Survey of barley and wheat diseases in the central highlands of Eritrea

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1 Phytopthol. Mediterr. (2004) 43, Survey of brley nd whet diseses in the centrl highlnds of Eritre AMOR H. YAHYAOUI 1, MOGENS HOVMOLLER 2, BRAHIM EZZAHIRI 3, AHMED JAHOOR 4, MOHAMMED HEDI MAATOUGUI 5 nd ASMELASH WOLDAY 6 1 Interntionl Center for Agriculturl Reserch in the Dry Ares, P.O. Box 5466 Aleppo, Syri 2 Dnish Institute of Agriculturl Sciences, Reserch Centre Flkkebjerg, 4200 Slgelse, Denmrk 3 Institut Agronomique et Vétérinire Hssn II, BP 6202-Instituts, Rbt, Morocco 4 Risø Ntionl Lbortory, Plnt Biology nd Biogeochemistry Deprtment, Building PRD-776, Post Office Box 49, Frederiksborgvej 399, DK-4000 Roskilde, Denmrk 5 Institut Technique des Grndes Cultures, Route de Tiret (Souffy), P.O. Box 184, Khemis-Milin, Ain-Defl, Algeri 6 Deprtment of Agriculturl Reserch nd Humn Resource Development, P.O. Box 1048 Asmr, Eritre Summry. Annul surveys of brley nd whet diseses were conducted in Eritre from 2000 to The surveys covered six zones of the centrl highlnds where brley nd whet re grown. The min diseses of brley were netform net blotch, spot-form net blotch, lef rust nd scld. Other, less importnt diseses were loose smut, covered smut, brley stripe nd septori lef blotch. Whet ws minly ffected by yellow rust nd lef rust. Loose smut, septori lef spot nd tn spot diseses were less prevlent. The verge incidence of these diseses vried ccording to the zone. Among brley diseses, net blotch incidence ws high in four of the six zones surveyed. Lef rust occurred t medium incidence in five zones. Loose smut ws more severe in the southern highlnd plins, while covered smut ws more common in the south-estern highlnd terrces. For whet, yellow rust incidence ws high in two zones. Ares with high incidence of yellow rust were not necessrily those with high incidence of lef rust. Lef rust ws importnt in the south-estern nd western highlnd terrces nd in the western highlnd plins. The number of diseses found in the sme field vried from 2 to 5. The south estern highlnd terrces, the western highlnd terrces nd the northern highlnd terrces hd the highest proportions of individul brley fields with three or more diseses. Key words: incidence, severity, hnfetse. Introduction Agriculture in Eritre is bsed on smllholder trditionl griculture chrcterized by subsistence frming nd low productivity. Cerel crops cover bout 95% of the re cultivted with over hlf million hectres in 1998 (Ministry of Agriculture, Deprtment of Lnd Resources nd Crop Corresponding uthor: A.H. Yhyoui Fx: E-mil:.yhyoui@cgir.org Production). Whet (Triticum estivum L.) nd brley (Hordeum vulgre L. emend. Bowden) re grown in the centrl highlnds, t n ltitude of over 1,500 m. The growing seson extends from June until December. Annul rinfll is bimodl, strting with little rin in April/My, followed by dry period nd nother wet period gin in July- October, during which time most of the rinfll occurs. Production of whet nd brley in Eritre remins very low; the ntionl verge yield for cerel crops does not exceed one ton per hectre. This is due to the lck of dequte gronomic prctices 39

