HEALTH STATUS OF TWO PLANTATIONS OF TULIP NEAR PULAWY AND FUNGI ISOLATED FROM FOLIAR PARTS AND BULBS

Agnieszka Piwoni
Department of Plant Protection and Quarantine, Agricultural University in Lublin, Poland

ABSTRACT

The research was carried out over the years 2000-2002, on 20 tulip cultivars grown in two commercial tulip plantations located in the South-Eastern Poland. The healthiness of plants was examined at the beginning and the end of flowering, and after digging and storage time.
The disease index values of above-ground plant parts ranged from 10.4 to 30.2. The most infected cultivars were ‘Christmas Surprise’, ‘Apricot Beauty’ and ‘Generał Eisenhower’.
From the above-ground plant parts most frequently isolated species were Alternaria alternata. Species Botrytis tulipae occurred more frequently on the foliar parts of tulips cultivated in Wojszyn at the beginning of flowering.
The mean disease index values of bulbs ranged from 2.5 to 10.4. The most infected cultivars were ‘Apricot Beauty’, ‘Oriental Splendour’ and ‘Czerwony Kapturek’.
From the diseased bulbs of tulips after digging, as well as after storage, the greatest number of fungi isolates belonging to the species P. verrucosum var. cyclopium were obtained.

Key words: tulip, cultivars, fungi, isolation, foliar parts, bulbs, disease index.

INTRODUCTION

Due to large diversity of flower shapes and colours, and the possibility of growth for different terms as park-, home-, garden-, cut-, and even pot-flowers, the tulips belong to the most popular spring flowers.

At present, the continuous increase of demand for planting suitable tulip bulbs is observed [14]. The high demand of home market for tulip bulbs requires an increase of the crop area, and more intense attention to the healthiness of plantations [2].

The growing cycle of ornamental bulb plants is also the time when many fungal diseases are spreading. The plants could be affected by pathogens, which survive in the soil or are born with bulbs in form of sclerotia and spores [23]. Very common and dangerous fungus species occurring on the tulip is Botrytis tulipae, which causes the disease called ‘tulip fire’. It causes severe damage wherever tulips are grown and has even been responsible for the total loss of tulip crops in some seasons [11]. In the springtime, when the shoots emerge above ground it comes to infection, the sprouts became covered with necrotic spots with mold and plenty of conidia. They start to spread the disease and initiate the occurrence of leaf and flower spots [23].

Fusarium oxysporum f.sp. tulipae is recognized as one of the most dangerous pathogens of tulips grown in Poland. High infected bulbs completely die off at the storage or after planting [24]. The fungus penetrates the bulb causing brown discoloration and dry rot of scales spreading up mostly from the roots and bulb base [23].

Penicillium verrucosum var. cyclopium causing ‘blue mold’ of stored tulip bulbs could impend of tulips plantations healthiness [23]. The fungi of Penicillium genus could penetrate the bulbs of ornamental plants through the wounds and natural cracks created by emerging roots and through the mechanically damaged fleshy scales. The temperature and humidity conditions in the storage room have also a strong effect on the infection by these pathogens of ornamental flowers bulbs in the resting phase [22].

Detailed description of diseases and pests of tulips was given by Gabarkiewicz et al. [12].

An intend of the present study was to estimate the disease index of 20 tulips cultivars grown in the South-Eastern Poland, identify of isolated fungi species and describe of occurring disease symptoms in connection with isolated fungi.

MATERIAL AND METHODS

The research was carried out over the years 2000-2002, on two commercial tulip plantations located in Wawolnica and Wojszyn near Puławy, with total area of about 2 ha. The healthiness of 20 tulip cultivars was examined in four periods – at the beginning and the end of flowering, and after croping and storage. At the flowering period, 20 randomly selected plants (4 × 5, diagonal of the beds) from each cultivar were evaluated and the samples of leaves and flowers showing disease symptoms were taken for examination. After digging and storage, 100 randomly selected bulbs from each cultivar were evaluated and the samples of diseased bulbs were taken for examination. On the plantation in Wawolnica the disease index was estimated for the following cultivars: ‘Angelique’, ‘Apricot Beauty’, ‘Barcelona’, ‘Czerwony Kapturek’, ‘Fusilier’, ‘Ile de France’, ‘Merry Christmas’, ‘Parade’, ‘Purissima’ and ‘Toronto’, and on the plantation in Wojszyn the cultivars: ‘Angelique’, ‘Apeldoorn’, ‘Apeldooorn’s Elite’, ‘Christmas Surprise’, ‘Generał Eisenhower’, ‘Merry Widow’, ‘Monte Carlo’, ‘Oriental Splendour’, ‘Powisle’ and ‘White Buqet’. On both plantations, the tulips were treated with certain pesticides. In Wojszyn, the plantation was sprayed with the following pesticides: Benlate 50 WP (benomyl), Dithane M45 WP (mancozeb), Sumilex 500 S.C. (procymidone) and Topsin 70 WP (methyl thiophanate). In Wawolnica, for the plants’ protection, the following chemicals were applied: Dithane 80 WP (mancozeb), Euparen 50 WP (dichlofluanid), Kaptan zaw. 50 WP (captan), Ronilan 50 WP (vinclozolin), Rovral Flo 255 S.C. (iprodione) and Owadofos 540 S.C. (phenitrothion). Also, the bulbs were dipped in a fungicide mixture containing Kaptan 50 WP (captan), Topsin 70 WP and Sumilex 500 S.C. right before planting.

