Tilling and Ecotilling for Crop Improvement

Abstract

The modern crop scientist has a large amount of available nucleotide sequence information to identify genes of potential agronomic importance. Using reverse genetic approaches, specific genes can be disrupted, and hypotheses regarding gene function directly tested in vivo. Although a number of reverse genetic methods have been introduced, many are limited in application because they are organism-specific, expensive, transgenic or only transiently disrupt gene function. However, traditional mutagenesis using chemical mutagens has been widely used as a forward genetics strategy to create many new crop plant varieties at relatively low cost. Mutagens such as ethyl methanesulphonate (EMS), cause stable point mutations and thus produce an allelic series of truncation and missense changes that can provide a range of phenotypes. TILLING (Targeting Induced Local Lesions IN Genomes) uses traditional mutagenesis and SNP discovery methods for a reverse genetic strategy that is high in throughput, low in cost, and applicable to most organisms. Over the past six years, TILLING has moved from proof-of-concept to production with the establishment of publicly available services for Arabidopsis, maize, lotus, and barley. Pilot-scale projects have been completed on several other plant species, including wheat. The protocols developed for TILLING have been adapted for the discovery of natural nucleotide diversity, a method termed EcoTILLING. Like TILLING, EcoTILLING is general and has been applied to plants as diverse as Arabidopsis and poplar. We review here current TILLING and EcoTILLING technologies and discuss the progress that has been made in applying these methods to many different plant species.