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ThesisItem Open Access Varietal screening of banana against anthracnose disease(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1984) Srinagesh, K L; KAU; Jose, P CLaboratory 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.ThesisItem Open Access Management of sheath blight disease of rice in relation to the population of the pathogen in soil(Department of Plant Pathology, College of Horticulture, Vellanikkara, 1987) Shaji, Alexander; KAU; Rajan, K MLaboratory, pot and field experiments were carried out to study the role of various physical, chemical and biological factors on the management of sheath blight disease of rice caused by Rhizoctonia solani Kuhn. (Thanatephorus Cucumerlis (Frank) Donk). Populations of total fungi, bacteria and actinomycetes in soil were enumerated at different stages of growth of the crop in order to assess their role in reducing the intensity and incidence of sheath blight disease. Results of the investigation revealed that the pathogen can be managed by deeper ploughing followed by submergence of the soil for a minimum period of two months. Amendments like glyricidia leaves, rice husk, lime and non edible oil cakes of marotti, neem and punna were useful in reducing the severity and spread of the disease. Fungicides like carbendazim and ediphenphos and the herbicide benthiocarb were also efficient in managing the disease. Rotation of rice with crops like tapioca, banana and brinjal was also useful. It was seen that amendments stimulated the population of saprophytes like Trichoderma viride in soil which are antagonistic to R. solani resulting in a subsequent reduction in population of the pathogen. In spite of the reduction in severity and spread of the disease, grain and straw yields were not enhanced by the treatments. More elaborate field trials are to be undertaken before landing on any ultimate conclusion regarding the use of these practices as tools for disease management.ThesisItem Open Access Studies on the seed borne diseases of rice in Kuttanadu(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Jose Joseph; KAU; Susamma PhilipSeveral fungi were isolated from the seeds of twelve varieties/cultivars of rice collected from different localities of Kuttanadu, the major rice growing tract of Kerala. Fungi were encountered extrenally as well as internally. Among the externally seed borne fungi, Aspergillus flavus was the most common with its occurrence on nine varieties followed by Bipolaris oryzae and Curvuleria lunata. Other fungi included Rhizopus stolonifer, Chaetomium gracile, Syncephalestrum racemosum, Fusarium moniliforms, Trichoderma virde, Sarocladium oryzae. Aspergillus niger, Alternaria padwickii, Fusarium gramineazum, Piricularia oryzae, A. fumigatus, A. quadrilineatus, Nigrospora oryzae and Penicillium spp. Among the varieties Jaya was found to harbour the maximum fungal population. The germination percentage was not found to be affected due to seed inoculationwith the predominant fungi viz. A. flavus, A. padwickii, B. oryzae, C. lunata and S. oryzae.ThesisItem Open Access Epidemiology and control of sheath rot disease of rice(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Krishnakumaran Nair, B; KAU; Chandrasekharan Nair, MStudies on symptomatology, epidemiology and control aspects of sheath rot disease of rice caused by Serocladium oryzae Cams & Hawksworth (= Acrocylindrium oryzae Saw.) were done in detail. The disease initiated as purplish-brown oblong lesions on the sheath of the flag leaf. At maturity lesions enlarged in size with grey -white centres and often covered the entire flag leaf sheath. Panicle often did not emerge but choked inside the affected sheaf itself. Artificial inoculation studies showed that under sufficient humid conditions the pathogen took an average five to eight days for initiation and 15 to 20 days for the complete development of the disease in rice plants. The pathogen was isolated from four naturally infected rice varieties, collected from three different culture (isolates viz., S1, S2, S3, S4, S5, S6 & S7) were selected based mainly on symptomatological variations and their comperative morphological characters were studied in detail. No appreciable differences were noticed in the morphological characters between isolates.ThesisItem Open Access Properties, host-range and control of cowpea mosaic virus(Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Sreelakha, L; KAU; Balakrishnan, SStudies were conducted on the cowpea mosaic virus disease commonly occurring in cowpea plants (Vigna unguiculata (L.) Walp) in Kerala The