Maize varieties that combine higher yield with better nutrient efficiency and stress tolerance could raise world production by up to 18% while cutting reactive nitrogen losses by more than a quarter, according to a study published in Science Bulletin. The work was led by Xiangyuan Wan and Xun Wei of the University of Science and Technology Beijing with China Agricultural University, Zhejiang University, Wageningen University & Research and the International Maize and Wheat Improvement Center (CIMMYT).

The team sorted 48 maize traits into four groups — resistance to pests and disease, tolerance of drought, heat, cold and salt, plant architecture suited to dense planting, and efficient use of nutrients — and merged 27,516 quantitative trait nucleotides and 3,272 trait loci into genetic clusters. That produced 293 genomic regions shared across the four groups, and 227 of 524 known genes fell within 98 common clusters, which the authors name as priority targets for fine mapping, gene editing and molecular breeding.

A survey of 539 varieties worldwide carrying at least one such trait showed that the easy traits dominate — insect resistance and herbicide tolerance — while nitrogen-use efficiency and cold or salt tolerance remain rare, and commercial varieties seldom combine three or more. A meta-analysis of 1,709 field observations from 96 studies put the yield gain of these varieties at 10.1%, or 12.7% after statistical adjustment, with insect resistance stacked on drought tolerance giving the strongest results.

The varieties converted absorbed nitrogen into grain 16.7% more efficiently, but their nitrogen uptake was 13% lower — a warning, the authors say, that yield must not be bought at the cost of roots that gather less nitrogen from the soil. Modelling on 561,359 soil and climate observations gave an upper limit of 18.1% more yield (145.8 million tonnes a year) and 26.6% lower reactive nitrogen losses (1.49 million tonnes) under full adoption; at today's adoption levels in lower-efficiency regions the near-term benchmark is about 9% more grain and 13% less nitrogen loss.

The gains depend on pairing the seed with the right fertiliser use, planting density, pest management and markets, and on getting experimental varieties into commercial production where they would matter most. The authors call for coordination across genetics, breeding, regulation, seed systems and farm management, with genomic selection, gene editing and multi-environment trials to stack the traits and policy support to put the seed in farmers' hands in high-need regions.

Source: Seed World Europe