2 A.H. Yhyoui et l. nd to vrious biotic stresses. Identifying the most common diseses nd their importnce is necessry first step in the estblishment of mngement strtegy integrting good culturl prctices, helthy seed nd genetic resistnce to reduce losses nd improve productivity of both whet nd brley. Disese surveys re useful mens to provide informtion on common diseses on cerel crops, their distribution in spce (gro-ecologicl zones) nd over time (yers), ccording to their incidence nd severity. The informtion generted from surveys cn be utilized to determine disese resistnce levels of cultivrs or lnd rces. The type of disese tht is most common (seed-borne, strw-borne or ir-borne) nd their ssocition my help in designing the mngement prctices needed for ech zone (Zdoks et l., 1979). Disese surveys were conducted in Eritre to identify the most common diseses of whet nd brley nd to help estblish mngement prctices better dpted to ntionl needs. Mterils nd methods Annul surveys were conducted from 2000 to The survey ws plnned for October ech yer when brley nd whet were between the flowering nd the grin filling growth stges. Frmers fields were ssessed for disese incidence nd severity following the procedure described by Stubbs et l. (1986) nd Zdoks et l., (1979). The zones surveyed re prt of the centrl highlnds, the only res where brley nd whet re grown. Theses zones cn be described s follows: Zone 1: South-Western Highlnd Plins (SWHP). Crops re dominntly brley nd whet in either pure stnds or s hnfetse ( mixture of brley nd whet). Other crops cultivted in this zone re tef, sorghum, mize nd food legumes. Zone 2: Southern Highlnd Plins (SHP). In this zone tef, sorghum, finger millet nd mize re by fr the most importnt crops becuse of the higher rinfll. Brley nd whet re cultivted mostly in pure stnds. Zone 3: South-Estern Highlnd Terrces (SEHT). Hnfetse is more common here thn brley nd whet s pure stnds; sorghum, finger millet nd legumes re grown to much lesser extent. Zone 4: Western Highlnd Terrces (WHT). Pure-stnd brley is the min crop, followed by whet nd hnfetse. Sorghum, finger millet nd legumes re grown much less frequently. Zone 5: Western Highlnd Plins (WHP). Brley nd hnfetse re more frequent thn purestnd whet. Other crops (whet, pe, chickpe, sorghum) re less common becuse soils in this zone tend to be shllow. Zone 6: Northern Highlnd Terrces (NHT). Brley followed by whet re the min crops, with hnfetse in third plce. Other crops re potto nd fb ben. In this zone 6-row brley types re more prevlent thn 2 row types. The zone is chrcterized by better rinfll, especilly in the higher terrces. A totl of 53, 89 nd 41 fields were surveyed in 2000, 2001 nd 2002 respectively (Tble 1). Fields hd minimum re of 0.5 hectre nd the minimum distnce between fields ws kept to 4 6 kilometers. Disese ssessment ws by wlking t rndom through field nd recording ny disese observed. The severity of ech disese ws determined using incidence nd severity prmeters (Jmes, 1971; Stubbs et l., 1986). Results nd discussion The most common diseses of brley nd whet in Eritre in re shown in Tbles 2 nd 3. The min diseses of brley were net-form net blotch (Pyrenophor teres f. sp. teres Scc.), spotform net blotch (Pyrenophor teres f. sp. mcult Scc.), lef rust (Puccini hordei Oth.) nd scld (Rhyncosporium seclis Oud.). Less importnt diseses were loose smut (Ustilgo nud [Jens] Rostr.), covered smut (Ustilgo hordei Pers.), brley stripe (Pyrenophr grmine S.Ito & Kuriby) nd Septori lef blotch (Septori psserini Scc). Whet ws minly subject to yellow rust (Puccini striiformis f. sp. tritici) nd lef rust (Puccini triticin Eriks). Less common diseses on whet were loose smut (Ustilgo tritici [Pers] Rostr.), Septori lef spot (Mycospherell grminicol [Fuckel] Schroeter; nmorph S. tritici in Dems) nd tn spot (Pyrenophor tritici repentis [Died] Dreschs). The min diseses on hnfetse (mixed brley nd whet) were lef rust nd net blotch for the brley component nd yellow rust nd lef rust for 40 Phytopthologi Mediterrne

3 Survey of brley nd whet diseses in Eritre Tble 1. Number of fields grown with brley, whet or hnfetse, in ech region in Survey zone Brley Bred Durum Hnfetse Brley Bred Hnfetse Brley Bred Durum Hnfetse whet whet whet whet whet SWHP SWHP SEHT WHT WHP NHT SWHP, South-Western Highlnd Plins; SWHP, Southern Highlnd Plins; SEHT, South-Estern Highlnd Terrces; WHT, Western Highlnd Terrces; WHP, Western Highlnd Plins; NHT, Northern Highlnd Terrces. Tble 2. Min brley diseses in Eritre in Disese Yer SWHP SHP NHT SWHP SHP SEHT WHT WHP NHT SWHP NHT Loose smut 1 /2 b 7/ /1 2/7 1/6 1 /4-2/10 2/8 Covered smut /7 5/6-02/12 3/10 - Brley stripe /10 1/8 Net blotch - 8/11 06/10 4/4 1/1 7/7 6/6 4/4 12/12 3/10 - Scld - 3/11 10/ /6-12/12 4/10 3/8 Septori lef blotch / /6 2/6 03/12 3/10 4/8 Lef rust - 6/11-4/4 1/1 7/7 6/6 4/4 12/12-1/8 For bbrevitions see Tble 1. b Fields with disese/totl fields surveyed. Tble 3. Min whet diseses in Eritre in Disese Yer SWHP SHP NHT SWHP SHP SEHT WHT WHP NHT SWHP NHT Loose smut 1/7 b - - 3/10 2/2 1/3 1/ /10 4/10 Septori lef blotch - - 5/7 4/10 2/2 1/7 1/ /10 - Tn spot /10 1/ / Lef rust 6/7 8/11 3/7 8/10 2/2 7/7 3/3 2/2 11/11 2/10 - Yellow rust 7/7 9/11 6/7 8/10 2/2 7/7 3/3 2/2 11/11 7/10 3/10 For bbrevitions see Tble 1. b Fields with disese/totl fields surveyed. Vol. 43, No. 1, April

