Showing papers in "Jarq-japan Agricultural Research Quarterly in 1993"

Methods and Strategy for Monitoring Race Distribution and Identification of Resistance Genes to Bacterial Leaf Blight (Xanthomonas campestris pv. oryzae) in Rice

Abstract: For controlling bacterial leaf blight of rice, caused by Xanthomonas campestris pv. oryzae, the use of resistant cultivars is the most economical and effective method due to the scarcity of effective bactericidal agents and to the need for preserving the environment. Against this background, the resistance genes to this disease so far identified will be reviewed. Under the collaboration between the Tropical Agriculture Research Center, Japan and the International Rice Research Institute, Philippines, the genes identified were rearranged from Xa-1 to Xa-12 based on the numbering system of rice gene symbols and then near-isogenic lines with single resistance genes were developed. By using these near-isogenic lines, the strategy for monitoring the race distribution and the methods of identification of new resistance genes are reviewed

Persimmon Breeding in Japan

Abstract: Achievements of persimmon breeding at the Fruit Tree Research Station in Japan over 50 years were reviewed. The main objectives included the breeding of fruits with the following characters: pollination constant non-astringent type (PCNA), early ripening, high eating quality, large size and absence of physiological disorders such as fruit crackings. Crossing to obtain PCNA progenies was limited to PCNA types since the PCNA trait was recessive to the non-PCNA one. Moreover, only a small number of PCNA progenies could be obtained even in BC, since persimmon is hexaploid. Crossing was initiated among a small number of native PCNA cultivars, which were all late ripening and exhibited fruit cracking habits. Although the frequency of early ripening progenies in earlier stages was low, after several generations, the fruit ripening time in the maternal population became markedly advanced. However, since these progenies could be obtained only through inbreeding within a narrow gene pool, serious constraints such as the production of small fruits should be overcome. Discipline: Horticulture Additional key words: astringency, fruit, fruit cracking, inbreeding, ripening Breeding at Fruit Tree Research Station Persimmon (DiosP)iros kalzi Thunb.) originated and has been mainly grown in China, Japan and Korea. Especially in Japan, it has been a major fruit crop for a long time, and even now, it ranks fifth in production. Therefore, many native cultivars have been developed all over the country. The oldest national horticultural research station in Japan was established at Okitsu, Shizuoka, in 1902. Its present name is Okitsu Branch, Fruit Tree Research Station (FTRS), Ministry of Agriculture, Forestry and Fisheries (MAFF). More than 1,000 cultivars were collected and identified from all over the country. Fifty-seven cultivars including Fuyuu and Jirou were selected and recommended for production in 1912.,. Subsequent efforts to introduce genetic resources from Korea and China enabled to identify a certain number of astringent cultivars, which were selected and recommended for extension but fai led to gain the status of majo1cultivars in Japan. The persimmon improvement program at Okitsu began in 1938, with emphasis placed on the improvement of the pollination constant non-astringent type (PCNA). Twenty-two PCNA selections derived from crossings among existing cultivars had been subjected to local adaptability tests in various districts all over the country. As a result, one cultivar was selected and released under the name of Suruga in 1959°. The fruits are late ripening, large with a cracking habit. Thereafter, crossing among native cultivars and the resulting F,s led to three PCN A selections, which were subjected to the second local adaptability test. lzu was selected among them and released in 19702>. The fruits are early ripening, with a high eating quality but cannot be well pre, served. The tree is not vigorous and not productive. The total number of progenies examined at Okitsu was approximately 2,500. Akitsu Branch of FTRS was established in 1968. The persimmon breeding program was carried over by the Akitsu Branch, thereafter. Orchards were established and seven PCNA selections of early to • Present address : Okinawa Branch, Tropical Agricultuve Research Center (lsigaki, Okinawa, 907 Japan)

