Efeito do tempo, substrato e temperatura na penetração de juvenis do segundo estádio de Meloidogyne javanica e Heterodera glycines em soja

Abstract

At 2 days after inoculation, independent of the substrate used, lower penetration of J2 of Meloidogyne javanica was observed compared to the other time points tested. When fine sand was used, greater penetration of J2 of M. javanica in soybean roots occurred at 4,4 days after inoculation. By using a mixture of soil and ground sand, the penetration increase was linear between at 2 and 8 days after inoculation. When the fine sand was used number of J2 of Heterodera glycines, in the roots was highest at 2 days after inoculation. In the mixture of soil and ground sand, the soybean roots had lowest number of J2 of H. glycines at 2 days after inoculation, decreasing evenly toward day 8. At 24ºC the penetration of J2 of M. javanica was higher (P< 0,05) regardless of cultivar resistance. However, in the resistant cultivar the penetration was not affected (P< 0,05) at temperatures between 24 and 28ºC. At 32ºC occurred significant decrease in penetration which reached 17,97% of the penetration observed at 28ºC and with similar values at 16 and 20ºC. In the susceptible cultivar the penetration decrease was significant at 28ºC and 32ºC, amounting to 34,74% of that at 24ºC, and even greater than that at 16 and 20ºC. At 12ºC penetration was not observed in any of the cultivars used. Considering H. glycines, the temperatures of 21,3ºC provided great penetration of J2 in the susceptible cultivar and at 22,4ºC in the resistant one. The penetration of J2 of H. glycines at 12 and 32ºC was similar in both susceptible and resistant cultivars, but corresponded approximately to half of that at the temperatures that were better for penetration.