Abstract
BackgroundPlant breeding requires numerous generations to be cycled and evaluated before an improved cultivar is released. This lengthy process is required to introduce and test multiple traits of interest. However, a technology for rapid generation advance named ‘speed breeding’ was successfully deployed in bread wheat (Triticum aestivum L.) to achieve six generations per year while imposing phenotypic selection for foliar disease resistance and grain dormancy. Here, for the first time the deployment of this methodology is presented in durum wheat (Triticum durum Desf.) by integrating selection for key traits, including above and below ground traits on the same set of plants. This involved phenotyping for seminal root angle (RA), seminal root number (RN), tolerance to crown rot (CR), resistance to leaf rust (LR) and plant height (PH). In durum wheat, these traits are desirable in environments where yield is limited by in-season rainfall with the occurrence of CR and epidemics of LR. To evaluate this multi-trait screening approach, we applied selection to a large segregating F2 population (n = 1000) derived from a bi-parental cross (Outrob4/Caparoi). A weighted selection index (SI) was developed and applied. The gain for each trait was determined by evaluating F3 progeny derived from 100 ‘selected’ and 100 ‘unselected’ F2 individuals.ResultsTransgressive segregation was observed for all assayed traits in the Outrob4/Caparoi F2 population. Application of the SI successfully shifted the population mean for four traits, as determined by a significant mean difference between ‘selected’ and ‘unselected’ F3 families for CR tolerance, LR resistance, RA and RN. No significant shift for PH was observed.ConclusionsThe novel multi-trait phenotyping method presents a useful tool for rapid selection of early filial generations or for the characterization of fixed lines out-of-season. Further, it offers efficient use of resources by assaying multiple traits on the same set of plants. Results suggest that when performed in parallel with speed breeding in early generations, selection will enrich recombinant inbred lines with desirable alleles and will reduce the length and number of years required to combine these traits in elite breeding populations and therefore cultivars.
Highlights
Plant breeding requires numerous generations to be cycled and evaluated before an improved cultivar is released
The ICARDA line was selected for its desirable tolerance to severe drought conditions, as well as its lack of yield losses when grown under severe crown rot (CR) infection with a response of moderately resistant to moderately susceptible (MRMS) in Latakia, Syria
The broad-sense heritability was calculated using the predicted variance components which were calculated using residual maximum likelihood, as described by Phenotypes displayed by standards Using multi-trait phenotyping, above and below ground traits including adaptive root traits seminal root angle (RA) and root number (RN), and economically significant diseases CR and leaf rust (LR) were screened (Fig. 2f )
Summary
Plant breeding requires numerous generations to be cycled and evaluated before an improved cultivar is released. For the first time the deployment of this methodology is presented in durum wheat (Triticum durum Desf.) by integrating selection for key traits, including above and below ground traits on the same set of plants This involved phenotyping for seminal root angle (RA), seminal root number (RN), tolerance to crown rot (CR), resistance to leaf rust (LR) and plant height (PH). In durum wheat, these traits are desirable in environments where yield is limited by in-season rainfall with the occurrence of CR and epidemics of LR. Durum wheat (Triticum durum Desf.) is one of the major staple crops in the Mediterranean region It is known for its unique properties such as hardness, yellow pigment and high protein content. Several studies have reported a number of highly virulent isolates of the leaf rust pathogen Puccinia triticina, causing leaf rust (LR), in major durum production areas such as North Africa [20], Southern Europe [21, 22], and West Asia [23] and have rendered susceptible many previously resistant durum cultivars
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