Author: arun joshi

Introgression of the high grain protein gene Gpc-B1 in an elite wheat variety of Indo-Gangetic Plains through marker assisted backcross breeding

Vinod Mishra arun joshi (2014)

Grain protein content (gpc) in wheat has been a major trait of interest for breeders since it has enormous end use potential. In the present study, marker-assisted backcrossing (mabc) was successfully used to improve gpc in wheat cultivar huw468. The genotype glu269 was used as the donor parent for introgression of the gene gpc-b1 that confers high gpc. In a segregating population, ssr marker xucw108, with its locus linked to gpc-b1 was used for foreground selection to select plants carrying gpc-b1. Background selection, involving 86 polymorphic ssr markers dispersed throughout the genome, was exercised to recover the genome of huw468. For eliminating linkage drag, markers spanning a 10 cm region around the gene gpc-b1 were employed to select lines with a donor segment of the minimum size carrying the gene of interest. Improved lines had significantly higher gpc and displayed 88.4–92.3 per cent of the recurrent parent genome (rpg). For grain yield, selected lines were at par with the recurrent parent huw468, suggesting that there was no yield penalty. The whole exercise of transfer of gpc-b1 and reconstitution of the genome of huw468 was completed within a period of two and half years (five crop cycles) demonstrating practical utility of mabc for developing high gpc lines in the background of any elite and popular wheat cultivar with relatively higher speed and precision.


Grain protein content Triticum aestivum Marker assisted selection Foreground selection Background selection CIENCIAS AGROPECUARIAS Y BIOTECNOLOGÍA

Enhanced resistance in wheat against stem rust achieved by marker assisted backcrossing involving three independent Sr genes

Vinod Mishra Arun Balasubramaniam Ramesh Chand arun joshi (2015)

Marker assisted backcrossing (MABC) was used to transfer the three stem rust (Puccinia graminis tritici) resistant genes Sr25, SrWeb and Sr50 into the popular Indian wheat cv. HUW234. The donor was the CIMMYT breeding line PMBWIR4, and each of the target genes was marked by a simple PCR assay. A three step screening strategy was adopted: the first screen comprised foreground selection, the second used markers lying close to the introgression borders to reduce the extent of linkage drag, and the last was background selection based on 149 informative microsatellite assays. Based on the background selection outcomes, at the BC1F1 generation the proportion of the genome fixed for cv. HUW234 alleles ranged from 55% to 67%. Three BC1F1 individuals were crossed a second time with cv. HUW234, resulting in the identification of six BC2F3 families carrying all three target Sr genes; the proportion of their genome inherited from cv. HUW234 ranged from 86% to 92%. BC2F4 and BC2F5 material was planted at three different locations under both disease-free and artificially induced epiphytotic conditions. Compared to recurrent parent, the improved Versions of cv. HUW234 displayed significantly superior resistance to stem rust, and their agronomic performance was as good as, or even marginally better than that of the source cultivar.



Genome-wide association mapping of spot blotch resistance in wheat association mapping initiative (WAMI) panel of spring wheat (Triticum aestivum L.)

Vinod Mishra Ramesh Chand arun joshi (2018)

Spot blotch (SB) caused by Bipolaris sorokiniana, is one of the most important diseases of wheat in the eastern part of south Asia causing considerable yield loss to the wheat crop. There is an urgent need to identify genetic loci closely associated with resistance to this pathogen for developing resistant cultivars. Hence, genomic regions responsible for SB resistance were searched using a wheat association mapping initiative (WAMI) panel involving 287 spring wheat genotypes of different origin. Genome-wide association mapping (GWAM) was performed using single nucleotide polymorphism (SNP) markers from a custom 90 K wheat SNP array. A mixed linear model (MLM) was used for assessing the association of SNP markers with spot blotch resistance in three consecutive years. Three traits were measured: incubation period, lesion number and area under the disease progress curve (AUDPC). Significant SNP markers were found linked to five, six and four quantitative trait loci (QTLs) for incubation period, lesion number and AUDPC respectively. They were detected on 11 different chromosomes: 1A, 1B, 1D, 4A, 5A, 5B, 6A, 6B, 6D, 7A, 7B with marker R2 range of 0.083 to 0.11. The greatest number of significant SNP-markers was found for lesion number and AUDPC on chromosome 6B and 5B, respectively, representing a better coverage of B-genome by SNPs. On the other hand, the most significant and largest SNP markers for incubation period were detected on 6A and 4A chromosomes indicating that this trait is associated with the A-genome of wheat. Although, QTLs for spot blotch resistance have been reported in wheat on these same chromosomes, the association of incubation period and lesion number with SB resistance has not been reported in previous studies. The panel exhibits considerable variation for SB resistance and also provides a good scope of marker-assisted selection using the identified SNP markers linked to resistant QTLs.