No abstract

Summary: Pot and field experiments were performed in Burkina Faso in 1987 and 1988 to evaluate the resistance of selected ‘low‐stimulant’ sorghum (Sorghum bicolor (L.) Moench) varieties to the parasitic weed (Striga hermonthica (Del.) Benth. In a pot experiment, the variety IS‐7777 supported the lowest number and had the latest emergence of Striga, compared with the other varieties tested. The varieties IS‐14825, IS‐6961, IS‐7739, IS‐14928 and IS‐14975 also had signifi cantly lower numbers of emerged Striga per pot than the resistant control Framida. The resist ance of IS‐7777 was confirmed in field experi ments, as was that of IS‐7739, IS‐6961 and IS‐14928. However, the yield potential of these poorly adapted varieties was low in Striga‐infested fields. The varieties IS‐14975, IS–14825 and Seguetana Niarabougou exhibited a low susceptibility associated with a grain yield equivalent to that of the other varieties in farm fields infested by Striga. As Seguetana is already grown by Sahelian farmers, its use could be recommended in the absence of resistant varieties adapted to Sahelian agroclimatic conditions. The exceptionally high level of restance exhibited by IS‐7777 could be exploited in studies on the genetics and mechanisms of resistance of the host plant to the parasite, as well as in sorghum improvement programmes.

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Printed ~n Ken!,a. All rights resr.r\ed SOURCES AND MECHANISMS OF RESIS'I'AN('E: 'TO SOR(;HIIM HEAD RUG, EURYSTYLL'S I~%lhlAC~~I.ATL!S 0I)H. I N WKS.1' AFRICA Abstract-Sorghum i s one of the most in1port;lnt cereal crops in West Africi~, i~n d t11e heed 1)up. Burystylus intntac111urir.s Odh. (Hemiptera: 5liridac.) i s the ke) pest of gri~iri sorghuni in this region. range of sorghuni genotypes \\ere cv;~luated for resistance to sorgliurn he;ltl bug 111 Sotlrt~;~ (hlali and Karnboinse (Hurkina Faso). (;enotypcs ('Shl .388. IS 14.332. hiillisor 84-7. Sakl~iki~, S 29 ill111 Kamboinselocal were resistant to head bug+. boll1 ilnder n i~t u r i~l illid headcagrscrcc~iing. Ilc;~d hug resistant genotypes hat1 a lolver percentage of hcatl hug d;lniagetl grain. 'I'II(. food qtri~lity of heid hug damaged grain was very poor and unaccept;~hle. ('ultivar non-preference was identified as ; I co~i~ponent of resistance to head l)ugs. and ('SS1 .I88 was nonpreferred conipi~red to K-35-I. Panicleco~iipactness was po\iti\ely associated w ith hrrltl IIII~ numbers and grain damage. However, genotypes with loose p;~nicles were also s~r c~p t i l~l e to I~~rgs. Long glumes (>5 nini), days to glunie opening (>I0 (lays after anthesis). >SO% co\cring of the gri~in by the glunies, and grain hardness contribute towards re4stance to I~urysr~luc ininruculn~u.\. 'l'his inforniation will be useful for developing a programme to 1)rec.d for rpsi\tancr 11) (hi+ inscct in Wp\t Africa. Kc?\ l+'orttv: E'ro.!\/yllr.~ ~tntt~c~c~rtlot~r\. Mirid'ir.. \orpll~rn~. I~IP\I-~~~IIII rv\l\l;tncc, IIIC~~I;IIII\III~ 01 rc\l\t;lllc.c, head hug.; Kesum&Divers genotypes de sorgho ont c'tk ebalu6s pour la r6sist;lnce il la punaise des panicllles du sorgho. Eurystylus imrnacularrts Odh. h Sotuha (Mali) et a Ka~nhoinsi. (Iiurkina Faso). I.64 genotypes CSIM 388, IS 14332, Malisor 84-7, Sakoika, S 29 et Karnboinsc local Ptaient relati\enient resistantsaux punaisesen criblage nature1 ou en cage. 1,esgenotypes resistants h la p~~n a i w i~vaient un pour centage moins eleve de graines endommagees par les punaises. Ida qualit6 ulimentairc dr4 graines endommagees etait tres faihle et inacceptable. L, a non preference des cultivars etait idenlifike comme une cornposante de la resistance aux punaises. I,e CSM 388 etait non prefere par rapport au E 35-1. 1, a densite de la panicule etait positivement asswiee aver les nombres de punaises et les degits aux graines. ('cpendant, les genotypes aver des panicules laches etaient kgalernent susceptihles aux punaises. Ides glurnes tongues (>5 rnrn), le nornbre de jours a I'ouverture des glurnrs (>20 jours apres I'anthese), >SO%' de couverture de la graine par les glurnes, ainsi que la durete de la graine contribuent a la resistance a Eurystylus.