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Open Access
Associative effect of azospirillum and bradyrhizobium on nodulation and growth of cowpea (viqna unquiculata (l.) walp,
(Department of Plant Pathology College of Horticulture Vellanikkara, 1992) Sunitha, Menon S.; KAU; Rajendran, Pillai M .V
Open Access
Deterioration of oil cake by fungi
(Department of Plant Pathology, College of Agriculture, Vellayani, 1989) Naseema, A; KAU; Wilson, K I
Fungi causing deterioration of coconut, groundnut and sesamum oil cakes were studied. ficremonium implicatum, Asperdllus aculeatus, A. flavus, A. fumigatus, A. nlaer, A. terreus, A. versicolor, Bipolaris hawaiiensis, Curvularia clavata, Monascus ruber, Penicillium aurantioqriseum, P. Pinophilum, Pestalotiopsis palmarum, Rhizomucor £usillus and Ehizopus stolonifer were obtained from coconut oil cake. Aspergillus flavus, A. niaer, A. terreus, A. versicolor, Gliocladium sp. Penicillium pinophilum, RhizoEUS or^zae and Rhizopus stolonifer were noticed in groundnut and Aspergillus candidus, A. flavus, A. fumigatus, A. nlaer, A. tamarii, A. terreus, Curvularia clavata, Eurotium. chevalieri, F"sarium pallidoroseum, Monascus ruber, Fenicilliuiu pinophilum, Pestalotiopsls palmarum and Rhizopus or^zae in sesamum oil cake. Of these, Acremonium implicatum, Aspergillus aculeatus, A. caeslellus, A. .f"-igatus, Bipolaris hawaiiensis, Curvularia clavata, Monascus ru^, Penicillium anrantlogriseum, P. pinophilum, Pestalotiopsls palmarum and Rhizomucor pusillus from coconut oil cake, Aspergillus versicolor, Gliocladium sp., Penicillium pinophilum, Rhizopus oryzae and R. stolonifer from groundnut and Aspergillus candidus, A. fumigatus, A. tamarli, A. terreus, Curvularia clavata, Eurotium chevalieri, Fusarium pallidoroseum,Monascus ruber, Penicillium pinophilum, Pestalotiopsis palmarum and Rhizopus oryzae from sesamum oil cake have not been reported earlier. * Aspergillus flavus and A. niger were isolated from all the samples of groundnut and sesamum oil cakes. In coconut oil cake, these two fungi were present in 88.89 and 77.78 per cent of the samples. A. terreus was isolated from 66.67 per cent of groundnut and 55. 56 per cent of coconut and sesamum oil cake samples. Penicillium pinophilum was obtained from 66.67 per cent of groundnut, 44.44 per cent of sesamum and 27.78 per cent of coconut oil cake samples. Wide variation was noticed in the population of fungi present in the oil cakes collected from different regions during different periods of the year. Oil cakes collected during June-July had the highest population, of fungi. The central and the northern regions recorded higher population of fungi than the southern region. Positive and significant correlation could be obtained between weather parameters and population of fungi in different oil cakes. Maximum correlation was noticed in relation to total rainfall. Qood mycelial growth of fungi was obtained in all the oil cakes incubated at 27, 29 and 32°C. Maximum mycelial growth was noticed at 100 per cent relative humidity. This was followed by 96.1 per cent and 92.9 per cent in the descending order. The oil content of the oil cakes was considerably reduced due to the growth of all the fungi tested individually and in combination. Maximum reduction v/as noticed due to the growth of Pestalotiopsis palmarum in coconut oil cake, Rhizopus stolonifer in groundnut and Fusarium pallidorosem in sesamum oil cake. In the case of combinations, Aspergillus flavus, A. niger and Penicillium pinophilum together caused maximum reduction in oil content of coconut oil cake. In groundnut, combined growth of A. flavus, A. niger and A. terreus caused maximum reduction in oil whereas, A. niger and P. pinophilum together effected maximum reduction of oil in sesamum oil cake. Oil cakes inoculated with different fungi showed considerable reduction in total carbohydrates, crude protein, free amino nitrogen, crude fibre and ash to the extent of 6.11 to 76.95 , 4 . 