Abstract
The resistance of cacao (Theobroma cacao. L)leaves to 10 isolates of Phytophthora palmivora(Butler) Butler was investigated in 18 genotypes of cacao in three experiments. Tissue-paper-mount and punch-inoculation methods were used to distinguish between resistance at the penetration and post-penetration levels based on lesion frequency and size, respectively. There was a 5–6 fold difference in aggressiveness among isolates collected from different locations in the islands of Trinidad and Tobago for both types of resistance. However, host genotype ×isolate interaction effects were not significant for resistance at both the penetration and post-penetration levels. A strong positive relationship (r = 0.8) was observed in the abilities of isolates to effectively breach the two types of resistance. This suggests that the same isolate can be used in screening for both types of resistance. No significant relationship was found between resistance at the penetration and post-penetration levels suggesting that the resistance mechanisms were different. Subsequent experiments using a wider range of cacao genotypes from the International Germplasm Collection, Trinidad, confirmed the initial results. These experiments indicate that resistance found using one isolate would be equally valid using other isolates of Phytophthora palmivora. The implications of the findings are discussed.
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Surujdeo-Maharaj, S., Umaharan, P. & Iwaro, A. A study of genotype-isolate interaction in cacao (Theobroma cacao L.): resistance of cacao genotypes to isolates of Phytophthora palmivora . Euphytica 118, 295–303 (2001). https://doi.org/10.1023/A:1017516217662
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DOI: https://doi.org/10.1023/A:1017516217662