Tuber Growth Rate Research Articles

Identification and functional analysis of the Dof transcription factor genes in sugar beet.

In this study, members of the BvDof transcription factor family were identified in the beet genome data (Beta vulgaris L.) Through systematic analysis, 22 BvDof family genes were found in the beet genome, and they were divided into nine groups by phylogenetic analysis. Fifteen members of the BvERF family were involved in the transition to rapid root tuber growth. There was a tandem replication during the generation of the Dof gene family in sugar beet. Bv1_zfms, Bv_ofna, Bv5_racn, and Bv6_augo may be involved in the regulation of secondary cambium development in the beet root tuber. Bv9_nood, Bv1_zfms, and Bv6_cdca may be related to the growth rate of root tubers. The results provide a reference for further elucidating the molecular mechanism of the BvDof transcription factor, which regulates the development of beet root tubers.

Small soil wetted proportion and emitter flow rate of drip irrigation enhance potato yield by improving soil water and aeration in the sandy loam in arid Northwest China

Creating an ideal soil microclimate through appropriate drip irrigation management practices is crucial for enhancing potato production. Field experiments were conducted during 2021 and 2022 in Wuwei, Gansu Province, Northwest China, with two soil wetted proportion levels (P1: 35 %, and P2: 55 %) and three emitter flow rates (F1: 1.3 L/h, F2: 2.0 L/h, and F3: 3.0 L/h). Results showed that for the same soil wetted proportion, soil water content was reduced in the 0–20 cm soil layer and increased in the 20–40 cm for F1 compared to F2 and F3, with no differences in the 40–60 cm depth. During the tuber initiation and bulking stages, the soil wetted proportion P1 increased soil oxygen saturation by 2.8 % and 0.7 % and reduced CO2 concentration by 26.7 % and 19.2 % in 2021 and 2022, respectively, compared to P2 in the 20–40 cm soil layer. The emitter flow rate F1 exhibited significantly greater soil oxygen (0.7–4.6 %) and lower CO2 concentration (16–46 %) than F2 and F3 in the 0–20 cm. Soil oxygen was significantly higher (0.5–2.1 %) and CO2 concentration was significantly lower (10–39 %) in the 20–40 cm in F1 than in F3. In the 0–40 cm soil layer, both the highest soil oxygen concentration and lowest CO2 concentration were observed for the P1F1 combination. The soil wetted proportion P1 increased average yield by 5.6 % in 2021 and 11.9 % in 2022 compared to P2, while F2 and F3 reduced yield by 2.4 % and 4.6 % in 2021, 4.1 % and 13.8 % in 2022 compared to F1. The soil wetted proportion P2 promoted source growth compared to P1 but limited sink expansion. Source capacity, sink growth, and average tuber growth rates decreased from F1 to F3. Overall, the 35 % soil wetted proportion and 1.3 L/h emitter flow rate are recommended for potato cultivation in sandy loam. This study clarified the importance of coordinating soil water and aeration by drip irrigation management to improve potato tuber production.

