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Screening for plant resistance to sorghum head bug, Calocoris angustatus Leth.*

Published online by Cambridge University Press:  19 September 2011

H. C. Sharma  and
V. F. Lopez
H. C. Sharma
Affiliation:
Cereals Entomology, ICRISAT, Patancheru, A.P. 502 324, India
V. F. Lopez
Affiliation:
Cereals Entomology, ICRISAT, Patancheru, A.P. 502 324, India
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Abstract

Sorghum head bug, Calocoris angustatus Leth. (Hemiptera: Miridae) is an important insect pest of sorghum in the semi-arid tropics. A technique to screen for resistance to head bugs under field conditions was tested. Planting infester rows of susceptible cultivars (CSH 1 or CSH 5), 20 days before the test material or planting early (40–45 days) flowering lines (IS 802, IS 13429 and IS 24439) along with the test material, split planting of test material at 15-day intervals, grouping test material according to maturity, and use of sprinkler irrigation to maintain high humidity, were found effective in increasing the efficiency of screening and selecting for resistance to head bugs.

A headcage technique to screen for resistance under no-choice conditions has also been developed. Panicles infested with 10 pairs of bugs at pre- and half-anthesis, result in maximum population build-up and grain damage under headcage. This technique is useful for confirming the resistance observed under field conditions.

Under natural infestation, five genotypes harboured relatively lower head bug numbers than the susceptible checks, but only three (IS 17610, IS 17618 and IS 17645) maintained their level of resistance under the headcage. Seed germination was > 70% in these genotypes compared to < 10% in CSH 1 and CSH 5.

Résumé

La punaise des panicules du sorgho, Calocoris angustatus Leth. (Hémiptères: Miridés), constitue un insecte ravageur important des régions tropicales semi-arides. Une technique de criblage au champ pour la résistance aux punaises des panicules a été normalisée. Le semis des rangs infestants de cultivars sensibles (CSH 1 ou CSH 5), 20 jours avant le matériel d'essai, ou le semis des lignées (IS 802, IS 13429 et IS 24439) à floraison nâtive (40–45 jours) au même temps que le matériel d'essai, le semis échelonné du matériel d'essai aux intervalles de 15 jours, le regroupement du matériel d'essai selon la maturité, ainsi que la mise en place de 1'irrigation par aspersion pour maintenir un niveau élevé d'humidité sont des moyens qui se sont avérés efflcaces dans l'augmentation de l'efficacité du criblage et de la sélection pour la résistance aux punaises des panicules.

Une technique de panicule encagée a également été mise au point pour le criblage pour la résistance dans des conditions de choix unique. Les panicules infestées avec 10 paires de punaises avant l'anthèse ont provoqué le maximum de pullulation et de dégàts aux grains sous la cage. Cette technique est utile pour la confirmation de la résistance observée en milieu réel.

En conditions naturelles, cinq génotypes entretenaient des nombres de punaises relativement inférieurs par rapport aux témoins sensibles. Mais seulement trois génotypes (IS 17610, IS 17618 et IS 17645) ont pu maintenir leur niveau de résistance sous la cage. La germination des semences était > 70% pour ces génotypes par rapport à < 10% chez CSH 1 et CSH 5.

Keywords

SorghumCalocoris angustatusresistance screeninghost-plant resistanceSorghoCalocoris angustatuscriblage pour la résistancerésistance de la plante-hôte
Type
Research Articles
Information
International Journal of Tropical Insect Science , Volume 13 , Issue 3 , June 1992 , pp. 315 - 325
Copyright
Copyright © ICIPE 1992

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References

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