Phenotypic expression of blast resistance gene Pi54 is not affected by its chromosomal position.

This is a novel report in which chromosomal position of the rice blast resistance gene Pi54 was not found to affect significantly the resistance phenotype or morphological traits. Blast disease caused by Magnaporthe oryzae is a serious constraint in rice production at global level. Pi54 gene imparts resistance against M. oryzae. Three different transgenic lines containing Pi54 and its orthologue Pi54rh were shown to be resistant to different races of M. oryzae. To determine the chromosomal location of Pi54 gene in transgenic lines, inverse PCR was performed. Our analysis showed that in two transgenic lines, Pi54 gene was integrated on chromosomes 6 and 10 at 12.94 and 22.30 Mb, respectively. Similarly, Pi54rh allele was integrated on chromosome 1 at 16.25 Mb. The Pi54 gene present on chromosome 6 was located in a non-coding region whereas in the other TP-Pi54 line, the gene was introgressed on chromosome 10 in between the coding region of SAP domain gene. The Pi54rh was also located in the non coding region flanked by the retrotransposon genes. These rice lines were evaluated for eight different traits related to seed and plant morphology and agronomic features for two consecutive years. The transgenic lines containing Pi54 gene have higher tiller number, grain weight, epicotyl length, and yield compared to the non-transgenic control. Multivariate correlation analysis shows that blast resistance was positively correlated with the number of tillers; thousand grain weight and epicotyl length. These results will facilitate precise utilization of Pi54 gene and its orthologue in breeding programs for the development of rice cultivars with broad spectrum and durable resistance to M. oryzae.