Potato Yield and Yield Components as Affected by Positive Selection During Several Generations of Seed Multiplication in Southwestern Uganda

Potato (Solanum tuberosum L.) is an important crop in Uganda but production is low. There is not a well-functioning official seed system and farmers use potato tubers from a previous harvest as seed. This study investigated how effectively the seed technology positive selection enhanced yield and underlying crop characteristics across multiple seasons, compared to the farmers’ selection method. Positive selection is selecting healthy plants during crop growth for harvesting seed potato tubers to be planted in the next season. Farmers’ selection involves selection of seed tubers from the bulk of the ware potato harvest. Positive selection was compared to farmers’ seed selection for up to three seasons in three field trials in different locations in southwestern Uganda using seed lots from different origins. Across all experiments, seasons and seed lots, yields were higher under positive selection than under farmers’ selection. The average yield increase resulting from positive selection was 12%, but yield increases were variable, ranging from − 5.7% to + 36.9%, and in the individual experiments often not significant. These yield increases were due to higher yields per plant, and mostly higher weights per tuber, whereas the numbers of tubers per plant were not significantly different. Experimentation and yield assessment were hampered by a varying number of plants that could not be harvested because plants had to be rogued from the experimental plots because of bacterial wilt (more frequent under farmers’ selection than under positive selection), plants disappeared from the experimental field and sometimes plants did not emerge. Nevertheless, adoption of positive selection should be encouraged due to a higher production and less virus infection of seed tubers in positive selected plants, resulting in a lower degeneration rate of potato seed tubers.</p

Impact of Positive Selection on Incidence of Different Viruses During Multiple Generations of Potato Seed Tubers in Uganda

Smallholder farmers in Uganda commonly use seed potato tubers from the informal sector, especially by seed recycling over several generations. Therefore, seed tubers are highly degenerated with viruses and other pathogens, resulting in poor yield and quality of the produce. Over one cycle of multiplication, degeneration management by positive seed selection was found to be efficient in reducing virus diseases compared with the farmers’ method of selection. The objective of this study was to assess to what extent positive selection over several seasons can reduce six different virus incidences in seed lots of different starting quality in southwestern Uganda. Multi-seasonal trials were carried out in three locations, with five seed lots from four sources and three cultivars. Detection of viruses was based on DAS-ELISA and Luminex xMAP technology. Analysis was carried out with analysis of variance (ANOVA) on angular-transformed percentages of virus incidence. Results showed fluctuations in some viruses over seasons with lower Potato leafroll virus (PLRV) and Potato virus X (PVX) incidences in lots from positive selection compared with lots from farmers’ selection. In contrast, some seed lots were initially highly infected with Potato virus S (PVS) and Potato virus M (PVM) and showed no reduction in virus incidence through positive selection. In general, little infection with Potato virus Y (PVY) and Potato virus A (PVA) was found. Based on these results, it is recommended that smallholder farmers are trained in positive selection to opt for less virus-infected plants and tubers, thus increasing potato production

Correction to: Transplanting hybrid potato seedlings at increased densities enhances tuber yield and shifts tuber-size distributions

The original version of the article was unfortunately published online without approval of that latest version by the authors of the article. Corrections for the too early published version are listed below (locations are indicated by Heading, paragraph, sentence): Introduction, 3rd paragraph, 1st sentence: incorrect hyphenation of “gen-otype”, should be changed to “geno-type” Table 1: the descriptive header cell, “Date of:” should cover both "Planting" and "Harvest" a headline below Field Locations, Experimental Design and Cultural Practices, 2nd paragraph, 4th sentence: Inconsistent use of Figure vs Fig.: “(Figure S3)” should be changed to “(Fig. S3)” Fig. 1: In the caption “(T-Σ, T-base = 0°Cd)” should be changed to “(T-Σ in °Cd, T-base = 0 °C)” Observations, Measurements and Calculations, 2nd paragraph, last two lines: in the previous version these last two lines were shifted to previous page. Also in the final version these two lines should be shifter to the previous page Fig. 2: The white lines between the figure caption and the main text is too large, 30% more compared to previous version. These white lines should be reduced

Hilling of Transplanted Seedlings from Novel Hybrid True Potato Seeds Does Not Enhance Tuber Yield but Can Affect Tuber Size Distribution