On the plantation in Wawolnica, tulip bulbs were stored in the shed whereas in Wojszyn in the barn with ventilation fittings.

The meteorological data concerning the examined plantations and the observation period were obtained from Puławy Meteorological Station.

During the plant sampling, the intensity of the plants’ damage was estimated according to the five-degree scale:

0 – absence of disease symptoms,
1 – minor disease symptoms – covering less than 10% of above-ground plant parts or bulbs’ surface,
2 – low disease symptoms – covering from 10 to 25% of above-ground plant parts or bulbs’ surface,
3 – middle disease symptoms – covering from 25 to 50% of above-ground plant parts or bulbs’ surface,
4 – high disease symptoms – covering more than 50 % of above-ground plant parts or bulbs’ surface,

Subsequently, the disease index was estimated for each cultivar using McKinney’s formula [16]:

Disease index =

a – sum of products of numerical scale index (infection degree) and corresponding number of plants
b – total number of tested plants multiplied by the highest numerical scale index

The results were analyzed statistically using Duncan’s test.

The infected plant samples were examined in a laboratory. Plant tissue fragments were placed on PDA medium in Petri dishes under sterile conditions. From each cultivar, 10 Petri dishes with 10 tissue fragments each were made. After a 7-day incubation period in a controlled temperature of 20°C, fungous colonies were transferred to PDA slopes and subcultured for their identification. The Penicillium genus fungi were grown and identified on selective media – Malt Agar and Czapek – Dox, and Fusarium genus fungi on SNA medium. Identification of the fungi species was performed using popular keys and monographs [1, 3, 4, 8, 10, 15, 18, 20].

RESULTS

On the above-ground plant parts of the examined tulips the following kinds of disease symptoms were observed:

– necrotic spots on leaves and flowers,
– splitting and tearing up of the leaf blade,
– drying up and blackening of the leaves tips.

The plants, from which Alternaria alternata was isolated, had characteristic symptoms such as dried up leaf tips and were covered with the black sporulations of fungus. On the leaves, from which Botrytis tulipae was isolated, the small, dark surrounded edges, slightly sunken, covered with brown-gray mycelium lesions were observed. Sometimes, the spots lesions merged to become large blotches and the leaves became split and torn. On the flower petals a lot of small light-brown necrotic spots were formed.

The tulip bulbs infected by Fusarium oxysporum were covered with dry, brown, leather-like lesions with darker border. The rot penetrated the flashy scales, which were covered with a cream coloured mycelium and mass of spores. Finally, the bulbs mummified.

From the bulbs showing dry, light sunken, yellow-brown lesions with dark brown margins, which surface was covered with green-blue mycelium and a mass of spores, the species Penicillium verrucosum var. cyclopium was isolated.

On the bulbs from which the species Botrytis tulipae was isolated, the occurrence of large, sunken, and brown-black in color lesions, bearing small, round, black sclerotia on their surface, were observed.

The evaluation of intensity of the above-ground plant parts damage showed that mean disease index values in the years 2000-2002 ranged from 12.5 to 27.5 on the plants grown on the plantation in Wawolnica, and from 10.4 to 30.2 on the plantation in Wojszyn (Table 1, Fig. 1, 2). The most infected cultivars on the plantation in Wawolnica were ‘Apricot Beauty’ (27.5), ‘Merry Christmas’ (18.8) and ‘Angelique’ (17.5), but the least infected cultivars were: ‘Fusilier’ (12.5), ‘Czerwony Kapturek’ (13.5), ‘Barcelona’ (14.8) and ‘Parade’ (14.8). On the tulip plantati on in Wojszyn, the highest disease index values were recorded for the following cultivars: ‘Christmas Surprise’ (30.2), ‘Generał Eisenhower’ (22.3), ‘Apeldoorn’ (21.7) and ‘Oriental Splendour’ (21.0), and the lowest for ‘White Buqet’ (10.4).

As a result of laboratory mycological analysis of infected plants, a total of 2208 fungal colonies, representing 29 species, were obtained from the above-ground plant parts at the beginning of flowering period, but 2078 fungal colonies, representing 23 species were obtained at the end of flowering period (Table 3). Among them, the species Alternaria alternata dominated. It was isolated from 70.9% of analyzed plant samples and its isolates made up 39.9% of the total colonies number (Tables 4, 5). This species was isolated from 21.7% of analyzed plant samples (Table 5) and its isolates dominated especially among obtained from plantation in Wawolnica, from which its isolates made up 45.3% of the total colonies number (Table 4, Fig. 3). On the plantation mentioned above, this species was isolated more frequently at the beginning of flowering. On the contrary, from the tulips grown on the plantation in Wojszyn Alternaria alternata was isolated more frequently at the end of flowering and its isolates made up 33.9% of the total number of colonies (Table 4, Fig. 4).