequilibrium based association mapping of micronutrients in common bean (Phaseolus vulgaris L.): a collection of Jammu & Kashmir, India.

Micronutrient deficiencies are of major concern in human health and plant metabolism. Iron (Fe), zinc (Zn), iodine (I), selenium (Se) are regarded as micronutrients having major impact on human health. More than 50% of populations mainly from developing countries are suffering from one or the other micronutrient malnutrition. Ensuring adequate supply of these micronutrients through diet consisting of staple foods, such as common bean (Phaseolus vulgaris L.) is must. Here, we evaluated common bean genotypes that were collected from various regions of Jammu and Kashmir, India for Fe, Zn and protein contents and used SSRs to identify the markers associated with these traits. We found significant variation among genotypes for Fe, Zn and protein contents. Genotype R2 was having 7.22 mg 100 g-1 of Fe content, genotype K15 with 1.93 mg 100 g-1 of Zn content and genotype KS6 with 31.6% of protein content. Diversity study was done using both cluster and structure based approach. Further, association mapping analysis using General Linear Method (GLM) approach was done to identify SSRs associated with accumulation of Fe, Zn and protein. 13 SSRs were identified that significantly (p < 0.05) showed association with Fe, Zn and protein contents in common bean. The markers associated with Fe were located on chromosome no. 2, 5, 6, 7, 9 and 10, markers associated with Zn were located on chromosome no. 1, 3, 5, 7 and 10 whereas only one marker located on chromosome no. 4 was found associated with protein content. These findings will provide potential opportunity to improve Fe and Zn concentrations in common bean, through molecular breeding.

Genetic Diversity and Population Structure of Basmati Rice (Oryza sativa L.) Germplasm Collected from North Western Himalayas Using Trait Linked SSR Markers.

One hundred forty one basmati rice genotypes collected from different geographic regions of North Western Himalayas were characterized using 40 traits linked microsatellite markers. Number of alleles detected by the abovementioned primers were 112 with a maximum and minimum frequency of 5 and 2 alleles, respectively. The maximum and minimum polymorphic information content values were found to be 0.63 and 0.17 for the primers RM206 and RM213, respectively. The genetic similarity coefficient for the most number of pairs ranged between of 0.2-0.9 with the average value of 0.60 for all possible combinations, indicating moderate genetic diversity among the chosen genotypes. Phylogenetic cluster analysis of the SSR data based on distance divided all genotypes into four groups (I, II, III and IV), whereas model based clustering method divided these genotypes into five groups (A, B, C, D and E). However, the result from both the analysis are in well agreement with each other for clustering on the basis of place of collection and geographic region, except the local basmati genotypes which clustered into three subpopulations in structure analysis comparison to two clusters in distance based clustering. The diverse genotypes and polymorphic trait linked microsatellites markers in the present study will be used for the identification of quantitative trait loci/genes for different economically important traits to be utilized in molecular breeding programme of rice in the future.

From genomics to functional markers in the era of next-generation sequencing.

The availability of complete genome sequences, along with other genomic resources for Arabidopsis, rice, pigeon pea, soybean and other crops, has revolutionized our understanding of the genetic make-up of plants. Next-generation DNA sequencing (NGS) has facilitated single nucleotide polymorphism discovery in plants. Functionally-characterized sequences can be identified and functional markers (FMs) for important traits can be developed at an ever-increasing ease. FMs are derived from sequence polymorphisms found in allelic variants of a functional gene. Linkage disequilibrium-based association mapping and homologous recombinants have been developed for identification of "perfect" markers for their use in crop improvement practices. Compared with many other molecular markers, FMs derived from the functionally characterized sequence genes using NGS techniques and their use provide opportunities to develop high-yielding plant genotypes resistant to various stresses at a fast pace.