28 to 68.03, 14.91 to 92.52, 1.25 to 92.55 and 0.17 to 65.16 per cent respectively. In the case of mineral nutrients like phosphorus, potassium, magnesium. calcium, copper and iron reduction ranging from 15.07 to 75.54, 23.13 to 94.41, 10.89 to 63.37, 28.78 to 90.20, 52.52 to 97.12 and 0.32 to 60.77 per cent respectively was noticed. Fourteen out of 2 0 isolates of Aspergillus flavus produced aflatoxins B^, and G2 in culture medium with maximum quantities being 1210, 1040 and 151 ppb respectively by the isolates from coconut oil cake. Eight out of 19 isolates of A. niger elaborated upto 222 ppb by the isolate from sesamum oil cake. When grown on the respective host material, A. flavus isolates from coconut oil cake produced maximum quantity of B^^, B^ and being 1517, 1092 and 272 ppb respectively. A. niger isolate from coconut oil cake produced B^^ upto 419 ppb. oil cakes treated with calcium propionate (0.6 per cent, w/w) were free from fungus growth throughout the period (180 days) of observation and showed minimum number of fungal propagules whereas, those kept as control had higher population of fungi than the treated ones, at all period.of observation. Oil cakes stored in polythene lined gunny bags had the least population of fungi, whereas those stored in ordinary gunny bag had very high population of fungi. These results revealed that fungal deterioration and spoilage of oil cakes could be prevented or reduced to the minimum by treatment with 0.6 per cent calcium propionate- and by using polythene lined gunny bags for storage arid transport.
Open Access
Fungal diseases of selected medicinal plants of Kerala
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1991) Sukumara, Varma A; KAU; ; Abi, Cheeran
Open Access
Study of bacterial leaf spot of betel vine- biochemical changes and control
(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Koshi, Abraham; KAU; James, Mathew
The bacterial leaf spot is one of the most serious diseases of betel vine in Kerala. The bacterium is one of the most serious disease of betal vine. Confidering the seriouness of the disease , studies were undertaken on the different aspects of the disease and to find out a suitable control /management practice.
Open Access
Leaf blight of banana and its control
(Department of Plant Pathology, College of Agriculture, Vellayani, 1993) Saj, KV; KAU; Sulochana, K K
Survey conducted to study the fungal pathogens causing leaf blight disease in banana in the three agricultural subdivisions of Thiruvananthapuram district, yielded seven fungal pathogens viz., colletotrichum musae, Curvularia sp, Guignardia musae, khuskia oryzae, Nodulisporium gregarium, Pestalotiopsis versicolor and Phaeoseptoria sp. Among these, Curvularia sp, Khuskia oryzae and Nodulisporium gregarium are new reports. Morphological characters and pathogenicity tests of all the seven isolated cultures were studied and described. Detailed studies were conducted on five fungal pathogens viz., C. musae, G. musae, K. oryzae, N. gregarium and Phaeoseptoria sp., since severe infections could be noticed by these fungi. Studies conducted on the growth and sporulation of pathogens on different, media indicated that Richard’s medium was the best for C. musae and G. musae, potato dextrose medium for K. oryzae and Phaeoseptoria sp. In the case of N. gregarium, potato dextrose agar and Czapek (Dox) broth were found to be the best solid and liquid media respectively for its growth. Best growth of C. musae, N. gregarium and Phaeoseptoria sp was obtained with maltose as the carbon source, whereas G. musae and K. oryzae utilized maximum starch and sucrose for their growth. Maximum mycelial weight of C. musae was obtained with sodium nitrate as nitrogen source, G. musae and K. oryzae with potassium nitrate, N. gregarium with glutamine and Phaeoseptoria sp. with asparagine. Potato dextrose broth and Richard’s solution were found to be best media for the toxin production by C. musae K. oryzae , G. musae and Phaeoseptoria sp. produced maximum toxin in Richard’s solution and N. gregarium in potato dextrose broth. Host range studies of the pathogen (s) conducted indicated that they can infect a number of economically important plants like, clove, cocoa, colocasia, nutmeg and tapioca, but none of the pathogens could infect clerodendron. Dithane M-45, calixin and Bavistin were able to inhibit the growth of the leaf blighting pathogens under laboratory conditions and under field conditions Dithane M-45 (0.2%) was found to be the best. Varietal screening trials showed that variety Rasakadali was moderately resistant/tolerant among the four popular varieties screened, whereas Nendran was the most susceptible variety.
