Enhancing the identification of genetic loci and transgressive segregants for preharvest sprouting resistance in a durum wheat population

Abstract

Preharvest sprouting reduces grain quality and lowers grade. Characterization of preharvest sprouting resistance is important in selection in breeding for transgressive segregation and understanding the genetics of the trait for identifying QTL. Methods of measuring dormancy and other factors contributing to preharvest sprouting resistance are varied. The objective of this study was to demonstrate the requirement of multiple methods of measurement over multiple durations of germination to maximize understanding of transgressive segregation and QTL for preharvest sprouting resistance within a segregating durum wheat population grown in multiple environments. Ninety-eight durum wheat (Triticum turgidum L. var. durum) recombinant inbred lines (RIL) from a cross of a minimally dormant line,

Maximizing the identification of QTL for pre-harvest sprouting resistance using seed dormancy measures in a white-grained hexaploid wheat population

“…The 5-10 spikes were threshed as a bulk for each experimental unit and seed germinations for evaluation with GI, GR and PG measures were performed as described by Knox et al (2012) for each of the seven environments. The trait measures, environments (locations by year) and days on which germination data were assessed are presented in Fig.…”

“…1. The number of seeds plated was 41-51 in 1997, 13-72 in 1998 and 26-128 in 1999 After the final counts for Swift Current 1999, the ungerminated seeds were treated with 4.0-6.0 ml of 0.5 mM gibberellic acid (GA 3 ) solution for 1 h to test the seeds viability as described by Knox et al (2012). Daily counts of germinated seeds were recorded for another 3 d. Any seed that failed to germinate was considered to be non-viable, and was excluded from the experimental total seeds.…”

“…Evaluation of threshed seeds, instead of intact spikes where the embryo is concealed by the lemma and palea, is used to characterize dormancy level. Germination index (GI), germination resistance (GR) and percent germination (PG) are common measurements for characterizing resistance to pre-harvest sprouting based on seed dormancy Singh et al 2010;Knox et al 2005Knox et al , 2012.…”

“…As with DePauw and McCaig (1991) in the study of heritability, in order to deal with the complexity of pre-harvest sprouting resistance and identify associated QTL, different tests such as wetting spikes in an artificial rain simulator, threshed seed germination counts for dormancy, and alpha-amylase activity measured by falling number have been conducted (Roy et al 1999;Mares et al 2005;Imtiaz et al 2008;Rasul et al 2009). Knox et al (2012) reported GI, GR and PG measures each at 7, 14 and 21 days intervals from the start of germination across multiple environments. The authors emphasized that measuring GR for longer and GI and PG for shorter duration of germination favor the selection of breeding lines with adequate (moderate to high) resistance to pre-harvest sprouting.…”

“…They determined the segregation to be complex with at least seven effective factors involved. The present study with the same hexaploid wheat population is an extension of the previous study by Knox et al (2012) in which GI, GR and PG measures were examined for three durations of germination counts in durum wheat. The objective of the present study was to maximize identification of QTL for pre-harvest sprouting resistance by analyzing three dormancy measures at multiple germination intervals across different environments.…”