Quality of Compost Produced from Animal Wastes

Abstract: The characteristics of animal waste composts produced in Japan were summarized. Animal waste composts are useful for supplying nutrients to plants and for improving the soil properties. The contents of nutrients in the composts were in the order of poultry > swine > cattle. Thus, the effectiveness as fertilizer foll owed the same order. The contents of heavy metals in the animal waste composts were studied. The content of copper was very high in the swine waste composts, and the content of zinc was also high in those from swine and poultry. Such high contents of heavy metals are caused by the addition of these elements to feeds. The objectives of composting were summarized. One of the objectives is to convert the raw animal wastes into products which are easy to handle and safe to health. Another objective is to convert the animal wastes into organic fertilizers which are safe for plant and soil. The maturing process of composting was characterized. Poultry wastes were more easily decomposed than cattle and swine wastes, and the decomposition rate of cattle wastes was almost similar to that of swine wastes. Maturity is an important factor related to the quality of the compost. The detection of nitrate by diphenylamine, the determination of cation-exchange capacity (CEC), and the germination test are recommended as methods of estimating the degree of maturity. Discipline: Soils, fertilizers and plant nutrition/Animal industry Additional key words: degree of maturity, maturing process, nutrients, organic fertilizer, recycling, soil conditioner Along with the enlargement of the scale of livestock farms, the management of wastes has become a serious problem in Japan. From the viewpoints of recycling as resources and prevention of environmental pollution, adequate application of animal wastes to croplands is needed. Animal wastes are very important resources for agriculture, because they contain many nutrients and improve the chemical, physical, and biological properties of soil. However, raw animal wastes are not generally suitable as organic fertilizers or soil conditioners, because they cannot be handled readily and their application to croplands may cause adverse effects on plant and soil. Composting can eliminate the problems to some extent, and is an effective way to promote the agricultural utilization of animal wastes. Quality contro l of the composts is very important to promote the recycling of animal wastes. The qualities required for the utilization of animal waste composts are

Effect of Hypocotyl Morphology on Survival Rate and Growth of Cucumber Seedlings Grafted on Cucurbita spp.

Abstract: Horizontal grafting, in which scion and rootstock are cut at the hypocotyl level transversely, is essential for mechanization of grafting. The present studies have been conducted to improve the survival rate and growth of cucumber grafted on Cucurbita spp. through horizontal grafting at the level of hypocotyls. The survival rate of the cultivar Nankyoku No. 2 (Cucumis sativus) with six vascular bundles at the hypocotyl was diferent when it was grafted on Unryuh No. 1 or Kongoh (C. moschata) with mainly six vascular bundles. The survival rate of the scion grafted on Dairoku (C. maxima) with mainly 12 vascular bundles was the lowest. It was found that the survival rate was inversely corelated with the diference in the diameters of the hypocotyls of the scion and rootstock. Dry weight value of the surviving scion was larger on Unryuh No. 1 than on Kongoh and the smalest on Dairoku. It is concluded that by minimizing the diference in the diameter of the hypocotyls between the scion and rootstock the survival rate and growth of cucumbers which are horizontaly grafted on Cucurbita spp. at the hypocotyl level could be enhanced. Discipline: Horticulture Additional key words: Cucumis sativus, grafting, rootstock, scion, vascular bundle

Soil-Borne Diseases and Ecology of Pathogens on Soybean Roots in Indonesia

Abstract: Studies on root diseases and causal fungi on soybean in Indonesia were carried out. Missing plants due to damping-off of seedlings occurred frequently. In addition, the average infection rates of root rots amounted to 60% of all the surviving plants toward the pod filling stage. The more severe root rot was, the lower the yield of soybean seeds. The isolates from the seedlings showing damping-off belonged mainly to either Pythium apanidermatum, Sclerotium rolfeii, anastomosis groups (AG) 4 and 7 of Rhizoctonia solani, AG-E and other AGs ofbinucleate Rhizoctonia spp. As time went on, the severity of the root rot symptoms increased rapidly and Fusarium spp. and binucleate Rhizoctonia were predominantly isolated from rotten roots in the great majority of the fields, except for one field where root rot disease caused by Cylindrocladium sp. occurred. All the isolates of S. rolfsii, R. solani AG-4 and AG-7, binucleate Rhizoctonia AG-E, P. aphanidermatum, P. myliotylum and Pythium sp. caused damping-off as well as root rot on soybean, whereas the isolates of F. solani and C.floridanum from soybean were pathogenic to the plants in the middle or late stage of growth. A new root rot disease caused by C.floridanum and damping-off disease caused by AG-7 and AG-E of Rhizoctonia spp. were detected for the first time in soybean fields in Indonesia. Discipline: Pl ant disease Additional key words: Cylindro cladium, Fus ari um, Pythium, Rhiz octonia, Sclerotium

