Sorghum (Sorghum bicolor) is the most important food

crop in savanna areas of the West and Central Africa

(WCA) region, including Mali, where grain yield averaged

0.71 t in 1999 (FAO 2001). Improved caudatum sorghum

cultivars have not been widely adopted in Mali (Yapi and

Debrah 1998). However, some of these cultivars such as

ICSV 1063 and ICSV 1079 were introduced in the

Kolokani area (about 130 km north of Bamako) by

Catholic missionaries in the late 1980s. They have since

spread and are being cultivated under the name

“Gadiabani” by many farmers in over 100 villages (SEPD

1995)

Cisse, B

Cisse, S

Cisse, T

Hamada, M A

Letourmy, P

Ratnadass, A

ICRISAT Open Access Repository

An Open Access Journal published by ICRISATSAT eJournal ⏐ ejournal.icrisat.org - 1 - December 2007 ⏐ Volume 5 ⏐ Issue 1An on-farm study of Striga as constraint to improved sorghum cultivarproduction in MaliA Ratnadass1,2*, B Cissé1 S Cissé1, T Cissé1, MA Hamada1 and P Letourmy31. ICRISAT-CIRAD, Samako, BP 320, Bamako, Mali2. CIRAD, URP SCRiD, Montpellier, F-34398 France3. CIRAD, UPR Biostatistique, Montpellier, F-34398 France*Corresponding author: alain.ratnadass@cirad.frIntroductionSorghum (Sorghum bicolor) is the most important foodcrop in savanna areas of the West and Central Africa(WCA) region, including Mali, where grain yield averaged0.71 t in 1999 (FAO 2001). Improved caudatum sorghumcultivars have not been widely adopted in Mali (Yapi andDebrah 1998). However, some of these cultivars such asICSV 1063 and ICSV 1079 were introduced in theKolokani area (about 130 km north of Bamako) byCatholic missionaries in the late 1980s. They have sincespread and are being cultivated under the name“Gadiabani” by many farmers in over 100 villages (SEPD1995).With the introduction of improved caudatum cultivars,head-bug is becoming a concern. A study was conductedin 1997 and 1998 that showed that the level of infestationand damage by this pest was influenced not only by thesorghum cultivar per se, but also by the size of the fieldsand their genotypic environment (Ratnadass et al. 2008).On the other hand, Striga hermonthica affects thelivelihood of some 300 million people in Africa, causingsevere and moderate damage in 21 and 22 countries,respectively (Berner et al. 1996). As Striga infestation isconsidered to be a major biotic constraint to sorghumproduction in the Kolokani area (Hoffmann et al. 1997),we measured this factor mainly to verify the extent towhich differences in yield could be ascribed to head-bugs(Ratnadass et al. 2008). The trial design (particularly thechange in design between 1997 and 1998) made it alsopossible to assess the influence of sowing date on Strigainfestation.Materials and methodsThe experimental design of the trial conducted in 1997and 1998 in the three Malian villages of Tioribougou,Wenia and Ntiobougou), with four sorghum cultivars,Bibalawili, Gadiabani, ICSH 89002 and Malisor 84-7)have been published by Ratnadass et al. 2008. Further tohead-bug observations, grain weight was also recordedon the second central row of each plot. In addition, thetotal number of Striga plants per plot was also recorded.During the 1997–98 dry season, soil samples from thetop 30 cm layer were taken in all large plots, at the fourangles, at the center, and half-way from the center on thediagonal, respectively, and the nine samples thusobtained were then sun-dried, pooled and divided using abox-divider so as to obtain a single composite sample of300–600 g. Subsequent analyses were carried out onthese composite samples at the International CropsResearch Institute for the Semi Arid Tropics (ICRISAT),Niger, Niamey: H+; Al3+; Na+; K+; Ca2+; Mg2+; ECEC(cmol+ kg-1); pH-H2O and pH-KCL (1:2.5); organic C(%); Bray-P1 (mg P kg-1).Individual and combined analyses of variance wereperformed using SAS software (SAS Institute Inc. 1999–2001). Results regarding small plots were analyzedseparately for each year due to the change in design. Forlarge plots, a combined analysis was conducted bykeeping only two DPB (distance from plot border) levelsfor 1998. Striga numbers were analyzed after log (n+1)transformation. Differences between cultivars andtreatments were determined with the F-test, and meanswere compared using LSD at the P <0.05 threshold.Citation : Ratnadass A, Cissé B, Cissé S, Cissé T, Hamada MA and Letourmy P, (2007) An on-farm study of Striga asconstraint