Abstract
The development of crops with better growth under suboptimal phosphorus availability would improve food security in developing countries while reducing environmental pollution in developed countries. We tested the hypothesis that maize (Zea mays) phenotypes with greater lateral root branching density have greater phosphorus acquisition from low phosphorus soils. Recombinant inbred lines with either 'many short' (MS) or 'few long' (FL) lateral root phenotypes were grown under high and low phosphorus conditions in greenhouse mesocosms and in the field. Under low phosphorus in mesocosms, lines with the MS phenotype had 89% greater phosphorus acquisition and 48% more shoot biomass than FL lines. Under low phosphorus in the field, MS lines had 16% shallower rooting depth (D95), 81% greater root length density in the top 20 cm of the soil, 49% greater shoot phosphorus content, 12% greater leaf photosynthesis, 19% greater shoot biomass, and 14% greater grain yield than FL lines. These results are consistent with the hypothesis that the phenotype of many, shorter lateral roots improves phosphorus acquisition under low phosphorus availability and merits consideration for genetic improvement of phosphorus efficiency in maize and other crops.
Highlights
The need to sustain a growing human population with a degrading natural resource base is a paramount challenge of the 21st century (Cordell et al, 2009; Godfray et al, 2010)
Low P availability reduced the lateral root length of primary, seminal, and crown roots, except for crown roots of many short’ (MS) lines, which were not affected by P availability (Fig. 1C).Total lateral root length was correlated with lateral root branching density (LRBD) of crown roots under LP conditions (Fig. 2)
The fact that we observed comparable benefits of the MS phenotype in two field seasons and in greenhouse mesocosms, and that these empirical results validate in silico predictions (Postma et al, 2014), reduces the probability that our results are confounded by biophysical or biotic factors present in any specific environment
Summary
The need to sustain a growing human population with a degrading natural resource base is a paramount challenge of the 21st century (Cordell et al, 2009; Godfray et al, 2010). In the low-input agriculture characteristic of developing nations, low P availability is a primary constraint to food production and economic development. Intensive fertilization in high-input agriculture causes massive environmental pollution. The improvement of P acquisition and use by crop plants is critical for economic, humanitarian, and environmental reasons (Vance, et al, 2003; Lynch, 2007, 2011; Withers et al, 2014; Cordell and White, 2015). Plants have evolved several strategies for P acquisition and use in low P environments, including efficient P utilization and enhanced acquisition (Lynch and Brown, 2001; Vance, 2001; Lambers et al, 2013; Miguel et al, 2015). Roots play a key role in P acquisition because of spatial variation in soil P availability resulting from its low mobility, and factors related to P availability, such as soil pH, microbial activity, and colloid
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