Banca de DEFESA: RIZELLE DE OLIVEIRA BARROS

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : RIZELLE DE OLIVEIRA BARROS
DATE: 27/02/2023
TIME: 08:30
LOCAL: CCAB
TITLE:

 Diversity and pathogenicity of Rhizoctonia anastomosis groups associated with alliums in Brazil

KEY WORDS:

Allium spp. Soilborne fungi. Root pathogen. ITS sequences. Phylogeny.
Aggressiveness.

PAGES: 45
BIG AREA: Ciências Biológicas
AREA: Bioquímica
SUMMARY:

Several factors can cause losses in the production of alliums (garlic, leeks, onions, and chives),
but diseases are very important. Among these, the damping-off of seedlings, basal rot of leaves
and dwarfing of adult plants, caused by fungi of the genus Rhizoctonia. The identification of
this fungus is based mainly on the classification into hyphal anastomosis groups (AGs). The
present study was undertaken to determine which Rhizoctonia species and AGs occur in
alliums production areas in Brazil using internal transcribed spacer region (ITS) sequencing of
ribosomal DNA (rDNA). Garlic, leeks, onions, and chives plants with damping-off of
seedlings, basal rot of leaves and dwarfing of adult plants were collected in 38 production areas
located in 12 municipalities and five Brazilian states from 2018 to 2022. From symptomatic
plant materials were performed isolations of the associated fungi and
obtained Rhizoctonia pure cultures. Forty-nine Rhizoctonia isolates were obtained from alliums
in Brazil. Genomic DNA was extracted from all Rhizoctonia isolates, and PCR amplifications
from the ITS-rDNA region were made with the ITS1 and ITS4 primers. PCR products were
purified and sequenced. Nucleotide sequences from Rhizoctonia reference isolates obtained
from GenBank were included in the analyses, and phylogenetic relationships were analyzed by
Maximum Likelihood method. The phylogenetic analysis of the ITS region allowed grouping
44 of the 49 Rhizoctonia isolates into five AGs, three of binucleate Rhizoctonia (AGA-A, AG-
F, and AG-K) and two of multinucleate Rhizoctonia, specifically R. solani (AG- 4 HGI and
AG-4 HGIII). Five isolates were identified as binucleate Rhizoctonia but did not cluster with
any AG described. This is the first worldwide report of the association of AG-F, AG-K, and
AG-4 HGI with garlic, of AG-A, AG-F, and AG-4 HGIII with leek, of AG-F with onion and
AG-A and AG-F with chives. There was a predominance of AG-A (40.8% of the isolates),
widely distributed in Brazilian production areas and associated with all allium species studied
here. Representative isolates of the found AGs were inoculated into onions, and there was a
significant difference in aggressiveness levels. This is the first detailed report on the
composition of Rhizoctonia AGs associated with alliums in Brazil.

BANKING MEMBERS:
Externo à Instituição - MARUZANETE PEREIRA DE MELO - UFPI
Externa à Instituição - ALICE MARIA GONÇALVES SANTOS - UFPI
Externa à Instituição - ELIANE MAYUMI INOKUTI - UFC
Interno - JUAN CARLOS ALVAREZ PIZARRO
Presidente - SAMI JORGE MICHEREFF