Influence of variety on the within-plant distribution of cassava green spider mite (Acari: Tetranychidae), and leaf anatomical characteristics and chemical components in relation to varietal resistance

Abstract

The within-plant distribution of the cassava green spider mite, Mononychellus tanajoa Bondar, and the anatomical characteristics and the chemical components relating to varietal resistance of cassava, were studied using 11 cassava genotypes with varying levels of resistance for two dry seasons and one wet season. The results show that M. tanajoa aggregates on the top leaves of cassava at low levels of resistance as compared with a more even within-plant distribution at higher levels of resistance. Thus, for accurate sampling of mite populations, it might be important to consider young and old leaves, not just the young leaves, in fields containing resistant and susceptible cassava genotypes. Correlations between the anatomical characteristics and mite population density and damage scores were not consistent across months, either within or over seasons. This suggests that leaf anatomical characteristics may not be important in the varietal resistance of cassava to M. tanajoa. During the dry season, mite population density was positively correlated with leaf nitrogen, potassium and phosphorus and negatively correlated with leaf calcium and fat. Only calcium was negatively associated with mite damage at the peak of the dry season (January 1993 and 1994). Breeding cassava genotypes with high levels of leaf calcium and fat, and low levels of leaf nitrogen, potassium and phosphorus, may improve the level of resistance to M. tanajoa.

Biological studies of Oligonychus punicae (Acari: Tetranychidae) on grapevine cultivars

“…Skorupska (1998) showed that stoma count on the abaxial surface, spongy and palisade mesophyll and total leaf lamina width affected growth of A. viennensis in apple cultivars. Conversely, Nukenine et al (2000) did not find any relation between anatomical features in cassava and resistance to the cassava green mite.…”

Comparative Demography of the Spider Mite,Oligonychus afrasiaticus,on four Date Palm Varieties in Southwestern Tunisia

“…Skorupska ( 1998 ) showed that stoma count on the abaxial surface, spongy and palisade mesophyll, and total leaf lamina width affected growth of Amphitetranychus viennensis in apple cultivars. Conversely, Nukenine et al ( 2000 ) did not find any relationship between anatomical features in cassava and resistance to the cassava green mite. Similarly, foliar anatomy of grape cultivars did not appear to hinder O. punicae feeding, because mites reached adulthood also on cultivars Red Globe and Sauvignon despite greater cuticle-epidermis thickness ( Vásquez et al 2008 ).…”

Seasonal suitability of three rubber tree clones to Calacarus heveae (Acari, Eriophyidae)

“…A possible explanation of these differences might be that the rubber trees studied by Daud and Feres (2007) were 18 years old, whereas the trees in the present study were only 6 years old. Previous studies have revealed that variation in susceptibility of a cultivar might result from differences in the ages of the plants studied (Nukenine et al 2000;Karban and Thaler 1999;Kearsley and Whitham 1989;Cook and Smith 1988). Another explanation of these variations in susceptibility might be that the plants used in this study differed genetically from the plants studied by Daud and Feres (2007), even though both supposedly belonged to the same clone.…”

“…toughness, trichomes) are key factors in the survival, reproduction and development of herbivorous arthropods (Awmack and Leather 2002). This factor may vary seasonally (Awmack and Leather 2002;Nukenine et al 2000;Rodriguez et al 1983) and between genotypes of a single plant species (Panizzi and Parra 2009;Resende et al 2008;Reinert et al 2004).…”