FUSARIUM HEAD BLIGHT OF WINTER RYE ( Secale cereale L . )

Investigations on Fusarium head blight of rye were carried out in the years 2005-2007 on 10 production fields in the Lublin region. The percentage of heads showing the fusariosis symptoms in the years 2005-2007 ranged from 0 to 7%. Mycological analysis of kernels and chaff obtained from heads with Fusarium blight (scab) symptoms showed that Fusarium avenaceum, Fusarium culmorum and Fusarium sporotrichioides were the largest threat to heads of this cereal. The species of Fusarium poae and Fusarium crookwellense were also isolated from infected rye heads. The dominance of particular species in infecting rye heads was determined by weather conditions.


INTRODUCTION
Fusarium head blight is a dangerous disease of cereals cultivated in different climatic zones (K i ec a n a , 1994; B o t t a l i c o , 1998; B o t t a l i c o and P e r r o n e , 2002; Š r o b a r o v á et al. 2008; M u th o m i et al. 2008).The first reports on scab of rye come from Canada from the 1950's.The species of F. avenaceum, F. culmorum, F. graminearum, F. poae and F. sporotrichioides were found to be the main cause of this disease (P a r r y et al. 1995; B o t t a l i c o , 1998; P a n i s s o n et al. 2003).For rye grown in Poland and Germany, F. culmorum and F. graminearum have a considerable importance in causing fusariosis of rye heads (K i e c a n a , 1988; M i e d a n e r et al. 2001; 2003).Among other species from the genus of Fusarium, some studies found the presence of F. avenaceum, F. poae and F. sporotrichioides as well as Microdochium nivale on infected heads of rye in our country (K i e c a n a , 1988; C h e ł k o w s k i , 1989; W a k u l i ń s k i and C h e ł k o w s k i , 1993).
By infecting heads and kernels of cereals, Fusarium spp.cause not only a decrease of the yield, but they are also dangerous to homoithermic organisms because the latter produce toxic metabolites in the infected kernels and these include trichothecene compounds, zearelenon, moniliformin and many others (M i e d a n e r et al. 2001; 2003; B o t t a l i c o and P e r r o n e , 2002).
Due to the lack of reports in phytopathological literature of recent years on Fusarium spp.colonizing rye heads and because of the common occurrence of toxin-producing species from the genus of Fusarium on other cereals, studies were undertaken on Fusarium head blight of rye grown in the Lublin region.
In each year of the study, the percentage of heads with fusariosis symptoms of was determined at the stage of full maturity of kernels (92 in Tottman's scale, 1987).Following the pattern of studies on spring barley (K i e c a n a , 1994), 400 heads (100 heads from each site of particular plantations) were analyzed from each field.
Next, 20 heads infected by Fusarium spp.were taken for laboratory analysis from each of the studied plantations.
100 kernels and 100 chaff from the heads, from each plantation, were taken for mycological analysis.
A mineral medium (Ł a c i c o w a , 1970) was used for the isolation of fungi from the plant material.The method of conducting the analysis was like that in the study by M i e l n i c z u k (2001).
Fungi from the genus of Fusarium were identified using the keys by N e l s o n et al. (1983) and B u r g e s s et al. (1988).Other species were identified according to the keys and monographs by K i e c a n a et al. (2009).
The information concerning the weather conditions during the investigations was obtained from the Department of Agrometeorology, University of Life Sciences in Lublin.