Effect of variety and irrigation on tuber growth rate of potato

Effect of variety and irrigation on tuber growth rate of potato

Bulking Behaviour of Promising Potato Varieties in Northern Region of Bangladesh

The experiment was conducted at Breeder Seed Production Centre, Bangladesh Agricultural Research Institute (BARI), Debiganj, Panchagarh during November to February of 2014-2015 to learn about the bulking behavior of promising potato varieties in Bangladesh with the suitable time of harvest for getting desirable yield. The experiment was employed with randomized complete block design (RCBD) with six harvesting time at 10 days interval started from 40 days after planting (DAP) and continued up to 90 DAP. Six promising potato varieties such as Bari Alu 40 (4.45w), Bari Alu 41 (5.183), Bari Alu42 (Agila), Bari Alu 43 (Atlas), Bari Alu 44 (Elgar) and Bari Alu 45 (Steffi) were included in the study. Tuber yield was increased up to 90 DAP for all the varieties. The highest tuber yield (55.86ton/ha) was recorded in Bari Alu 45 (Steffi) and the lowest yield of tuber was observed in Bari Alu 43 (Atlas) at 90 DAP. The tuber yield increase rate of Bari Alu 45 (Steffi), Bari Alu 41 (5.183), Bari Alu 42 (Agila) and Bari Alu 40 (4.45w) were reasonable up to 90 DAP, while the increase rate of Bari Alu 43 (Atlas) was reasonable up to 80 DAP and Bari Alu 44 (Elgar) was up to 70 DAP. Bari Alu 44 (Elgar) may be harvested as early variety among the varieties. The percent dry matter was increased up to 90 DAP for all the varieties. The growth rate of tuber was higher at 60–70 DAP for all the varieties except Bari Alu 41 (5.183). In case of Bari Alu 41 (5.183) tuber growth rate was higher at 70-80 DAP. Finally, our study demonstrated that, the optimal period to harvest potatoes is 90 days after planting (DAP), when the tubers are at their largest size, have the most yield, and have accumulated the maximum dry matter.

Quantifying source-sink relationships of drip-fertigated potato under various water and potassium supplies

Water and fertilizer supply can affect the processes of assimilate production (source) and assimilate accumulation (sink), thereby causing differences in potato yield. However, little is known about the coupling effects of irrigation amount and potassium rate on potato tuber yield and its potential source-sink relationships. The objective of this study was to quantify how water and potassium supplies affected the source-sink relationships of drip-fertigated potato after tuber emergence. A two-year field experiment was conducted during the potato growing seasons of 2019 and 2020, with three irrigation levels (W1: 60% ET c , W2: 80% ET c and W3: 100% ET c , where ET c is the crop water requirements) and four potassium rates (K0: 0 kg ha -1 , K1: 135 kg ha -1 , K2: 270 kg ha -1 and K3: 405 kg ha -1 ). The results showed that compared with K0, the treatments viz ., K1, K2 and K3 increased average tuber yield by 1.3%, 17.3% and 15.5% in 2019 and 10.7%, 24.0% and 19.3% in 2020, respectively. However, compared with W3, the treatments viz ., W1 and W2 reduced the average tuber yield by 8.0% and 12.9% in 2019 and 8.9% and 14.7% in 2020, respectively. The beta sigmoid growth function well fitted the relationship of source capacity and sink capacity. The source capacity and source activity increased with the increase of potassium rate under W2 and W3 in 2019 and under W3 in 2020, while the sink capacity and sink activity first increased and then declined with the increasing potassium rate. Increasing water and potassium supply generally increased the vegetative growth and tuber growth time. The tuber growth rate first increased and then decreased with the increase of potassium rate, while it increased with the increasing irrigation amount. The sink-source ratio decreased with the increase of potassium rate, but there was no significant difference between K1 and K2, and the sink-source ratio under K3 was significantly lower than that in the other potassium treatments. It was concluded that potato was in source-sink balance under K1 and K2, but not under K3. The quantitative approach produced parameters that characterized the differences of source and sink capacity in response to various water and potassium supplies. Sufficient irrigation (W3) with moderate potassium application (K2) increased potato yield mainly by maintaining its source-sink balance. • A model approach was proposed to quantify source-sink relationships of potato under various water and potassium supplies. • The mechanism analysis of yield difference from various water and potassium supplies was conducted by source-sink balance. • Source-sink capacity was affected by different water and potassium management practices. • The sink-source ratio was not significantly different between 135 and 270 kg ha -1 , indicating the source-sink balance. • Various water and potassium application amounts influenced plant potassium absorption and tuber yield.

Role of Tuber Developmental Processes in Response of Potato to High Temperature and Elevated CO2.