Quality evaluation of rice in Japan

Abstract: Quality evaluation of rice in Japan can be carried out by the application of sensory test and physico-chemical determinations. The former is a basic method although it requires a large amount of samples and many panellers. The latter is an indirect method to estimate the eating quality based on the chemical composition, cooking quality, gelatinization temperature and/or the physical properties of cooked rice. Although it is impossible to estimate accurately the eating quality by only one physico-chemical determination, if a rapid, simple and more accurate method to evaluate rice quality could be developed, it would be very useful for both the producer and the consumer of rice. Discipline: Food/Postharvest Additional key words: amylose, physico-chemical determination, sensory test

Mechanism of resurgence of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Yponomeutidae)

Abstract: The role of predators and parasites was evaluated by artificially excluding them for the estimation of the DBM mortality. The results showed the importance of ground-dwelling predators such as the lycosid spider which was a major biotic mortality agent of DBM at immature stages based on an immunological test; the incidence of this spider decreased by the application ofmethomyl. The LC-'l of the lycosidPardosa astrigera was around 10 ppm against about 7,500 ppm for the fourth instar DBM larvae using the dipping method and about 20,000 ppm for third instar larvae by feeding methomylcontarninated cabbage leaves. Applications of sublethal concentrations of methomyl to fourth instar larvae and pupae of DBM resulted in the increase of the fecundity of the adults which emerged. The adult females derived from the treated pupae laid a larger number of eggs with a higher rate offertilization than the untreated check. The application of methomyl thus may actually cause a resurgence of the insect population through the following mechanisms: (1) insecticide resistance, (2) differential mortality levels between DBM and its predator which is a major factor in the control, and (3) stimulation of the reproductive potential. Discipline: Insect pest Additional key words: Bras sic a, I ycosi d spiders, natural enemy, predator, resistance

Use of Osmia cornifrons for Pollination of Apples in Aomori Prefecture, Japan

Abstract: A mite, Chaetodactylus nipponicus, invades nests of Osmia corni.frons to feed on pollen which has been stored by the bees in the nests for their off spring. The mite al so adversely affects the flight of the bees by clinging to their bodies. Two methods of control of the mite were developed. In the first one a selective insecticide was used. Egg mortality from the mite decreased markedly by supplying the bees with nest sources treated with 60 ppm endosulfan. Furthermore, by spraying the nest entrance two to three times every second or third day during the flying period, the mite could be controlled without any lethal effect on the bees. In the second method, differential mortality from high temperatures was used, as pre-pupae of 0. cornifrons are resistant to high temperatures due to the diapause while during this period, the mites are still reproducing and are sensitive to high temperatures. Most orchards require the application of insecticides in late April. To avoid the exposure of the bees to insecticide sprays, emergence from nests is delayed by storing the nests at 0-5°C from early to late April. Even though the period of storage exceeds 20 days, the activity of the bees is normal. Discipline: Horticulture Additional key words: cold storage, control of Chaetodactylus nipponicus, life history, mortality factors, pesticide application

New Lines Harboring du Genes for Low Amylose Content in Endosperm Starch of Rice

Abstract: Two lines of rice, Tankei 1915 and 2019 with a low amylose content were registered as breeding materials in 1992. There lines were selected in the progeny foll owing the treatment of the Japanese rice cultiv ars, Kinm aze and Kochihibiki with methyl-ni troso-ure a (J)i.[NU). T ankei 1915 was characterized by a dull endosperm which could be distinguished from waxy and nonwaxy endosperms. The amylose content ofTankei 1915 was 9.2%, half of the content of the parental cul ti var, Kinmaze. The line harbors the du-1 gene which is responsible for lowering the amylose content and is located at a locus independent of the waxy (wx) locus on Chromo some 6. The other line, Tankei 2019, was characterized by a dull endosperm which is visually similar to the waxy endosperm. The amylose content ofTankei 2019 was 6.3%, one-third of the content of the parental cul ti var, Kochihibiki. This line harbors the du-2 gene which is responsible for the decrease of the amylose content and is located at a locus independent of the wx and du-1 loci. The new type of endosperm starch of rice grains may contribute to the improvement of the eating quality of cooked rice and the development of new products in the food industry. Discipline: Crop production Additional keywords: dull endosperm, grain quality, Oryza saliva, starch property

