This research was conducted to investigate the influence of plant growth biostimulants on quantitative and qualitative characteristics of potato (Solanum tubersom cv. Sante) in randomized complete blocks design with eight treatments and three replications at Behbahan Agricultural Research Station in one year (2019-2020). Treatments included: control (no application of plant growth biostimulants), humic acid, free amino acid (L), amino acid-Zn, amino acid-K, amino acid-Ca, amino acid-K-Ca and combine application of humic acid, amino acid-Zn and amino acid-K-Ca. The results showed plant growth biostimulants (except free amino acid) significantly increased total and marketable tuber yield as compared with control. The treatment of combined significantly increased total and marketable yield in comparision to other treatments. Biostimulants significantly decreased unmarketable yield and its components (small tubers, cracked tubers and tubers with secondary growth) as compared with control. Application of biostimulants significantly increased the tuber protein percentage and concentrations of nitrogen, phosphorus (except amino acid-K, amino acid-Ca and amino acid-K-Ca) and potassium tubers (except amino acid-Ca). Amino acid-Ca and the treatment of combined significantly increased dry matter content. Application of growth biostimulants (except amino acid-K and amino acid-Ca) significantly decreased concentration of tuber nitrate. According to the results, application of combined plant growth biostimulants for cultivation of Sante cultivar is recommended.

In order to evaluate the effects of cultivar and planting density on yield and yield components of potato, an experiment was conducted during 1996 in Bostan Abad (46, 50 N, 37° 51’ E) located at 55km east of Tabriz, Iran. A factorial experiment based on randomized complete block design with three replications was used. Combination of five cultivars; Alpha, Draga, Cozima, Morene and Auola, with three planting densities; 50000, 62500 and 75000 plants per ha-1 (27, 22 and 18cm between plants on the row and 75 cm row spacing,. respectively) were used as experimental factors. The number of tubers per plant and per square meter, tuber diameter, mean tuber weight, tuber weight per plant and tuber yield were significantly affected by cultivars. Cozima had higher number of tuber per plant and per square meter, tuber diameter, mean tuber weight, tuber weight per plant and tuber yield (39.5 t ha-1) among the cultivars evaluated. All the traits under study were affected by plant density. Number of tuber per plant, tuber diameter, mean tuber weight, tuber weight per plant and dry matter percentage of tuber were decreased as plant density increased, but number of tuber per square meter increased significantly. The tuber yield increased by increasing the plant density from 50000 to 62500 and decreasod thereafter when the density was raised from 62500 to 75000. Tuber yield showed significant correlations with number of tuber per plant and per square meter and tuber weight per plant. On the basis of the result of this study, planting Cozima and Auola cultivars with 62500 plants per ha-1 in Bostan Abad, may be recommended.

This research was conducted to study the effect of PGPR (Plant Growth Promoting Rhizobacteria) on mini-tuber yield and absorption of nutrients in the greenhouse of Seed and Plant Certification and Registration Research Institute in 2012. Minituber derived from tissue culture of two potato cultivars (‘Agria’ and ‘Sante’) which were inoculated with 116 and 173 strains of Pseudomonas and two species of Bacillus (B. megaterium and B. Subtilis) all along with control treatments as separately and in mixture with each other. A pot experiment was conducted using factorial based on randomized complete design with four replications. After tuber-filling stage nutrient elements percentage was assayed. After harvesting, minitubers were separated and total yield in standard size was determined. Inoculation of PGPRs had a significant effect on yield and nutrient elements. The rate of absorption of nutrients and minituber production of two varieties showed a significant difference. Mean Comparison of traits showed that dual inoculation of two types of bacterial treatments had the most influence on the absorption of nutrients as well as the number minituber in standard size compared to the control (non-inoculated). ‘Sante’ cultivarproduced the highest number of minituber compared with cv. ‘Agria’. According to the results, dual and separate inoculation of potatoes with PGPR not only intensify the synergy effects through growth and developments of roots, but also increase the nutrients absorption which cause enhancement of the tuberization and yield.

The soils of potato production fields in Ardabil due to alkalinity and not having a proper crop rotations are deficient in micronutrients. To evaluate the effect of these micronutrients on the yield and some traits affecting potato tubers an experiment was conducted in a complete randomized block design with three replications in Ardabil during 2012. Micronutrient treatments used were the various concentrations of iron and zinc (0.002, 0.004 and 0.008 concentrations of these elements as Fe1Zn1, Fe1Zn2, Fe1Zn3, Fe2Zn1, Fe2Zn2, Fe2Zn3, Fe3Zn1 and Fe3Zn2) and a control treatment (Fe0Zn0). Analysis of variance of traits under study showed statistically significant differences among treatments in terms of tuber yield, number of tubers per plant, tuber size, skin thickness and volumetric weight and dry weight of tubers. The highest tuber yield (48.10 t.ha-1) and maximum skin thickness were obtained from Fe1Zn3 treatment. The highest tuber number belonged to Fe2Zn1 (0.004 and 0.002 concentrations of iron and zinc) and Fe1Zn3 (0.002 and 0.008 concentrations of iron and zinc). Tuber weights higher than 35 grams and highest volumetric tuber weight were produced by using Fe3Zn2. The conclusion is this that using Fe1Zn3 treatment (0.002 and 0.008 concentrations) resulted in highest tuber yield and thickness of tuber skin.

