Organic amendments conditions on the control of Fusarium crown and root rot of asparagus caused by three Fusarium spp.

Abstract

<p><em></em><em>Fusarium oxysporum</em> (<em>Fo</em>), <em>F. proliferatum</em> (<em>Fp</em>) and <em>F. solani</em> (<em>Fs</em>) are causal agents associated with roots of asparagus affected by crown and root rot, a disease inflicting serious losses worldwide. The propagule viability of <em>Fusarium</em> spp. was determined on substrate artificially infested with <em>Fo</em>5<em>, Fp</em>3<em> </em>or <em>Fs</em>2 isolates,<em> </em>amended with either poultry manure (PM), its pellet (PPM), or olive residue compost (ORC) and, thereafter, incubated at 30 or 35°C for different periods. Inoculum viability was significantly affected by these organic amendments (OAs) in combination with temperature and incubation period. The greatest reduction in viability of <em>Fo</em>5 and <em>Fs</em>2 occurred with PPM and loss of viability achieved was higher at 35°C than at 30ºC, and longer incubation period (45 days). However, the viability of <em>Fp</em>3 did not decrease greatly in most of the treatments, as compared to the infested and un-amended control, when incubated at 30ºC. After incubation, seedlings of asparagus `Grande´ were transplanted into pots containing substrates infested with the different species of <em>Fusarium</em>. After three months in greenhouse, symptoms severity in roots showed highly significant decreases, but <em>Fp</em>3 caused lower severity than <em>Fo</em>5 and <em>Fs</em>2. Severity reduction was particularly high at 30ºC (by 15 days incubation for <em>Fs</em>2 and by 30-45 days for <em>Fo</em>5), after PPM treatment, as well as PM-2% for <em>Fo</em>5<em> </em>and <em>Fs</em>2 incubated during 30 and 45 days at both temperatures, and with ORC (15-30 days incubation). Moreover, assessment of plants fresh weight showed significantly high increases in <em>Fo</em>5 and <em>Fs2</em>, with some rates of the three OAs tested, depending on incubation period and temperature.<br /><strong></strong></p>