Genotype- by-environment interaction for marketable tuber yield in advanced potato clones using AMMI and GGE methods

Analysis of genotype-by-environment interaction (GEI) is critical in the local potato breeding and selection programme to obtain information on the performance of the genotypes for yield adaptability and stability. The objective of this study was to assess the marketable tuber yield of 18 advanced potato clones compared to the commercial variety Spunta at four locations (Bigara, Réduit, St. Antoine and Rivière du Poste), representative of four major soil types in Mauritius. They were analysed for adaptability and stability using the additive main effects and multiplicative interaction (AMMI) model and genotype main effect and genotype x environment interaction (GGE) biplot. Five clones gave significantly the highest marketable tuber yield in terms of overall ranking with yield increase of 47.4% to 59.6% over the control variety Spunta. AMMI analysis of variance detected significantly (P < 0.001) higher proportion of variation in marketable tuber yield due to environment (42%); followed by genotype x environment interaction (21%) which justified multi-locational testing. AMMI1 biplot demarcated clones 142/161/2 and 142/161/5 as high yielding and most stable while AMMI 2 biplot identified the winning genotypes for a specific environment. Thus, clones142/161/4 and 161/142/16 had specific adaptation to Bigara, 29/5/2 and 21/5/3 were adapted to St. Antoine, 21/5/10 to Rivière du Poste whereas 29/5/3 was adapted to Réduit. The GGE biplots identified clones 142/161/2 and 142/161/5 as the two most desirable genotypes close to the “ideal genotype”. The “which- won- where” view of the GGE biplot further pointed to the presence of two mega-environments, which corresponded to the sub-humid irrigated/humid environments (Réduit, St. Antoine and Rivière du Poste) and the high altitude super-humid environment (Bigara). These results showed that in future both AMMI and GGE methods can be integrated in the local potato breeding programme to select superior genotypes through multi-year and multi-locational yield evaluation. &nbsp

Agronomic Evaluation Study on Wheat Cultivation in Mauritius

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CARRYOVER OF SOIL-APPLIED HERBICIDES ON FLUE-CURED TOBACCO

An outbreak of a tobacco leaf disorder characterized by interveinal chlorosisof lowermost leaves was recorded for the first time in fields on the BeauChamp Sugar Estate in October 2003. Given that tobacco is grown on sugarcane rotational lands, herbicide simulation trials were conducted from 2005to 2007 at Réduit, Richelieu and Beau Champ to determine whether theresidual effects of one or more of the pre-emergence and post-emergenceherbicides commonly used in sugar cane might be responsible for thecharacteristic chlorotic symptoms. On all three sites, symptoms ofinterveinal and marginal chlorosis and necrosis of leaves were reproducedfollowing tobacco transplantation in plots previously sprayed with eitherKarmex Flo, Karmex Flo + Velpar, Atrazine + Velpar + Terbo, Tebusan,Garlon, DCMU or Tebusan + DCMU. Such symptoms could thus beattributed to carryover of herbicides of the phenylurea (Tebusan, DCMUand Karmex Flo), pyridine (Garlon) and triazinone (Velpar) families. Sincethe carryover effects of these herbicides reduced tobacco yield and quality,growers are henceforth recommended to avoid fields sprayed with theseherbicides during the last or two-last sugar cane cropping cycles.Keywords: Flue-cured tobacco, herbicides, interveinal yellowing, leafdisorder

Use of Unprocessed Coal Bottom Ash as Partial Fine Aggregate Replacement in Concrete

This paper investigates the use of unprocessed coal bottom ash as fine aggregate replacement in structural concrete in an attempt to contribute to a sound management of coal ash on the island of Mauritius. The coal bottom ash was obtained from FUEL thermal power station and had a loss of ignition of 11%. Experiments were conducted by replacing fine aggregate with bottom ash by weight in varying percentages (20%, 30%, 40%, 60%, and 80% respectively). The results showed that an increase in bottom ash content causes workability and plastic density to decrease and bleeding to increase. Moreover, above 40% replacement of bottom ash, compressive strength, flexural strength, and modulus of elasticity decreased sharply. In addition, an increase in bottom ash content improved the drying shrinkage performance of the concrete. The research also shows that 20% is the optimum percentage replacement to achieve favorable strength and good strength development pattern as a normal concrete mix with time. Unprocessed bottom ash from FUEL power station can thus be used as fine aggregate replacement in concrete for that specific percentage replacement. However, investigation should be carried out on the durability of the concrete.Keywords: unprocessed bottom ash, fine aggregate replacement, structural concret

