ISHS Acta Horticulturae 705: V International Walnut Symposium
RESISTANCE ATTITUDE OF JUGLANS REGIA L. PROVENANCES TOWARDS ANTHRACNOSE (GNOMONIA LEPTSTYLA (FR.) CES ET DE NOT.) |
| Authors: | N. Anselmi, A. Mazzaglia, L. Scaramuccia, C. De Pace |
| Keywords: | English walnut, progenies, genetic selection, tolerance, Marssonina juglandis |
| Abstract:
Anthracnose by Gnomonia leptostyla is one of the most important diseases of walnut for timber production; it causes necrosis on leaves and branches and premature phylloptosis often with very relevant damages. An investigation on the resistance to anthracnose infections of eight Italian provenances of walnut (Juglans regia L.), each represented by some half-sib progenies (HS), selected for timber and planted in two different plantation sites, was carried out. Twenty-two HS families were considered, some of them were contemporarily present in each plantation, others in only one. The incidence of the disease on each of about 400 trees (phenotypes) was evaluated during the summer 2001 both by the “number of necrotic spots on 100 cm2 of leaf surface” and by the “percentage of leaf surface that underwent necrosis”. During the following autumn the occurrence of premature phylloptosis was also monitored. The collected data has been arranged in two-way contingency tables and subjected to a goodness of fit test of the observed frequencies. The χ2-test of independence have been used to identify the provenances with the highest proportion of J. regia HS progenies resistant to anthracnose. Interestingly, the different environmental conditions, related to plantation site, influenced the whole disease intensity but not the specific behaviour of each single provenance towards the disease. None significant difference was observed among the HS families. On the other hand, two provenances, Ponte Biforco and Carda, demonstrated to be the source of highest proportion of resistant HS plants; Borgo alla Collina showed intermediate proportion of resistant HS plants and the provenances Rifiglio, Ponte a Poppi and the group of provenances named “others” (Arcidosso, Scopetone and Arboreto ISSA) were sources of the lowest proportion of resistant HS plants. There is statistical correlation between anthracnose incidence and premature phylloptosis. Considering the phylloptosis, the provenances Ponte Biforco, Carda and Rifiglio appeared to be more tolerant than others. The information obtained on provenances resistant to anthracnose could be very valuable as basis for the organisation of breeding resources and the production of improved material to be used in new plantations. | |
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