Potato is adapted to cool environments, and there is concern that its performance may be diminished considerably due to global warming and more frequent episodes of heat stress. Our objectives were to determine the response of potato plants to elevated CO2 (700 μmol/mol) and high temperature (35/25 °C) at tuber initiation and tuber bulking, and to elucidate effects on sink developmental processes. Potato plants were grown in controlled environments with treatments at: Tuber initiation (TI), during the first two weeks after initiating short-day photoperiods, and Tuber bulking (TB). At TI, and 25 °C, elevated CO2 increased tuber growth rate, while leaves and stems were not affected. Whole-plant dry matter accumulation rate, was inhibited by high temperature about twice as much at TI than at TB. Elevated CO2 partially ameliorated high temperature inhibition of sink organs. At TI, with 25 °C, elevated CO2 primarily affected tuber cell proliferation. In contrast, tuber cell volume and endoreduplication were unaffected. These findings indicate that the TI stage and cell division is particularly responsive to elevated CO2 and high temperature stress, supporting the view that attention should be paid to the timing of high-temperature stress episodes with respect to this stage.

Influence of different tuber weight on growth parameters of greater yam under Udaipur region

The present investigation was conducted to evaluate the effectiveness of different weight of tuber to improving of growth and yield of greater yam (Dioscorea alata L.) under Udaipur region. The study was carried out at Horticulture Farm, Department of Horticulture, Rajasthan College of Agriculture, Udaipur during June, 2017 to March 2018. The experiment were comprising with different weight of tubers (25g, 50g, 75g, 100g, 125g, 150g, 175g, 200g, 225g and 250g) and three replications. The vegetative growth parameters were significantly influenced by different weight of tubers. Seven parameters of growth namelydays to sprouting maximum speed of emergence, no. of leaves per vine after four months, vine length after four months, girth of vines after four months were observed. The data were collected to identify the growth rate of tubers. The results revealed that the highest tuber weight (250gm) showed the maximum growth performance days to sprouting, speed of emergence, no. of leaves per vine after four months, vine length after four months, girth of vines after four months, while sprouting percentage (50g,100g) and survival percentage (225g) also significantly affected by tuber weight. As a conclusion, largest tuber weight of yam showed great potential to cultivate larger yam seed which may be used for larger yam production or direct consumption.

Organic Fertilizers Effect on Potato (Solanum tuberosum L.) Tuber Production in Sandy Loam Soil

Potatoes are one of the most common and important vegetable crops in the world and carrying different health benefits that make them all the more essential as a staple dietary item for much of the world’s population. The high nutrient content, ability to adapt to marginal environments, relative ease of cultivation and low cost and high productivity are attributes that make potatoes one of the principal and most important sources of food and income for developing countries. Considering the importance of organic manure for potato cultivation, the experiment was conducted to evaluate the effect of four organic fertilizers on potato tuber production in sandy loam soil. The most popular and easily available two potato cultivars namely Cardinal and Diamant and four organic fertilizers viz., cowdung at the rate of 8 t ha-1, chicken manure at the rate of 8 t ha-1, Rangpur Dinajpur Rural Service (RDRS) developed organic fertilizer at the rate of 740 kg ha-1 and Northern organic fertilizer at the rate of 500 kg ha-1 along with a control. The results revealed that the plant height, number of leaves, leaves fresh weight, yield contributing characters and yield were significantly different and higher in organic fertilizers over control. The highest plant height, leaf number, leaf fresh weight, total dry matter, absolute growth rate, tuber growth rate, tubers plant-1 and larger tuber size were observed in chicken manure which resulted the highest tuber yield (29.71 t ha-1) followed by cowdung (28.67 t ha-1) with same statistical rank. The third highest tuber yield was recorded in RDRS organic fertilizer (26.42 t ha-1) and Northern organic fertilizer (26.00 t ha-1). Besides, the potato cultivar, cardinal gave the highest tuber yield (26.39 t ha-1) compare to diamont (24.57 t ha-1). Finally, the potato cultivar cardinal and organic fertilizers, chicken manure followed by cowdung are recommended for potato cultivation in Rangpur region due to the highest yield production as well as maximum benefit-cost ratio.

