Abstract
New management practices must be developed to improve yam productivity. By allowing non-destructive analyses of important plant traits, image-based phenotyping techniques could help developing such practices. Our objective was to determine the potential of image-based phenotyping methods to assess traits relevant for tuber yield formation in yam grown in the glasshouse and in the field. We took plant and leaf pictures with consumer cameras. We used the numbers of image pixels to derive the shoot biomass and the total leaf surface and calculated the ‘triangular greenness index’ (TGI) which is an indicator of the leaf chlorophyll content. Under glasshouse conditions, the number of pixels obtained from nadir view (view from the top) was positively correlated to shoot biomass, and total leaf surface, while the TGI was negatively correlated to the SPAD values and nitrogen (N) content of diagnostic leaves. Pictures taken from nadir view in the field showed an increase in soil surface cover and a decrease in TGI with time. TGI was negatively correlated to SPAD values measured on diagnostic leaves but was not correlated to leaf N content. In conclusion, these phenotyping techniques deliver relevant results but need to be further developed and validated for application in yam.
Highlights
Yam (Dioscorea spp.) tuber is a staple food for millions of people in tropical areas [1]
Important traits for tuber yield formation are: (i) emergence rate as the first emerged plants contribute most to the final tuber yield measured at field level [5,6]; (ii) foliage development as maximum leaf area index is correlated to final tuber yield [7] due to improved light interception, and lower weed infestation and soil erosion [3]; and (iii) the N nutritional status, because N leaf status is one of the main factors driving leaf formation and growth [7]
In such experiments yams are planted at a density of one plant per m2, the leaf area index can reach values of up to eight, this plant can reach a height of several meters if it finds a climbing support and the growth period may last nine months
Summary
Yam (Dioscorea spp.) tuber is a staple food for millions of people in tropical areas [1]. West Africa produces more than 90% of the world tuber production over 8.5 million of hectares [1,2]. Conducting field experiments to study these factors with destructive sampling requires large fields, a lot of time and labor. In such experiments yams are planted at a density of one plant per m2, the leaf area index can reach values of up to eight, this plant can reach a height of several meters if it finds a climbing support and the growth period may last nine months. Following single plants during the growing season with non-destructive methods would be useful to study more precisely the impacts of specific treatments on yam growth under field conditions
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