Results of studies on plant health in organic cultivation on the background of other farming systems

A. Lukanowski1, A. Baturo1, Cz. Sadowski1 and J. Kus2

Abstract - Investigations concerned effect of organic and other farming systems on cereal health status. Research material were roots, stem bases, leaves, ears and harvested grain of winter wheat and spring barley. Results showed lower health of spring barley in organic system, while this farming system did not affect winter wheat negatively. Fusarium spp. were prevalent among pathogens of winter wheat in all systems and in the case of spring barley - in integrated and conventional system. The exception was organically grown barley where Bipolaris sorokiniana dominated. Alternative seed treatment methods used in these studies did not limit growth of B. sorokiniana considerably, but some tendencies to lower incidence of this species on barley seedlings were noted. Antagonistic strain of Trichoderma viride did not show advantageous effect as biological seed treatment agent. 

Introduction
The cereals are main element in the crop rotation schemes applied in Poland. They are affected by a number of diseases and pests. A change of farming system, from conventional to integrated or organic, may lead to an increase of the number of predominant crop diseases (Tamis and Brink, 1999). Certified organic farms are obliged to fulfill many legal requirements, but regulations concerning plant health and quality of organic products are still not completed. There are some data (Trewavas, 2001) indicating that food from organic farms may be more exposed for contamination by mycotoxins produced by fungi than conventional food, where anti-fungal chemical agents are applied. 
	Information on phytopathological aspect of health of plants grown in organic system often are of popular nature and are not based on scientific data. That was the main reason to begin the series of research concerning an effect of different farming systems on cereal health and yield quality (fungal species composition occurring on roots, stem bases and grain) with the special respect to organic cultivation. Such information is of great importance for disease incidence control in cereal crops. 

Methods
Research on health of winter wheat and spring barley were conducted in 1998-2004 on experimental fields cultivated in organic, integrated and conventional systems as well as in monoculture (only in the case of winter wheat) owned by Institute of Soil Science and Plant Cultivation in Pulawy as well as in certified private organic farm in Kielpin (Kujawy and Pomerania voivodship). 
	Research material were roots, stem bases, ears and harvested grain. Plant health was determined with a proper scales, results were transformed into Disease Index (DI) and statistically analyzed. Diseased roots, stem bases and harvested grain were also mycologicaly analyzed. Plant material was put onto Petri dishes with acidified (pH 5.5) PDA medium and outgrowing fungi were determined with mycological keys.

Results
Infestation of roots and stem bases of wheat varied and highly depended on growth phase. 
	Causal agents of disease symptoms observed on wheat were mainly fungi from genus Fusarium. They occurred in lower intensity on stem bases of plants cultivated in organic system in comparison with other analyzed systems. In the case of roots there were no differences in their health with the exception for monoculture where DI was the highest (Table 1).

Table 1. Effect of farming system on infestation of winter wheat roots and stem bases, Pulawy 1999-2004 (DI in %).
System	
Organic	Integrated	Conventional	Monoculture	
Root infestation	
16.9
b*	16.8
b	17.0
b	50.5
a	
Stem base infestation	
36.5
d	44.0
b	40.5
c	52.4
a	
*Values in the same line followed by different letters are significantly different
	Occurrence of Fusarium Head Blight (FHB) varied in particular years of investigations, but the lowest per cent of infected ears was noted in organic system (Table 2).
	Settlement of harvested grain by Fusarium spp. was differentiated and depended the most on year of research (weather conditions during infection) and in lower degree on cultivation system and variety. Generally, lower number of grain infected with Fusarium spp. was observed in organic system. This result deserves to be emphasized because chemical protection of organically grown plants is not allowed, so potential risk of occurrence of these fungi on grain harvested here may be high, especially during warm and wet growing seasons.

