The growth defect of lrt1 , a maize mutant lacking lateral roots, can be complemented by symbiotic fungi or high phosphate nutrition

Abstract

The growth of three maize (Zea mays L.) mutants, each impaired in the formation of one individual element of its root system, was compared under "natural" limiting phosphate conditions (0.1 mM). Mutant plants exhibiting a reduction in root hairs (rth3-1) or a depletion of crown and brace roots (rtcs) grew as well as the corresponding wild-type plants. However, mutant plants lacking lateral roots (lrt1) showed a strong reduction in plant growth. The growth defect of lrt1 was overcome when it was grown in association with an arbuscular mycorrhizal fungus, Glomus mosseae. Establishment of symbiosis was associated with the occurrence of a new type of lateral root. These new lateral roots were stunted and highly branched, giving rise to a bush-like structure. Supply of high phosphate (1 microM) ameliorated the growth of lrt1 plants too, but less efficiently than the symbiosis did. Hence, arbuscular mycorrhizal fungi as well as phosphate functionally complemented the lrt1 mutation.

Cereal mycorrhiza: an ancient symbiosis in modern agriculture

“…This point has been illustrated in the extreme case of the maize mutant lateral root1 (lrt1), a mutant deficient in lateral root growth. This mutant is highly intolerant of low phosphate conditions, but can be partially rescued by formation of an AM symbiosis [20]. Thus, it can exhibit higher responsiveness compared with wild-type siblings, although the greatest difference is in performance in the absence of AM colonization.…”

Genetic variation for root architecture, nutrient uptake and mycorrhizal colonisation in Medicago truncatula accessions

“…A review by Hetrick (1991) on the affect of mycorrhizal colonisation on root architecture highlighted the difficulties of unravelling the effect of mycorrhizal colonisation and improved nutrition on root architecture changes. Since then, experiments using a maize mutant that lacks lateral roots when non-mycorrhizal (NM) but does produce lateral roots when colonised by AM fungi showed an increase in plant nutrition in AM plants (Paszkowski and Boller 2002).…”

Phosphate Deprivation in Maize: Genetics and Genomics

“…Maize, as opposed to Arabidopsis, is efficiently colonized by arbuscular mycorrhizal fungi (Paszkowski and Boller, 2002), and, as in other species, this interaction significantly increases shoot growth rate, P content, dry matter accumulation, and rate of photosynthesis under P-limiting conditions (Parniske, 2008). In maize, the benefit to the plant can vary depending on the fungal species, soil P status, and genotype (Gavito and Varela, 1995;Kaeppler et al, 2000;Bressan and Vasconcellos, 2002;Wright et al, 2005;Sawers et al, 2010).…”