RESULTS
Field observations carried out at the stage of full maturity of kernels in rye sown on the plantations of the Lublin region pointed to the occurrence of plants with fusariosis symptoms on the heads.In all the plantations, the heads were diminished, whereas on chaff there was visible an orange-rosy powder, especially at the points of contact with the rachis, which consisted of the mycelium and spores of Fusarium spp.The kernels from the infected heads were usually smaller and of white-greyish colour.In 2005 the percentage of heads showing fusariosis symptoms ranged from 0 to 5, in 2006 from 0 to 0.5, and in 2007 from 1 to 7 (Fig. 1).As a result of mycological analysis of kernels from the heads with the disease symptoms, over the 3 years of the study 2837 colonies of fungi were isolated, while 929 isolates were obtained from chaff (Table 1).In the years 2005, 2006 and 2007 Fusarium spp.colonies amounted to, respectively, 33%, 41% and 21% of all fungal isolates from kernels, whereas isolates from chaff accounted for 41% (2005), 23% (2006) and 48% (2007), and they were represented by: F. avenaceum, F. crookwellense,F. culmorum. F. poae and F. sporotrichioides (Table1).Regardless of the vegetation season, the species of F. avenaceum and F. culmorum distinguished themselves by causing general infection of heads.During the study years, F. avenaceum isolates amounted from 35.7% (2005) to 42.5% (2007), whereas isolates of F. culmorum from 25.8% (2006) to 29.2% (2005) of all Fusarium spp.from kernels (Fig. 2).In the case of chaff, F. avenaceum isolates amounted from 33.3% (2005) to 47.7% (2006), whereas F. culmorum from 30.0% (2007) to 37.8% (2005) of all Fusarium spp.from chaff (Fig. 3).
Besides, in each year of the study, the species of F. sporotrichioides were frequently obtained from infected kernels, and their isolates amounted from 11.4% of total Fusarium spp.from kernels in 2007 up to 27.0% in 2006 (Fig. 2).On the other hand, in the case of chaff, the colonies of this fungus constituted from 13.6% to 24.1% of all Fusarium spp.(Fig. 3).The proportion of F. crookwellense and F. poae in the years in question ranged, respectively, from 2.9% to 8.7% and from 5.6% to 9.6% of all isolates from kernels (Fig. 2), and from 0% to 1.8%, and from 1.8% to 7.1% of total colonies from chaff (Fig. 3).
Isolates of other fungi belonged to the following: Alternaria alternata (37.68% of all isolates from kernels and chaff over the 3 years of the study), Aspergillus flavus (0.16%), Bipolaris sorokiniana (0.21%), Botrytis cinerea (0.27%), Chaetomium globosum (0.24%), Cladosporium cladosporioides (3.24%), Epicoccum nigrum (23.74%),Penicillium verrucosum var.cyclopium (0.21%) as well as nonsporulating forms (1.3%) (Table 1).100) 1055( 100) 353 ( 100) 2837( 100) 929 ( 100) 3766 ( 100) k -isolates obtained from kernels, ch -isolates obtained from chaff The temperature in the Lublin region during the 2005 growing season (the period of heading, flowering and grain maturation of winter rye) was higher as compared to the long-term means in months of April, May and July from 0.2 o C to 2.1 o C, while in June air temperature was about 0.4 o C lower compared to the long-term means.On the other hand, rainfall exceeded the longterm means in May and July by, respectively, 67.52% and 41.13%.The lowest rainfall was recorded in April of that year -only 47.94% of the normal level. In 2006 air temperature between April and July was higher than the long-term mean by 0.5 o C (June) to 4.2% o C (July).The percentage of normal rainfall ranged from 8.74 in June to 269.06 in July.In 2007 air temperature was higher than the long-term mean by 1.3 o C in April to 2.0 o C in May.On the other hand, rainfall exceeded the long-term mean in May, June and July, respectively, by 37.61, 29.31 and 11.82%.The lowest amount of rainfall was observed in April of 2007 -44.84% of the normal level (Table 2).