Physiological Assessment of Water Stress in Potato Using Spectral Information.

Water stress in potato (Solanum tuberosum L.) causes considerable losses in yield, and therefore, potato is often considered to be a drought sensitive crop. Identification of water deficit tolerant potato genotypes is an adaptation strategy to mitigate the climatic changes that are occurring in the Cundiboyacense region in Colombia. Previous studies have evaluated potato plants under water stress conditions using physiological analyses. However, these methodologies require considerable amounts of time and plant material to perform these measurements. This study evaluated and compared the physiological and spectral traits between two genotypes, Diacol Capiro and Perla Negra under two drought levels (10 and 15 days without irrigation from flowering). Reflectance information was used to calculate indexes which were associated with the physiological behavior in plants. The results showed that spectral information was correlated (ρ < 0.0001) with physiological variables such as foliar area (FA), total water content (H2Ot), relative growth rate of potato tubers (RGTtub), leaf area ratio (LAR), and foliar area index (AFI). In general, there was a higher concentration of chlorophyll under drought treatments. In addition, Perla Negra under water deficit treatments did not show significant differences in its physiological variables. Therefore, it could be considered a drought tolerant genotype because its physiological performance was not affected under water stress conditions. However, yield was affected in both genotypes after being subject to 15 days of drought. The results suggested that reflectance indexes are a useful and affordable approach for potato phenotyping to select parent and segregant populations in breeding programs.

Phenological sensitivity to high temperature stress determines dry matter partitioning and yield in potato

Effect of high temperature stress through different dates of planting and growing inside temperature tunnel were investigated in two contrasting potato cultivars Kufri Surya and Kufri Chipsona-3. High temperature exposure at early, late and tunnel environment delayed tuber initiation and shortened the bulking duration of both the potato cultivars. High temperature significantly decreased crop growth rate, tuber growth rate and net assimilation rate. Under high temperature, K. Chipsona-3 and K. Surya recorded 26–71% and 16–40% reduction in marketable yield. Yield attributes such as number of tubers, mean tuber weight and dry matter of tubers were significantly reduced in K. Chipsona-3. Moreover, higher phenological sensitivity of K. Chipsona-3 under high temperature stress resulted in reduced dry matter partitioning towards tuber. Our results demonstrated that phenological shift under high temperature stress is critical during tuber initiation that decides number of tubers and marketable yield in potato. Temperature inside poly-house tunnel was most detrimental for tuber initiation as well as bulking stage. Thus, precautions should to be taken to explain yield losses under growth chamber or tunnel conditions, which do not represent natural field conditions. Among two potato cultivars, K. Surya showed higher temperature tolerance as compared to K. Chipsona-3 under all high temperature environments. This could be attributed to higher assimilate partitioning efficiency of K. Surya towards tuber during bulking phase.

Mulch and planting depth influence potato canopy development, underground morphology, and tuber yield

The response of potato (Solanum tuberosum cv Haryeong) to mulching and different planting depths was evaluated during 2010–2013. Two different plastic mulches, black and clear polyethylene (PE) were compared with the unmulched control and seed tubers were planted at 5-, 10-, 15-, and 20-cm depths in each treatment. The objectives were to determine how mulching and planting depth affected the canopy development, underground morphology, and tuber yield. Early emergence, canopy development and tuber growth rate were improved in the mulched treatment; while delayed or decreased as the depth of planting increased. The number of stems per plant increased as seed pieces were planted closer to the soil surface in two of the four seasons, but was not affected by mulches except for 2012. Stolon length was longest in black mulches, especially on upper part of underground stem, but it was long on lower part of the stem in unmulched potatoes. Percent tuber bearing stolons were increased in the mulches and deep (10–20cm) planted potatoes. Particularly, on the lower part of underground stem, a higher percentage of tubers were formed irrespective of mulches and planting depth. Harvest index was significantly higher in clear PE mulches in two of the four seasons while it was not affected by planting depth. Mulching potatoes produced higher total and >80g yields, while varying the depth of planting affected the total yield which was lower in the deepest (20cm) planted potato.