major symptoms caused by cowpea mosaic virus infection in cowpea plants were vein banding, inter- veinal chlorosis mosaic mottling and general stunting of the plants. Transmission studies showed that the virus could be transmitted through mechanical means, grafting, through seeds and by means of aphid vectors. The virus was found to be transmitted by the aphids, Aphis craccivora. Aphis gossvpii and Aphis malvae. Among the three species of aphids, Aphis craccivora was found to be the most efficient vector. The percentages of transmission obtained by A. craccivora, A. gossypii and A. malvae were 90,65 and 45 respectively. Studies on the physical properties of the virus revealed that the virus had a thermal inactivation pointbetween 50 and 55°C, dilution end point between 10“"* and —2 10 , longevity in vitro of 8 h at room temperature and24 h at 8°C. The minimum acquisition feeding and inoculation feeding period were found to be 30 s each. But the percentage of transmission was maximum when an acquisition feeding of 10 rain and inoculation feeding of 15 rain were given. Pre-acquisition fasting up to a period of 2 h increased the percentage of transmission, whereas the post-acquisition fasting decreased the efficiency of transmission. The vector was found to retain the virus for 1-2 h. Maximum percentage of transmission was obtained with 10 aphids and the symptoms appeared within 14 days after inoculation. Host-range studies revealed that the virus is restricted to the family Leguminosae and Chenopodiaceae. Varietal screening trial with ten different varieties of cowpea showed that all the ten varieties were susceptible to virus infection. C-152 was found to have the highest susceptibility of 100 per cent infection. C.G.104 showed some resistance with 13.33 per cent infection. In serological studies the cluster bean mosaic virus and sword bean mosaic virus were found to be related to cowpea mosaic virus. The antiserum titre and end point of virus in the present study were found to be between 1;1024 and 1:2048 and 1:512 and 1:1024 respectively. Studies on the effect of virus infection on growth of cowpea plants showed that there was significant reduction in height of the plant, number of pods produced and length of pods. Observations on natural incidence of cowpea mosaic virus indicated that cowpea mosaic virus is the major disease among the different virus diseases affecting t cowpea. Among the infected plants 57 per cent showed cowpea mosaic virus. The results of the experiments to find out the effect of leaf extract sprays on cowpea mosaic virus infection indicated that the disease could be effectively controlled by pre-inoculation sprayings with leaf extracts of Bougainvillea sp. and Eupatorium odoratum.ThesisItem Open Access Studies on the effect of age of plant and host nutrition on bacterial leaf blight of rice and its control(Department of Plant Pathology, College of Agriculture, Vellayani, 1985) Sreelatha, K; KAU; Sasikumar NairA study on tho effect of age of plants and host nutrition on the incidence of bacterial leaf blight of rice caused by Xanthomonas camoestris pv oryzae was conducted at the College of Agriculture, Vellayanl, Trivandrum during 1933-84. The field experiment to evaluate the comparative efficacy of different control measures of bacterial leaf blight was laid out in a farmers field at Kainakary in Kuttanad. The effect of age of plants on the incidence of bacterial leaf blight was studied using three popular varieties of rice namely T (N)l Jay a and IR-20 at four critical stages of plant growth ouch as seedling maximum tillering panicle initiation and early flowering stages. At flowering stage the onset of disease symptoms was noticed only on the seventh day while it was observed on the fifth day in all the three varieties for the remaining three stages of plant growth* T(N)1 was found to be the most susceptible variety to bacterial leaf blight followed by Jaya and IR-2Q. Among the four stages maximum tillering stage was the most susceptible stage to bacterial leaf blight. The study on the effect of host nutrition on the incidence of bacterial leaf blight indicated that when higher doses of nitrogen were added, the onset of symptoms were earlier on the fifth day after inoculation with the pathogen while at lower levels# the symptom appeared only on the seventh day. The main effect of nitrogen and potassium on the disease intensity was significant while the effect of phosphorus and minor element was insignificant. The application of nitrogen in general increased the disease intensity while the application of potassium decreased toe same. But at higher