Loading...
Theses
Browse
8 results
Search Results
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 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 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 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.ThesisItem Open Access Yellow vein mosaic disease of pumpkin in Kerala(Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Jayasree, P K; KAU; Balakrishnan, SYellow vein mosaic disease of pumpkin ( Cucurbita moschata Dutch. ex Poir) caused by a virus, was investigated which was prevalent in Vellayanl and nearby localities. The symptoms appeared as faint yellowing of finer veins which later on develop into characteristic vein yellowing. In advanced stages of infection, chlorotic areas were seen on the leaf lamina along with vein yellowing symptoms. The size of the leaves was reduced markedly.The growth of infected plants was severely retarded. The infected plants produced less female flowers and when Infected at a later stage produced undersized fruits. Histopathological studies showed a reduction in thickness of the chlorotic portions of the infected leaves and the palisade cells were shortened and loosely packed. The mesophyll cells contained only few chloroplasts. The virus was not sap transnissible. But it could be transnitted through grafting* The virus was hot found to be transmitted through seeds.ThesisItem Open Access Studies on leaf curl disease of sesamum(Department of Plant Pathology, College of Agriculture, Vellayani, 1984) Jayasree, M; KAU; Balakrishnan, SLeaf curl disease of sesamum, its symptomatology, mode of transmission, vector-virus relationships, the pattern of spread under field conditions and the extent of loss caused by the disease were investigated. Major symptoms of the disease were abaxial curling of the leaves, thickening of the veins on the under surface of the leaves, leathery appearance of the leaves and reduction in the size of leaf lamina. The plants remained stunted and produced few flowers and pods when infection occurred during the early stages of the plant growth. When infection occurred during later stages there was production of flowers and pods hut to a limited extent. This particular virus could he transmitted by wedge and side grafting and by the whitefly Bemisia tabaci Genn. The minimum, acquisition feeding period was found to be 10 min and the minimum inoculation feeding period was 20 min. The vector required an incubation period of 28 h to become viruliferous. Even a single whitefly was found to be capable of transmitting the virus. Once the vector acquired the virus it would retain it till its death. Negative results were obtained in the case of sap and seed transmission showing that this particular virus was not sap and seed transmissible.
