I am adapting an old technique to be used as a simple way for plant breeders to figure out how big a job they are facing when they seek to screen new (as from a plant explorer or seed library) crop accessions ("varieties"). I would like an estimate of the percentages of truly resistant plants in your experience, or in papers you can cite. These percentages might be used as examples in a brief article, but in any case they are only the beginning of the estimate.
Here is one example I grabbed from the literature that is typical. They screened all 16,000 soybean accessions in the USDA germplasm repository and found 805 passed the first test. Then they did a field evaluation with 530 of those and found two that held up.
For a statistics example, it is worth noting that they did not sample the existing germplasm collection, they tested the entire population. So if one is making inferences about the collection, then that should be taken into account. The collection is obviously a sample of the existing natural variation, but that variation may not be accessible to the researcher.
Article Genetics and mapping of adult plant rust resistance in soybe...
This is the paper (2008, with the same research group) Thomas Björkman mentioned. I attach it here in case other people want to read.
Thank you very mush Thomas Björkman and Yuan-Yeu Yau These papers will help me a great deal. .
They especially hit the mark because the population in which I am interested is the population in, and being obtained by, the seed libraries. I suspect that the plant explorers like the, now historical Popenoe, somewhat represented the explorer's interests, as do the seeds submitted by other sources represent their inclinations.
I have worked on soybeans a little, but these papers are decades more up to date. Thanks again.
You are welcome, Lewis Maccarter.
This is another case (on rice, 2014):
Large scale germplasm screening for identification of novel rice blast resistance sources.
Vasudevan K1, Vera Cruz CM2, Gruissem W1, Bhullar NK1.
Author information
1. Plant Biotechnology, Department of Biology, ETH Zurich (Swiss Federal Institute of Technology) Zurich, Switzerland.
2. International Rice Research Institute (IRRI), Los Banos, Philippines.
Abstract
Rice is a major cereal crop that contributes significantly to global food security. Biotic stresses, including the rice blast fungus, cause severe yield losses that significantly impair rice production worldwide. The rapid genetic evolution of the fungus often overcomes the resistance conferred by major genes after a few years of intensive agricultural use. Therefore, resistance breeding requires continuous efforts of enriching the reservoir of resistance genes/alleles to effectively tackle the disease. Seed banks represent a rich stock of genetic diversity, however, they are still under-explored for identifying novel genes and/or their functional alleles. We conducted a large-scale screen for new rice blast resistance sources in 4246 geographically diverse rice accessions originating from 13 major rice-growing countries. The accessions were selected from a total collection of over 120,000 accessions based on their annotated rice blast resistance information in the International Rice Genebank. A two-step resistance screening protocol was used involving natural infection in a rice uniform blast nursery and subsequent artificial infections with five single rice blast isolates. The nursery-resistant accessions showed varied disease responses when infected with single isolates, suggesting the presence of diverse resistance genes/alleles in this accession collection. In addition, 289 accessions showed broad-spectrum resistance against all five single rice blast isolates. The selected resistant accessions were genotyped for the presence of the Pi2 resistance gene, thereby identifying potential accessions for isolation of allelic variants of this blast resistance gene. Together, the accession collection with broad spectrum and isolate specific blast resistance represent the core material for isolation of previously unknown blast resistance genes and/or their allelic variants that can be deployed in rice breeding programs.
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