to improved sorghum cultivar production in Mali. Journal of SAT Agricultural Research 5(1).An Open Access Journal published by ICRISATSAT eJournal ⏐ ejournal.icrisat.org - 2 - December 2007 ⏐ Volume 5 ⏐ Issue 1ResultsIn small plots. In our analysis of the 1997 small plotdata, the effect of cultivar in small plots was notsignificant for Striga infestation and grain yield (Table1). The cultivar effect in large plots was significant forStriga infestation, but not for yield. The effect of localitywas highly significant for Striga infestation and yield.There were no significant interactions involving Strigainfestation and yield in small plots in 1997.In the analysis of the 1998 small plot data, the effect ofcultivar in small plots was significant for Strigainfestation, but not for grain yield (Table 2). The cultivareffect in large plots was highly significant for Strigainfestation and grain yield. The locality effect wassignificant for grain yield, but not for Striga infestation.There were significant interactions between cultivars inlarge plots and locality for Striga infestation and grainyield.In 1997, grain yield in small plots was significantlyhigher for ICSH 89002 than for Malisor 84-7, with theother cultivars being intermediate (Table 3), while in1998, Malisor 84-7 and Bibalawili still had the lowestand highest yield, respectively, but the differences werenot significant (Table 4). In 1997, grain yield in smallplots taken as a whole was higher when located along theborder of a large Malisor 84-7 plot, and significantlylower when located along the border of a large Gadiabaniplot (Table 3).In 1998, overall grain yield in small plots was higherwhen they were located in the center of ICSH 89002 andMalisor 84-7 plots, and significantly lower when locatedin the center of large Gadiabani and Bibalawili plots(Table 4).As for Striga infestation, there were no differencesbetween cultivars in small plots, irrespective of thecultivar in large plots in 1997, while infestation of smallplots within the large Gadiabani plot was significantlyhigher (Table 5). In 1998, overall infestation was lowerthan in 1997, and remained high (about the same level asin 1997) only in small Bibalawili plots, and in small plotswithin the large Bibalawili plots, respectively (Table 6).Table 1. Mean squares (MS) and their significance1 from a combined analysis of variance of Striga infestation and sorghumgrain yield in small plots in 1997.Source of variation df Striga infestation MS2 Grain yield MSResidual 9 1.586 0.1464F1 (cultivar in small plot) 3 0.49 NS 0.3731 NSF2 (cultivar in large plot) 3 6.47 * 0.5203 NSF3 (locality) 2 16.70 ** 2.799 ***F1 × F2 9 0.42 NS 0.1179 NSF1 × F3 6 1.19 NS 0.1850 NSF2 × F3 6 4.03 NS 0.3422 NSF1 × F2 × F3 18 0.66 NS 0.2011 NS1. Significance in the F-test: * = Significant at 5% level; ** = Significant at 1% level; *** = Significant at 0.1% level; NS = Not significant at5% level.2. Natural logarithm of number of Striga plants per plot plus 1.Table 2. Mean squares (MS) and their significance1 from a combined analysis of variance of Striga infestation and sorghumgrain yield in small plots in 1998.Source of variation df Striga infestation MS2 Grain yield MSResidual 9 (6) 0.413 0.1805F1 (cultivar in small plot) 3 2.43 * 0.2781 NSF2 (cultivar in large plot) 3 8.20 *** 2.9100 ***F3 (locality) 2 (1) 0.95 NS 2.6654 **F1 × F2 9 0.58 NS 0.2658 NSF1 × F3 6 (3) 0.08 NS 0.1570 NSF2 × F3 6 (3) 1.98 * 0.9350 *F1 × F2 × F3 18 (9) 0.87 NS 0.2404 NS1. Significance in the F-test: * = Significant at 5% level; ** = Significant at 1% level; *** = Significant at 0.1% level; NS = Not significant at5% level.2. Natural logarithm of number of Striga plants per plot plus 1.An Open Access Journal published by ICRISATSAT eJournal ⏐ ejournal.icrisat.org - 3 - December 2007 ⏐ Volume 5 ⏐ Issue 1Table 3. Grain yield (t ha-1) of sorghum cultivars observed in small plots: combined analysis of 1997 data at Tioribougou,Wenia and Ntiobougou in Mali.Cultivars in small plots_____________________________________________________________________Cultivars in large plots Bibalawili Gadiabani ICSH 89002 Malisor 84-7 Mean1Bibalawili 1.250 1.032 1.536 1.005 1.206abGadiabani 1.347 0.883 0.773 0.646 0.912bICSH 89002 1.209 1.074 1.360 1.066 1.177abMalisor 84-7 1.377 1.503 1.631 1.165 1.419aMean2 1.296AB 1.123AB 1.325A 0.971B 1.1841. Means within the column followed by the same lower