The roadside botanist, bananas and cassava biodiversity

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Roadside Botany ...
Roadside Botany ...

 

This week’s roadside botany in the Brazilian Cerrado: eleven wild species of cassava, Manihot, extensive bananas and exceptional biodiversity. The morning showed the remarkable cassava plant breeding project in the context of EMBRAPA Cerrados, and their evaluation programme for Musa genotypes, while the afternoon looked at wild species.

In a tour led by Luiz Carvalho (part of the FAO/IAEA programme – see blog), Eduardo Alano Vieira introduced us to the large cassava (manihot, manioc or tapioca) crossing programme, involving 30000 seedlings per year and some novel characteristics: not just yield, biotic and abiotic stress resistance, but including sugary as well as starchy forms, those with altered post-harvest physiological deterioration (PPD) and

Segregating trial plots of F3 cassava crosses
Segregating trial plots of F3 cassava crosses

 

with a range of colours from important micronutrients or provitamins – illustrations here show root sections.

Cassava roots varying in colour and starch/sugar content
Cassava roots varying in colour and starch/sugar content

 

We went on to see the banana genotype evaluation collection, with Tadeu Graciolli Guimaraes. We had the chance to eat the various genotypes the researchers have been working with. One banana genotype was rather flavourless and starchy (Prata Ana), but two others emphasized what we in the temperate countries miss: Garantida II with citrus flavours overlaying a sweet smooth texture, while Caipira had a more savoury and vanilla custard taste. But the research project (presented in Portugal earlier this year – Tadeu Graciolli Guimaraes et al. Yield and agronomical behaviou of banana (Musa spp.) genotypes in Brazil’s Central plateau. In: INTERNATIONAL HORTICULTURAL CONGRESS, 28., 2010, p. 749, (see http://bit.ly/hmMF0q [PDF]) was a model of its type: 22 Musa genotypes are being grown at more than 20 locations without any inputs and being evaluated for a substantial number of agronomic, disease, yield and other traits. This type of experiment needs careful management. In fact, the plants were remarkably healthy (not least because this is not a banana-growing area and largely disease free), although there were gaps where the six replicates of genotype Maca had died from Fusarium (Panama disease) within a few months of planting.

Banana genotypes
Banana genotypes

 

Of the remaining genotypes, only one showed serious yellow sigatoka (there is no black sigatoka [seen in this field – text addition made May 2011] in Brazil – “yet” as Andrew James from CICY in Mexico reminded us several times!).

I can remember several unfortunate cases (as no doubt can the others involved) where I have stopped a bus full of molecular biologists and rushed off into the field margins, or declined the coffee on offer after a long drive to have the chance to botanize in the area around a motorway service station (on at least two occasions, on different continents, picking up armed guards in the process). So then off to some real roadside botany – the first part along 4×4 tracks, but the second part involving the verges of a 6-lane highway (see opening illustration). The highway margins gave an excellent view of the purpose of the storage root of cassava. Unlike many other vegetatively propagated crops, root segments do not grow to new plants, but provide storage for rapid regrowth of the plant after the spring rains, or after fire damage.

Wild manihot regrowth soon after fire
Wild manihot regrowth soon after fire

 

The area we walked through had been burned less than a month ago, but was completely green. While my swiss-army knife was more than up to cutting the cultivated roots, the Manihot vericosa and M. gracilis of the afternoon involved cutting through wood. Why did the root change from woody to starchy? Surely the function of a starch store is different from a woody root store.

Manihot stipularis - a tiny species
Manihot stipularis - a tiny species

 

Later, we got to see the miniature Manihot stipularis – a plant flowering when smaller than a finger, contrasting with the morning’s cultivars reaching up to 3m.

Woody storage root of Manihot violacea
Woody storage root of Manihot violacea

 

Interestingly, the road verge had been burnt about three weeks before our visit, so we could see the high level of regeneration – allowing classic pictures of the cerrado vegetation. What fantastic diversity, and I hope threats can be mitigated (see Ratter et al., 1987; and more recently Collevatti et al. 2009 Phylogeography and disjunct distribution in Lychnophora ericoides (Asteraceae), an endangered cerrado shrub).

 

Campo Cerrado vegetation, Brazil
Campo Cerrado vegetation, Brasil

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3 COMMENTS

  1. I note in the above article that Andrew James of CICY says there is no black leaf streak/ black Sigatoka in Brazil (yet).

    When did he say this? The disease was first recorded in Brazil in 1998 (Cordeiro et al. 1998 in Infomusa 7(1), 31) and has since spread to almost all regions. There is even a record of M. fijiensis on Heliconia in Brazil (Gasparotto et al. 2005 in Fitipato. bras. 30 (4), 423-425).

    • Many thanks for the correction; my comment was wrong and it must have been with reference to this field, so I have edited the post. The Cordeiro, de Matos and de Oliveira et Silva citation in Infomusa http://www.musalit.org/pdf/IN990065_en.pdf is is an excellent paper. It discusses that yellow Sigatoka has been present in Brazil since the 1940s, and that yellow Sigatoka is usually replaced by black Sigatoka where both diseases are present because of the higher aggressiveness of black Sigatoka. The article also notes that black Sigatoka can cause 100% yield loss without control measures, and the intensive spraying of fungicides needed to control the disease (as high as 40 per year, four times as many as needed to control yellow Sigatoka) may be too costly for small and medium growers. Many banana and plantain cultivars are resistant to yellow Sigatoka, while highly susceptible to black Sigatoka – Caipira, illustrated in the post, is resistant to black Sigatoka. Cordeira et al. also discuss that use of resistant genotypes, as well as having environmental, sustainability and economic benefits, will decrease disease inoculum and hence slow spread of the disease.

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