A wheat genotype developed for rapid leaf growth copes well with the physical and biological constraints of unploughed soil

Conventional wheat ( Triticum aestivum L.) cultivars grow slowly in unploughed soil because of physical and biological constraints. Here a conventional cultivar ( Janz) is compared with a novel experimental line ( Vigour 18), bred for high leaf vigour, to explore the hypothesis that a vigorous wheat grows better in unploughed soil. Roots of both genotypes in unploughed soil were three times more distorted with 30% shorter apices and 60% shorter expansion zones than roots in ploughed soil, because of voids between blocky peds and packed sand particles that impeded root apices. More than half the root length contacted dead, remnant roots. Vigour 18 roots grew 39% faster, were thicker and distorted less than Janz roots in unploughed soil, but developed similarly in ploughed soil. Vigour 18 shoots grew 64% faster in unploughed soil, but 15% faster in ploughed soil. Fumigation of unploughed soil improved the growth of Janz only. We suggest that faster root growth, different exudates promoting a more beneficial rhizosphere micro. ora, or modified shoot responses are possible mechanisms to explain Vigour 18' s superior growth. Vigorous genotypes may present a new opportunity for increased productivity with conservation farming.