Infection Types in Rice-Xanthomonas campestris pv.oryzae Interaction

Abstract: The resistance reactions of rice varieties to bacterial leaf blight caused by Xanthomonas campestris pv. oryzae were grouped into three types: symptomless, browning and small yellow lesions. In the resistance reaction controlled by the resistance genes Xa-1, Xa-7 and Xa-10 no symptoms were observed, while the reaction controlled by Xa-2, Xa-4, Xa-4•, xa-5 and xa-8 was characterized by small yellow to limited yellow lesions. The resistance reaction controlled by Xa-3, Xa-4~. Xa-6, xa-9 was characterized by brown necrosis. The population levels of the incompatible strain were lower than 106 cfu per inoculated leaf in the symptomless and browning type of resistance reactions. In the resistance reaction with small yellow lesions, the bacterium multiplied to the level of 107 cfu per inoculated leaf. Histological observation showed that multiplication and translocation of the incompatible strains were very limited compared with those of the compatible ones. !tis concluded that the infection types in the host-parasite interaction are caused by the degree of multiplication of the bacterium in the host tissues and ability of the host tissues to undergo necrosis. Discipline: Plant pathology Additional key words: resistance gene, resistance re action, rice bacterial leaf blight

Calf Production by In Vitro Fertilization of Follicular Oocytes Matured In Vitro

Abstract: The procedure for bovine in vitro fertilization (NF) involving the collection of ovaries at the slaughterhouse, maturation of oocytes in vitro (NM), capacitation and insemination in vitro and development to blastocysts in vitro is well established. Transportation of ovaries in physiological saline at 23 and 38°C afforded a large number of oocytes capable to develop to blastocysts after in vitro maturation and fertilization. The follicular contents were scrubbed out with a small spoon after incision of the follicle to collect a large number of oocytes ( 13.4 per pair of ovaries) rather than aspiration with an 18-G needle (7.2 per pair of ovaries). Cleavage ability after maturation and in vitro fertilization depended on the characteristics of the cumulus cells surrounding the oocytes. A period of 20 hr for the culture to achieve maturation and for the time of the insemination was prefer-· able to 24 or 28 he for the development to blastocyst. For in vitro capacitation of sperm, heparin was effective and the oocytes fertilized by heparin-treated sperm developed well to full term after transfer to recipient cat tie. Bovine IVM/IVF can be used for commercial beef calf production and for the supply of embryos with known stages of development for research purposes and for the development of new technologies. Discipline: Animal Industry/Biotechnology Additional keywords: blastocyst, bovine, capacitation, embryo, spontaneous maturation

Effects of Row Cover on the Growth of Leafy Vegetables in Summer in the Subtropical Zone of Japan

Abstract: The environmental conditions under row covers are characterized by the attenuation of strong radiation, the alleviation of the increase of the soil temperature and the maintenance of the soil moisture and atmospheric humidity in comparison with the conditions prevailing in open fields. The wind-breaking effect and the effect on the preservation of the soil and air moisture were more conspicuous under direct cover as compared with floating cover. However, the increase of the soil and air temperature was significantly suppressed and the damage caused by pests was less pronounced with the floating cover. Germination and early growth of Pak-choi were promoted by covering. Plant height and leaf area of Pak-choi increased, while the dry matter decreased under the covers, resulting in a more etiolated plant growth. The quality of the products was satisfactory. The optimum environmental conditions for the growth of Pak-choi were as follows: air temperature, 25°C; soil temperature, 25°C; soil moisture, pF 1.25-1.75; wind velocity, 0.4-1.4 mis and higher relative humidity (80%). Row cover appears to be suitable for use in the tropics as well as in the subtropics. Discipline: Crop production/Agricultural environment Additional key words: cheese-cloth, direct cover, floating cover, Pak-choi, wind-break net

Encapsulation of Somatic Embryos of Carrot and Promotive Effects on the Growth of Plantlets in vitro

Abstract: Encapsulation of somatic embryos is considered to be an effective method for mechanical handling of fragile somatic embryos. Encapsulation method of somatic embryos using sodium alginate and calcium chloride solutions and growth of plantlets from encapsulated embryos were investigated. It was concluded that the optimum hardness of the capsule was 2.0 N/cm2 based on the germination percentage of embryos, growth of plantlets and ease of handling. The growth of the carrot plantlets was promoted by encapsulation of somatic embryos compared with the plantlets from naked, unencapsulated embryos due to the removal of the water and nutrient stress to which embryos are readily exposed at the early stage of development. Discipline: Horticulture Additional key words: capsule hardness, encapsulation method, germination percentage, sodium alginate

