Soil-Borne Pathogens and Their Interactions with the Soil Environment

Abstract

Wheat yields in thirteenth century Europe have been estimated at 385 kg ha⁻¹ (Pretty 1990; Houghton 1996), more than half a millennium later, by 1939 they had been increased to little more than 2 t ha⁻¹. Subsequently, in the period 1952–1986 scientific and technologically based innovation applied to farming increased yields by an average value of 2.6% pa. It is predicted that wheat yields will rise to 10.48–13.69 t ha⁻¹ by 2015, with a current theoretical biological ceiling of 19.2 t ha⁻¹ (Britton 1990). These rising yields have been accompanied by a tenfold increase in the amount of nitrogen applied to wheat in 1943/1945–1994 (Houghton 1996). They represent one example of what has been achieved by a combination of genotype (plant breeding) and environmental modification increasing the nutrients available to the plant in step with its physiological demands and fending-off consequential invasions by pests and pathogens attendant on rapid growth and high yields. Burgeoning human populations, reaching an estimated 10 billion by 2050, demand that similar yield increases are continued and accelerated. The environmental and climatic consequences arising from a policy of raising yield solely by increasing inputs are becoming apparent as dangerously unsustainable. Dramatic changes in the manner by which crops are husbanded are required with the aim of achieving increased yield but with minimal damage to the world’s ecosystems (Dixon and Margerison 2009). Concomitant with the need to continue and accelerate yield increases in order to fill empty stomachs and enhance lifestyles far greater control of pests and pathogens using intelligent, integrated and environmentally benign methods based on sound scientific knowledge of the intimate relationships of beneficial microbes, roots, soil and pest and pathogen biology is required for the health of our planet’s environment and biodiversity. So far, our knowledge of soil ­microbiology is at best scant and fragmentary and at worst non-existent. Yet as shown in this book the agronomic opportunities for enhanced productivity offered by the soil and its inhabitants are huge.