Bassi, F. M. | bioRxiv Science

bioRxiv2023

Genomic regions of durum wheat involved in water productivity.

Durum wheat is a staple food of the Mediterranean Basin, mostly cultivated under rainfed conditions. As such, the crop is often exposed to moisture stress. Therefore, the identification of genetic factors controlling the capacity of genotypes to convert moisture into grain yield (i.e. water productivity) is quintessential to stabilize production despite climatic variations. A global panel of 384 accessions was tested across eighteen Mediterranean environments (Morocco, Lebanon, and Jordan) representing a vast range of moisture levels. The accessions were assigned to water responsiveness classes, with genotypes Responsive to Low Moisture reaching an average + 1.5 kg ha-1 mm-1 advantage. Genome wide association studies (GWAS) revealed that six loci explained the majority of this variation. A second validation panel tested under moisture stress confirmed that carrying the positive allele at three loci on chromosomes 1B, 2A and 7B generated an average water productivity gain of + 2.2 kg ha-1 mm-1. Interestingly, loci on chromosome 2A is novel. The three loci were tagged by Kompetitive Allele Specific PCR (KASP) markers, and these were used to screen a third independent validation panel composed by elites tested across moisture stressed sites. The three KASP combined predicted up to 34% of the variation for grain yield at 65% accuracy. These loci are now ready for molecular pyramiding and transfer across cultivars to improve the moisture conversion of durum wheat. HighlightLoci controlling drought tolerance were identified using a solid strategy, involving 3 different panels. Those loci associated enables higher water productivity and grain yield.

plant biology↗

bioRxiv2018

Yield performance of chromosomally engineered durum wheat-Thinopyrum ponticum recombinant lines in a range of contrasting rain-fed environments across three countries

Introgressions of Thinopyrum ponticum 7AgL chromosome segments, spanning 23%, 28% and 40% of the distal end of durum wheat 7AL arm, were previously shown to contain multiple beneficial gene(s)/QTL for yield-related traits, in addition to effective disease resistance (Lr19, Sr25) and quality (Yp) genes. In the present study, durum wheat near isogenic recombinant lines (NIRLs), harbouring each of the three introgressions, were included for the first time in multi-location field trials, to evaluate general and environment-specific effects of the alien chromatin on 26 yield-related traits. The results from nine different trials across contrasting environments of Italy, Morocco and South Australia over four years revealed that the overall impact of 7AgL introgressions into the tetraploid wheat background did not imply, except in one environment, major yield penalty. The comprehensive effect of the three 7AgL segments on individual yield-contributing traits, resulted in significant increases of biomass m-2 (+9%), spike number m-2 (+13%), grain number m-2 (+11%) and spikelet-1 (+8%), but also in a general, significant decrease of grain weight (-8%). When the separate NIRLs were analysed, each of the three 7AgL segments turned out to be associated with variation of specific yield components. The effects of the 40%-long segment proved to be the most stably expressed across environments and involved significant increases of spike and grain number m-2 (13% and 15%, respectively), grain number spike-1 (10%) and spike fertility index (46%), though accompanied by a significant decrease in thousand grain weight (-23%). In spite of this trade-off between grain number and grain weight, their interplay was such that in four trials, including dryer environments, a grain yield advantage was observed. This evidence, and comparison with the two other NIRLs, substantiates the hypothesized existence of major gene(s)/QTL for grain number in the most proximal 28-40% 7AgL region, exclusive to the 40%-long 7AgL introgression. The present study represents an important validation of the use of chromosomally engineered genetic stocks for durum wheat improvement, targeting not only disease resistance and quality traits but also relevant yield components.

genetics↗