Abstract
ABSTRACT Meloidogyne enterolobii associated with Fusarium solani causes the guava decay, which is the main factor of yield loss in guava crops and limits guava production in Brazil. Therefore, searching for guava genotypes (Psidium spp.) with resistance to M. enterolobii is important to control this root-knot nematode. The objective of the present work was to evaluate the reaction of Psidium spp. accessions from the Germplasm Bank of the Bahia State University (UNEB) to different levels of inoculation with M. enterolobii. Guava seedlings were inoculated with 600, 1,600, and 2,000 eggs + J2 second stage juveniles of M. enterolobii and the root fresh weight, total number of eggs (TNE), and reproduction factor (RF) were evaluated. The results were subjected to ANOVA and means were clustered using the Scott-Knott test at 5% probability. The diversity of accessions was estimated using the Tocher's clustering and UPGMA methods. The nematode RF reduced in some accessions with increasing inoculation levels of the nematode. However, the RF increased in some accessions with high levels of inoculation. Plants of the Y50 accession were immune or resistant to M. enterolobii, indicating variability of reaction of plants to the nematode within the Psidium genus. The resistance of Psidium accessions to M. enterolobii needs to be measured with different inoculation levels to verify the existence of false-positive results, since the evaluated accessions, including the Paluma cultivar, presented distinct reactions regarding RF in the three levels of inoculation used.
Highlights
Psidium guajava L. is the most important species of the Psidium genus; it is widely grown and adapted to tropical and subtropical climates (FRANZON, 2009)
The fruits produced by this species have high commercial value, are rich in minerals and vitamin C, contains several medicinal active ingredients (PEREIRA; NACHTIGAL, 2000; AMAYA; FARFAN, 2009; MARQUES et al, 2016), and is used to produce jams and jellies (MANICA et al, 2000; SÃO JOSÉ et al, 2003)
Araçá species are widely distributed in Brazil (FRANZON, 2009); P. schenckianum Kiarsk, P. guineense, and P. grandifolium Mart were found in the Bahia semiarid region (SANTOS et al, 2014); these species were sampled, and currently form a collection of about 100 accessions belonging to the Bahia State University (UNEB), in Juazeiro, BA, Brazil
Summary
Psidium guajava L. (guava) is the most important species of the Psidium genus; it is widely grown and adapted to tropical and subtropical climates (FRANZON, 2009). The guava crop has the highest economical value among Psidum species; this genus has other wild species, known in Brazil as araçá trees, such as P. guineense Swart, P. shenckianum Kiarsk, and P. cattleianum Sabine; these species produce edible fruits with exotic flavor and high concentrations of vitamin C, which can be consumed fresh or processed (jams or jellies) and have raised the interest of pharmaceutical industries because of their high potential for economic exploitation (FRANZON, 2009; SANTOS et al, 2014). Studies have been conducted using different methodologies and criteria to classify accessions of Psidium spp. as resistant or susceptible to Meloidogyne enterolobii Yang & Eisenback. This nematode is the main cause of losses in guava crops, limiting guava production in Brazil (PEREIRA et al, 2016). M. enterolobii infection is associated with soil fungi (GOMES et al, 2011), leading to a synergistic interaction that causes even greater damage to crops (GOMES et al, 2017; CASTRO et al, 2017)
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