Open Access
Varietal screening of banana against anthracnose disease
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1984) Srinagesh, K L; KAU; Jose, P C
Laboratory and field studies of the varietal screening of banana against anthracnose disease were conducted at the college of Horticulture. Vellanikkara and at Banana Research Station, Kannara respectively during 1981-1983. In the field the infection started at the distal end of the banana fruit and in course of time the infected fruit became blackened, shriveled and mummified. After Harvest, the symptoms appeared as small brown spots which enlarged quickly and coalesced forming larger patches. The affected areas were covered with orange to salmon pink coloured conidial masses. The detailed morphological studies of the fungus proved that the anthraemose disease of banana is caused by colletrichum cloeosporioides cooko and massee, the imperfect stage of glomerella cinoulata spauld and shrenk. Twenty five varieties of banana fruit were screened in vitro at different stages of development against anthracnose disease. The varieties showed different degrees of susceptibility at various developmental stages of the fruit. The pooled analysis of the data showed that the variety nendra padaththi followed by palayankodan, jurmani kunthali, boodida bontha bathes, peyan, kanchikela, pisang mas and kapok were found to be highly resistant. The varieties Zanzibar, adakka kunnan, klue teparod, chinia, nendran, venneettu mannan, koduppilla kunnan, hybrid sawai, poocha kunnan, red banana and boodles altafort were found to be resistant to the disease. The variety robusta was found to be susceptible. The varieties njalipoovan, pisang lilin, dwarf Cavendish, matti and gros Michel were found to be highly susceptible. The major chemical constituents of banana fruit viz. reducing sugars, total sugars starch, crude fibre, crude protein and tannin at different developmental stages of twenty five varieties were analysed. The reducing sugars and total sugar were found to increase steadily from immediately after female phase to ripened stage in all the varieties. The starch and crude fibre contents, though increased steadily upto full maturity. Declined sharply at the ripening stage. The crude protein and tannin contents were maximum at immediately after female phase but steadily decreased and were minimum at ripening phase. There was a significant positive correlation between reducing sugars, total sugars and per cent disease intensity at three fourth maturity. High sugars were responsible for susceptibility to the disease. A significant negative correlation was obtained between crude protein and per cent disease intensity at half maturity. A significant negative correlation was also obtained between tannin and per cent disease intensity at one fourth and half maturity stages. High crude protein and high tannin contents were responsible for resistance to the disease.