First Occurrence of Soybean Southern Stem Canker in Paraguay

Abstract: Southern stem canker of soybean was detected on more than 10 cul ti vars in 3 and 13 locations in Itapua and Alto Parana prefectures in Paraguay, respectively. Symptoms and signs on the diseased soybean plants were identical with those reported for the disease previously. Morphology and characteristics of the pathogen both on the host and artificial media agreed with the descriptions of Diaporthe phaseolorum f. sp. meridionalis (anamorph: Phomopsis phaseoli f. sp. meridionalis). About 150 isolates were obtained from the diseased soybean plants. Soybean plants inoculated with some of the isolates showed symptoms typical of the disease 2-3 weeks after inoculation. It was shown for the first time that the disease occurred in Paraguay. Discipline: Plant diseases Additional key words: Diaporthe phaseolorum f. sp. meridionalis, phomopsis phaseoli f. sp. meridionalis, Glycine max

Factors Influencing the Rooting of Cut-Sprouts in Sweet Potato

Abstract: One of the limiting factors for dry matter production in sweet potato (lpomoea batatas Lam) is the establishment of cut-sprouts or cuttings. To improve the establishment of cut-sprouts, factors affecting the rooting of cut-sprouts were investigated. First, the effect of the soil temperature on rooting was investigated. The optimum soil temperature for rooting and varietal differences, varietal differences in rooting ability at a low soil temperature, and the effect of high soil temperature stress on the rooting were analyzed under controlled environment. The effect of vinyl mulching on rooting and the formation of tuberous roots was analyzed under field conditions. Second, the effect of holding (storage) of cut-sprouts on rooting was investigated. Beneficial effect of holding for 5 to 10 days on the rooting, formation of tuberous roots and yield was revealed. The physiological mechanisms of the beneficial effect of holding were al so analyzed. Discipline: Crop production Additional keywords: establishment of cut-sprouts, formation of tuberous roots, holding, lpomoea batatas, soil temperature

Induction of Nitrogenase and Hydrogenase Activities in the Free-Living State of Bradyrhizobium japonicum

Abstract: Effect of components in the medium on the induction of the nitrogen-fixing activity in the free-living state of slow-growing soybean nodule bacteria, B.japonicum, was studied using five strains each of Hup+ and Hup-. Nitrogenase activity was expressed regardless of the oxygen concentration in a defined solid medium (G:M) while glutamine, malic acid and molybdenum were found to be the essential components for the expression of the nitrog enase activity. Uptake hydrogenase activity was also expressed on the same nitrogenase induction medium (GM). Effect of the medium composition on the expression of the uptake hydrogenase activity was different from that for the nitrogenase activity. Glutamine, malic acid and molybdenum, were not essential for the expression of the uptake hydrogenase activity. This newly developed method on defined solid medium can be used for the evaluation of the nitrogen-fixing activity of strains in Bradyrhizobium. Discipline: Soils, fertilizers and plant nutrition Additional key words: C)I 2 reduction, medium, nitrogen-fixing activity, root nodule, slow-growing bacteria, uptake hydrogenase

Growth of Trees Planted in Degraded Forest Land

Abstract: Fast-growing tree species planted in the Makiling forest in Los Banos, Laguna and degraded forest land in Carranglan were examined to analyze the characteristics and productivity of these tree species in each area. Acacia auriculiformis was found to be the most adapted species to degraded land, followed by yemane (Gmelina arborea). Yemane showed excellent growth where the physical soil properties were improved. Yemane and teak (Tectona grandis) were fire-tolerant species and their growth gradually improved. Annual height increment ofDipterocarpaceae seedlings planted under A. auriculiformis ranged from 30 to 40 cm and the height of some of them exceeded 4 m. Litter on the Acacia forests amounted to more than 1,500 g/m2. The values were almost twice those of tree species for long-rotation forests in Los Banos. Discipline: Forestry and forest products Additional keywords: fast-growing species, long rotation, plantation, underplanting

Balance and Profitability of Private Forestry in Japan

Abstract: The market price of wood in Japan is considerably affected by the price of imported logs, which account for 75% of the wood supply. The decrease in the log prices in recent years has brought about a depreciation of the price of stumpage, while the cost of producing logs is rising due to constant increases in wages and material costs. This situation results in the decrease in the profitability of forestry year after year. The internal rate of return (IRR) in forestry that was most recently computed was around 1.5%. Furthermore, the shortage in forestry labor has become a major problem. At the same time, national expectations of the purposes of forests, such as environmental conservation, are triggering the development of new forestry projects and changes in the current management policy to increase the profitability of forestry activities. Discipline: Forestty and forest products Additional keywords: forest net income, forest work, internal rate of return, management cost, private forest land

