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Backyard domestication

There’s a “dump heap” hypothesis of agricultural origins which suggests that people first got interested in actively managing and manipulating plants for food or other products when they saw them sprouting out of piles of garbage in and about settlements. There they could observe them daily and experiment with them. A slight variation on this theme — involving corrals in pastoralist campsites rather than garbage dumps — has been proposed for the domestication of quinoa.

One of the things that might have happened in these fertile micro-environments in close proximity to human habitations is that different related species might have been brought accidentally together, leading to hybridization and the development of interesting new — polyploid — types. But there really hasn’t been much empirical evidence for this.

No more. A new paper ((Colin E. Hughes, Rajanikanth Govindarajulu, Ashley Robertson, Denis L. Filer, Stephen A. Harris, and C. Donovan Bailey. Serendipitous backyard hybridization and the origin of crops. PNAS published August 17, 2007, 10.1073/pnas.0702193104.)) looks at the domestication of the legume tree Leucaena in Mexico, where it is grown for food (it is also used as a fodder in some parts of the world). A variety of evidence is discussed which suggests that there has indeed been much hybridization among up to 13 different wild species of Leucaena in Mexican backyards. This has proved “a potent trigger for domestication.” The authors think a similar thing also happened in Mexico with two other perennial crops, Agave and Opuntia.

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Animal Health for the Environment and Development

We sometimes talk about agricultural biodiversity as if there’s a line that separates it from other kinds of — wild — biodiversity, but of course it doesn’t work like that. There are all kinds of intearactions. For example, diseases can move from wild to domesticated species. Given all the zoonotic diseases that have made the news lately, it seems like it would be sensible to look at human, domestic animal and wildlife health together, rather than in isolation from each other. But apparently such an integrated approach is pretty rare. An initiative of the Wildlife Conservation Society is trying to change all that:

…improving livestock health not only improves human nutrition and incomes, but in the case of zoonotic diseases also contributes directly to improved human health. In addition, healthier domestic animals contribute to securing healthier wildlife (and vice versa), decreasing chances of disease transmission at the livestock/wildlife interface. These cross-sectoral benefits are not all “automatic,” but require that explicit linkages be made between improved food security and health and more sustainable environmental stewardship from the household and community levels on up.

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Fungal agricultural biodiversity

More today about fungi as important constituents of agricultural biodiversity. Following the recent post on the microsymbiotic Frankia, I ran across a couple of papers on other fungi and their interactions with crop plants in agricultural systems. 

First, there’s Trichoderma. According to a recent review in Soil Biology and Biochemistry ((Francesco Vinale, Krishnapillai Sivasithamparam, Emilio L. Ghisalberti, Roberta Marra, Sheridan L. Woo and Matteo Lorito, Trichoderma-plant-pathogen interactions. Soil Biology and Biochemistry. In Press, Uncorrected Proof.)):

Trichoderma spp. are among the most frequently isolated soil fungi and present in plant root ecosystems. These fungi are opportunistic, avirulent plant symbionts, and function as parasites and antagonists of many phytopathogenic fungi, thus protecting plants from disease. So far, Trichoderma spp. are among the most studied fungal BCAs [bio-control agents] and commercially marketed as biopesticides, biofertilizers and soil amendments. Depending upon the strain, the use of Trichoderma in agriculture can provide numerous advantages: (i) colonization of the rhizosphere by the BCA (“rhizosphere competence”) allowing rapid establishment within the stable microbial communities in the rhizosphere; (ii) control of pathogenic and competitive/deleterious microflora by using a variety of mechanisms; (iii) improvement of the plant health and (iv) stimulation of root growth.

Then there’s arbuscular mycorrhizal fungi (AMF). Another paper ((Christine Picard, Elisa Baruffa and Marco Bosco, Enrichment and diversity of plant-probiotic microorganisms in the rhizosphere of hybrid maize during four growth cycles. Soil Biology and Biochemistry. In Press, Uncorrected Proof.)) in the same journal suggests that different maize genotypes had quite different effects on the AMF population in the soil in which they were grown, stimulating “their own adapted phylogenetic AMF subgroups.” According to the authors:

Several new sets of data obtained in this way would be necessary to have a significant view of the actual beneficial interactions between rhizospheric microorganisms and plant roots; but we are confident that such an effort will lead to the definition of new criteria for the rapid breeding of sustainable varieties.

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Solanaceous information

There’s a global online monograph of the genus Solanum called Solanaceae Source. Each species treatment includes illustrations, a clickable list of specimens, links to molecular data and a dot distribution map (which mashes herbarium specimen locality data with Google Maps), among other things. The National Science Foundation (NSF) funds the project as part of the Planetary Biodiversity Inventories mission. Collaborators are eligible for small awards in support of their contributions to the completion of the worldwide Solanum monograph.