Survival of Acidovorax citrulli in infected melon tissues and in different edafoclimatic conditions

Abstract

The survival of Acidovorax citrulli Aac1Rif was accessed in infected melon tissues (fruits and leaves) incorporated to the soil at 0, 5, 10 and 15 cm depth, in seven different types of soil, at temperatures 10, 15, 20, 25, 30 and 35 ºC and moisture field capacity of 50 and 100% in the absence of the host plant. Aac1Rif was detected in melon tissues at 0, 5 and 10 cm until 21 days and at 15 cm until 14 days. The highest and lowest relative extinction rate of the population (RERP) for Aac1Rif occurred respectively in fruit tissues and leaf tissues at depths of 0 and 5 cm. Aac1Rif survived in seven types of soil only for three days. The lowest RERP occurred at 10 or 15 ºC and the highest at 30 or 35 ºC. Greater concentrations of Na+, silt, and greater populations of actinomycetes and Trichoderma were correlated with highest RERP of the Aac1Rif in the soil. There was significant difference between RERP at 100% and 50% of field capacity. The soil was not considered potential primary source of A. citrulli inoculum. Infected melon fruits and leaves in soil were considered as such sources, at least for 21 days.

Survival of Erwinia psidii in epiphytic, soil and eucalyptus leaf debris conditions

“…Leaf debris from clones buried under both soil conditions significantly increased leaf decomposition and shortened the survival of E. psidii. This is directly related to moisture and soil properties that influence leaf decomposition (Alves et al, 2018;Graham & McGuire, 1987), which accelerates the decline of the pathogen population in the leaf (Goto et al, 1975;Sikirou & Wydra, 2004). Specifically, in non-sterile soil for both eucalyptus clones, bacterial survival in the leaves was even lower compared to the sterile soil (Figures 5c and 6c).…”

“…Typical soil invaders, these bacteria become easy targets for autochthonous antagonistic agents present in soil microbiota. Although further studies are needed to elucidate the effects of native soil from eucalyptus forests on the Erwinia psidii population, our hypothesis is that the decline of the bacterial population may have occurred due to antagonistic microbial activity (Alves et al, 2018;Choi et al, 2019;Fulcon, 1920;Graham et al, 1989;Janse, 2005;Kritzman & Zutra, 1983). Hildebrand et al, (2001) attributed the short persistence of E. amylovora in non-sterile soil to the toxic derivatives produced by native microorganisms, as well as the pathogen's poor ability to compete for nutrients.…”