Effect of Gibberellic Acid on the Growth Rate and Physiological Age of Tubers Cultivated from True Potato Seed

The time of application of gibberellic acid on potato tuber growth and physiological ageing was studied. Potato plants derived from botanical seed were sprayed at five stages during their growth cycle, and tubers were harvested at 10-day intervals after treatment. It was found that hybrid Chacasina F1 forms tubers until approximately 50 days after transplantation irrespective of the season (spring or autumn). Foliar sprays with gibberellic acid 30–50 days after transplantation suppressed the growth of pre-formed tubers for about 10 days after application and promoted the induction of new tubers, leading to a higher number of tubers per plant in comparison with the untreated control. This temporary effect of gibberellic acid resulted in a reduction in mean tuber weight, but generally without affecting the total weight (yield) of tubers per plant. In addition, gibberellic acid affected the physiological age of the tubers by inducing the breakage of bud dormancy at all stages of tuber growth. Overall, at all harvest times except 90DAT, earlier sprouting and/or a higher number of sprouted buds per tuber were observed for the treatments in which GA was applied within 20 days of harvest.

Simulating cultivar variations in potato yields for contrasting environments

Potato (Solanum tuberosum L.) is a major food commodity becoming increasingly important for food security, especially in the developing world. The rising demand for potatoes combined with yield gaps and potential adverse impacts from climate change call for strategies for yield improvement and environmental adaptation. Crop growth models can help identify and assess such strategies. In this study, the SUBSTOR potato model was used in a systematic assessment of all cultivar parameters in the model in a range of environments including temperate, subtropical, and tropical regions to identify options for future crop improvement and to develop strategies for climate change adaptation in potato production. Our results show that yield responses to changes in cultivar parameters are specific to the environment. Some changes are less effective in subtropical and tropical environments and more effective in increasing yields in temperate environments. Solar radiation, day length, and temperature are the environmental factors that constrain the effectiveness of cultivar parameters in changing yields. The simulated variation in yields among environments was larger than the variation from changes in cultivar parameters. The impact of cultivar parameter changes on yield also varied with the cultivar parameter. The potential tuber growth rate was the cultivar parameter with the strongest effect on yields. Changes in the potential tuber growth rate parameter can lead to large yield changes in tropical highlands and temperate environments that have high solar radiation to ensure sufficient assimilate production for a larger sink. Results also suggest that improving crop management (e.g., N input) is more important for increasing yields than the potential in cultivar improvement. The study showed that crop modeling can help assess alternative strategies of yield improvement and support targeting and prioritization of efforts to improve crop productivity across different environments, based on an improved understanding of genotype by environment by management interactions. Results also showed how crop models can yield insights relevant for climate change adaptation even when only using weather data of the current climate.

Responses of growth, physiological traits and tuber yield in Helianthus tuberosus to seasonal variations under tropical area

Seasonal variations affect growth and yield of a crop, primarily by changing its phenological developmental processes. The objective of the present study was to evaluate seasonal variation effects on growth and development of Jerusalem artichoke. The experiment was conducted during the early-rainy seasons in June–September 2011 and the post-rainy seasons in September–December in 2011, and two seasons were repeated in 2012 at the Field Crop Research Station of Khon Kaen University. A randomize complete block design (RCBD) with 5 replications was used. Four Jerusalem genotypes including JA 89, HEL 65, CN 52867 and KT 50-4 were used. Results indicated similar phenological development between the early and post rainy-seasons. However, high temperature combined with long photoperiod during the early-rainy seasons delayed tuber initiation and extended maturity. Low temperature and short photoperiod was a favorable condition for tuber development but reduced vegetative and reproductive development. On average, tuber dry weights and tuber growth rate were higher in the post-rainy season compared to the early-rainy season. On the other hand, biomass and crop growth rates were higher in the early-rainy seasons compared to the post-rainy seasons. The knowledge obtained in this study is important for Jerusalem artichoke production and selection of Jerusalem artichoke genotypes in the tropical climate.

