Identification of QTLs in oil palm (Elaeis guineensis Jacq.) using SSR markers through association mapping.

Oil palm (Elaeis guineensis Jacq.) is a perennial vegetable and a high oil-yielding crop (4-6 t/ha). There is a large scope for increasing the oil yield by selecting elite planting material for breeding programme in germplasm evaluation, characterization and utilization. In the present study, a diverse range of 150 oil palm genotypes were characterized using 12 quantitative variables with 54genomic microsatellite markers. A wide variation was observed in the morphological traits among indigenous populations. Highly significantand positive correlations were observed between vegetative dry matter (VDM) and total dry matter (TDM) (0.862), and height and height increment (0.838). The first two principal component analyses explained 67.7% of total variation among morphological traits. The genotypes IC0610001-59 (Pune-2) and IC0610001-60 (Pune-2) were found highly promising based on less height increment, more TDMwith high yield. For the mapping study, general linear model (GLM) approach, quantitative-trait loci (QTL) for annual height increment, number of bunches, bunch yield and bunch index were linked to simple-sequence repeat (SSR) loci mEgCIR3649 with phenotypic variance of 15.08, 10.43, 11.74, 15.39. TDM and VDM were linked to mEgCIR0192 (27.34 and 24.19%), mEgCIR3684 (16.84 and 18.30%), SPSC00163 (18.8 and 15.39%) and mEgCIR0555 (16.47 and 18.81%), with at a significant threshold (P) level of B0.001 and by mixed linear model (MLM) approach. TDM was linked to mEgCIR0555 with phenotypic variance of 20.72%, bunch yield and bunch index were linked to mEgCIR2813 at phenotypic variance of 17.11% and 12.88%, respectively, at a significant threshold (P) level of B0.01.

Cross-genera transferability of rice and finger millet genomic SSRs to barnyard millet (Echinochloa spp.).

Barnyard millet (Echinochloa spp.) is an important crop from nutritional point of view, nevertheless, the genetic information is very scarce. In the present investigation, rice and finger millet genomic SSRs were used for assessing cross transferability, identification of polymorphic markers, syntenic regions, genetic diversity and population structure analysis of barnyard millet genotypes. We observed 100% cross transferability for finger millet SSRs, of which 91% were polymorphic, while 71% of rice markers were cross transferable with 48% polymorphic out of them. Twenty-nine and sixteen highly polymorphic finger millet and rice SSRs yielded a mean of 4.3 and 3.38 alleles per locus in barnyard millet genotypes, respectively. The PIC values varied from 0.27 to 0.73 at an average of 0.54 for finger millet SSRs, whereas it was from 0.15 to 0.67 at an average of 0.44 for rice SSRs. High synteny was observed for markers related to panicle length, yield-related traits, spikelet fertility, plant height, root traits, leaf senescence, blast and brown plant hopper resistance. Although the rice SSRs located on chromosome 10 followed by chromosome 6 and 11 were found to be more transferable to barnyard millet, the finger millet SSRs were more polymorphic and transferable to barnyard millet genotypes. These SSR data of finger millet and rice individually as well as combined together grouped the 11 barnyard millet genotypes into 2 major clusters. The results of population structure analysis were similar to cluster analysis.

Association mapping of agro-morphological characters among the global collection of finger millet genotypes using genomic SSR markers.

Identification of alleles responsible for various agro-morphological characters is a major concern to further improve the finger millet germplasm. Forty-six genomic SSRs were used for genetic analysis and population structure analysis of a global collection of 190 finger millet genotypes and fifteen agro-morphological characters were evaluated. The overall results showed that Asian genotypes were smaller in height, smaller flag leaf length, less basal tiller number, early flowering and early maturity nature, small ear head length, and smaller in length of longest finger. The 46 SSRs yielded 90 scorable alleles and the polymorphism information content values varied from 0.292 to 0.703 at an average of 0.442. The gene diversity was in the range of 0.355 to 0.750 with an average value of 0.528. The 46 genomic SSR loci grouped the 190 finger millet genotypes into two major clusters based on their geographical origin by the both phylogenetic clustering and population structure analysis by STRUCTURE software. Association mapping of QTLs for 15 agro-morphological characters with 46 genomic SSRs resulted in identification of five markers were linked to QTLs of four traits at a significant threshold (P) level of ≤ 0.01 and ≤ 0.001. The QTL for basal tiller number was strongly associated with the locus UGEP81 at a P value of 0.001 by explaining the phenotypic variance (R (2)) of 10.8%. The QTL for days to 50% flowering was linked by two SSR loci UGEP77 and UGEP90, explained 10 and 8.7% of R (2) respectively at a P value of 0.01. The SSR marker, FM9 found to have strong association to two agro-morphological traits, flag leaf width (P-0.001, R(2)-14.1 %) and plant height (P-0.001, R(2)-11.2%). The markers linked to the QTLs for above agro-morphological characters found in the present study can be further used for cloning of the full length gene, fine mapping and their further use in the marker assisted breeding programmes for introgression of alleles into locally well adapted germplasm.

In-silico mining, type and frequency analysis of genic microsatellites of finger millet (Eleusine coracana (L.) Gaertn.): a comparative genomic analysis of NBS-LRR regions of finger millet with rice.

In recent years, the increased availability of the DNA sequences has given the possibility to develop and explore the expressed sequence tags (ESTs) derived SSR markers. In the present study, a total of 1956 ESTs of finger millet were used to find the microsatellite type, distribution, frequency and developed a total of 545 primer pairs from the ESTs of finger millet. Thirty-two EST sequences had more than two microsatellites and 1357 sequences did not have any SSR repeats. The most frequent type of repeats was trimeric motif, however the second place was occupied by dimeric motif followed by tetra-, hexa- and penta repeat motifs. The most common dimer repeat motif was GA and in case of trimeric SSRs, it was CGG. The EST sequences of NBS-LRR region of finger millet and rice showed higher synteny and were found on nearly same positions on the rice chromosome map. A total of eight, out of 15 EST based SSR primers were polymorphic among the selected resistant and susceptible finger millet genotypes. The primer FMBLEST5 could able to differentiate them into resistant and susceptible genotypes. The alleles specific to the resistant and susceptible genotypes were sequenced using the ABI 3130XL genetic analyzer and found similarity to NBS-LRR regions of rice and finger millet and contained the characteristic kinase-2 and kinase 3a motifs of plant R-genes belonged to NBS-LRR region. The In-silico and comparative analysis showed that the genes responsible for blast resistance can be identified, mapped and further introgressed through molecular breeding approaches for enhancing the blast resistance in finger millet.