4 A.H. Yhyoui et l. the whet component (Tble 4). The incidence of net blotch on brley nd yellow rust on whet ws higher thn the incidence of the other folir diseses. The verge incidence vried ccording to the zone surveyed (Tbles 5 nd 6). Among brley diseses, net blotch incidence ws high in four zones (SHP, SEHT, WHT, nd WHP), medium in one, SWHP, nd low in one, NHT. The second most importnt disese of brley, lef rust, occurred t medium incidence in five zones, nd t low incidence in one. Loose smut ws most common in the southern highlnd plins, while covered smut ws most common in the south-estern highlnd terrces. For whet, the incidence of yellow rust ws high in two zones, nd medium in three others. Ares with high incidence of yellow rust do not necessrily lso hve high incidence of lef rust. Lef rust ws common in the south-estern highlnd terrces, the western highlnd terrces nd the western highlnd plins. The number of Tble 4. Averge incidence (%) of some diseses (net bloch, lef rust, brley yellow rust nd whet lef rust) on hnfetse (brley+whet) fields in Eritre in Hnfetse component Disese Surveyed zones SWHP SHP SEHT WHT WHP NHT Brley Net blotch Lef rust Whet Yellow rust Lef rust For bbrevitions see Tble 1. Tble 5. Averge incidence (%) of brley diseses in fields in Eritre in Zone surveyed Loose Covered Net Scld Septori Lef smut smut blotch lef blotch rust SWHP SHP SEHT WHT WHP NHT For bbrevitions see Tble 1. Tble 6. Averge incidence (%) of whet diseses in fields in Eritre in Zone surveyed Loose smut Septori lef blotch Tn spot Lef rust Yellow rust SWHP SHP SEHT WHT WHP NHT For bbrevitions see Tble Phytopthologi Mediterrne

5 Survey of brley nd whet diseses in Eritre Tble 7. Number of diseses per field found on brley nd whet in Eritre in Crop Number of diseses Zone SWHP SHP SEHT WHT WHP NHT Brley 2 4/4-2/7 1/6 _ - 3-1/1 4/7 1/6-5/ /7 3/6 _ 6/ /6-1/12 Whet 2 6/10 5/7 2/3 2/2 3 2/10 2/7 8/11 4 1/10 _ 1/3 1/11 5 1/10 _ 2/11 For bbrevitions see Tble 1. diseses found in the sme field vried from 2 to 5 (Tble 7). The south-estern highlnd terrces, the western highlnd terrces nd the northern highlnd terrces hd the highest proportion of brley fields with three or more diseses. In the cse of whet, fields with less thn three diseses were not uncommon. The min cerel diseses in Eritre re seedborne (prticulrly for brley) stubble trnsmitted or wind-borne. To reduce the incidence of seedborne diseses frmers must use helthy seed. A wide rnge of stubble-borne blotch diseses ffect brley lndrce cultivrs nd these diseses hve evolved to epidemic levels. Good mngement, combining good culturl prctices with the selection of resistnt cultivrs is necessry to control these diseses. Regrding the rusts, it is well known tht there is wide rnge of virulent rust pthotypes tht re cusing the brek down of widely utilized sources of resistnce in whet. To reduce the impct of cerel diseses such s the rusts on whet nd lef blotch diseses on brley, frmers hve dopted mixtures of whet nd brley, known s hnfetse. Hnfetse cultivtion is common in mny cerel-growing res nd is one wy of reducing disese epidemics, which re common both on whet nd on brley. However, the benefits of hnfetse in reducing disese is often lost by combining low-qulity cerel crop species. It is therefore importnt to develop new mixtures of brley nd whet bsed on the selection of resistnt components with pproprite gronomic chrcters for greter yield. Literture cited Jmes W.C Mnul of ssessment keys for plnt diseses. Cndin Development Agency Pub. No Ministry of Agriculture, Deprtment of Lnd Resources nd Crop Production, Strengthening of Agriculturl Reserch in Eritre. Technicl report: FAO-Government Coopertive Progrm, 95 pp. Stubbs R.W., J.M. Prescott, E.E. Sri nd H.J. Dubin, Cerel Disese Methodology Mnul, Mexico, D.F., Mexico, CIMMYT. Zdoks J.C. nd R.D. Schein, Epidemiology nd Plnt Disese Mngement. Oxford University Press, New York, NY, USA, 427 pp. Accepted for publiction: Mrch 8, 2004 Vol. 43, No. 1, April