Resistance of Grafted Tomato with Guozhen 1 as Stock against Root Knot Nematodes in Field

[Objective] This study aimed to study the resistance of grafted tomato with Guozhen 1 as stock against root knot nematodes. [Method] Tomato seedlings were grafted with Guozhenl （T1） and Solanum torvum （T2） as the rootstock, respectively. Self-rooted tomato seedlings were treated as the control （CK）. The resistance of tomato against root knot nematodes was compared among the three treatments. [Result] Compared with those in the T2 and CK groups, the yield of tomato in the T1 group was increased by 17 436.75 and 31 753.65 kg/hm2 respectively, the plant height was increased by 10.55 and 14.54 cm respectively （P〈0.05）, and the stem diameter was increased by 0.56 and 1.13 cm respectively （P〈0.05）. The disease indexes of root knot nematodiasis in the three treatments were 0.55, 10.42 and 45.31, respectively, and there were significant differences among them （P〈0.05）. [Conclusion] This study will provide a theoretical basis for the control of root knot nematodes in tomato by grafting.

Missense mutation of a class B heat shock factor is responsible for the tomato bushy root-2 phenotype

The bushy root-2(brt-2)tomato mutant has twisting roots,and slower plant development.Here we used whole genome resequencing and genetic mapping to show that brt-2 is caused by a serine to cysteine(S75C)substitution in the DNA binding domain(DBD)of a heat shock factor class B(HsfB)encoded by SolycHsfB4a.This gene is orthologous to the Arabidopsis SCHIZORIZA gene,also known as AtHsfB4.The brt-2 phenotype is very similar to Arabidopsis lines in which the function of AtHsfB4 is altered:a proliferation of lateral root cap and root meristematic tissues,and a tendency for lateral root cap cells to easily separate.The brt-2 S75C mutation is unusual because all other reported amino acid substitutions in the highly conserved DBD of eukaryotic heat shock factors are dominant negative mutations,but brt-2 is recessive.We further show through reciprocal grafting that brt-2 exerts its effects predominantly through the root genotype even through BRT-2 is expressed at similar levels in both root and shoot meristems.Since AtHsfB4 is induced by root knot nematodes(RKN),and loss-of-function mutants of this gene are resistant to RKNs,BRT-2 could be a target gene for RKN resistance,an important trait in tomato rootstock breeding.Gene&accession numbers SolycHsfB4a-Solyc04g078770.