Heterosis in wheat

Evaluation of heterosis in Australian wheat

Melissa Garcia1, Pooja Vashist1, Mihiranga Ovitigala1, Chris Brien2, Martin Nguyen2, Delphine Fleury1, Peter Langridge1. 1 Australian Centre for Plant Functional Genomics, School of Agriculture, Food and Wine, University of Adelaide, Waite Campus, Urrbrae, South Australia, 5064 2 Phenomics and Bioinformatics Research Centre, University of South Australia, Mawson Lakes Campus, Mawson Lakes, South Australia , 5095

Yield improvements from conventional crop breeding in wheat have tapered off over the past decade. Consequently, there is renewed interest in technologies that offer major yield advantages particularly for low yielding environments. One of the most promising options is to capture the yield benefits from heterosis in a hybrid wheat program. The impact of heterosis in wheat has not received the level of attention seen in other crops, particularly maize. Although wheat is a self-pollinated species, reports of the yield benefit in hybrids range from 5% to over 20%, depending on the study and the nature of the crosses.

In order to evaluate the impact of heterosis in Australian elite germplasm, crosses were made between three Australian varieties and ten diverse lines from different regions around the world. The diverse lines were chosen based on genetic diversity detected with the 9K SNP array as well as the country of origin.

Cross Combinations

Phenotyping

1. The Plant Accelerator (TPA)- Adelaide • Automated imaged (20 to 60 DAS) • Well-watered • Relative growth rates

2. Semi-controlled field conditions

• Urrbrae (South Australia) • Drought and Well-watered

Fig1. Relative growth curves of F1 hybrids (green lines), male parents(blue lines) and female parent s(red lines).:

Line Origin

Kite Australia

Carazinho Brazil

Kazakhstan Line 9 Kazakhstan

Kazakhstan Line 10 Kazakhstan

Pastor Mexico

Volcani DD1 Israel

AC Barrie Canada

Xiaoyan 54 China

Alsen USA

H45 Australia

Males

•Gladius

•Mace

•Scout

Females

Results Better parent heterosis (BPH) was calculated for seeds per spike and thousand grain weight (TGW). BPH for seeds per spike ranged from -55% to 39%, with an average of -13%, while BPH for TGW ranged from -35% to 22% , with an average of 2%. Some hybrids showed higher BPH values under drought as compared to the well-watered condition. A strong correlation was observed between the trait values under the drought and the well-watered conditions in the -field experiment, but no correlation was observed between field and TPA. The relative growth curves obtained from the analysis of the TPA image data showed little variation among genotypes, with hybrids and inbreds showing similar patterns (Fig1). Seeds per spike has shown a negative correlation with the area of the plant at later developmental stages, while single grain weight and flowering time showed a positive correlation with area at later stages. Seeds per plant was positively correlated with the plant area at earlier developmental stages (Fig2).

Fig2. Heat map of the correlation of the different traits with the area of the plants at different days after sowing.

Conclusions

• Average better parent heterosis was low, but some crosses showed high BPH for all traits

• Hybrids and inbreds seem to have similar relative growth rates

• More data is necessary to understand the relationship between plant area and the other traits