Searching for candidate genes for a spike length and density QTL in wheat (Triticum aestivum L.)

PRETINI NICOLE; ALONSO, MARÍA P; CRESCENTE JUAN MANUEL; ZANG J; DUBCOVSKY JORGE; GONZÁLEZ FG; VANZETTI, LEONARDO

Congreso; 1er Simposio Internacional de Mejoramiento genético vegetal; 2021

OBJECTIVES: The spike structure is a trait of interest in wheat breeding. Shorter spikes with higher density (reduced rachis length between spikelets) were recently associated with increased spike fertility, grain number and yield per spike (Pretini et al. 2021). The objective of this work is to detect candidate genes for a QTL of spike length (SL) and spike density (SD) detected in two independent mapping populations.MATERIALS AND METHODS: Two mapping populations were used, a 182 RIL from UC1110 [UC] x PI610750 [PI] (P1) which was genotyped using SSRs + DArTs and a 102 DH lines derived from Baguette 19 [B19] x BIOINTA 2002 [B2002] (P2) genotyped with 90K SNPs. The P1 and P2 were evaluated for SL and SD in 6 and 5 environments respectively. The QTL Cartographer 2.5 software (Wang et al. 2012) was used to detect the QTL for SL and SD. The validation and degree of dominance were carried out by ANOVA using an F2 (n=264) population from the crosses of the DH24 x DH22 lines of the P2 population. The degree of dominance (D) was estimated according to Falconer, (1960). The exons capture of the four parents is also available and the annotation of the mutations was performed by VEP application from EnsemblPlants (https://bit.ly/3cP8Ltb). The gene expression was analyzed using the platform Wheat Expression Browser (https://bit.ly/2U5v2fy).RESULTS: Several QTLs were observed for both traits in P1 and P2 populations. However, a QTL on chromosome 5A showed a similar position for SL and SD in both populations. In P1, the QTL is flanked by markers wPt-4419 (68.2cM, 504.8Mb) and wPt-0707 (72.7cM, 524.2Mb) with its maximum peak of LOD 10.65 for SL and 12.55 for SD at marker barc330 (72,1 cM; 523.8 Mb). On the other hand, in P2 the QTL is flanked by markers Kukri_c31411_690 (47.7cM, 495.9 Mb) and BS00023076_51 (49.3cM, 524.7Mb) with its maximum peak of LOD 9.55 for SL and 5.48 for SD at marker Excalibur_c53772_302 (48.8cM, 522.1 Mb).The segregation of the KASP marker used for the validation and calculation of the degree of dominance in the F2 population did not differ significantly from those expected in the assumption of a 1:2:1 Mendelian segregation (X2 = 2.21 = 0.35>p>0.30). The one-way ANOVA revealed a significant effect of the peak marker for SL (P