Resistance To Striga Asiatica (L.) Kuntze In Sorghum: Parent Characterisation And Combining Ability Analysis

Abstract

Pot experiments were conducted to assess the resistance of five sorghum [Sorghum bicolor (L.) Moench] cultivars namely, DC 75, SV-1, SAR 16, SAR 19 and SAR 29 to witchweed [Striga asiatica (L.) Kuntze] infestation. These genotypes were evaluated in two separate experiments, for resistance under S. asiatica infestation, and for yield without infestation. F2 progeny resulting from a four parent half diallel cross involving SV-1 and SAR cultivars were evaluated under S. asiatica infestation. The SAR and SV-1 cultivars were also screened for witchweed seed germination stimulant production using the agar gel technique. Cultivars SAR 19 and SAR 29 supported significantly lower S. asiatica counts than DC 75, SV-1 and SAR 16. They also delayed emergence of S. asiatica by more than 10 weeks relative to DC 75, SV-1 and SAR 16. Using agar assays, SAR 19 and SAR 29 had the least witchweed seed germination distances of 5.9 mm and 6.9 mm, respectively, compared to SAR 16 which had 15.4 mm and SV-1 which had 25.6 mm. Combining ability analysis for S. asiatica counts at maximum emergence revealed that additive genetic factors were preponderant for witchweed counts. Usually, SAR 16 is regarded as a resistant cultivar though its reaction to witchweed in these experiments revealed that it is susceptible. Cultivar SV-1 was susceptible, DC 75 was tolerant and SAR 19 and SAR 29 were resistant.Des essais en pots ont \ue9t\ue9 conduits pour \ue9valuer la r\ue9sistance de cinq cultivars de sorgho [Sorghum bicolor (L.) Moench] \ue0 savoir: DC 75, SV-1, SAR 16, SAR 19 et SAR 29 \ue0 l'infestation de l'herbe magicienne [Striga asiatica (L.) Kuntze]. Ces g\ue9notypes ont \ue9t\ue9 \ue9valu\ue9s en deux essais s\ue9par\ue9s, pour la r\ue9sistance \ue0 l'infestion de S. asiatica et pour le rendement sans infestation. La descendance F2 provenant des hybrides d'un demi diall\ue8le de quatre parents comprenant des cultivars SV-1 et SAR ont \ue9t\ue9 \ue9valu\ue9s sous l'infestion de S. asiatica. SV-1 et le cultivar SAR ont \ue9t\ue9 aussi cribl\ue9s pour la germination des semences de l'herbe magici\ue8nne stimulant la production en utilisant la technique de gel agar. Les cultivars SAR 19 et SAR 29 ont support\ue9 significativement un nombre faible de S. asiatica plus que DC 75, SV-1 et SAR 16. Ils ont aussi retard\ue9 l'\ue9mergence de S. asiatica plus de 10 semaines relativement \ue0 DC 75, SV-1 and SAR 16. Utilisant des essais agar, SAR 19 et SAR 29 ont eu la moindre germination des semences de la mauvaise herbe avec des distances de 5.9 mm et 6.9 mm respectivement, en comparaison avec SAR 16 qui avait 15.4 mm et SV-1 ayant eu 25.6 mm. L'analyse de l'aptitude de combinason pour les comptes de S. asiatica \ue0 l'\ue9mergence maximale a r\ue9v\ue9l\ue9 que les facteurs g\ue9n\ue9tiques additifs \ue9taient pr\ue9ponderants pour les comptes de striga. SAR 16 est normallement consid\ue9r\ue9 comme cultivar r\ue9sistant bien que sa r\ue9action au striga dans ces essais ont r\ue9v\ue9l\ue9 qui'il \ue9tait sensible. SV-1 \ue9tait sensible, DC 75 tol\ue9rant alors que SAR 19 et SAR 29 \ue9taient r\ue9sistants