Effect of Transplanting Dates and Plant Population on Growth Parameters of Potato (Solanum Tuberosum L.) Raised from True Potato Seed (Tps)

ABSTRACT A field experiment was conducted during the rabi season of 2007- 2008 and 2008-2009 at Paschim Medinipore, West Bengal to study the effect of transplanting dates and plant population on growth parameters of potato raised from TPS. Dry matter accumulation per plant was more in early transplanted (December 3) and sparsely populated (60 cm x 15 cm) crop. The highest leaf area index was observed in early transplanted crop with closer spacing (40 cm x 10 cm) at 60 days after transplanting. The highest crop growth rate, tuber bulking rate and tuber growth rate values were also recorded in early and closely transplanted TPS crop between 45- 60 days after transplanting during both the years under investigation

Plant Canopy, Tuber Yield and Growth Analysis of Potato under Moderate and Severe Drought Condition

Four CIP potato clones with 1 check variety Asterix were grown during 2010-11 and 2011-12 at Horticulture Research Farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University, Gazipur, Bangladesh to observe the effect of water stress on canopy structure, yield and growth rate of potato. The study validated that all the genotypes showed reduction in plant height, number of above ground shoots per plant, tuber number per plant and yield by different degrees of drought. Significant yield reduction was found among the genotypes due to drought treatments. Genotype CIP 396244.12 and CIP 393371.58 performed better in severe drought condition in producing higher number of tuber per plant and yield. CIP 396244.12 produced the highest leaf area index in all drought treatments whereas the CIP 391004.18 produced the minimum. In all stage of growth, crop growth rate was affected by different drought treatments where CIP 396244.12 showed the highest crop growth rate followed by CIP 393371.58 and CIP 391004.18 being the lowest. Under severe and moderate drought condition genotype CIP 396244.12 maintained a higher tuber growth rate but under well watered condition CIP 396244.12 and Asterix achieved superior.

수확시기와 야간온도가 유색칼라(Zantedeschia)의 구근생산에 미치는 영향

This experiment was carried out to determine optimal culture conditions for the production of tubers of Calla (Zantedeschia elliottiana 'Golden Affair' and 'Black Magic') in Korea highland. In vitro produced plantlets and tuberlets of Calla 'Golden Affair' and 'Black Magic' were planted plastic film greenhouse and grown for 100, 120, 140 days, with different night temperature treatments (<TEX>$0{\sim}10^{\circ}C$</TEX> : no heating, 10, <TEX>$15^{\circ}C$</TEX>). In both cultivars, tuber size(tuber diameter, tuber height) and tuber weight increased with increasing cultivation period when the night temperature was maintained at <TEX>$10^{\circ}C$</TEX>. The largest tuber diameter in vitro produced plantlets was 5.8cm in 'Black Magic' and 3.2cm in 'Golden Affair', and daily tuber growth rate was 1.110g in 'Black Magic' and 0.092g in 'Golden Affair' under the culture conditions. Consequently we think that tuber harvest date was Oct. 30 and night temperature was <TEX>$10^{\circ}C$</TEX> and no heating that was proper method of tuber production. However we had selection of <TEX>$10^{\circ}C$</TEX> treatment for tuber production because it appeared freezing damage occasionally in highland late in October.

Temperature changes the dynamics of trace element accumulation in Solanum tuberosum L.

