Abstract
The major limiting factor for production and productivity of finger millet crop is blast disease caused by Magnaporthe grisea. Since, the genome sequence information available in finger millet crop is scarce, comparative genomics plays a very important role in identification of genes/QTLs linked to the blast resistance genes using SSR markers. In the present study, a total of 58 genic SSRs were developed for use in genetic analysis of a global collection of 190 finger millet genotypes. The 58 SSRs yielded ninety five scorable alleles and the polymorphism information content varied from 0.186 to 0.677 at an average of 0.385. The gene diversity was in the range of 0.208 to 0.726 with an average of 0.487. Association mapping for blast resistance was done using 104 SSR markers which identified four QTLs for finger blast and one QTL for neck blast resistance. The genomic marker RM262 and genic marker FMBLEST32 were linked to finger blast disease at a P value of 0.007 and explained phenotypic variance (R2) of 10% and 8% respectively. The genomic marker UGEP81 was associated to finger blast at a P value of 0.009 and explained 7.5% of R2. The QTLs for neck blast was associated with the genomic SSR marker UGEP18 at a P value of 0.01, which explained 11% of R2. Three QTLs for blast resistance were found common by using both GLM and MLM approaches. The resistant alleles were found to be present mostly in the exotic genotypes. Among the genotypes of NW Himalayan region of India, VHC3997, VHC3996 and VHC3930 were found highly resistant, which may be effectively used as parents for developing blast resistant cultivars in the NW Himalayan region of India. The markers linked to the QTLs for blast resistance 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 blast resistant alleles into locally adapted cultivars.
Highlights
Finger millet (Eleusine coracana (L.) Gaertn.) (2n = 4 x = 36), subspecies coracana, belongs to the family Poaceae, genus Eleusine in the tribe Eragrostideae
Five genic simple sequence repeats (SSRs) markers were designed from the finger millet nucleotide binding site – leusine rich repeat (NBS-LRR) region, whereas 12 primer pairs were designed from the rice NBS-LRR region which includes the blast resistance gene sequences
The hypothetical chromosomal location of the primers designed from the Expressed sequence tag (EST) sequences and the rice SSR loci was given in figure S1
Summary
Finger millet commonly known as ragi (India), bulo (Uganda), wimbi (Swahili), and tellebun (Sudan) is an important food crop cultivated widely in arid and semi-arid regions of the world, especially in East Africa, India and in other Asian countries including Sri Lanka and China [1]. One of the major limiting factors for production and productivity of finger millet crop is blast disease caused by Magnaporthe grisea (anamorph Pyricularia grisea). This disease has been identified as the highest priority constraint to finger millet production in Eastern Africa, and India since most of the genotypes are highly susceptible [3]. The causal organism of blast disease Magnaporthe grisea is a causative agent of rice blast
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