Genetic control of duration of pre-anthesis phases in wheat (Triticum aestivum L) and associated traits: leaf number and phyllochron

GONZALEZ F.; TERRILE I.; VANZETTI L. S.; BÖRNER A.; PLIESKE J.; GANAL M.; RÖDER M.

Conferencia; First Latin-American Conference on Plant Phenotyping and Phenomics for plant breeding; 2015

Wheat (Triticum aestivum L) production is critical for human diet. It has been predicted that an increase by ca. 50% from current volumes is necessary to fulfil the projected growth of wheat demand. As the cropped land will hardly increase, production should rise mainly via higher on-farm yields which are closely linked to cultivar´s potential yield. Time to anthesis is the main trait defining adaptation to the environment and thereby the yield potential of cultivars (i.e. the maximum yield without water, nutrient or biotic restrictions). The fine-tuning of the relative duration of pre-anthesis phases could modify the yield potential of cultivars already adapted to the environment. If the period of spike growth is increased without changing the anthesis date (via longer duration of the pre-anthesis reproductive phase from first node to anthesis, 1N-AN, and a reduction of previous phases from emergence to first node, E-1N), the number of fertile florets and grains would increase (being associated with higher spike growth) and thus raising the yield potential. To fine-tune wheat development up to anthesis, the environmental and genetic basis that control the vegetative and reproductive pre-anthesis phases should be known. Two double haploid populations with a common parent derived from the cross of French x CIMMyT elite germplasm (Baguette 19 x BioINTA 2002 and Baguette 11 x BioINTA 2002) were genotyped with the 90K SNPS Infinium array and sown during two years under field conditions in a temperate area with mild winters (Region II of the Argentine production area at 33º 51? S, 60º 56? W). The duration of the following pre-anthesis phases were determined: (i) from emergence to first detectable node (E-1N: leaf + spikelet differentiation phases), (ii) from first detectable node to flag leaf appearance (1N-FL) and (iii) from then to anthesis (FL-AN), where most florets develop and die. The number of leaves emerging from main stems (LN) and the rate of appearance (phyllochron) in each sub-phase were also measured. The E-AN phase ranged from ca 1,300 to 1,800ºcd for B19 x B2002 while it varied from ca. 1,300 to 1,600 for B11 x B2002. The duration of pre-anthesis sub-phases also showed variation within each population, ranging from 20 to 46% for E-1N and from 2 to 3 fold for 1N-FL and FL-AN. The LN appeared during E-1N ranged from ca. 8.2 to 11.5 while the LN appeared during 1N-FL phase varied from ca. 1.1 to 3.9. The phyllochron of the first leaves (E-1N) ranged from ca. 86 to 111 ºCd/leaf, while the one of the later leaves (1N ?FL) varied from 60 to 258 ºCd/leaf (considering both populations). The phyllochron showed moderate to low narrow sense heritability. Based on the marker analysis and map information of the SNP markers, two main QTLs were detected in both populations affecting most of the evaluated traits. The first QTL mapped on chromosome 5A with the peak marker being in the Vrn-A1 gene and the second QTL was on the 5B chromosome with the peak marker in the Vrn-B1 gene. The two genes significantly affected the pre-flowering E-1N and 1N-FL sub-phases and significant epistatic interactions between them were detected. Winter alleles in Vrn-A1 and Vrn-B1 genes increased the duration of the E-1N phase sub-phase but reduced the duration of the following 1N-FL sub-phase. In the case of FL-AN, only the Vrn-B1 showed a significant effect with the winter allele increasing the duration of the sub-phase. Additionally both genes affected the LN in the E-1N sub-phase, and only Vrn-A1 affected the LN in the 1N-FL sub-phase. Winter alleles produced an increment in the final LN in the affected sub-phases. Finally, no relevant effect was detected on phyllochron of leaves. These results will help to manipulate wheat development to anthesis to improve yield potential.