Open Access
Effect of plant protection chemicals on foliar pathogens and Phylloplane microflora of rice
(Department of Plant Pathology, College of Agriculture, Vellayani, 1989) Gokulapalan, C; Chandrasekharan Nair, M
The present investigation was undertaken to assess the effects of plant protection chemicals on the important fungal pathogens and phylloplane microflora of rice. An attempt has been made to identify potential biological control agents to combat sheath blight disease causing havoc to rice cultivation in Kerala. Both under pot culture conditions and during the course of field trials at two locations viz., Adoor and Karamana, Kerala, the fungicide carboxin was found to be the best treatment for reducing the incidence and intensity of sheath blight and sheath rot diseases of rice. The fungicide was found to be the least harmful to the epiphytic microflora of the rice plant. In some instances the population of phylloplane antagonists of R. solani, including Trichoderma harzianum, T. viride, Penicillium oxalicum and Aspergillus aculeatus were found to be enhanced by the application of carboxin. The total disease incidence and yield loss were significantly reduced by the application of edifenphos. The rice variety Karthika was found to be significantly tolerant to sheath blight and sheath rot compared with the rice variety Jyothy. The fungicides carboxin and mancozeb at 500ppm did not inhibit the growth of the phylloplane antagonists of R. solani viz., Trichoderma harzianum and T. viride under in vitro conditions. Several micro-organisms isolated from the rice phylloplane were found to exhibit in vitro antagonism towards R. solani. These include Aspergillus aculeatus, A. niger, Chaetomium globosum, Penicillium oxalicum, Trichodema harzianum, T. viride, several bacteria and a few basidiomycetous yeasts. The phylloplane antagonists, Trichoderma harzianum, T. viride and Penicillium oxalicum were found to readily parasitise R. solani hyphae leading to coiling, penetration followed by disintegration and death of the mycohost. When these antagonists were cultured on bran and tried for their efficacy as potential biocontrol agents of R. solani, it was found that these fungi could significantly reduce the incidence and intensity of sheath blight of rice, though this was not comparable with the effect of the fungicide carboxin.
Open Access
Vascular streak dieback of cocoa and its management
(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1996) Ajay Kumar, K M; KAU; Koshy, Abraham
Vascular streak dieback (VSD) is a destructive disease of cocoa. Corticium culture medium, Water agar, Potato dextrose agar gave promising results in isolation of the pathogen. Petiole and midrib gave maximum success in isolation. Potato dextrose agar and Corticium culture media supported the growth of the fungus. Fusarium sp. And Colletotrichum gloeosporioides were the major contaminants interfering in the isolation of VSD. The morphological characters of the pathogen were studied from the sporophores occurring on naturally infected cocoa plants. Based on these characters, the pathogen causing VSD was identified as Oncobasidium theobromae Talbot and Keane. The disease produced various typical symptoms on leaves and stems of infected plants like pale green colour of leaves and subsequent yellowing with green islets, defoliation, brown marks on the scars of fallen leaves, axillary bud growth of the infected stem, rusty discolouration of cambium, vascular streak, whitish sporophores on the leaf scar of fallen infected leaves and finally the death of the infected twig. Histopathological studies showed the presence of fungal mycelium in the xylem vessels. Transmission studies by grafting and budding revealed no establishment of buds or grafts. But there was vascular streaking. No seed transmission was observed. In general Kitazin and Bavistin as a seed treatment had an effect on the height of plant and leaf production. Evaluation of cocoa types planted at three seed gradens indicated that some of them possess resistance/tolerance against VSD. Variation in disease incidence and intensity of VSD was noted in germplasm VI. Calixin spraying had an effect in preventing the incidence of the disease in seedlings.
Open Access
Survival of Xanthomonas campestris pv. Oryzae and its Control in Kuttanad
(Department of Plant Pathology, College of Agriculture, Vellayani, 1996) Mary, C A; KAU; Sasikumar Nair
