Comparison of potato (Solanum tuberosum L.) tuber size distribution fitting methods and evaluation of the relationship between soil properties and estimated distribution parameters

Accurate estimation of tuber size distribution (TSD) parameters in discretely categorized potato (Solanum tuberosum L) yield samples is desirable for estimating modal tuber sizes, which is fundamental to yield prediction. In the current work, systematic yield digs were conducted on five commercial fields (N = 119) to compare the Weibull, Gamma and Gaussian distribution functions for relative-likelihood-based goodness-of-fit to the observed discrete distributions. Parameters were estimated using maximum likelihood estimation (MLE) for the three distributions but were also derived using the percentiles approach for the Weibull distribution to compare accuracy against the MLE approaches. The relationship between TSD and soil nutrient variability was examined using the best-fitting model's parameters. The percentiles approach had lower overall relative likelihood than the MLE approaches across five locations, but had consistently lower Root Mean Square Error in the marketable tuber size range. Negative relationships were observed between the percentile-based shape parameter and the concentrations of Phosphorus and Nitrogen, with significant (non-zero-overlapping 95% confidence interval) regression coefficients for P (−0.74 ± 0.33 for distribution of proportional tuber numbers and −1.3 ± 0.62 for tuber weights). Stem density was negatively associated with the scale and mode of tuber number (regression coefficients −0.98 ± 0.63 and −1.08 ± 0.78 respectively) and tuber weight (regression coefficients −0.99 ± 0.78 and −1.04 ± 0.69 respectively) distributions. Phosphorus is negatively related to the scale of the tuber-number-based distribution while positively associating with the tuber weight distribution. The results suggest that excess P application was associated with the increase in small tubers that did not contribute significant weight to the final yield.

Interactive Effects of Vermicompost and Seed Tuber Size On the Production of Potato (Solanum Tuberosum L.)

An experiment was conducted to find out the effect of vermicompost and seed tuber size on the yield of Potato. The experiment consisted of two factors, i.e., factor A: Vermicompost level (Vc-4): Vc1: 0 t/ha, Vc2: 3 t/ha, Vc3: 6 t/ha and Vc4: 9 t/ha; factor B: Tuber size (T-5): T1: 5 - 10 g, T2: 10 - 20 g, T3: 20 - 30 g, T4: 30 - 40 g and T5: >40 g. Vermicompost was found to have a significant effect on most of the yield contributing parameters. Results showed that yield parameters increased with increasing vermicompost level irrespective of tuber size. Among the 20 treatment combinations, vermicompost @ 9 t/ha with tuber size > 40 g produced the maximum yield (31.33 t/ha) that was 216.82% higher than Vc1T1. Bangladesh J. Bot. 50(3): 695-700, 2021 (September)

Yield and Yield Contributing Attributes Of Potato as Influenced by Vermicompost And Seed Tuber Size

Low yield is crucial bottleneck for potato production in Bangladesh. The application of vermicompost may enhance the yield of potato. The experiment was consisted of two factors, i.e., Factor A: - Vermicompost level (Vm1-4): Vm1: 0 t ha-1, Vm2: 3 t ha-1, Vm3: 6 t ha-1 and Vm4: 9 t ha-1; Factor B:- Tuber size (T1-5): T1: 5-10 g, T2: 10-20 g, T3: 20-30 g, T4: 30-40 g and T5: > 40 g. The experiment was conducted in a split-plot design with three replications. Vermicompost had significant effect on most of the yield contributing parameters investigated under present study. Results revealed that yield parameters increased with increasing vermicompost level irrespective of tuber size. Among the twenty (20) treatment combinations, vermicompost at the rate of 9 t ha-1 with tuber size > 40 g produced the maximum yield (31.33 t ha-1) that was 53.53 % higher than that of control with 3273.01 $ of monetary advantage. Therefore, present study suggests that potato growers may use vermicompost for increasing yield of potato in Bangladesh. SAARC J. Agric., 19(1): 71-79 (2021)

Agro-techniques for Production of Seed Size Tubers in Conventional Seed Potato Production System–A Review

The seed potato cost is very important component in total potato production and account for 30 to 70% which varies depending on the country or region. Tuber size is an important factor to decide the seed requirement per unit area. Seed size affects total yield, graded or marketable tuber yields. Standard seed tuber of 25–125 g weight (30–55 mm) is known as seed size tubers in India. Obtaining seed size tuber is important for achieving higher potential of the cultivars. The tuber size profile can be reduced or expanded by altering inter and intra row seed spacing, controlling days of growth by planting late or killing vines/haulm early, regulating inputs like fertilizer and water etc. An ideal combination of plant population, row width, and in-row seed spacing for a particular variety were the major factors for optimizing tuber size. Variation in tuber bulking ability in different genotypes results in variation in proportion of seed size tubers among different varieties. 70–80 days haulm killing found most suitable for getting higher proportion of seed size tubers in high bulking varieties. Proper management of N, P and K fertilizers is considered very important to maximize tuber yield and attain desirable quality. Variability in nitrogen dose/ha was observed which ranged from 100–150 between different regions of the world. Hence proper combination of above Agro-techniques should be adopted in seed production programme as per the region for getting higher proportion of seed size/plantable seed tubers.

