Failures of Attack by the Top Borer, Scirpophaga excerptalis Wlk. in Relation to Resistance in Sugarcane Genotypes

Autor: M. Mohanasundaram, N. Mukunthan
Rok vydání: 1998
Předmět:
Zdroj: International Journal of Tropical Insect Science. 18:293-300
ISSN: 1742-7592
1742-7584
DOI: 10.1017/s1742758400018518
Popis: Two types of failures of attack by the top borer, Scirpophaga excerptalis Wlk., and their relation to sugarcane resistance to deadheart formation were studied in 164 genotypes of sugarcane for three years at two locations, viz., Karnal (Haryana State) and Chakia (Bihar State) in India. Attacks were unsuccessful either because of failure of neonate larvae in the mid-rib to reach the spindle (Type 1) or failure of older larvae in the spindle to reach the meristem (Type 2). Type 1 failure was frequent (19.2 to 26.7 %) while Type 2 was rare (2.9 to 5.1 %) among the genotypes. Larval dispersal and mortality were influenced by several factors related or unrelated to resistance and occurred concurrently in the same genotypes. This led to variation in larval mortality even among genotypes with the same levels of Type 1 failure. Those genotypes (Co 1223, Co 1224, E 276, Co 7224, Co 745, E 128, Co 62235, E 132, E 50, CoS 767 and CoJ 67) that had high scores of both Type 1 failure (14 to 18) and larval mortality (13 to 17) had the lowest percentages of deadhearts (11.8 to 24.4%). Type 2 failure was not related to resistance; the highly resistant genotypes, Co 1223, Co 1224, E 276, Co 62235, E 132, CoS 767 and F133, showed no Type 2 failure. Furthermore, genotypes IA 3017 and Co 7322 which had the highest Type 2 failure scores of 9 and 12 respectively, had 61 and 36% deadhearts respectively. It is concluded that Type 2 failure may be caused by larval mortality in the spindles due to diseases and/or asphyxiation by accumulated rain water.
Databáze: OpenAIRE
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