DISCUSSION
The results of the study carried out in the years 2005-2007 show that Fusarium head blight of rye grown in the north-eastern part of the Lublin region occurred in each year of the study, with the proportion of infected heads not exceeding 7%.The studies conducted in the conditions of the Lublin region indicate a similar frequency in the infection of triticale heads by fungi of the Fusarium genus (Kiecana, 1986), while this frequency was higher in the infection of wheat heads (Ł a c i c o w a et al. 1987) and oat panicles (M i e l n i c z u k , 2001).
The studies show that the species of F. avenaceum, F. culmorum and F. sporotrichioides  The common occurrence of F. avenaceum on rye heads in each year of the study, varying from year to year, is explained by high tolerance of this fungus to temperature and humidity (K i e c a n a , 1994; M i e ln i c z u k , 2001; K i e c a n a et al. 2003; X u et al. 2008).
The present authors' earlier studies showed that the species of F. avenaceum posed a threat to rye grown in the Lublin region, mainly due to its high harmfulness to seedlings of this cereal (K i e c a n a et al. 2009).
The present study confirmed that the infection of rye heads by F. culmorum -like in the case of barley heads and oat panicles -is favoured by hot weather with passing rainfalls (K i e c a n a , 1994; M i e ln i c z u k , 2001; M i e d a n e r et al.1993; 2001).In the case of the present study, such weather conditions occurred in the years 2005 and 2007 and it is these conditions that account for a considerable proportion of the species under discussion in the infection of rye heads in these growing seasons.
It has been established that in Poland F. culmorum has a significant proportion in the infection of root and stem bases of rye (P a ł y s et al. 2004; K i e c a n a et al. 2009).
In 2007 the species of F. crookwellense, besides F. culmorum, occurred on rye heads with greater frequency as compared to the other years.It should be supposed that weather conditions conducive to the development of this fungus are similar to the requirements of F. culmorum as far as the climatic conditions are concerned.
Every year, a considerable number of F. sporotrichioides isolates were obtained from the analyzed rye heads with the symptoms of fusariosis.Earlier, this species was isolated from the heads of barley (K i e c a n a , 1994; P e r k o w s k i et al. 1997), wheat (T ó t h , 1997) and oat panicles (M i e l n i c z u k , 2001).Fusarium sporotrichioides has been found to be the cause of chaff necrosis and leaf spot in the state of Minnesota (V a r g o and B a u m e r , 1986), changes in the colour and consistency of barley and oat kernels (K i e c a n a , 1994, M i e l n i c z u k , 1999) as well as necrosis of roots and leaf sheath of oat seedlings (K i e c a n a and K o c y ł a k , 1999).
The species frequently isolated from the analyzed rye heads included F. poae.This fungus commonly occurred on oat panicles in the Lublin region (K i e c a n a and P e r k o w s k i , 1998; K i e c a n a et al. 2005).Under different cultivation conditions, F. poae is considered to be the cause of fusariosis of cereal heads in Europe (T ó t h , 1997; T h r a n e , 2001; M i e l n i c z u k , 2001), and in other continents (T e k a u z et al. 2004; M u t h o m i et al. 2008).
Like in the case of other cereals, A. alternata was frequently observed on rye heads (K i e c a n a , 1994; M i e l n i c z u k , 2001; M u t h o m i et al. 2008).
Epicoccum nigrum, which was frequently isolated from rye kernels and chaff, was found to be the cause of wheat leaf spot (G o e l and G u p t a 1979 according to T i n g and R e e d l e r 1991).
The presence of the polyphagous species of B. cinerea on the heads was probably caused by the stimulating effect of pollen on the germination of spores, which made heads infection at the stage of anthesis possible.Earlier investigations of P o k a c k a (1987) concerning rye allow such an interpretation.

Fig. 1 .
Fig. 1.Percentage of rye heads with fusarium head blight symptoms in the years 2005-2007 are the cause of rye scab, as in the case of other cereals (K i e c a n a , 1994; M i e l n i c z u k , 2001; V a n č o et al. 2007; Š r o b a r o v á et al. 2008).The proportions of particular species in infecting heads are determined by weather conditions (K i e c a n a , 1994; M i e l n i c z u k , 2001; B o t t a l i c o and P e r r o n e , 2002; X u et al. 2008).
Fig. 2. The proportion of individual species in all Fusarium spp.isolates obtained from rye kernels in the years 2005, 2006 and 2007Fungi isolated from rye kernels and chaff obtained from heads with fusariosis (scab) symptoms Fig. 3.The proportion of individual species in all Fusarium spp.isolates obtained from rye chaff in the years 2005, 2006 and 2007Table 1

Table 2
Air temperature and rainfall in the growing season -in the period of heading, flowering and grain maturation of winter rye, in the years[2005][2006][2007]