Evaluating the Drought Tolerance of Seven Potato Varieties on Volcanic Ash Soils in a Medium-Term Trial

One of the main factors limiting the productivity of potatoes (Solanum tuberosum L.) is water stress. Two irrigation systems: full irrigation (I) and rainfed conditions (R), were compared over the growing seasons from 2012–13 to 2019–20. The evaluated varieties were Desiree, Karú-INIA, Patagonia-INIA, Puyehue-INIA, Yagana-INIA, Yaike, and Porvenir. This study determined (i) the yield and tuber size distribution, (ii) their relationship between productivity and environmental conditions, and (iii) the most drought-tolerant varieties based on drought tolerance indices. Nine indices including yield index (YI), tolerance index (TOL), mean productivity (MP), geometric mean productivity (GMP), harmonic mean (Harm), stress tolerance index (STI), harmonic mean productivity (HMP), yield reduction (Yr), and stress susceptible index (SSI) were calculated by using tuber yield under I and R conditions. Tuber yield under R conditions decreased by 27 and 34%. However, the highest yield under R conditions occurred in years with more precipitation between 60 and 120 days after planting (DAP; ±60 mm). Under R conditions, the varieties Porvenir, Patagonia-INIA, Yaike, and Puyehue-INIA showed more tolerance to water stress. Water stress negatively affected tuber size distribution, reducing the production of tubers with size >65 mm by 50–60%. The best indices to study drought tolerance were TOL, MP, GMP, Harm, STI, and HMP. This study suggests that in southern Chile, an area with big yield potential, typically cultivated as rainfed, with cool temperate climate conditions and favorable soil properties for potatoes, as Andisols, available rainfall is still a constraint for yield. Therefore, using more water stress-tolerant varieties and providing supplementary irrigation between 60 and 120 DAP are critical to optimize yield and avoid the failure of the crop in years with remarkably low precipitations, which will be more pronounced in the future according to weather trends. These results exemplify how much we can lose in productivity in rainfed conditions even in one of the most favorable areas for growing potatoes in the world and how risky this situation can be for the performance of the potato farms in the future.

Confounding Factors in Container-Based Drought Tolerance Assessments in Solanum tuberosum

Potato is an important food crop with high water-use-efficiency but low drought tolerance. The bottleneck in drought tolerance breeding is phenotyping in managed field environments. Fundamental research on drought tolerance is predominantly done in container-based test systems in controlled environments. However, the portability of results from these systems to performance under field conditions is debated. Thus, we analyzed the effects of climate conditions, container size, starting material, and substrate on yield and drought tolerance assessment of potato genotypes compared to field trials. A leave one out assessment indicated a minimum of three field trials for stable tolerance prediction. The tolerance ranking was highly reproducible under controlled-conditions, but weakly correlated with field performance. Changing to variable climate conditions, increasing container size, and substituting cuttings by seed tubers did not improve the correlation. Substituting horticultural substrate by sandy soil resulted in yield and tuber size distributions similar to those under field conditions. However, as the effect of the treatment × genotype × substrate interaction on yield was low, drought tolerance indices that depend on relative yields can be assessed on horticultural substrate also. Realistic estimates of tuber yield and tuber size distribution, however, require the use of soil-based substrates.

Characteristics and yield of basic seeds of native potato (Solanum goniocalyx) obtained in temporary immersion bioreactor under greenhouse conditions

The characteristics and yield of basic seeds of two native Peruvian potato varieties "Peruanita" and "Amarilla Tumbay" (Solanum goniocalyx), obtained in temporary immersion bioreactors under greenhouse conditions, were evaluated in order to obtain quality seeds in a continuous and sustainable way to guarantee farmers' production and to meet national demand. For this purpose, microtubers and cuttings obtained by temporary immersion bioreactors (TIB) were cultivated in an area of 240 m2 at 3.201 masl, a completely randomized block design was applied with a bifactorial arrangement (varieties x propagules) of 4 treatments and 3 repetitions. The variables evaluated were: survival (SP) and plant height (AP) at 30 days, number of tubers per plant (NT), tuber diameter (DT), tuber weight (PT), tuber size (TT), tuber skin color (CP) and yield in kg per 14.05 m2 (R). Tubers produced from the microtubers stood out from the cuttings in yield for basic seed, presenting an R=26.89 ± 0,483 kg.14.05 m-2, PT= 0,12 ±0,0036 kg and a TD= 22.59 ±0,451 mm; being the variety "Peruanita" the most optimal in number and weight of tubers per plant for basic seed. The basic seed coming from microtubers was obtained in 5 months, being an alternative to guarantee a constant production, allowing to take care of the demand of farmers and to lower the costs of production.