Abstract: Botrytis cinerea, B. gladiolorum, Curvularia lunata, Fusarium oxysporum f.sp. gladioli and Stemphylium botryosum isolated from corms and leaves of Gladiolus were tested for their pathogenic potential. Former four were proved to be pathogenic to the corms while except F. oxysporum f. sp. gladioli all other fungi were able to cause leaf spots. Corm sprounting and plant height was considerable reduced by B. gladiolorum, F. oxysporum f. sp. gladioli and C. lunata. Corm sprouting was improved when Gladiolus corms infested with corm rotting fungi were sown after dipping in different fungicides. Out of four fungicides Bavistin followed by Dithane M-45 poved to be the best fungicide for the control of B. gladiolorum, B. cinerea and F. oxysporm f. sp. gladioli while Topsin-M was found effective against C. lunata.
Introduction
Gladiolus (Gladiolus columbine) popularly known as the "Sword Lily", is an ornamental bulbous plant native to South Africa. It belongs to the monocot family lridaceae. In Pakistan progress has been made in the recent years for the improvement of the Gladiolus in respect of its floriferousness. A number of shades and colors have been developed in Gladiolus flower out of which white, pink and yellow are commonly grown on commercial scale. Due to availability of a variety of colors, it has become popular as cut flower and its cultivation has been started on commercial scale in Pakistan also.
Gladiolus plant is affected by a number of diseases, out of which Gladiolus corm rots. Fusarium wilt and leaf spots are most destructive diseases. Drayton (1928) reported Botrytis disease of Gladiolus from Canada and the same disease has also been reported by Drayton (1929) and Van Poeteren (1938) from Holland, Moore (1939) from England, Dodge and Laskaris (1941) from Long Island, New York and Wade (1945) from Australia. Magie (1948), McClellan and Marshall (1950), Magie (1951) and Bald (1953). Parmelee (1954) reported Curvularia lunata and Curvulria Trifolii from corms and leaves of Gladiolus. Jackson (1961) conducted some studies on Curvularia diseases of Gladiolus and found that Curvularia was associated with corms and leaves. Mirza and Shakir (1991) reported Fusarium oxysporum f. sp. gladioli from corms and roots and Botrytis gladiolorum and Myrothecium roridum from corms and leaves of Gladiolus for the first time from Pakistan. Sohi (1992) worked on diseases of ornamental plants and reported Fusarium oxysporum f. sp. gladioli from corms and roots and Botrytis gladiolorum, curvularia sp. and Stemphylium sp. from corms and leaves of Gladiolus from India.
Singh and Arora (1994) worked on chemical control of Fusarium corms rot of Gladiolus and found that fungicide Emisan-6 followed by Bavistin increased percent corm sprouting of Gladiolus. They further concluded that captan followed by Topsin-M was also effective against the fungus as height of plants over control was improved by these fungicides. Since, a little work has been done on diseases of Gladiolus and their control in Pakistan. Therefore it was planned to conduct studies on the pathogenicity and eradication of some diseases of Gladiolus.
Materials and Methods
Isolations
Diseased specimens of corms, leaves and flowers of Gladiolus collected from nurseries of Faisalabad city, were brought to the laboratory for isolation of fungi. Infected parts showing different symptoms were cut into 4-5 mm pieces with the help of scissors and surface sterilized with 5 percent commercial bleaching solution sodium hypochlorite for about two minutes. The surface sterilized pieces of corms, leaves and flowers were plated separately in petridishes (9 cm) containing Potato Dextrose Agar (PDA) and incubated at 25±2°C. After 4-5 days the fungi were isolated and identified according to Ellis (1971) and Booth (1971) and maintained on artificial medium (PDA) for further experiments.
Pathogenicity by Inoculation Experiments
A. Corms
All the five fungi isolated from corms and leaves were tested for their pathogenic potential. Healthy corms were surface sterilized with 5 percent commercial bleaching solution and infested with spore suspension prepared by adding whole contents of one 15 days old culture plate (9 cm) of each fungus to 200 ml of distilled sterilized water. Corms thus infested were incubated at different temperature i.e. 10°C, 15°C, 20°C, 25°C and 30°C. Twenty five infested corms were incubated at each temperature. One hundred twenty five corms were inoculated with each fungus. Data on percent recovery of different fungi at different temperatures were recorded.
B. Leaves
Healthy leaves of Gladiolus plants were inoculated by spraying sport suspension of 15 day old culture of four fungi which were isolated from leaves of Gladiolus. Fifteen plants were inoculated with each fungus and were covered by polythene bags for 48 h to maintain the humidity. Sterilized water was sprayed with automizer to provide necessary moisture for infection to take place. Data regarding symptoms appearance were recorded after one week and two weeks. Leaves showing symptoms caused by different fungi, were detached for re-isolations and confirmations of pathogenicity.
