Unravelling the molecular genetic basis of Striga resistance in cereals: integrating Quantitative Trait Loci (QTL) and genomic approaches.

Lead Research Organisation: University of Sheffield
Department Name: Animal and Plant Sciences

Abstract

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Technical Summary

Striga species are angiosperm parasites that cause devastating losses in crop yield throughout sub Saharan Africa. The use of Striga-resistant cultivars would represent a cost effective control measure, however, such a strategy is limited by a lack of resistant germplasm and by a lack of understanding of the molecular genetic basis of host resistance to Striga. Over the last 5 years we have carried out an extensive screening programme in rice and have identified cultivars that show good post-attachment resistance to S. hermonthica. Using a mapping population of rice we have identified some Quantitative Trait Loci (QTL) underlying the resistance. In this project we propose to take an integrative approach to identify and investigate the molecular genetic basis of resistance to Striga in rice by combining our extensive knowledge of Striga-host interactions, our novel plant growth systems and modern genomic and comparative genomic techniques for the improvement of both the rice and sorghum crop in Africa. Our specific objectives are: (1) To screen selected African rice cultivars for resistance to different ecotypes of S. hermonthica, S. asiatica and S. aspera and to determine the phenotype of the resistance. (2) To identify QTL underlying resistance in rice to these different ecotypes and species of Striga using two different mapping populations of rice in order to select the most genetically stable QTL for use in Marker Assisted Breeding Programmes (MAB). (3) To identify genes that are up and down regulated in rice roots undergoing a resistance reaction and, by integrating the results with the QTL data, to identify candidate resistance genes and (4) to utilize our knowledge of the molecular genetic basis of resistance in rice to Striga species to take a comparative genomic approach to identify and confirm the existence of homologous QTL and resistance genes in sorghum.
 
Description We have screened 25 adapted rice cultivars in the lab/rhizotron and field. Out of these cultivars we have found 5 cultivars with effective resistance (based on multiple mechanisms) against Striga hermonthica (NERICA-1, -2, -5 and -10 and IR49255-B-B-5-2) and 5 cultivars with effective resistance against Striga asiatica (NERICA-1, -3, -4, -5, and -17). As most of these cultivars are already released in many African countries, they are readily available to rice farmers. Rice farmers working in the upland environments where problems with Striga are prominent, are generally poor subsistence farmers (often women). Rice cultivars with resistance to Striga and general high yields, as the ones we identified through this work, comprise a very helpful and relevant technology for these resource-poor farmers as they will enable them to raise (and sustain) yields by one to several tonnes per ha (we have found yield differences of upto 3 tonnes/ha), compared to traditionally grown cultivars.

The discovery of the same Striga-resistance QTL on Chromosome 12 in different mapping populations is currently being followed up in the BBSRC SCPRID grant where we have identified candidate genes for resistance. As the resistance is broad spectrum we expect it to be very useful in breeding programmes to improve resistance to Striga in farmer preferred varieties.
Exploitation Route See above
Sectors Agriculture, Food and Drink
 
Description We have screened 25 adapted rice cultivars in the lab/rhizotron and field. Out of these cultivars we have found 5 cultivars with effective resistance (based on multiple mechanisms) against Striga hermonthica (NERICA-1, -2, -5 and -10 and IR49255-B-B-5-2) and 5 cultivars with effective resistance against Striga asiatica (NERICA-1, -3, -4, -5, and -17). As most of these cultivars are already released in many African countries, they are readily available to rice farmers. Rice farmers working in the upland environments where problems with Striga are prominent, are generally poor subsistence farmers (often women). Rice cultivars with resistance to Striga and general high yields, as the ones we identified through this work, comprise a very helpful and relevant technology for these resource-poor farmers as they will enable them to raise (and sustain) yields by one to several tonnes per ha (we have found yield differences of upto 3 tonnes/ha), compared to traditionally grown cultivars. The discovery of the same Striga-resistance QTL on Chromosome 12 in different mapping populations is currently being followed up in the BBSRC SCPRID grant where we have identified candidate genes for resistance. As the resistance is broad spectrum we expect it to be very useful in breeding programmes to improve resistance to Striga in farmer preferred varieties.
First Year Of Impact 2011
Sector Agriculture, Food and Drink
Impact Types Economic