case letters are not significantly different, Bonferroni test, P = 0.05.2. Means within the row followed by the same letters are not significantly different, Bonferroni test, P = 0.05.Table 4. Grain yield (t ha-1) of sorghum cultivars observed in small plots: combined analysis of 1998 data at Tioribougou,Wenia and Ntiobougou in Mali.Cultivars in small plots____________________________________________________________________Cultivars in large plots Bibalawili Gadiabani ICSH 89002 Malisor 84-7 Mean1Bibalawili 1.267 1.044 1.111 0.644 1.017bGadiabani 1.244 0.933 0.844 0.933 0.989bICSH 89002 2.089 2.311 2.000 1.289 1.922aMalisor 84-7 1.467 1.467 1.556 1.867 1.589aMean2 1.517A 1.439A 1.378A 1.183A 1.3071. Means within the column followed by the same lower case letter are not significantly different, Bonferroni test, P = 0.05.2. Means within the row followed by the same letter are not significantly different, Bonferroni test, P = 0.05.In large plots. This analysis was conducted on means ofthe two or three DPB levels. Although the design slightlychanged, an effort was made to combine data from bothyears, while keeping only the extreme two DPB levels in1998, so that the data from that year would match those of1997. Large plot variance was significant for grain yieldand Striga infestation. There was no significant effect forthe latter, while for grain yield (with an overall mean of1.22 t ha-1), the only significant effects concerned thelocality and cultivar-year interaction. There was nodifference in Striga infestation based on the DPB in thelarge plots (overall mean of 0.5 plants m-²).Besides biotic stress (Striga and head-bugs; seeRatnadass et al. 2008), soil quality did not account forvariations in yield between localities, or between plots inthe same locality, since the only noteworthy result wasthe higher H+ and Al3+ content, and consequently lowerpH (and to a lesser extent K+, Ca2+ and Mg2+ contents) inBibalawili and ICSH 89002 plots at Ntiobougou. Thislikely explains the lower yields on large plots recorded atNtiobougou, and also the significant effects andinteractions involving yield observed in small plots.DiscussionIn the absence of any biotic stress, the border effectshould be reflected by lower competition betweensorghum plants grown in plots bordering large plots, andtherefore higher yield. In the absence of a difference inStriga infestation, differences in head-bug damage (asreported in Ratnadass et al. 2008) could account for theabsence of a significant difference in yield.The significant interaction between year and cultivarwith respect to Striga infestation could be ascribed to thedifferences in sowing dates. Differences in planting datesin 1998 could have accounted for differences observed inStriga infestation via differences in soil temperature (ie,in case of delayed crop planting, Striga seeds are unableto germinate and seedlings fail to attach to host rootsystems due to unfavorably low soil temperatures duringthe middle of the rainy season, according to Hoffmann etal. 1997).Actually, it is striking that in 1997, when all cultivarswere sown at the same time (Ratnadass et al. 2008), therewas no difference in Striga infestation in small plots of allAn Open Access Journal published by ICRISATSAT eJournal ⏐ ejournal.icrisat.org - 4 - December 2007 ⏐ Volume 5 ⏐ Issue 1Table 6. Striga infestation (no. per m²) observed on sorghum cultivars in small plots: combined analysis of 1998 data atTioribougou, Wenia and Ntiobougou in Mali.Cultivars in small plots______________________________________________________________________Cultivars in large plots Bibalawili Gadiabani ICSH 89002 Malisor 84-7 Mean1Bibalawili 4.2 (2.95)2 0.5 (1.34) 1.1 (1.78) 0.7 (1.42) 1.7 (1.87a)Gadiabani 0.4 (1.64) 0.1 (0.46) 0.3 (1.52) 0.1 (0.83) 0.2 (1.11b)ICSH 89002 0.0 (0.23) 0.1 (0.46) 0.0 (0.37) 0.0 (0.00) 0.0 (0.26c)Malisor 84-7 0.3 (1.11) 0.1 (0.60) 0.4 (1.00) 0.0 (0.00) 0.2 (0.68bc)Mean3 1.87 (1.48A) 0.2 (0.72BC) 0.5 (1.17AB) 0.2 (0.56C) 0.5 (1.16)1. Means within the column followed by the same lower case letter are not significantly different, Bonferroni test, P = 0.05.2. Log (1+n) − transformed values (total number of plants per 15 m² plots) are given in parentheses.3. Means within the row followed by the same letters are not significantly different, Bonferroni test, P = 0.05.cultivars (Table 5), while in 1998, small plots ofBibalawili, which were sown