levels of nitrogen a similar positive effect of potassium was not observedThesisItem Open Access Effect of root-knot nematode Meloidogyne incognita on nodulation in cowpea(Department of Plant Pathology, College of Agriculture, Vellayani, 1986) Nirmala Moni, D; KAU; Sasikumar NairAn investigation was carried out at Colloge of Agriculture , Vellayani, Kerala, to study the effect of Infeatation with Meloidogyne incognita on nodulation and 1 1 formation in cowpea. Ten varieties of cowpea, New Era Pathenettumaniyan, HG-22, PTB-1 PTB-2, 0-152, Sundari, V-16, V-37 and V-240 were initially screened for resistance to this nematode. She plants were inoculated with 1000 second stage larvae of H.incognita on 14th day and various observations on gall number, gall fresh weight, nodule number, nodule fresh weight leaf number plant height, root length# fresh and dry weight of shoot and nematode population in infested root and soil were taken on 50th day of plant growth. Eight varieties namely Pathinettumaniyan HG-22 PSB-1 0152 Sundari V-16 V-37 and V-240 were found resistant while two varieties new Era and PTB-2 were highly susceptible to this nematode.ThesisItem Open Access Effect of inoculation of vesicular-arbuscular mycorrhiza on nodulation and phosphorus uptake in cowpea(Department of Plant Pathology, College of Agriculture, Vellayani, 1987) Meena Kumari, K S; KAU; Sasikumar NairA study on the effect of inoculation of vesicular- arbuscular mycorrhiza and Rhizobium on nodulatlon, phosphorus uptake and yield in coupe a was conducted at College of Agriculture, Vellayani, Trivandrum during 1983-85. Three separate pot culture experiments were conducted during this Investigation; Initially, ten cowpea varieties were screened for the natural incidence of YA-mycorrhiza., There were significant differences between varieties in their mean mycorrhizal index; The infection was maximum in C-152 which had an average index of 1.19. This was significantly higher than that of varieties such as CG-11, HG-22, PTB-1, RC-25, S-488, IT-16 and V-38; The application of rock phosphate had a significant effect in enhancing the mycorrhizal infection in all varieties except in S-488. The cowpea variety which had the maximum mycorrhizal index under natural conditions m s further used to study the effect of age of host plant on mycorrhizal infection. This ms significantly higher on 45th day. The application of rock phosphate at the rate of 30 kg P2 O5/ha had a uniform significant effect in enhancing the mycorrhizal infection at different stages of plant growth. In the last part, a detailed study on the combined effect of VA-mycorrhiza and Rhizobium inoculation on nodulation, phosphorus uptake and yield in cowpea was conducted. Observations were taken at two stages of plant growth, on. 45th day and at the time of harvest. A uniform treatment effect on various plant characters studied was observed only at the time of harvest. The number of nodules formed per plant and their fresh (and dry weights were significantly higher in the treatment combination consisting of the standard culture of VA-mycorrhiza, Rhisobium inoculation and the application of rock phosphate at the rate of 30 kg P205/ha. The fresh and dry weights of plants and the mean mycorrhizal index were also maximum in this (MSR+RP) treatment.ThesisItem Open Access Evaluation of various herbicides on the control of sheath blight disease (Rhizootonia solani Kuhn) on rice(Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Lakshmy, T R; KAU; Chandrasekharan Nair, MBoth in vitro and in vivo studies on the effect of few common herbicides on Rhizoctonia solani and on sheath blight of rice, were carried out. The in vitro studies revealed that Propanil (Stam P.34) vras the most toxic herbicide to Rhizoctonia solani Kuhn, the rice sheath blight pathogen, which completely inhibited nycelial growth at a very low concentration of 125 ppm. Benthiocarb, Nitrofen (Tok E.25) and Butachlor also have high potentiality in decreasing radial growth and also in inhibiting the formation of sclerotia Soil borne sclerotia was found the major source of inoculam in initiating sheath blight diseases. Among the various herbicides tested, Nitrofen, Propanil and Butachlor reduced the degree of pathogenicity of soil borne sclerotia of R. solani* Propanil effected maximum reduction of sheath blight in pot culture experiments followed by Nitrofen. Butachlor and Nitrofen were equally effective in reducing sheath blight under pot culture, experiment. Nitrofen (Tok E.25) applied at 1.5 kg ai, 1.75 leg ai were equally effective as Hinosan in reducing sheath blight in field trial also.
