Biochemical responses of coffee resistance against Meloidogyne exigua mediated by silicon

Abstract

Coffea arabica cultivars Catuaí 44 and IAPAR 59, susceptible and resistant, respectively, to the root knot nematode Meloidogyne exigua, were grown in pots containing Si-deficient soil amended with either calcium silicate (+Si) or calcium carbonate ()Si). There was an increase of 152 and 100%, respectively, in Si content of root tissue of cvs Catuaí 44 and IAPAR 59 in the +Si compared to the )Si treatment, but no significant difference between Si treatments for calcium content. Plants, assessed 150 days after inoculation (d.a.i.) showed that the number of galls (NG) and number of eggs (NE) significantly decreased by 16AE8 and 28AE1% respectively, for susceptible cv. Catuaí 44 in the presence of Si, whilst both NG and NE were significantly lower for cv. IAPAR 59 compared to the susceptible cultivar regardless of Si treatments. In a separate experiment, biochemical assays were carried out 5 and 10 d.a.i. There was no significant difference between Si treatments and cultivars for concentration of total soluble phenolics. The concentration of lignin-thioglycolic acid (LTGA) derivatives significantly increased by 11AE5% in roots of nematode-inoculated plants of susceptible cv. Catuaí supplied with Si. In roots of inoculated plants of resistant cv. IAPAR 59, the increase was 23 and 10%, respectively, for treatments with and without silicon. Peroxidase (POX), polyphenoloxidase (PPO) and phenylalanine ammonia lyase (PAL) activities significantly increased in roots of inoculated plants compared with roots of non-inoculated plants, regardless of cultivar or Si treatment. In +Si treatments at 10 d.a.i., POX activity in roots of nematode-inoculated plants of cvs Catuaí 44 and IAPAR 59 increased by 39AE9 and 31AE3%, respectively; PPO increased by 54AE9 and 56AE1%; and PAL activity was also higher at 26AE6 and 62AE9%. It was concluded that supplying Si to coffee plants increases root resistance against M. exigua by decreasing its reproductive capacity.Keywords: Coffea arabica, host resistance, lignin, phenolics, root-knot nematode IntroductionThe root-knot nematode Meloidogyne exigua is one of the most serious agronomic constraints affecting coffee (Coffea arabica) production in Brazil. This nematode causes typical rounded galls, mostly on newly formed roots, which are initially white to yellowish brown and turn dark brown as the root becomes older (Campos & Villain, 2005). Egg masses are produced either in the cortex beneath the root epidermis or less commonly protruding outside the cortex. Severe weakening of coffee trees is caused by M. exigua, and yield losses arising from its parasitism range from 10 to 20% (Bertrand et al., 1997). However, depending on the nematode biotype and the region where the coffee is grown, for example in Rio de Janeiro state, yield losses can be up to 45% (Barbosa et al., 2004). The main C. arabica cultivars available to growers are susceptible to M. exigua (Campos & Villain, 2005), which has a great reproductive capacity and is widely disseminated among the Arabica coffee production areas in Br...

Defense responses to Meloidogyne exigua in resistant coffee cultivar and non-host plant

“…Even so, reproduction of the nematode did not take place, since no eggs were found. It is thought that compounds connected to plant defense response are involved in this interaction, as reported by Silva et al (2010). These authors observed an increase in the activities of peroxidases, polyphenoloxidases and phenylalanine-ammonia-lyases as well as a higher concentration of lignin and phenolic compounds in the roots of the resistant coffee cultivar infected by M. exigua.…”

Proteção local, não sistêmica, do silicato de potássio reduz os sintomas da ferrugem do cafeeiro

“…Catuaí 44) crescidas em solução nutritiva contendo Si não apresentaram aumento no período de incubação e no período latente da ferrugem e nem mesmo redução no número de pústulas por folha, área pustular, expansão de pústulas e área abaixo da curva do progresso da ferrugem ou aumento na atividade de quitinases, β-1,3-glucanases e peroxidases. Porém, para a interação cafeeiro-Meloidogyne exigua, houve redução no número de galhas e de ovos do nematóide em associação com um aumento na concentração de lignina e na atividade de peroxidases, polifenoloxidases e fenilalanina amônia-liases no sistema radicular de plantas de cafeeiro da cultivar Catuaí 44 crescidas na presença de silicato de cálcio (Silva et al, 2010). Pereira et al (2009) relataram redução na severidade da ferrugem do cafeeiro com a aplicação foliar de silicato de potássio, porém não houve aumento na atividade de quitinases, ß-1,3-glucanases, peroxidases, polifenoloxidases, fenilalanina amônia-liases e lipoxigenases.…”

Effect of Nutrition and Soil Function on Pathogens of Tropical Tree Crops

“…As mentioned above (Section 4.2), silicon (Si) supplied to coffee plants was shown to decrease the number of rust lesions on leaves; Si also has an effect on resistance to nematodes. Silva et al (2010) found that a lower number of M. exigua galls and eggs occurred in the roots of coffee (C. arabica) plants that had been inoculated with the nematode and provided with Si, compared to control plants which were not supplied with Si.…”