A simulated warming manipulation was conducted to evaluate the effects of temperature increase on cadmium (Cd), lead (Pb), copper (Cu), iron (Fe) and zinc (Zn) accumulation in Solanum tuberosum L. at Dingxi, Gansu, in the semiarid northwest of China. The objective of this study was to determine if temperature increases significantly changed trace element concentrations and contents in the different ecosystem compartments by affecting soil content, soil solubility and plant capture. The results reveal that an increase in temperature will lead to a significant change in trace element concentrations and contents in Solanum tuberosum L. The strongest effects of a 3°C temperature increase are increased Cu, Zn and Fe leaf concentrations of 25, 27 and 24%, respectively; but decreases in Cd, Pb, Fe, Zn and Cu tuber concentrations of 27, 55, 41, 29 and 23%, respectively. The increasing concentrations of some trace elements in Solanum tuberosum L. leaves are related to greater retranslocation, photosynthetic capacity and growth. Warming decreases the concentrations of some trace elements in tubers, implying that tuber growth rate exceeds its metal uptake rate at higher temperatures. Indeed, it is expected that by the year 2050 the increased temperature will have induced a decrease of concentrations of Cd, Pb, Cu, Fe and Zn of 9.1, 11.5, 18.5, 16.8 and 15.8%, respectively, in tubers in the study area. In addition, the results indicate that a 1–3°C increase in temperature will improve the availability of selected trace elements and transfer potential of these elements from soil to Solanum tuberosum L.

Field performance, yield components and nitrogen utilization efficiency of potato plants grown from hydroponic small tubers

Despite the available reports on hydroponic potato production, little is known about its field establishment, yield components and efficiency of nitrogen (N) use from small hydroponic tubers (HT) planted in fields. Three sizes of HT (0.7 g, 5 g, and 10 g) and conventional cut seed tubers (CT) of about 40 g of medium-early maturity cultivar ‘Superior’ were planted at the Highland Agriculture Research Center, Pyeongchang, Korea, on 20 May 2005 and 23 May 2006, and their field performances were compared. Increasing seed size resulted more emergence, faster shoot growth soon after emergence, higher N utilization efficiency (plant dry matter accumulation / plant N accumulation), higher tuber growth rate (TGR) and dry matter production, and higher fresh tuber yields. The first tuber formation and bulking were observed in CT plants followed by HT plants of 5 g and 10 g. The time to tuber formation and tuber bulking in 0.7 g HT plants was the longest and delayed by 6 or 8 days compared to CT plants. Accumulation of tuber dry matter increased linearly from the period of tuber formation to near harvest. During the period, increasing seed size gave a significant increase in dry matter production in tubers. Tuber fresh yield of 0.7 g HT plants was 55% of that of CT plants, while those of larger HT (5 g and 10 g) plants were 75% and 80%, respectively. The results suggested the potential of using HT (5 to 10 g) for direct field planting.

How does soil fertility affect yam growth?

Yams (Dioscorea spp.) are known to be very demanding in terms of soil fertility. The influence of deleterious soil fertility on the growth of yams, however, has not yet been studied. A field study was carried out in Côte d'Ivoire, in a fertile forest site and in a low fertility savanna site, submitted to identical climatic conditions, to determine how soil fertility affects Leaf Area Index, Leaf Area Ratio, Crop Growth Rate, Tuber Bulking Rate, Radiation Interception, Radiation Use Efficiency and final tuber yields in D. alata and D. rotundata, grown in the presence of adequate fertilizers. While germination and establishment of both species were not affected by the site, growth parameters of D. alata were superior to those of D. rotundata. This resulted in higher yields of D. alata, when compared to D. rotundata. Only the radiation use efficiency was higher in D. rotundata than in D. alata. Both species reached higher Crop growth rate and Tuber bulking rate and produced higher fresh tuber yields at the forest site than at the savanna site, reflecting the known demand of yams for high fertility soil. Correlation analyses showed significant relationships between the mean Leaf Area Index measured over the entire growth period, Tuber Growth Rate calculated between tuber initiation and harvest, and fresh tuber yields, suggesting that the development of leaf area is determining the growth rate of the tuber which itself determines the fresh tuber yield. The decrease in D. alata tuber yields at the savanna site was explained by a decrease in Leaf Area Index, while the decrease in D. rotundata tuber yields at this site was explained by a decrease in Radiation Use Efficiency. Both effects might have been the consequence of a suboptimal nitrogen and potassium nutrition at the savanna site.