   In order to study the effect of plant distance and tuber size on yield and yield components of potato varieties, a factorial experiment was conducted based on randomized complete block design, at research station of Islamic Azad university, Tabriz branch during 2003-2004. Factors were variety in two levels, seed distance on planting rows in two levels and four levels of tuber size. Results of two year combined analysis showed that three way interaction of "year*variety*plant distance" for main stem numbers trait was significant, expressing different response of variety and plant distance upon mentioned trait in two years. Also interaction of year*variety, year*plant distance and year*tuber size for yield was significant, that represented different response of varieties for yield and different impressibility of yield by plant distance and tuber size during two years. Results revealed that Mourn was superior to Cosmos variety in most studied traits. Plant distance of 20 cm on implant rows increased yield and main stem numbers and 25 cm planting distance was impressible for production of less small and more moderate and large tubers. Tuber size of 35-55 mm was the best size in all studied traits. Overally, the results showed that treatment compound of Mourn variety, 20 cm seed distance and 35-55 mm tuber size was the best treatment. However, while the farmers have to cut tuber, the treatment compound of Mourn variety, 20 cm seed distance and oversize of 55 mm tuber was the most desirable treatment. According to different responses of potato varieties to plant distance and tuber size, incorporation of variety, plant density and tuber size.should be regarded to obtain high yield.

Given the importance of potato in the economy and people’s nutrition, as well as planting of disease-free seeds, it seems necessary to produce healthy seeds through tissue culture. This study was conducted during 2012-2013 at the Research Center of Agricultural University of Tajikistan aiming to evaluate the effect of different sizes of mini-tuber on yield and yield components of potato crop. Agria variety plantlets derived from tissue culture were grown in pots; the yielded mini-tubers were divided according to size into lighter than 1 g, 1-5 g, 5-10 g, and heavier than 10 g treatments, which then were evaluated in randomized complete block design in four replications. The results showed that tuber weight, the mean of bush yield, and the yield per area unit increased following the increase in mini-tuber weight. The highest mean number of tubers was produced from 5-10 g mini-tubers. Examination of other traits showed that the mean number of eyes and diameter of tubers increased by increasing mini-tuber weight. According to the results, mini-tubers lighter than 1 g are not suitable for planting.

In order to investigate the effect of removing inflorescence and seed tuber size on yield and yield components of potato, the experiment was conducted using a factorial method based on randomized complete block design with three replications in a farm located in evoghlu region of Khoy city, during spring of 2014. The first factor was removal of inflorescence at two levels including removal and nonremoval of inflorescence and the second factor was the seed tuber size at six levels including 25-35 g, 35-45 g, 45-55 g, 55-65 g, 65-75 g, and 75-85 g. The results indicated that the effect of removing inflorescence and seed tuber size was significant on tuber size, weight of tuber in plant, the number of branches and leaves in plant, leaf area index and tuber yield. So that the highest leaf area index (5. 48) obtained from the treatment of inflorescence removing and tuber yield also in the treatment of inflorescence removing increased by 2. 68 tons per hectare (%15). In regard with seed tuber size, the highest rates of tuber yield were 22. 64 and 21. 89 tons per hectare which were respectively obtained for seed tuber sizes of 65-75 g and 75-85 g. There was no significant difference between these two sizes of seed tuber in regard with tuber yield. Therefore, inflorescence removing is effective in yield increasing due to elimination of un useful sink, also seed tuber size of 65-75 g is recommended in order to save seed consumption and reduce costs.

A factorial experiment based on a randomized complete block design with three replications was carried out in order to study the effects of tuber size, nitrogen fertilizer and harvest date on yield and yield components of potato. This experiment was conducted in a grower’s farm in Uraki village located in Chabahar city, in 2011. In this experiment, the treatments were two levels of tuber size (smaller and larger than 35 mm), four levels of nitrogen fertilizer (0, 60, 120 and 180 kg ha-1) and two levels of harvest date (105 and 112 days after emergence). The results of analysis of variance indicated that effects of tuber size, nitrogen rate and tuber size × nitrogen rate interaction effect were significant for all of the studied traits at 0.01 probability level. Effect of harvest date was significant on total tuber yield, number of large tubers, tuber yield and dry matter. The results of this experiment indicated increasing nitrogen up to 120 kg ha-1,increased total tuber number, number of large tubers, tuber yield and dry matter. But using up to 180 kg of nitrogen per hectare reduced these traits. According to the results of this research, it seems that under our experiments condition, tuber size larger than 35 mm, using 120 kg nitrogen per hectare which harvested 112 days after emergence date of tubers (1st of April) produced 41500 kg ha-1 tuber which is suitable to gain the highest yield of tubers for planting the ''Sante'' cultivar.

In order to determine the most suitable planting date for maximum production of seed tuber yield in potato cultivars, this experiment performed with four potato cultivars (Agria, Marfona, Savalan and Ceaser) at four planting dates (April 9th, April 30th, May 20th and June 10th) by using split plot experiment based on randomized complete block design in three replications at Ardabil Agricultural and Natural Resources Research Station during 2009. During growth stage, the traits were like plant height, main stem number per plant, tuber number and weight per plant and total and marketable tuber yield were measured. Analysis of variance from measured traits showed that planting dates and cultivars in traits like plant height, main stem number per plant, tuber number and weight per plant and total and marketable tuber yield and interaction of between cultivar × planting date plant height, main stem number per plant and tuber number per plant were significantly different. The highest total and marketable tuber yield, tuber number and weight per plant, plant height and main stem number per plant were obtained from second planting date (April 30th) and the lowest from latest planting date (June 10th). The difference between total and marketable tuber yield in the second planting date (April 30th) as compared with the latest planting date (June 10th) was 13.35 ton ha-1. Savalan had the highest plant height, main stem number per plant, tuber number and weight per plant and total and marketable tuber yield. Relationship of total tuber yield with plant height, main stem number per plant, tuber number and weight per plant and marketable tuber yield were positive and significant. According to the results, planting date of April 30th was suitable for maximum production of tuber yield of cultivar Sabalan.