Prevention of Aflatoxin Contamination in Thai Maize 1. Infection of Thai maize with Aspergillus flavus

Abstract: Shelling was found to be the most critical process for the infection of Thai maize with Aspergillus.flavus. Infection was initiated from damaged maize kernels. In fully mature maize kernels, A . .flavus infection was slower but a higher rate of aflatoxin contamination was detected compared to immature ones. Discipline: Postharvest technology Additional keywords: carcinogenic, mature maize, shelling

A New Breaking Strength Tester BSTW-1

Abstract: The author developed anew apparatus BSTW-1 to measure the breaking strength and compared the measurements of the breaking strength of plastic straws, wheat and rice culms using BSTW-1 and E0-3. It was concluded that BSTW-1 was more convenient and more useful to measure the breaking strength in studies on lodging resistance. Also, the number of samples required to measure the breaking strength at the basal part of the rice culm was discussed. Discipline: Crop production/Experimental apparatus and method Additional key words: breaking strength, development of apparatus, e stim ati on of number of samples, lodging resistance

Production of Transgenic Tomato Plants with Specific TMV Resistance

Abstract: An F1hybrid between Lycopersicon esculentum and L. peruvianum was found to be highly suitable for Agrobacf2rium-mediated gene transfer. Transgenic plants were prepared which carried an introduced chimeric TMV coat protein gene cDNA expressing the coat protein under the control of the 35S RNA gene promoter from cauliflower mosaic virus. Ltbl, a specific TMV mutant strain was used to assay the resistance conferred by the introduced coat protein gene, since the transgenic plants as well as the parent Fl plant carried the Tm-2 gene that expresses resistance to wild type TMV strains but not to Ltbl. Coat protein was found to accumulate in fully developed fresh 1 eaves at a level of ab out 2. 5 μg per g fresh weight in a pl ant designated as 8804-150 that expressed the strongest resistance among the pl ants examined. The resistance was confirmed to be transmissible to the next generation. The 8804-150 plant was selected for further studies including field tests on biosafety and performance of the TMV resistance. Discipline: Biotechnology Additional key words: Agrobacf2rium-mediated transformation, coat protein gene, Lycopersicon esculentum, Lycopersicon peruvianum

Runoff Analysis in a Catchment Area Covered by Tropical Forests Using a Robust Multiple Regression Model 2. Analysis and application

Abstract: Actual rainfall runoff modeling involves two kinds of procedures: identification of the optimum parameters and selection of suitable data. Although many reports described automatic procedures to obtain the optimum parameters of models, few proposed a suitable procedure of data selection. In these papers a new multiple regression model which enables to identify the optimum parameters of linear runoff and select suitable data for the modeling oflinear runoff is described. The method based on the robust statistical theory is referred to as RFMD (robust fixed maximum discharge) method developed in the past decade. In this paper, this method was tested by using the original data of the Muda and Pedu dams in Malaysia. Compared to the FMD method, the RFMD method can supply similar models for long-term analysis and improved models for short-term analysis which contains irregular data. Discipline: Irrigation, drainage and reclamation Additional key words: robust estimation, runoff analysis, tropical forests, multiple regression analysis Introduction In the former paper1> the authors introduced the robust multiple regression method into runoff analysis in relation to the FMD method. A robust estimation method can omit the biased effect of error distribut ion. In this paper, the model was appl ied to the rainfall runoff analysis of a catchment covered by tropical forests where the data may contain some unexpected errors. The biweight method in the M estimation method was selected for analysis in the former paper. It is homologous to the FMD method from the view point of separation of the linear runoff component. This paper analyzed this robust multiple regression method in relation to the FMD method in which the rate of robustness strongly depends on the percentage of irregular data. In this paper a long-term analysis and a short-term analysis are presented. Long-term analysis of a catchment covered by tropical forests The following analysis was performed on the original data in a catchment covered by tropical forests. The object area was selected in the basin of two irrigation dams, the Pedu and Muda dams, in the Kedah province in Malaysia. The acreage is 1,551.1 km2 and the basins of the two dams are connected by a tunnel for the passage of the runoff discharge. Therefore, the basins of the two dams can not be separated. They are treated as a connected basin. Fig. I shows the outline of the basin. Inflow and rainfall data covering a 12 year period from 1971 to 1982 were used for the calculation.