ahead of other cultivars(due to its longer cycle), sustained significantly higherinfestation (Table 6). Similarly, overall infestation ofsmall plots was significantly higher in large plots ofGadiabani in 1997 (when this cultivar was sown on thesame date as all other cultivars, including Bibalawili; seeTable 5), while in 1998, this overall infestation of smallplots was significantly higher in Bibalawili, the only early-planted cultivar (Table 6).So, it was sowing date which seemed to influenceStriga infestation, at least for the cultivars considered(notably guinea vs caudatum).However, late sowing may also have a negative impacton yield. Therefore, a technique such as mulching, whichboth allows early sowing (due to water conservation) andStriga suppression (via lower soil temperature) would bemore advisable. Actually, in northern Cameroon,Brachiaria mulch was observed to have a positive effecton the main sorghum crop, notably by lowering soilTable 5. Striga infestation (no. per m²) observed on sorghum cultivars in small plots: combined analysis of 1997 data atTioribougou, Wenia and Ntiobougou in Mali.Cultivars in small plots_______________________________________________________________________Cultivars in large plots Bibalawili Gadiabani ICSH 89002 Malisor 84-7 Mean1Bibalawili 1.2 (2.06)2 0.4 (1.34) 1.7 (1.57) 0.7 (1.49)  1.0 (1.61b)Gadiabani 2.0 (2.70) 2.3 (2.81) 3.9 (2.86) 1.9 (2.74)  2.5 (2.78a)ICSH 89002 2.6 (1.95) 0.2 (1.19) 0.2 (0.92) 0.2 (0.80)  0.8 (1.22b)Malisor 84-7 0.2 (1.00) 0.3 (1.52) 0.6 (1.63) 0.1 (0.83)  0.3 (1.24b)Mean3 1.5 (1.93A) 0.8 (1.71A) 1.6 (1.74A) 0.7 (1.47A)  1.2 (1.69)1. Means within the column followed by the same lower case letter are not significantly different, Bonferroni test, P = 0.05.2. Log (1+n) − transformed values (total number of plants per 15 m² plots) are given in parentheses.3. Means within the row followed by the same letter are not significantly different, Bonferroni test, P = 0.05.temperature, which resulted in lower Striga incidence(Naudin 2002).Acknowledgments. These studies were funded throughICRISAT’s and CIRAD’s core budgets. The authorsthank farmers at Ntiobougou (Jeremie Diarra), Tioribougou(Tiema Diarra), and Wenia (Siraba Traore), for fruitfulcollaboration, B Sidibe (ICRISAT-Mali) for technicalassistance and A Bationo (ICRISAT-Niger, Niamey) forsoil sample analyses.ReferencesBerner DK, Kling JG and Singh BB. 1996. Strigaresearch and control – a perspective from Africa. PlantDisease 79:652–660.FAO. 2001. FAOSTAT agriculture data. (http://www.fao.org)An Open Access Journal published by ICRISATSAT eJournal ⏐ ejournal.icrisat.org - 5 - December 2007 ⏐ Volume 5 ⏐ Issue 1Hoffmann G, Diarra C, Ba I and Dembélé D. 1997.Parasitic plant species of food crops in Africa: Biologyand impact study in Mali. Agriculture and Development13:30–51.Naudin K. 2002. Systèmes de culture sur couverturevégétale. Saison 2001-2002. DPGT-Garoua-Cameroun.Rapport d’activité Juin 2001-Février 2002. Garoua,Cameroun: CIRAD-Sodecoton.Ratnadass A, Cissé B, Cissé S, Cissé T, Hamada MA,Chantereau J and Letourmy P. 2008. Combined on-farm effect of plot size and sorghum genotype onsorghum panicle-feeding bug infestation in Mali.Euphytica 159:135–144.SAS Institute Inc. 1999–2001. SAS/STAT release 8.02.Cary, North Carolina, USA: SAS Institute Inc.SEPD. 1995. Adoption study on two ICRISAT sorghumvarieties: ICSV 1063 and ICSV 1079 in Kolokani, Mali.Output-oriented report presented at the ICRISAT SGProjects Consultative Group Meeting, Bamako, Mali,11–14 December 1995. Patancheru 502 324, AndhraPradesh, India: Socio-Economics and Policy Division,International Crops Research Institute for the Semi-AridTropics. 6 pp.Yapi AM and Debrah SK. 1998. Evaluation de l’impactdes recherches variétales de sorgho et de mil en Afriquede l’Ouest et du Centre. Pages 215–221 in Améliorationdu sorgho et de sa culture en Afrique de l’Ouest et duCentre: actes de l’atelier de restitution du programmeconjoint sur le sorgho ICRISAT-CIRAD, 17–20 March,1997, Bamako, Mali (Ratnadass A, Chantereau J andGigou J, eds.). Collection Colloques, Montpellier, France:Cirad-ca.

An on-farm study of Striga as constraint to improved sorghum cultivar production in Mali

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An on-farm study of Striga as constraint to improved sorghum cultivar production in Mali

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