The present investigation was taken up to understand the factors responsible for the recurrence of bacterial blight disease in a severe from only during the additional crop season in Kuttanad. The mode of survival of the pathogen during and in between the two major cropping seasons of Kuttanad region were also studied in detail. An extensive survey was also conducted among 115 farmers in 12 Krishibhavans of Kuttanad taluk for this purpose to collect specific informations on existing cultural practices, crop variety, nature and distribution of weed flora and self sown rice plants in and around rice fields and on wether data from June 1992 to March 1994. The efficacy of two different methods of spraying, prophylactic and curative using streptocycline, mixture of streptomycin and oxytetracycline in the proportion 1:9, Bactrinol – 100 cowdung extract on the control of bacterial blight disease was tested under field condition at Nedumudi in Kuttanad. The survey showed that there was considerable variation in the incidence of bacterial blight in Kuttanad taluk. Among the 12 Krishibhavan areas the disease incidence was maximum in Ramankari and Nedumudi and minimum in Kavalam, Kainakary and Muttar. In Neelamperoor and Thalavadi areas there was no incidence of this disease during the period of survey. Between the two major cropping seasons the disease incidence was more during the additional crop season than during Punja season. Red Triveni and Jyothy were the most popular varieties cultivated in the area and more than 50% of the farmers cultivate Red Triveni. It was observed that the variety Red Triveni as highly susceptible to bacterial blight disease. The isolate of the pathogen Xanthomonas oryzae pv. Oryzae from the rice variety Red Triveni was capable of both gelatin liquefaction and starch hydrolysis. The pathogen X. oryzae pv. oryzae was found to survive for a maximum period of 42 days in infected seed, 105 days in infected straw, 56 days in infected stubbles at room temperature, 24 days in infected stubbles under dry land condition and 14 days under wet land condition. The pathogen did not survive in soil and water. Weeds like Oryza sativa var. fatua and Paspalum conjugatum served as alternate host for the pathogen. Bacterial blight infected self sown rice plants could be seen in Kuttanad during the cropping and non cropping seasons. Due to certain specific reasons, the cultivation practices were often found to extend beyond the normal cropping seasons in the region resulting in the chances of survival of bacterial blight pathogen in the host plant itself. The specific weather conditions during the additional crop season played an important role for the severity of bacterial blight desease in this season in Kuttanad. The pathogen X. oryzae pv. oryzae was tested for sensitivity to antibiotics, Bactrinol – 100 and cowding extract under in vitro conditions. The maximum growth inhibition was obtained with oxytetracycline followed by chloramphen icol which was statistically on par with oxytetracycline. The effect of increasing concentrations of oxytetracycline in combination with streptomycin on growth of X. oryzae pv. oryzae was studied with 100, 250 and 500 ppm concentrations. The growth inhibition increased not only with the concentrations of antibiotic from 100–500 ppm but also with increasing concentration of oxytetracycline. The maximum zone of growth inhibition was obtained with 1:9 proportion of streptomycin and oxytetracycline. The five treatments selected for field evaluation trial included streptocycline at 500 ppm, streptomycin + oxytetracycline (1:9) at 250 ppm and 500 ppm, Bactrinol -100 at 500 ppm and fresh cowdung extract at 20g/1. Two different spraying methods, prophylactic and curative were evaluated in two rice varieties, T(N) 1 and jyothy. The reduction in disease index by prophylactic and curative sprayings was maximum after spraying with cowdung extract 20g/1. As regards to two methods of spraying, significant reduction in per cent disease index was obtained with curative spraying. The maximum per cent increase in grain yield over control was obtained after curative spraying with 500 ppm streptomycin and oxytetracycline mixture in jyothy followed by cowdung extract 20 g/l. In T(N) 1 and jyothy both by prophylactic and curative spraying, the thousand grain weight was maximum with cowdung extract 20 g/1. As regards to two method of spraying, significant increase in grain yield and thousand grain weight was obtained after curative spraying. In T(N) 1, both by prophylactic and curative spraying the per cent increase in straw yield was maximum with a mixture of streptomycin and oxytetracycline at 500 ppm and jyothy with cowdung extract 20g/1. In T(N)1 significant reduction in chaff per cent was recorded by prophylactic spraying while in Jyothy no significant difference was obtained by the two methods of spraying. In both these varieties the reduction in chaff per cent was maximum by spraying with cowdung extract (20g/1). It was observed that two prophylactic spraying with selected bactericidal agents, neither resulted in any significant reduction in disease index nor increase in yield as compared to curative spraying. This could be due to the fact that in Kuttanad bacterial blight disease usually occurred only around the panicle initiation stage or even later. Therefore a need based curative spraying schedule would be most effective for the control of bacterial blight disease in Kuttanad. On working out the economic benefits of controlling bacterial blight it was observed that there will be economic return only from spraying infected plants of both (T(N) 1 and jyothy with cowdung extract 20g/1. The return from plants sprayed with all other treatments in the investigation was low when compared to unsprayed control plants. Thus it will be economically advantageous to use cowdung extract to control bacterial blight of rice.

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