C. Effect of fungus on corms sprouting (%) and plant height (cm) of Gladiolus
Corms of Gladiolus were surface sterilized with 5 percent commercial bleaching solution for 2 minutes and then infested with spore suspension of each fungus prepared by method mentioned above for 5 minutes and after 24 h of infestation were sown in pot (30 x 33 cm) filled with sterilized soil. Soil was sterilized by soaking in 5 percent commercial solution of farmaline at the rate of 10 Lm–3 of soil which was then covered with plastic sheets for three days and was exposed to the air for two more days. one hundred corms inoculated with each fungus were sown and data regarding percent corm sprouting were recorded after one month. Height of plant were recorded after 90 and 120 days as Gladiolus attains maximum height in 110-130- days. In control treatment surface sterilized corms were dipped in sterilized water for 5 minutes and sown in pots. Data on percent increase in corm sprouting and plant height were recorded for interpretation of results.
Chemical control
An experiment on fungicidal dip treatment of corms of Gladiolus was conducted in which surface sterilized corms infested with spore suspension of four corm rotting fungi according method already mentioned were incubated at 25±2°C for 48 h to ensure infection of fungi. Corms inoculated with different fungi were dipped in 0.2% solution of four fungicides namely Bavistin, Captan, Dithane M-45 and Topsin-M for 5 minutes separately and were sown in pots (30 x 33 cm). 25 corms were used in one replication while experiment was run in quadruplicate. Data on percent corm sprouting were recorded one month after sowing.
Results and Discussion
Isolations were made from diseased corms, leaves and flowers which revealed that Botrytis gladiolorum, B. Cinerea, Curvularia lunata and Stemphylium botryosum were assocated with corms and leaves of Gladiolus where as Fusariam oxysporuym f.sp. gladioli was isolated only from corms and roots (Table 1). Spore masses on flowers of B. gladiolorum and B. Cinerea were also noted.
All the isolated fungi were tested for their pathogenic potential and it was observed that B. gladiolorum. B. Cinerea, C. lunata and F. oxysporum f.sp. gladioli were invariably pathogenic to the corms of Gladiolus (Table 2). It is evident from Table 2 that recovery of fungi was different at different temperatures. Botrytis gladiolorum and B. cinerea were recovered maximum at 15°C (21/25) and 17/25) respectively while their recovery decrease with the increase of temperature. Curvularia lunata gave different response as compare to other fungi as it gave maximum recovery at 30°C while at lower temperatures ranging to 10-20 C, it did not show any response our these results are in confirmity with those McClellan and Marshall (1950). As for as Fusarium oxysporum f.sp. gladioli is concerned it gave good performance at 25°C temperature while at higher temperature it gave reduced recovery (16/25) which varifies the finding of Singh and Arora (1994). In case of Stemphylium botryosum no recovery was there at any temperature. Except F. oxysporum f.sp. gladioli, all the four fungi produced different spots on leaves of Gladiolus (Table 3). Our these results regarding isolations and pathogenicity are inconfirmity with those of Bald (1953), Jackson (1961), Magie (1948, 1951), Young (1955), Mirza and Shakir (1991) and Sohi (1992) who isolated the same fungi from corms and leaves of Gladiolus and found them pathogenic. Form an experiment conducted on percent corm sprouting and plant height, it was concluded that except S. botryosum all the four fungi reduced corm sprouting ranging from 14.28% to 51.02%.
| Table 1: | Isolation of fungi associated with different parts of gladiolus |
| Table 2: | Recovery of fungi from infested corms at different temperatures |
| Table 3: | Pathogenicity of the fungi isolated from the leaves of Gladiolus |
| Table 4: | Effect of different fungi on corms sprouting (%) and Plant height (cm) of Gladolus |
| Table 5: | Effect of fungicidal diptreatment on cormsprouting (%) of Gladiolus infested with corm rotting fungi |
BG = Botrytis gladiolorum; BC = Botrytis Cinerea; CL = Curvularia lunata; F. Oxy = Fusarium oxysporum f.sp. gladioli | |
Similarly plant height was also reduced by these fungi ranging from 5.21% to 35.93% after 90 day and 5.26% to 37.29% after 120 days which indicate that S. botryosum might not be corm rotting fungus while others all fungi were seems to be pathogenic to corms of Gladiolus (Table 4). On the other hand in case of leaf inoculation experiments. S. botryosum was proved to be a leaf spotting fungus which varify the results of Sohi (1992) who reported this fungus as cause of leaf spot of Gladiolus. As a result of confirmation of pathogenic nature of fungi to the corms of Gladiolus some fungicides were evaluated for their effectiveness against above mention fungi. In this experiment corms infested artificially with above mention fungi were dipped in fungicidal solution which revealed that Bavistin proved to be the best fungicide against B. gladiolorum and F. oxysporum f. sp. gladioli as corm sprouting was increased in both the cases. These results are in confirmity with those of Singh and Arora (1994) who also observed that Bavistin improves corm sprouting. In the same experiment Topsin-M gave its effectiveness against C. lunata while Dithane M-45 proved its performance against F. oxysporum f. sp. gladioli (Table 5). These results indicate that one fungicide can not be used against all the fungi of one host rather different fungicides should be used against different fungi as clear from our studies on Gladiolus.