Lower sensitivity in responses to root competition and soil resource availability in a new wheat cultivar than in an old wheat landrace

Aims Crops can change their traits in relation to resource and competitive environments during domestication. However, experimental evidence for the competitiveness of old versus new grain cultivars under different resource availability or competition pressure remains rare. Methods We used two experiments to examine competitiveness and magnitude of responses to soil fertility of two spring wheat cultivars. We manipulated root competition by growing plants with plastic or mesh partitions. Soil resources (i.e. nutrients and water) were added by using nutrient solutions with low or high frequency. Biomass, individual height and tiller number were measured when individuals reached maturity. Results The old Monkhead had greater growth redundancy (i.e. growth of resource-acquiring organs did not necessarily increase seed production) than the new 92–46. However, 92–46 had lower sensitivity in response to soil resource availability than Monkhead. Monkhead individuals allocated more resources to roots at the expense of seed production in the presence of root competition with 92–46 relative to the absence of root competition, reflecting a greater competitiveness in Monkhead. In contrast, 92–46 refrained from growing more roots in competition with Monkhead, and it may develop a more conservative strategy. Conclusions Our results show wheat crops can fall into the growth redundancy, and the magnitude was greater in the old cultivar Monkhead due to higher competitiveness than the new 92–46. Our findings underlie the importance of experimental test for competitiveness between old and new crop cultivars and highlight crop breeding should select cultivars with low individual competitiveness and high population performance.