Use of Thermotherapy and Natural Antifungal Compounds against Post Harvest Diseases on Apples

In France, short hot water treatment (2/3min.) can now be applied in food industry. As far as Ph/yctaena vagabunda is concerned (Ienticel spot disease or -G/oeosporiuma) hot water treatments are very effective. We know now more about the hot water risk injuries : only a few varieties can be treatAn .aL52. aC. By contrast, at 50°C a lot of varieties are not susceptible tO hot water risk injury. Unfortunately Golden delicious apples can not b_e_trèai.acLlt-5G-2Cf3 min., a slight change of skin coloration is unacceptable commercially. In fact, Golden delicious apples are the most susceptible to thermotherapy. In this case it is possible however to lower the temperature up to 48 aC. Such a treatment is completely safe for ali varieties assayed, but the efficacy is less than the 50 aC treatment. In that case we can use some natural antifungal compounds extracted from edible plants. Eugenol and natural clove oil, have been selected in our laboratory as the best antifungal compounds in fight lenticel spot disease. Considerable experiments have been performed on Golden delicious apples, finally a combination of hot water treatment (48 aCf3 min.) and eugenol (1,5g a.i.ll) gives a hight efficacy without any skin injury. A prolonged antifungal effect was obtained as expected. Hot water treatment can be applied immediatly in food industry. In the case of eugenol, we have to wait 2003 to get it commercially available for organic farmers (XEDA INTERNATIONAL). If we are able in food industry to combine hot water treatment, the use of natural compounds and for biofungicides (such as yeasts), it could be reasonably envisaged to obtain a very high efficacy close to that of chemical treatments

Resistance to fungicides and streptomycin in Phytophthora parasitica : genetic determinism and use in hybrid determination

Progeny of #Phytophthora parasitica$ derived from the pairings between metalaxyl-resistant MET.1 (A2) carrying homozygous dominant resistance and S1 (A1) wild-type consisted of selfs from each parent and hybrids carrying heterozygous dominant resistance. Similar results were obtained when dimetomorph-resistant DT.1 (A1) carrying homozygous dominant resistance was paired with wild-type S2 (A2). Progeny from the pairing between homozygous Str resistant (A1) to streptomycin and A2 resistant to metalaxyl consisted of selfs and hybrids resistant to either streptomycin or metalaxyl but not both. These results suggest that streptomycin-resistance is cytoplasmic. Progeny from the pairing between homozygous metalaxyl-resistant MET.1 (A1) and homozygous Str (A2) resistant to streptomycin consisted of 28 selfs from A1, 32 selfs form A2, 2 hybrids resulting from the union of A1 oogonium with an A2 antheridium. Progeny from the pairing between homozygous dimetomorph and streptomycin-resistant DT.1 (A1) with wild-type S2 (A2) consisted of 22 selfs A1, 14 selfs A2 and 12 hybrids, two of them resulted from the union A2 oogonium with an A1 antheridium. (Résumé d'auteur

Dimethomorph and metalaxyl sensitivity in somatic hybrids of Phytophthora parasitica obtained by protoplast fusion

Protoplasts were successfully isolated from wild-type and mutant strains of #Phytophthora nicotianae var. #parasitica using Novozym 234. Putative somatic hybrids were recovered following protoplast fusions from the first time to dimethomorph resistant strain P 310 (Dim r) or metalaxyl P 26 (Met r) by selection on agar amended with dimethomorph and metalaxyl. Fusion products from this cross were resistant to dimethomorph and metalaxyl. Zoospore progeny from the fusion products retained this phenotype, suggesting that nuclear fusion had taken place. (Résumé d'auteur

Olive anthracnose: a yield- and oil quality-degrading disease caused by several species of Colletotrichum that differ in virulence, host preference and geographical distribution

Pathogen profileOlive anthracnose causes fruit rot leading to its drop or mummification, resulting in yield losses and the degradation of oil quality. Taxonomy and distribution: The disease is caused by diverse species of Colletotrichum, mostly clustering in the C. acutatum species complex. Colletotrichum nymphaeae and C. godetiae are the prevalent species in the Northern Hemisphere, whereas C. acutatum sensu stricto is the most frequent species in the Southern Hemisphere, although it is recently and quickly emerging in the Northern Hemisphere. The disease has been reported from all continents, but it attains higher incidence and severity in the west of the Mediterranean Basin, where it is endemic in traditional orchards of susceptible cultivars. Life cycle: The pathogens are able to survive on vegetative organs. On the fruit surface, infections remain quiescent until fruit maturity, when typical anthracnose symptoms develop. Under severe epidemics, defoliation and death of branches can also occur. Pathogen species differ in virulence, although this depends on the cultivar. Control: The selection of resistant cultivars depends strongly on pathogen diversity and environmental conditions, posing added difficulties to breeding efforts. Chemical disease control is normally achieved with copper-based fungicides, although this may be insufficient under highly favourable disease conditions and causes concern because of the presence of fungicide residues in the oil. In areas in which the incidence is high, farmers pathogen interactions is basal for the deployment of durable and effective disease control strategies, whether based on resistance breeding, agronomic practices or biological or chemical controlinfo:eu-repo/semantics/publishedVersio

Relevance of hot water treatments for decay control

In France, postharvest decay can lead to important losses in the case of stone fruits, as for pome fruits. Many farm-research trials with natural fungicides (vegetal extracts, mineral compounds) gave no satisfying results yet, and conventional growers also face difficulties to manage diseases with resistance appearance, and inputs reduction strategy to fit consumers expectations. Postharvest treatments seem to have an interest to decrease development of decay (Monilia sp., Rhizopus sp., Penicillium sp.,...) in storage rooms. Hot water treatment offers many advantages (compared to active compounds used after harvest) that will be presented hereafter. Its use in packing houses however remains tough, since cultivar susceptibility to heat injury may vary, professional needs and constraints are often different, and because industrial offer is still limited