http://ir.lib.ruh.ac.lk/handle/iruor/19204 2026-04-26T20:05:41Z 2026-04-26T20:05:41Z Ranawake, A.L. Nakamura, C. http://ir.lib.ruh.ac.lk/handle/iruor/19521 2025-06-16T05:53:01Z 2011-06-08T00:00:00Z

Development of a method for testing dehydration tolerance rice(oryza sativa L.) and its application to a recombinant inbred line population Ranawake, A.L.; Nakamura, C. A recombinant inbred line population derived from Japonica rice cultivar Hyogokithanishiki and Indica rice cultivar Hokuriku-142 is a valuable source for genetic and molecular studies as these two parents have different origins. Characterization of the two parents under different biotic and abiotic stress conditions exploits novel research areas such as QTL analysis. In the present study two parents were evaluated for dehydration tolerance using Petri dish method and nursery box method. Average root length, shoot length, root dry matter and shoot dry matter weight were evaluated in each method. Shoot length in nursery box method gave a significant difference between two cultivars with Hygokithanishiki dehydration tolerant and Hokuriku-142 dehydration susceptible. The method was applied to evaluate 163 recombinant inbred lines (RILs) derived from the two parents for dehydration tolerance. The trait showed a normal distribution in the population with some transgressive lines expressing greater dehydration tolerance than dehydration tolerant parent Hyogokithanishiki. Therefore nursery box method is proposed as a reliable method for the evaluation of dehydration tolerance of rice cultivars and this method is suitable for evaluating germplasm collections and breeding populations for dehydration tolerance in rice breeding.

2011-06-08T00:00:00Z Karunaratne, M.D.S.U. Karunaratne, M.M.S.C. Ekanayake, H.M.R.K. http://ir.lib.ruh.ac.lk/handle/iruor/19513 2025-06-16T04:33:21Z 2011-09-22T00:00:00Z

Biology of the palm weevil, rhabdoscelus maculatus in selected foliage palm nurseries in Sri Lanka Karunaratne, M.D.S.U.; Karunaratne, M.M.S.C.; Ekanayake, H.M.R.K. A study on the Biology of the palm weevil Rhabdoscelus maculatus was carried out at Tropiflora Ornamental Palm Nurseries in Sri Lanka. This weevil, an important pest of ornamental palms, was detected for the first time in Sri Lanka at Tropiflora Nurseries. Although the incidence of this weevil is restricted to ornamental palms at present, there is a potential threat of the weevil becoming a pest of important cultivations such as coconut and sugarcane. The present investigation was therefore, carried out to confirm the identification of this weevil and to study its biology. The identification of the palm weevil was confirmed as R. maculatus Gyllenhal, 1838 and is the first record in Sri Lanka. Biological, morphological and behavioural aspects of the weevil were studied under laboratory, semi-natural and natural conditions. The adult is a small, reddish-brown weevil (10.38- 12.62 mm in length) with two black markings on the elytra and two on the thorax. The female is slightly larger than the male. The rostrum of the female is longer and more curved than that of the male. The ventral surface of the rostrum is roughened in the male while it is smooth in the female. Adult weevils are nocturnal in habit and hide in plant sheaths and debris during the day. They fly only short distances at a time but flight during the day was not observed. Mature female lays eggs inside cavities made in the leaf sheath. Under laboratory conditions, the period for egg incubation is 5.00 + 0.82 d. The larva is creamy white and legless with a round, highly sclerotized, reddish brown head capsule. Larvae feed on stem tissues rapidly and make tunnels. The frequency distribution analysis of head capsule width revealed six larval instars. Early weevil infestation of palms is indicated by a jelly like substance oozing out of the holes in the leaf sheaths. R. maculatus larva takes about 7.75+ 3.70 weeks to complete its de velopment and then pupate inside a cocoon made of tightly bound, fibrous material completing the pupal stage in 2.50 + 0.76 weeks. The total life cycle of this weevil is completed in 10-12 weeks. The life span of adult weevils is between 8-10 months under semi-natural conditions and four weevil generations per year occur under natural conditions.

2011-09-22T00:00:00Z Ofuoku, A.U. Egho, E. Enujeke, E. http://ir.lib.ruh.ac.lk/handle/iruor/19475 2025-06-13T10:19:57Z 2011-12-29T00:00:00Z

Propensity of cowpea (vigna unguiculata) farmers to adopt neem in controlling pest in Delta state, Nigeria Ofuoku, A.U.; Egho, E.; Enujeke, E. This study was conducted to determine the factors that influence the propensity of cowpea farmers to adopt neem in controlling pests in Delta State, Nigeria. Data were collected from a sample population of 125 cowpea farmers from ten randomly selected Local Government Areas of Delta State. The data were elicited from the respondents with the use of structured interview schedule and questionnaire, while descriptive statistics and multiple regression analysis were used to analyze the data. The recommended neem technologies at different stages of adoption process were neem seed oil/extract; neem leaves solution, neem seed powder, and neem kernel powder. The grand mean adoption score and adoption index were 0.70 and 0.140 respectively. The low level of adoption was attributed to lack of extension contact, scarcity of neem, and poor level of subscription to farmers’ groups. The level of education, age of farmers, farm size, farm income, household size, extension contact, membership of farmers’ groups, cost of technology were the major factors that influenced the propensity of cowpea farmers to adopt neem technologies in pest control at 0.05 level of significance. It was recommended that more extension agents be employed; progressive approaches to extension delivery be encouraged and propagation of neem plants be encouraged.

2011-12-29T00:00:00Z Sandika, A.L. http://ir.lib.ruh.ac.lk/handle/iruor/19474 2025-06-13T09:56:52Z 2011-11-11T00:00:00Z

Impact of middlemen on vegetable marketing channels in Sri Lanka Sandika, A.L. Vegetable are produced on a year round basis and a large number of farmers are involved in the process of production. However, many people criticize the vegetable marketing system due to fluctuating prices. In this background, this paper attempts to identify the long-term behaviour of Market Margin (MM) of middlemen on vegetable marketing channels in Sri Lanka. This study was mainly done by using secondary data. Nominal market price, producers price and market margin (MM) of beans, carrots, beets, pumpkin and brinjals have increased in a similar percentage in parallel to the prevailing rapid inflation within the last two decades. Therefore, it is clear that the prices of the vegetables have increased due to the high rate of inflation in the country. The MM for the all the vegetables was generally less than 50 %. Average MM of selected vegetables like bean, carrot, beet, pumpkin and brinjals were 42%, 44%, 44%, 49% and 43.5%, respectively. It was also observed that usually when the Retail Price (RP) and Producer Prices (PP) increase the MM decrease and vice versa. It is clear that when the RP and PP are high the middlemen try to control the market prices by reducing their MM. It may help to protect the consumers directly because RP and PP normally increase due to low supply of the production of vegetable and/or high demand for it. When the prices are low they try to get more benefits by increasing their MM as a rational entrepreneur.

2011-11-11T00:00:00Z