Root growth in response to nitrogen supply in Chinese maize hybrids released between 1973 and 2009

Abstract

Root growth has a fundamental role in nitrogen (N) use efficiency. Nevertheless, little is known about how modern breeding progress has affected root growth and its responses to N supply. The root and shoot growth of a core set of 11 representative Chinese maize (Zea mays L.) hybrids released between 1973 and 2009 were investigated under high N (4 mmol L(-1), HN) and low N (0.04 mmol L(-1), LN) levels in a solution culture system. Compared with LN, HN treatment decreased root dry weight (RDW), the root: shoot ratio (R/S), and the relative growth rate for root dry weight (RGR(root)), but increased the total root length (TRL) and the total lateral root length (LRL). The total axial root length (ARL) per plant was reduced under HN, mostly in hybrids released before the 1990s. The number of seminal roots (SRN) was largely unaffected by different N levels. More recently released hybrids showed higher relative growth rates in the shoot under both HN and LN. However, the roots only showed increased RGR under HN treatment. Correspondingly, there was a positive linear relationship with the year of hybrid release for TRL, LRL and ARL under HN treatment. Together, these results suggest that while shoot growth of maize has improved, its root growth has only improved under high N conditions over the last 36 years of selective breeding in China. Improving root growth under LN conditions may be necessary to increase the N use efficiency of maize.

Use of genotype‐environment interactions to elucidate the pattern of maize root plasticity to nitrogen deficiency

“…The significant G × E and identified Q × E effect suggested that crop breeder needs to use different selection progress under different nitrogen levels. Wu et al () found that root growth has not improved under low N conditions over the last 36 years of selective breeding in China. Several studies revealed modified root architecture can enhance root uptake (Uga et al ; Mu et al ), and ideotype RSA has been proposed for efficient N acquisition (Mi et al ; Lynch ).…”

Nitrogen Nutrition, Its Regulation and Biotechnological Approaches to Improve Crop Productivity

“…Urea transporting DUR3 proteins also participated in nitrogen remobilization. ciated with nitrogen remobilization [239] [330] [331]. TIP1; 3 and TIP5; 1 are expressed in the mature pollen.…”

“…P. trichocarpa consists of 6 AMT1 and 8 AMT2 proteins [171]. Rice DUR3 gene codes for a 721 residue long membrane-protein and showed similar expression and regulation patterns as that of Arabidopsis DUR3 gene [239] [240].…”

Root morphology in response to nitrogen supply in mid-season indica rice cultivars released in different decades

“…Because of the great differences in growth period and pattern between the old and new rice cultivars, it is difficult to clarify how genetic improvements contribute to root growth in rice. For example, for a solution culture system, Wu et al suggested that total root length increased with increasing year of release for maize hybrids, while shoot dry weight, root dry weight and leaf area decreased (Wu et al, 2011). However, using similar materials to Wu et al in the field, Chen et al reported that dry matter production had increased, and modern maize since 1990 had reduced root length density (Chen et al, 2014).…”

“…The decreasing LN/HN ratio (r=−0.4334)also suggest that roots of the new super rice cultivars were less responsive to LN ( Figure 1A). Modern rice cultivars are commonly selected under high nutrient supply, resulting in their high tolerance to high N rates and less response of root growth to low N (Wu et al, 2011). Adventitious root length showed no change in the cultivars prior to the 1980s, but was decrease in later cultivars for LN ( Figure 1G).…”