Kebede Woldetsadik

Antifungal Activity of Some Plant Extracts against (Colletotrichum Musae) the Cause of Postharvest Banana Anthracnose

The present study was conducted to determine the efficacy of extracts of some plant species against Colletotrichum musae. Methanolic extracts of 21 plant species were screened for their inhibitory effect against C. musae using paper disc method and spore germination assay. Among them, extract of Prosopis juliflora exhibited superior antifungal activity (30.7 mm), followed by Acacia albida (19 mm) as compared to nill in the control. On the other hand, carbendazim, which was used as a standard chemical check, demonstrated by far the highest inhibition zone of 51.7 mm diameter. Extracts from A. albida, Dovalis abyssinica and P. juliflora reduced conidial germination to 0.2, 0.5 and 0.3%, respectively, which didn’t vary statistically from 1.2% in Carbendazim. Six plant species, viz., A. albida, Azadirachta indica, Argemone mexicana, D. abyssinica, P. juliflora and Vernonia amygdalina, that showed high to moderate antifungal activity in the preliminary screening, were further tested for their thermal stability at 60°C and for the efficacy of their aqueous extracts against C. musae. Extracts of the tested plant species were found to be heat stable and aqueous extracts of A. albida showed the highest antifungal activity (18 mm), followed by P. juliflora (12.3 mm). Further studies need to be undertaken to isolate the active compounds from those extracts with fungicidal potential.

Evaluation of Antifungal Activity of Plant Extracts against Papaya Anthracnose (Colletotrichum gloeosporioides)

Antifungal activities of nineteen plant extracts were tested in 2010 with the objectives of screening potential plant extracts against Colletotrichum gloeosporioides under in vitro and anthracnose caused by Colletotrichum gloeosporioides, on papaya (Carica papaya L.) during storage. Ethyl acetate extracts of Lantana camara resulted in the highest inhibition (with inhibition zone of 35.3 mm) and showed strong activity against C. gloeosporioides. Inhibition levels of spore germination that reached 88.7, 85.8, 85.1 and 84.6% were recorded over the control by extracts of Lantana camara, Lantana viburnoides, Echinops sp. and Ruta chalepensis. Four aqueous extracts were evaluated for control of anthracnose under in vivo for 14 days, and Echinops sp. (25%) was found to be most effective in the reduction of disease development and maintaining the overall quality of papaya fruit. Further studies on isolation and characterization of the active (antifungal) compounds are needed.

Shallot yield, quality and storability as affected by irrigation and nitrogen

Summary Field experiments were conducted to evaluate growth, yield and quality of shallot (Allium cepa var. ascalonicum Baker) under three levels of irrigation and nitrogen fertilization, on a clay soil in the sub-humid tropical climate of eastern Ethiopia from 1999 to 2002. Treatments comprised furrow irrigation at three moisture levels (75, 50 and 25% available soil moisture) and three nitrogen levels (0, 75 and 150 kg ha–1), using two local shallot cultivars. Bulb yield and mean bulb weight of both cultivars were higher at irrigation levels of 75% than at 50% or 25% available soil moisture. Total weight and rotting losses of bulbs were highest at the irrigation level of 75% and least at 25% available soil moisture in the cultivar ‘DZ-sht-91’, while in cultivar ‘Fedis’ irrigation treatments did not affect storability. The best irrigation water-use efficiency was obtained with irrigation at 50% available soil moisture. Nitrogen at 75 or 150 kg ha–1 increased the pyruvic acid content of bulbs. Application of nitrogen tended to increase mean bulb weight in ‘Fedis’ while ‘DZ-sht-91’ receiving no nitrogen had heavier bulbs. No significant effects were observed on the yield, dry matter, soluble solids and storability of bulbs due to the nitrogen fertilization. No interaction effects were observed between N and irrigation treatments. Irrigation at 75% available soil moisture is suggested for shallots destined for immediate use.

Season, and Nitrogen Source and Rate Affect Development and Yield of Shallot

ABSTRACT Three field experiments were conducted in 1999 and 2000 to assess the response of shallots (Allium cepa var. ascalonicum Backer) to nitrogen fertilizer sources and rates in eastern Ethiopia. Treatments comprised three nitrogen sources, urea, ammonium nitrate and ammonium sulphate, each at 0, 50, 100, 150 and 200 kg ha−1 N. Bulb yield was significantly increased with nitrogen fertilization up to 150 kg ha−1 in the main rainy season of 2000 when supplemental irrigation was applied. However, fertilization significantly reduced growth and yield of shallot in the main rainy season of 1999 and the short rainy season of 2000 under rain-fed conditions. Fertilization tended to increase bulb number per plant while reducing mean bulb weight. The dry matter and total soluble solids of bulbs from fertilized plots were either higher than or similar to those of unfertilized shallots. Ammonium nitrate produced significantly higher yields of shallots than ammonium sulphate, but did not differ from urea. Nitrogen source did not have significant effects on plant height, leaf number, bulb weight or bulb diameter. Higher nitrogen levels increased leaf and bulb nitrogen contents at harvest. The results indicated that nitrogen fertilizer should not be used for rain-fed shallots under low moisture regimes. Supplemental irrigation is essential in order to achieve high yields with nitrogen fertilization practices.

