Novel approaches in plant breeding for rhizosphere-related traits

Abstract

Selection of modern varieties has typically been performed in standardized, high fertility systems with a primary focus on yield. This could have contributed to the loss of plant genes associated with efficient nutrient acquisition strategies and adaptation to soil-related biotic and abiotic stresses if such adaptive strategies incurred a cost to the plant that compromised yield. Furthermore, beneficial interactions between plants and associated soil organisms may have been made obsolete by the provision of nutrients in high quantity and in readily plant available forms. A review of evidence from studies comparing older traditional varieties to modern high yielding varieties indeed showed that this has been the case. Given the necessity to use scarce and increasingly costly fertilizer inputs more efficiently while also raising productivity on poorer soils, it will be crucial to reintroduce desirable rhizosphere-related traits into elite cultivars. Traits that offer possibilities for improving nutrient acquisition capacity, plantmicrobe interactions and tolerance to abiotic and biotic soil stresses in modern varieties were reviewed. Despite the considerable effort devoted to the identification of suitable donors and of genetic factors associated with these beneficial traits, progress in developing improved varieties has been slow and has so far largely been confined to modifications of traditional breeding procedures. Modern molecular tools have only very recently started to play a rather small role. The few successful cases reviewed in this paper have shown that novel breeding approaches using molecular tools do work in principle. When successful, they involved close collaboration between breeders and scientists conducting basic research, and confirmation of phenotypes in field tests as a 'reality check'. We concluded that for novel molecular approaches to make a significant contribution to breeding for rhizosphere related traits it will be essential to narrow the gap between basic sciences and applied breeding through more interdisciplinary research that addresses rather than avoids the complexity of plant-soil interactions.

Finger millet (Eleusine coracana L.) grain yield and yield components as influenced by phosphorus application and variety in Western Kenya

“…Finger millet varieties efficiency on the use of available phosphorus might also be due to the plants mechanism to secrete phosphatases which are key drivers of rhizosphere activities that influenced P uptake. These chemical and biological processes in the rhizosphere determine the mobilization and acquisition of soil nutrients, microbial dynamics, and controls nutrient use efficiency of crops, thus profoundly influencing crops productivity (Hinsinger 2009, Richardson et al 2009, Wissuwa et al 2009). Optimal availability of P resulted in an in increase of nutrient use efficiency by the provision of adequate energy and an early proliferation of growth attributes which increased the grain yield potential.…”

Flavonoids in plant rhizospheres: secretion, fate and their effects on biological communication

“…Thus, molecular breeding methods that increase flavonoid accumulation and/or alter flavonoid composition are promising for crop improvements. The rhizosphere is recognized as being a frontier in plant breeding (Wissuwa et al 2009), as shown by the soybean breeding program in Brazil, in which the disuse of nitrogen fertilizers led to a Bradyrhizobium strain more efficient in nitrogen fixation (Drinkwater and Snapp 2007). Manipulation of plant metabolites, especially those secreted into the rhizosphere, could be the basis for the next-generation rhizosphere breeding program for better utilization of rhizosphere biological communication.…”

Nitrogen use efficiency of bread wheat: Effects of nitrogen rate and time of application

“…However, improved varieties are often developed without considering their ability to grow and yield under low soil nutrient status, and have been selected for high yields under high nutrient input conditions (Wissum et al, 2009). Feil (1992 indicated that varieties producing large amounts of biomass seemed to have more NUPE, which could decrease NUTE thereby also decreasing total NUE of modern varieties.…”