2013 Annual Report
1a.Objectives (from AD-416):
The primary objective of this proposal is to identify genes related to tolerance to phosphorous (P) deficiency in sorghum, with a focus on homologs of the rice phosphorous uptake efficiency gene, Pup1, in sorghum. Once sorghum P efficiency genes are identified, this information and new knowledge will be transferred to the Sorghum Molecular Breeding (SorghumMB) project for deployment into breeding programs. This project is based on the work of an interdisciplinary research team from Embrapa (Brazil), USDA-ARS at Cornell University in Ithaca, JIRCAS in Japan, IRRI in the Philippines, Moi University in Kenya, ICRISAT in Mali and Niger, and INRAN in Niger. The findings from this research sets the foundation for a molecular breeding program targeting marginal soil areas in southern Mali, Niger and Kenya and other areas of Sub-Saharan Africa to improve food security and farmer’s income.
The specific objectives are:
1. Identify homologs of rice Pup1 that are associated with traits related to P deficiency tolerance in sorghum and also clarify the role of the sorghum Al tolerance gene, SbMATE, in tolerance to low P.
2. Validate genes associated with P deficiency tolerance in sorghum.
1b.Approach (from AD-416):
This project will undertake a comparative genomics strategy based on association analysis to validate the role of sorghum homologs of Pup1 as bona fide P deficiency tolerance genes. Here, Pup1 validation in sorghum will be done within a molecular genetic framework that should allow for the isolation of other P deficiency tolerance genes and their pyramiding in sorghum for exploring additive effects. In addition, this same platform will be used to study a possible role of AltSB in improving P acquisition in sorghum. This project sets the foundation for a molecular breeding program targeting marginal soil areas in Mali, Niger, Kenya, and other African NARS to improve food security and farmer’s income.
In the third year of this project, we continued to use genetic and molecular methods to study sorghum genes that are homologs to the phosphorous (P) uptake efficiency in rice, Pup1, which is a protein kinase. In rice this gene appears to increase the size of the root systems to allow the root system to mine more P from the soil under low P conditions – which confers P acquisition efficiency (the ability to maintain yields under low P conditions). This year, the major finding of the project is the discovery of genetic markers within the DNA sequence of sorghum homologs of the rice Pup1 gene that may be associated with root traits involved in sorghum P acquisition efficiency in the field. Validation that these Pup1 genetic markers are associated with P acquisition efficiency is the next necessary step before we can begin to use these markers for the molecular breeding of improved P acquisition efficiency in sorghum. We have developed and genotyped by next generation DNA sequencing a large sorghum bi-parental mapping population that has significant variation for root system traits. This population will be used to validate the results described above. After this final step, we expect to have a clear picture of the use of sorghum Pup1 homologs as tools to improve P acquisition efficiency in sorghum.