Table 2. Per cent of winter wheat ears with FHB symptoms, Pulawy 1999-2002.
System	Year	
	1999	2000	2001	2002	1999-2002	
Organic	9.2 b*	0.5 ab	0.9 b	20.0 c	7.7 c	
Integr.	17.0 a	0.6 ab	4.8 a	27.8 b	12.6 a	
Conven.	19.1 a	0.1 b	0.8 b	19.5 c	9.9 b	
Monoc.	19.6 a	1.0 a	1.3 b	32.6 a	13.6 a	
*Values in the same column followed by different letters are significantly different
	Spring barley cultivated in organic system showed higher level of infestation by fungi in comparison to conventional and integrated system. The serious problem is the fungus, Bipolaris sorokiniana, that infects plants from the earliest stages and causes foliar spot blotch, root and stem base rot, black point on grains as well as head and seedling blight. Severe infection can result in serious yield decrease or drying out of infected plants producing no seeds (Knudsen et al., 1995; Kumar et. al., 2002). Ears and grain produced in organic system were more intensively (over 60%) infected by B. sorokiniana, while Fusarium spp. dominated in conventional and integrated system (Table 3). 

Table 3. Grain infected (%) by B. sorokiniana and Fusarium spp. in organic (O), integrated (I) and conventional (C) farming systems in 1998-2001
Fungus	O	I	C	
Bipolaris sorokiniana	65.3	7.8	16.8	
Fusarium avenaceum	5.8	28.8	22.3	
Fusarium culmorum	1.0	3.5	4.8	
Fusarium graminearum	1.8	6.0	3.8	
Fusarium poae	15.3	30.2	32.5	
	The main species causing leaf disease (net blotch) was Drechslera teres that was noted in high intensity in organic system. 
	Fusarium ssp., apart from harvested grain, were also isolated from roots and stem bases. Results showed that Fusarium spp. was not more serious problem in organic system. Further, grain obtained in organic system can be less infected by Fusarium spp. It is extremely important from a nutritional point of view because of potential ability of these fungi to produce mycotoxins. These results do not confirm reports of Eltun (1996), who noted higher concentration of deoxynivalenol and nivalenol in samples of organically produced grain in comaprison with these collected in conventional system. Barley grain, harvested in the organic system, contaminated mainly with B. sorokiniana, can be a threat especially in the case of using it as sowing material. To minimise the sources of primary infection, the studies on usefulness of natural substances approved for seed treatment in organic farming were also conducted. Effect of grain treatment with Biochikol 020 PC (chitosan), Biosept 33 SL (grapefruit seed extract), conidia of antagonistic strain of Trichoderma viride and thermotherapy on seedlings health in comparison with control trial was tested
	Four year long studies revealed that grain treatment with Biosept resulted in a little lower plant infection. This preparation also stimulated development of antagonistic species Gliocladium roseum. Obtained results showed that alternative seed treatment methods used in these studies did not limit fungal growth considerably, but some tendencies to lower incidence of B. sorokiniana on barley seedlings were observed. Antagonistic strain of T. viride did not show advantageous effect as biological seed treatment agent. 
	
Conclusions
1. Organic plant production does not have to result in reduced wheat grain quality in the aspect of its settlement by Fusarium spp. Consumers of organic products should not be afraid of higher risk of mycotoxin accumulation comparing with grain harvested in other cultivation systems.
2. Organic system was more favourable for development of B. sorokiniana compared with other systems. It suggests that organically produced sowing material could be a threat for plant health. Thus, special attention should be paid to minimise the sources of primary infection with methods acceptable in organic system

References
Eltun, R. (1996). Norvegian Journal of Agricultural Sciences 10:7-21.
Knudsen, I., Hockenhull, J. and Jensen, D.F. (1995). Plant Pathology 44:467-477.
Kumar, J.P., Schäfer, R., Hückelhoven, G., Langen, H., Baltruschat, E., Stein, U., Nagarajan, K. and Kogel, H. (2002). Molecular Plant Pathology 3(4): 185-95.
Tamis, W.L.M. and van den Brink W.J. (1999). Conventional, integrated and organic winter wheat Agriculture, Ecosystems and Environment 76:47-59.
Trewavas, A. (2001). Nature 410:409-410.