Variation of Silicon in Soils and Maize plants along altitudinal gradients and its relationship with distribution of Lepidoptera Stem Borers

Abstract

Maize is the main staple crop of most communities of the East African mountains but the yield is affected by both biotic and abiotic factors. While soil nutrients increase the maize yields, infestation of maize fields by Lepidopteran pests such as, Chilo partellus (Crambidae) and Busseola fusca (Noctuidae) generally reduces the yields. In addition to enhancing maize yields, some soil elements such as silicon (Si) aid plants in overcoming abiotic and biotic stresses. Hence, any factor that induces Si deficiency in soil might be detrimental to the plant growth and its resistance to insect pests and diseases. Understanding the variation of Si level in soil and maize and their relationship with stemborer is crucial in promoting maize production in East Africa.This study evaluated the Si levels in both soil and maize plants cultivated along three altitudinal gradients of East African mountains (Machakos Hills, Taita Hills and Mount Kilimanjaro) characterized by graded changes in climatic conditions. The study also linked the Si level in maize plants to lepidopteran pests’ distribution. The amount of silicon in maize plant was analyzed using UV-spectrophotometer while the amount of silicon in soil was analyzed using Inductively-Coupled Plasma (ICP). One-way and two-way ANOVA tests were conducted for data analyses. The means were separated by multiple mean comparison tests following ANOVA using R 2.15.3 (R Development Core Team, 2013). Silicon levels in both soil and maize decreased significantly with a concomitant rise in altitude. This result was not only attributed to soil characteristics but also to environmental conditions. Low temperatures at higher altitudes negatively affected Si assimilation by maize plants. Chilo. partellus and Busseola fusca significa variations, differences in distribution of insect pests along altitudinal gradient could be attributed to variation in maize Si levels. Chilo partellus appeared more tolerant to increasing maize Si levels than Busseola fusca.