In Vitro and In Vivo Activity of Selected Plant Extracts against Papaya (Carica papaya L.) Anthracnose (Colletotrichum gloeosporioides)

Anthracnose is the major postharvest disease of papaya wherever the fruit crop is grown. The present investigation was conducted with the objectives of evaluating plant extracts for their activity against Colletotrichum gloeosporioides in vitro and for controlling anthracnose on artificially inoculated ‘solo’ papaya fruit. Plant specimens were collected from Ambo and Haramaya, Ethiopia, dried under shade and extracted using methanol. Out of 18 plant extracts tested, nine of them showed activity against C. gloeosporioides. Methanol extract of Echinops sp. of 10 μL from the concentration of 50 mg/ml resulted in the highest inhibition zone of 13.5 mm against mycelial growth of C. gloeosporioides. Spore germination of C. gloeosporioides was reduced by 98.7%, 97.7% and 97.3% over the control by extracts of Echinops sp., Thymus serrulatus and Ocimum lamifolium, respectively. Among four botanicals evaluated in vivo as 10% and 25% aqueous extracts, Echinops sp. at 25% concentration kept disease severity score at 1.3 out of 5 (i.e. less than 1% fruit surface affected) and maintained quality of papaya fruit during 14 days experimental period. Further study is necessary on sensory analysis and developing botanicals as natural fungicides.

Shallot Yield, Quality and Shelf-life as Affected by Nitrogen Fertilizer

Shallot (Allium cepa var ascalonicum Baker) can be a substitute where bulb onion (A. cepa L. var cepa) does not do well. However, production and productivity of shallot can be limited due to poor soil fertility; lack of improved production techniques; unimproved varieties, and high post-harvest losses. Farmers in northeastern Ethiopia rarely apply fertilizers to shallot. A field study was undertaken in that region in 2007/2008 to determine effects of nitrogen fertilizer on yield and shelf-life of shallot. Treatments were 0, 50, 100, and 150 kg·ha−1 N and cvs. ‘Huruta,’ ‘Negelle,’ ‘Dz-sht-68,’ and a local landrace. Application of 150 kg·ha−1 of N increased marketable and total bulb yields by 26% over the control. The highest and the lowest marketable bulb yields were for ‘Dz-sht-68’ and the local landrace, respectively. In storage nitrogen fertilization increased bulb weight loss in all cultivars, with weight loss being highest for the local landrace. Nitrogen fertilization at 150 kg·ha−1 N increased bulb rotting up to 79% over the control. Shallot shelf-life was of short duration. Application of 100 kg·ha−1 N was optimal for shallot bulb production without affecting bulb quality.

Effect of hot-water treatments in vitro on conidial germination and mycelial growth of Colletotrichum musae isolates

Anthracnose caused by Colletotrichum musae is the most important postharvest disease of banana fruit. The present study was conducted to evaluate the sensitivity of C. musae isolates to hot water treatment in vitro. The effect of hot water treatment (HWT) in vitro was determined by placing conidial suspensions and plugs of agar with mycelia of 12 single spore isolates of C. musae in hot water bath at 45, 50 and 55°C for 2, 5, 8, 11, 14 and 17 min. Percent inhibition of conidial germination and colony growth increased with increased temperature and time combinations. HWT at 55°C for 5 min had an equivalent inhibition of conidial germination and reduction of mycelial growth to that of HWT at 50°C for 17 min in the 12 C. musae isolates. Remarkable variability in thermo-tolerance was found among 12 isolates of C. musae and isolate HC2 and HC3 were found to be the most sensitive, while DL1 and DL2 were comparatively heat tolerant isolates. Key words: Banana anthracnose, Colletotrichum musae, hot water treatment, sensitive, tolerant.

Influence of Nitrogen and Phosphorus Application on Bulb Yield and Yield Components of Onion (Allium Cepa L.)

RESEARCH ARTICLE Influence of Nitrogen and Phosphorus Application on Bulb Yield and Yield Components of Onion (Allium Cepa L.) Negasi Tekeste, Nigussie Dechassa, Kebede Woldetsadik, Lemma Dessalegne and Abuhay Takele Aksum University, College of Agriculture, P O Box 314, Shire, Ethiopia Department of Plant Sciences, Haramaya University, P O Box 138, Dire-Dawa, Ethiopia Melkassa Agricultural Research Centre, P O Box 2500, Adama, Ethiopia