for maximum impact, high yielding improved varieties with significant yield advantages must be targeted to farmers and localities that value this trait most. explaining farmers’ demand for yield can serve as a means of targeting the development and dissemination of high yielding varieties. this paper analyzes data collected from 395 farmers in northern ethiopia using a zero-limit tobit regressi...

We summarize the findings of a recently completed study of the productivity impacts of international crop genetic improvement research in developing countries. Over the period 1960 to 2000, international agricultural research centers, in collaboration with national research programs, contributed to the development of "modern varieties" for many crops. These varieties have contributed to large i...

When measured under midday fi eld conditions, modern varieties of maize (Zea mays L.) often have substomatal carbon dioxide concentration (Ci) values in excess of those required to saturate the photosynthetic carbon dioxide assimilation rate (A). This results in lower leaf transpiration effi ciency (TE), the ratio of photosynthesis to transpiration, than potentially achievable for a given rate ...

Many centers of crop domestication and diversity are experiencing rapid changes in agriculture practices resulting in the loss of crop varieties and the knowledge and customs that have sustained them (Brush 2004; Harlan 1975). Germplasm diversity is threatened by several factors including: replacement by high-yielding varieties, a shift to cash crop cultivation, change in land use, economic inc...

Crop improvement is a multifaceted micro-evolutionary process, involving changes in breeding approaches, planting configurations and consumption preferences of human beings. Recent research has started to identify the specific genes or genomic regions correlate to improved agronomic traits, however, an apparent blank between the genetic structure of crop elite varieties and their improving hist...

The use of modern crop varieties is a dominant method of obtaining high yields in crop production. Efforts to identify suitable varieties, with characteristics that would increase crop yield under future climate conditions, remain essential to developing sustainable agriculture and food security. This work aims to evaluate potential genotypic adaptations (i.e., using varieties with increased ab...

IInstitutional analysis can be used to understand the value placed on crop diversity by farmers as a social process, and to uncover the market-related constraints and incentives that influence farmer management of genetic resources. This is particularly important for capturing the dynamics of crop populations and the collective impact of individual decisions regarding crop diversity. In the app...

Nitrogen is essential for plant growth, and N fertilization allows farmers to obtain high yields and produce sufficient agricultural commodities. On the other hand, nitrogen losses potentially cause adverse effects to ecosystems and to human health. Increasing nitrogen use efficiency (NUE) is vital to solve the conflict between productivity, to secure the demand of a growing world population, a...

Modern plant breeding tends to focus on maximizing yield, with one of the most ubiquitous implementations being shorter-duration crop varieties. It is indisputable that these breeding efforts have resulted in greater yields in ideal circumstances; however, many farmed locations across Africa suffer from one or more conditions that limit the efficacy of modern short-duration hybrids. In view of ...

The food security issue was addressed by the development of "modern agriculture" in the last century. But food safety issues and environment degradation were the consequences suffered as a result. Climate change has been recognized as the result of release of stored energy in fossil fuel into the atmosphere. Homogeneous crop varieties, machinery, pesticides and fertilizers are the foundation of...