A methodological study on participatory barley breeding II. Response to selection

Farmer participation is increasingly seen as a key to develop technologies which are more relevant to farmers' communities. In plant breeding, farmer participation is seen as key to increase the probability of adoption of new varieties. This paper addresses the issue of selection efficiency in participatory plant breeding by testing the effect of selection environment and of who did the selection in one cropping season (1997) on the performance of the selected lines in the following cropping season (1998). Selection environment had a larger effect on response to selection than who did the selection, confirming the importance of decentralized selection. Selections made by the breeder and the farmers in 1997, differed in 1998 for a number of traits, but seldom for grain yield. When the difference for grain yield was significant, breeder's selection was more effective on station, while farmers' selection was more effective in farmers' fields. The results of this study indicate that it is possible to organize a plant breeding program with the objective of adapting crops to a multitude of both physical and socio-economic environments: such a breeding program will, at the same time, increase productivity and stability, enhance biodiversity and produce environmentally friendly cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Changes in chemical and biological soil properties as induced by anthropogenic disturbance: A case study of an agricultural soil under recurrent flooding by wastewaters

Monitoring the environmental impact of anthropogenic disturbance on soil ecosystem is of great importance for optimizing strategies for soil use, conservation and remediation. The aim of this study was to assess whether and to what extent a long-term, human-induced disturbance could have affected main chemical and biological properties in an agricultural soil. The study site was a hazel (Corylus avellana L.) orchard located in the area surrounding the volcanic apparatus of Somma-Vesuvius (Southern Italy). For the last two decades, the site has been repeatedly subjected to floodings by wastewaters containing not only alluvial sediments but also potentially hazardous compounds from illegally disposed wastes. Soil disturbance was assessed by a multitechnique approach, which combined chemical, biochemical and physiological (Biolog^®) methods together with community fingerprinting by denaturing gradient gel electrophoresis (DGGE) and amplified ribosomal DNA restriction analysis (ARDRA). A hazel site never subjected to flooding provided the control soil. Soil sampling was repeated three times over a 1-year period. The effect of flooding by wastewaters, sampling time and their interaction were statistically evaluated. Under wastewater flooding, soil pH and most organic matter-related pools, i.e. total organic C, total N, and active soil C-resources such as basal (SBR) and substrate-induced respiration (SIR) and microbial biomass C (MBC) were all increased; whereas sampling time mostly affected two active-N pools, namely K₂SO₄-extractable N (Extr-N) and potentially mineralizable N that varied unconcurrently in tested soils. Also the electrical conductivity varied across samplings. Parameters related to microbial maintenance energy (ATP and qCO₂) were higher in the flooded soil, even though they were not statistically affected by wastewater flooding or by sampling time. The Biolog^® method evidenced that under recurrent flooding, soil microbial populations became functionally more uniform when compared to the control soil. Molecular fingerprinting of PCR-amplified 16S rDNA targets revealed that, along with seasonal shifts, a marked change in the genetic structure of total bacterial community occurred in the flooded soil. Furthermore, compositional shifts in the actinomycete community were less marked and mostly influenced by seasonal effects. Yet, a decreased genetic diversity in the ammonia-oxidizing bacteria community was evidenced in the flooded soil by ARDRA. Thus both the genetic and the functional structure of native soil bacterial populations were changed under repeated flooding by wastewaters. Repeated sampling over a 1-year period allowed us to reveal soil disturbance effects beyond seasonal variations.