Joseli S. Tatagiba

Biological control ofBotrytis cinerea in residues and flowers of Rose (Rosa hybrida)

Microbial isolates from living petals, petal residues and leaf residues of rose, and from laboratory collections, were evaluated for control ofBotrytis cinerea in rose. In leaf residues artificially infested withB. cinerea, isolates of the filamentous fungiGliocladium roseum, FR136 (unidentified) andTrichoderma inhamatum reduced sporulation of the pathogen by >90%, other filamentous fungi were 25–90% effective, and those of yeasts and bacteria were <50% effective. In artificially inoculated petal residues, no microbe reduced sporulation ofB. cinerea by >75%, but isolates ofCladosporium oxysporum and four yeasts were 51–75% effective, and three filamentous fungi, eight yeasts andBacillus subtilis isolates were 26–50% effective. Isolates ofT. inhamatum, C. oxysporum andG. roseum performed best againstB. cinerea among isolates evaluated in leaf residues naturally infested with the pathogen and indigenous microorganisms. Totals of ten isolates of filamentous fungi (includingC. oxysporum andC. cladosporioides), two of yeasts and five ofBacillus subtilis completely prevented lesion production byB. cinerea in detached petals, and a further six isolates of filamentous fungi (includingG. roseum) and six yeasts were 90–99% effective. Isolates ofC. oxysporum, C. cladosporioides andB. subtilis, the most effective microorganisms againstB. cinerea in flower buds, reduced number of lesions in the range of 42–65% compared with 59–89% for à standard fungicide (vinclozolin). It is suggested that application of leading antagonists Jo living rose leaves and flowers should optimize control of inoculum production byB. cinerea when the tissues die. Optimal biocontrol of lesion production in flower buds requires a better understanding of the microenvironment of petals.

Dois novos sistemas de diagnose precoce da meleira do mamoeiro

Two new systems of early diagnosis of papaya sticky disease Papaya sticky disease was first reported affecting papaya (Carica papaya) in Brazil in the late 80s. Today this disease is found in the papaya production areas throughout Brazil, and in some of them it became the main limiting factor for the papaya industry. The primary disease symptom is an excessive exudation of highly fluid latex that becomes dark as result of oxidation and turns the fruit unmarketable. It is caused by a new virus that has an isometric particle (40-50 nm in diameter), and a unique 12 kb long dsRNA molecule. Since its diagnosis is done mainly by observation of the symptoms on the fruit, infected plants may be source of inoculum for several months before diagnosis. Another form of diagnosis is the detection of dsRNA from leaves and latex using CF11 columns. This is a laborious system not suited to large scale usage. The present work presents two cheap and fast diagnostic protocols. These protocols use latex obtained from fruits, leaves and stems, and are based on the extraction and visualization of nucleic acids. Presence of the virus is confirmed by the visualization of dsRNA on agarose (1%) gel in 1X TBE. Using these protocols it is possible to confirm the presence of the virus in young and assymptomatic plants.

Minimum number of assessment times to compare chemical control treatments for papaya fruit anthracnose

The chemical treatment evaluation in the field to control post-harvest fruit anthracnose (Colletotrichum gloeosporioides) requires a suitable disease incidence assessment on harvested papaya (Carica papaya) fruits. The minimum number of papaya fruit harvests was determined for valid treatment comparison in field trials for anthracnose chemical control. Repeatability analysis was done using previously published data. The coefficient determination (R2) estimate range, using four methods, and based on means of 12 assessment times, was 92.58 < R2 < 94.45%. The number of assessment times required for R2=90% varied from seven to nine. The R2 values of 85.1 < R2 < 91.3% estimated by ANOVA suggested that any seven successive assessment times were sufficient for treatment comparison.