Root distribution patterns of white yam (Dioscorea rotundataPoir.): a field study

Abstract

The productivity of white yam (Dioscorea rotundata Poir) must increase to sustainably meet the demand of the increasing populations in the developing world where this is a staple crop. Although this could be achieved through the use of mineral fertilizers, reports indicate limited effects of these inputs on tuber yield. We hypothesized (i) that D. rotundata has a small and shallow root system and (ii) that this root system does not respond to mineral fertilizer application. Two field experiments were conducted in Cô te d'Ivoire in year 1 and in year 2 to test these hypotheses. In the first field experiment we measured biomass production, as well as root density during plant growth in fertilized and unfertilized plots while in the second experiment, we analysed the distribution pattern of roots in horizontal and vertical root profiles in fertilized plots. The root system of D. rotundata consisted of seminal, adventitious and tubercular roots. Only the adventitious roots remained alive until the end of the growth cycle. The root length density was very low with a maximum of 0.25 cm cm (3 . No roots were observed in the 15Á30 cm horizon at 50 cm from the plant's crown. The horizontal and vertical root maps revealed that roots were mostly distributed in clumps, and there was a good correlation between the two methods of root sampling for this species. Fertilizer application had no significant effect on plant biomass, fresh tuber yield or on root growth. However, thinner and longer roots and higher tuber yields were observed in year 1 than in year 2. The different weather conditions and more specifically the higher soil temperature might explain the results obtained in year 1. Therefore, it could be recommended to farmers not to fertilize D. rotundata.

Root System Architecture and Abiotic Stress Tolerance: Current Knowledge in Root and Tuber Crops

“…Recent studies in sweetpotato indicate direct influence on RSA of spatial and temporal availability of water and N availability similar to model systems (Villordon et al, 2014a). In yam, Hgaza et al (2012) found no fertilizer response of tuber yield but a positive correlation between thinner, longer roots with tuber yield.…”

“…Only one reference was found for yams, the second most important root crop in Sub-Saharan Africa 1 , which described two distinct well-organized root systems: the seminal root system and the adventitious, more definitive root system (Charles-Dominique et al, 2009). Other studies in yam only focused on root morphology at crop harvest stage in response to fertilization (Melteras et al, 2008; O’Sullivan, 2008; Hgaza et al, 2012). Iwama et al (1977) specifically analyzed root systems and the relationship between root systems and tuber yield in potato (Iwama et al, 1981).…”

Effect of leaf thinning on shoot growth and tuber yield of white Guinea yam

“…In addition, leaf thinning might also depress root growth (Hodgkinson & Becking, 1978). Although the relationship between root growth and tuber yield was not clear in white Guinea yam (Hgaza et al, 2012), Villordon et al (2014) indicated that lateral root development is related to yield formation in tuber crops. These results suggest that leaf thinning after the onset of tuber growth should be avoided and thinning at an earlier growth stage is preferable.…”

Root Branching and Nutrient Efficiency: Status and Way Forward in Root and Tuber Crops

“…Charles-Dominique et al (2009) concluded the importance of studying the yam root system architecture as a whole and simultaneously in order to understand its growth, development and tuber formation. In a similar study, Hgaza et al (2012) documented the response of the RSA of water yam ( Dioscorea alata ) and white yam ( Dioscorea cayennensis subsp. rotundata ) to mineral fertilizer application under field conditions.…”

“…Results revealed three root types (seminal, adventitious and tuber roots) and differences in root length density, root mass density and specific root length correlated directly with higher temperature and not with fertilizer application when compared to controls. Hgaza et al (2012) concluded that tuber formation was independent from seminal and adventitious root development and mineral nutrition did not affect final tuber yield.…”