A novel cropping system for potato was tested for two consecutive years under normal Dutch agronomic conditions. Seedlings from two experimental genotypes of hybrid true potato seeds were produced in a greenhouse nursery and transplanted into the field 5 weeks after sowing to assess tuber yield levels and to study effects of hilling on tuber yield and number, tuber size distribution and tuber greening. Field experiments had a split-plot design with hilling treatments as the main plots and genotypes as the sub-plots. Final harvest was at 122 and 132 days after transplanting in 2017 and 2018, respectively. Hybrid seedlings were transplanted into small initial ridges and irrigated straight after planting. Three hilling treatments were applied between transplanting and 100% canopy cover. Treatment ‘zero hilling’ did not receive any additional hilling after transplanting. Treatments ‘double hilling’ and ‘triple hilling’ received two and three additional hilling treatments, respectively. Total tuber yields at final harvest in both years were not affected by the hilling treatments. Yields for the respective genotypes were 26 and 30 Mg/ha in 2017 and 25 and 32 Mg/ha in 2018. Total tuber numbers were only affected by hilling treatments in 2017, where under hilled conditions, plants produced more tubers compared with plants under zero hilling. Plants under zero hilling yielded more tubers in size class > 40 mm compared with triple hilling in 2017. In 2018, no significant effects of hilling on tuber numbers were found, but the trend was similar to that in 2017.</p

Crop Cycle Length Determines Optimal Transplanting Date for Seedlings from Hybrid True Potato Seeds

The technology of hybrid breeding in diploid potatoes creates opportunities to design novel and improved cultivation systems based on hybrid true potato seeds. A promising cultivation pathway to produce seed or ware tubers is by transplanting greenhouse-raised seedlings into the field. This study explored the effects of transplanting date and seedling age on tuber yield, using greenhouse-raised seedlings. Field trials with experimental hybrid genotypes were conducted in three consecutive years. In 2017 and 2018, 4- and 6-week-old seedlings were transplanted at four dates: March, April, May and June. In 2019, transplanting dates included April, May and June and seedling age was 5 weeks. In 2018, the March planting experienced severe frost during the initial field period resulting in crop failure. In 2017 and 2019, plants could withstand shorter and less severe frost events. Seedling age did not significantly affect tuber parameters. Transplanting in June resulted in lower marketable yield (> 28 mm) compared with earlier transplanting dates when crops were harvested in September. At full crop senescence, no differences in marketable yield were observed. The optimal transplanting window, taking into account weather-related risks, is approximately between early April and end May. For some genotypes, crop cycle length was observed to be a more important yield-determining factor than transplanting date

Effect of Planting Density and K2O:N Ratio on the Yield, External Quality, and Traders' Perceived Shelf Life of Pineapple Fruits in Benin

Quality, shelf life, and yield of a pineapple fruit are the important attributes for the producers and customers in the pineapple value chain of Benin, whereas poor quality, short shelf life, and low yield are the main constraints. We quantified the effects of planting density and K2O:N fertilizer ratio on the pineapple yield, external quality, and perceived shelf life in four on-farm experiments with cv. Sugarloaf in Benin; two experiments were installed in the long rainy season and two in the short rainy season. A split-plot design was used with the planting density as the main factor at three levels: 54,000, 66,600, and 74,000 plants.ha−1. The K2O:N ratio was a subfactor with three levels: K2O:N = 0.35 (farmers' practice), K2O:N = 1, and K2O:N = 2. The results showed that both factors had no effect on the crop development variables (such as the number of functional leaves and D-leaf length) at the moment of flowering induction. The planting density had no effect on the total weight per fruit, infructescence weight, total fruit length, infructescence length, crown length, or the fruit shelf life as perceived by traders. The yield increased from 54.9–69.1 up to 90.1 t.ha−1 with an increase in the planting density. The yield increase was not at the expense of the fruit weight. Increased K2O:N ratio led to a higher fruit weight whereas the fruit length was not affected. The shelf life of fruits produced at a K2O:N ratio of 1 and as perceived by traders was 6 days longer than that of fruits produced at a ratio of 0.35 (farmers' practice). Based on these results, we suggest the fresh pineapple farmers in Benin to use a combination of 66,600 plants.ha−1 with a K-fertilization scheme based on a K2O:N ratio of 1 to meet the expectation of both producers and customers in terms of fruit yield and fruit quality