Optimized breeding strategies for multiple trait i

Authors: Ting Peng Xiaochun Sun Rita H Mumm

Publish Date: 2013/08/15

Volume: 33, Issue: 1, Pages: 105-115

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Abstract

Multiple trait integration MTI is a multistep process of converting an elite variety/hybrid for valueadded traits eg transgenic events through backcross breeding From a breeding standpoint MTI involves four steps single event introgression event pyramiding trait fixation and version testing This study explores the feasibility of markeraided backcross conversion of a target maize hybrid for 15 transgenic events in the light of the overall goal of MTI of recovering equivalent performance in the finished hybrid conversion along with reliable expression of the valueadded traits Using the results to optimize single event introgression Peng et al Optimized breeding strategies for multiple trait integration I Minimizing linkage drag in single event introgression Mol Breed 2013 which produced single event conversions of recurrent parents RPs with ≤8 cM of residual nonrecurrent parent NRP germplasm with ~1 cM of NRP germplasm in the 20 cM regions flanking the event this study focused on optimizing process efficiency in the second and third steps in MTI event pyramiding and trait fixation Using computer simulation and probability theory we aimed to 1 fit an optimal breeding strategy for pyramiding of eight events into the female RP and seven in the male RP and 2 identify optimal breeding strategies for trait fixation to create a ‘finished’ conversion of each RP homozygous for all events In addition nextgeneration seed needs were taken into account for a practical approach to process efficiency Building on work by Ishii and Yonezawa Optimization of the markerbased procedures for pyramiding genes from multiple donor lines I Schedule of crossing between the donor lines Crop Sci 47537–546 2007a a symmetric crossing schedule for event pyramiding was devised for stacking eight seven events in a given RP Options for trait fixation breeding strategies considered selfing and doubled haploid approaches to achieve homozygosity as well as seed chipping and tissue sampling approaches to facilitate genotyping With selfing approaches two generations of selfing rather than one for trait fixation ie ‘F2 enrichment’ as per Bonnett et al in Strategies for efficient implementation of molecular markers in wheat breeding Mol Breed 1575–85 2005 were utilized to eliminate bottlenecking due to extremely low frequencies of desired genotypes in the population The efficiency indicators such as total number of plants grown across generations total number of marker data points total number of generations number of seeds sampled by seed chipping number of plants requiring tissue sampling and number of pollinations ie selfing and crossing were considered in comparisons of breeding strategies A breeding strategy involving seed chipping and a twogeneration selfing approach SC + SELF was determined to be the most efficient breeding strategy in terms of time to market and resource requirements Doubled haploidy may have limited utility in trait fixation for MTI under the defined breeding scenario This outcome paves the way for optimizing the last step in the MTI process version testing which involves hybridization of female and male RP conversions to create versions of the converted hybrid for performance evaluation and possible commercial release

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