Retracted: Effect of Penetron Admix on the Properties of Concrete

Retraction of Paper entitled: ‘Effect of Penetron Admix on the Properties of Concrete’ (Authors: A S Cadersa* and D Zephir)It has been brought to our attention by the CEO of the Penetron (Mauritius) Limited that Penetron Products were tested at the University of Mauritius and the results were published by the above authors without prior permission from the Company. After discussion with one of the authors, the CEO of the above Company and the representatives of University of Mauritius, it was agreed that the paper be removed from the databases, as it causes inconveniences to their American Partner, Penetron.We hereby make a request for the above paper to be retracted from AJOL.This research investigates the effects of the waterproofing admixture Penetron Admix on the fresh and hardened properties of structural concrete and assesses whether the product is suitable for use on construction projects in Mauritius. A grade 25 control mix (mix Y-0) and three mixes, each containing different percentages of admixture, were batched. The three mixes were labeled (Y-1), (Y- 2) and (Y-3) and contained 0.8%, 2% and 3% admixture by weight cement respectively. The water/cement ratio was kept constant throughout the experiments. The properties of concrete which are considered most useful on site, like workability, setting time and strength were investigated. The results showed that Penetron Admix enhanced the properties of the concrete. With the standard dosage of 0.8%, the characteristic strength of concrete at 28 days was increased by 15%. The optimum percentage of Penetron Admix for maximum strength, which is the most important concrete property, was found to between 2%- 2.2% by weight of cement. The permeability decreased drastically with the use of the product, namely 80% decrease at the standard dosage of 0.8% dosage. No major change was observed for the hardened density. The admixture also increased the workability and setting time of the fresh mix, but these effects were significant only with mixes containing 2% and 3% dosage.Keywords: waterproofing admixture, structural concrete, effects on concrete propertie

Use of Coal Bottom Ash as Mechanical Stabiliser in Subgrade Soil

This paper presents the laboratory investigation work which forms part of a full scale research road project in Mauritius where coal bottom ash is used as mechanical stabiliser in a saprolitic subgrade soil. Three mixtures of subgrade soil and CBA were investigated in the laboratory, each containing varying percentages of coal bottom ash by weight (15%, 30%, and 40%, resp.). The laboratory research indicated that the mechanical properties of the subgrade soil are improved with the addition of bottom ash. Highest values for soaked and unsoaked CBR values were obtained for the mixture containing 30% by weight of bottom ash, which were 145% and 95%, respectively, as compared to 40% and 55% for the subgrade soil alone. Upon addition of coal bottom ash, a considerable decrease in swelling potential during soaking was observed for the mixture containing 40% by weight of CBA. The swell decreased from 0.17% for the subgrade soil alone to 0.04% for the mixture containing 40% by weight of CBA. Moreover, a CBA content of 30% resulted in a mix of intermediate plasticity as compared to the subgrade soil which is highly plastic. It is concluded that coal bottom ash can be used successfully as a mechanical stabilizer in the experimental subgrade soil by addition of 30 to 40% of CBA

Tropical potato clones with larger canopies do not affect the growth, yield and yield components of intercropped sugar cane

About 80% of the potato produced in Mauritius comes from an intercrop with sugarcane. Recently, several new tropical clones with higher yields have been proposed to growers. Since their higher yields are associated with larger canopies, five trials were conducted in 1997 and 1998 to investigate whether the new clones affect the yield and yield components of intercropped cane. Percent and duration of canopy cover of tropical clones were significantly higher than those of traditional temperate clones. Canopy cover was also higher in intercropping than in pure stands.The potato had no significant effect on tiller density, number of millable cane, sucrose content, cane and sugar yield of intercropped cane. There were no relationships between either potato canopy cover duration or potato yield and relative cane yield. This confirms that even potato with larger canopies and higher yields do not affect intercropped cane growth and yield. Key Words: Mauritius, potato/sugarcane intercrop, sucrose content, tiller density (African Crop Science Journal 2001 9(1): 59-66

Echinococcus multilocularis infection in India: first case report proved at autopsy

The occurrence of Echinococcus multilocularis is reported in India for the first time. The patient was a young man, various clinical diagnoses were made and he finally died after an attempted membranotomy for suspected membranous obstruction in the inferior vena cava. Autopsy revealed classical E. multilocularis infection of the liver with direct spread of the inferior vena cava, the right atrium and through the diaphragm into the base of the left lung. It also had caused an outflow tract obstruction to the hepatic venous flow by direct physical pressure distorting the proximal intrahepatic portion of the inferior vena cava. In addition the patient had multi-valvular lesions of rheumatic origin and a terminal infective endocarditis due to staphyloccal infection