BEHAVIOR OF SOME WALNUT VARIETIES UNDER JUVENILE PHASE TO BACTERIOSE AND ANTRACNOSE ATTACK

Florin Cristian Marin,Mihaela Sumedrea,Mirela Calinescu,Emil Chitu

doi:10.33045/fgr.v36.2020.06

Abstract

Walnut (Juglans regia L.) is an important species for the European and Romanian fruit growing, but, despite its resilience, it can be attacked by specific diseases such as bacteriose (Xanthomonas arboricola pv. juglandis (Pierce) Dye) and anthracnose (Gnomonia leptostyla D.C. Trav) which due to the climatic changes became more active than in the past decades. This paper presents results on the behavior of 48 walnut varieties preserved into the new collection established at RIFG Pitesti Romania to the field infections with these pathogens, their resilience in juvenile phase and their overall classification. The data collected reveal that the microclimate conditions during years of the study (2018-2020) were very favorable for the walnut diseases attack. The correlations monthly average temperatures (*C) -- average leaf wetness hours sum (h/month) and monthly average precipitation sum (mm) -- average leaf wetness hours sum (h/month), contributed to the infections speed and diseases development on the studied biologic material. For these the coefficients R2=0.6086*** (r=0.7801***, n=35) and R2=0.5584*** (r=0.7472***, n=35) were calculated. Under such circumstances, the best behavior on the walnut blight had the varieties: 'Făleşti', 'Geoagiu 453', 'Jupâneşti', 'Miroslava', 'Novaci', 'Timval', 'Valcor', 'Valrex', 'Velniţa', 'Victoria' and 'Vlădeşti' with damages degree DD% on leaves no higher than 0,03. Also, The most resilient on anthracnose attack on leaves were the varieties: 'Argeşean', 'Gemenea 20', 'Pestişani', 'Pecianski', 'Schinoasa', (DD%=0.13), 'Valcris' (DD%=0.11), 'Codrene', 'Secular RM', 'Sibişel 265' (DD%=0.10) and 'Valrex' (DD%=0.05).

Highlights

Solemn presence in our national culture and history, the walnut (Juglans regia L.) is a constant presence in the Romanian landscape and national fruit growing, being appreciated for its fruits, whom kernel is consumed both fresh and processed, for his high quality wood, and for the ecological and aesthetical attributes of the tree
The data collected reveal that the microclimate conditions during years of the study were very favorable for the walnut diseases attack
On can see the precipitation deficit in April, but leaf wetness was ranging between 79-130 h/month in May, 168.8-188.3 h/month in June and 98.3-139.3 h/month in July which were very favorable for walnut blight exponential development and infection

Summary

Introduction

Solemn presence in our national culture and history, the walnut (Juglans regia L.) is a constant presence in the Romanian landscape and national fruit growing, being appreciated for its fruits, whom kernel is consumed both fresh and processed, for his high quality wood, and for the ecological and aesthetical attributes of the tree. It is very important the use of walnut as source of pharmaceutical active substances. On the infected shoots the necroses progress daily, the shoots die progressively or are improper to be used for grafting

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