Improving Phosphorus Efficiency in Sorghum by the Identification and Validation of Sorghum Homologs for Pstol1, a Rice Gene Responsible for a Major Phosphorous Uptake QTL (Pup1)

Low availability of P in the soil is one of the main constraints for plant development and crop production in tropical regions. The rice gene Pstol1, which encodes a protein kinase that enhances early root growth and P acquisition, was recently cloned and characterized. We employed comparative genomics to identify sorghum Pstol1 homologs and then validated them as bona fide genes underlying tolerance to P deficiency in sorghum. A sorghum association panel was phenotyped for agronomic performance under low P in the field and well as for root morphology traits; also SNPs within sorghum Pstol1 homologs were identified. Our data suggests that SNPs within sorghum Pstol1 homologs are associated both with changes in root morphology/root system architecture, as well as with P acquisition traits. Gene validation  was conducted via phenotyping members of a large sorghum recombinant inbred line population that was genotyped by sequencing (GBS). The results indicate that some Pstol1 homologs co-localize with QTLs controlling root morphology traits and shoot dry weight. Association analysis was also conducted in a sorghum landrace panel adapted to West Africa that was phenotyped in pots for yield traits on low P soils. From this study we found that SNPs within Pup1 homologs were significantly associated with traits related to P uptake and yield under low P conditions. Furthermore, consistent allelic effects were observed in both panels. The same alleles increased P uptake in Brazil and Africa, indicating that multiple Pup1 homologs play a role in P uptake and efficiency in sorghum.  Our results indicate that Pup1 homologs in sorghum have the ability to enhance P uptake and crop performance on low P soils by a mechanism related to early root growth enhancement, similar to Pup1 in rice.