The activity and reproduction of storage mold and insects are favoured by warm temperature (Delouche, 1973). Carrot seeds are susceptible to heat and moisture stress and in the presence of adverse storage temperature and moisture, quality of seed is deteriorated by the growth of fungi (Lauritzen, 1926; Hewett, 1964; Neergaard, 1977; Shakir and Khan, 1992). Some fungi produce toxin in seed under certain favourable environmental condition which may affect germination of seed (Hansen, 1954). However, information on carrot storage fungi is not adequately available in Pakistan. The study was therefore undertaken to know the kind of seed mycoflora and their incidence on stored carrot produce.
Materials and Methods
Collection of seed samples: Thirty six samples of carrot seed were collected from different divisions of Punjab during the year 1996 and stored in laboratory at room temperature (25°C). These seed samples were drawn according to procedure of ISTA (1993).
Detection of fungi from storage seed: Four hundred seeds form each samples were tested by standard blotter method using twenty seeds per 90 mm plate. These seed were incubated for eight days at 20±2°C under alternating cycle of 12 hours light and dark. Seeds were examined under steromicroscope (mangification 6×50). Fungi were primarily identified on the basis of their growth habit and final identification of species was done from pure cultures using pertinent literature.
To know the kind and extent of storage fungi, 36 seed sample of carrot collected from different Divisions of Punjab were analysed. A total of 20 seed-borne fungi were detected, using blotter paper method. Among these, Alternaria alternata, A. radicina, Aspergillus spp, Rhizopus sp. and Fusarium pallidoroseum were dominant ad observed in greater number of seed samples.
|Table 1:|| Storage fungi associated with seeds of carrot
|Table 2:|| Seed-borne fun i of carrot (Caucus carafe)
Seed infection percentage of A. radicina and A. dauci was greater followed by Aspergillus spp. while Fusarium pallidoroseum. Stemphylium botryosum, Drechslera spp. and Curvularia spp. had very low seed infection percentage (Table 1), Storage saprophytic fungi including species of Arthrobotrys, Chaetomium and Rhizopus were also observed but not counted. A greater recovery of fungi was recorded from seed samples collected from gujranwala division followed by Sargodha division (Table 2).
Carrot seed is susceptible to high moisture and int the presence of adverse storage conditions (temperature and moisture) its quality is affected by the growth of fungi especially A. rasdicina. To know the kind of seed mycofibra and their incidence on stored carrot seeds, 36 seed samples were collected from different divisions of the Punjab after two to three months of storage and then were kpt for one month at room temperature (25°C). A total of 20 fungi were detected. The dominant and wider prevalehce of Aftemaria alternata, A. radicina, Aspergillus, Rhizopus and Fusarium spp., were observed. Among these fungi, A. radicina is known to cause seedling mortality and formation of toxic metabolites which decrease the viability and germination of carrot seeds (Shakir and Khan, 1992; Hansen, 1954).
In present investigation, major field fungi detected in stored carrot seed were A. radicina and A. dauci. The difference in type of fungi and percentage recovery of fungi were found to be associated with conditions of carrot seed storage in different areas especially conditions prevailing at seed maturity and harvesting stage of the crop. A greater recovery of fungi from storage seeds collected from Gujranwala, indicates that storage conditions of that area were not suitable for safe storage of carrot seeds (due to high humidity). Therefore, efforts are needed to avoid use of such infested seeds by using health technology.