Zoltan Kevei, Eduardo Larriba, María Dolores Romero-Bosquet, Miriam Nicolás-Albujer, Tomasz J. Kurowski, Fady Mohareb, Daniel Rickett, José Manuel Pérez-Pérez & Andrew J. Thompson

Theoretical and Applied Genetics; Published March 8 2024

The use of tomato rootstocks has helped to alleviate the soaring abiotic stresses provoked by the adverse effects of climate change. Lateral and adventitious roots can improve topsoil exploration and nutrient uptake, shoot biomass and resulting overall yield. It is essential to understand the genetic basis of root structure development and how lateral and adventitious roots are produced. Existing mutant lines with specific root phenotypes are an excellent resource to analyse and comprehend the molecular basis of root developmental traits. The tomato aerial roots (aer) mutant exhibits an extreme adventitious rooting phenotype on the primary stem. It is known that this phenotype is associated with restricted polar auxin transport from the juvenile to the more mature stem, but prior to this study, the genetic loci responsible for the aer phenotype were unknown. We used genomic approaches to define the polygenic nature of the aer phenotype and provide evidence that increased expression of specific auxin biosynthesis, transport and signalling genes in different loci causes the initiation of adventitious root primordia in tomato stems. Our results allow the selection of different levels of adventitious rooting using molecular markers, potentially contributing to rootstock breeding strategies in grafted vegetable crops, especially in tomato. In crops vegetatively propagated as cuttings, such as fruit trees and cane fruits, orthologous genes may be useful for the selection of cultivars more amenable to propagation.

See https://link.springer.com/article/10.1007/s00122-024-04570-8

Figure 3: Wound-induced AR formation in aer shoot explants. (A) AR emergence of AC (light blue), AC-Tm-2.^a (dark blue) and aer (red) explants. (B) Rooting capacity of shoot explants at 10 days after whole root excision of young tomato hypocotyls (DAE). (C) Images of growth of shoot explants in glass jars for 10 days. (D) Percentage of hypocotyl length with ARs at 10 DAE. (E) Representative images of rooted shoot explants at 10 DAE. (F) Increase in the number of ARs in shoot explants over the studied time. Asterisks in B, D and F indicate significant differences (p value < 0.01) between genotypes; n.s., non-significant differences. Scale bars: 25 mm (C, E).