GENERATIVE DEVELOPMENT OF RED BEET GROWN IN THE FIELD AND IN PLASTIC TUNNELS

Barbara Jagosz
Institute of Plant Biology and Biotechnology, University of Agriculture in Krakow, Poland

ABSTRACT

The purpose of this research was to investigate the influence of both the growing method and the cultivars/lines characteristics on the seed stalk architecture and the yield and quality of red beet clusters. The plant material, consisting of 16 mono- and multigerm breeding lines and commercial cultivars, were grown in the field and under plastic tunnels. Most of the morphological traits, such as the seed stalk height, the number of shoots and the percentage of bushes with main stem plants, were comparable in both growing methods. The method of cultivation also had no effect on the yield and the 1000-cluster weight. The clusters collected in the tunnels germinated slower but resulted in higher germination capacity than the clusters harvested in the field. Most of the individual lines and cultivars grown at the same time in the tunnels and in the field presented comparable values of the studied features during generative development of plants. The results of this experiment confirm the possibility of using tunnels for growing red beet seed plants during the seed production of both mono- and multigerm cultivars.

Key words: cluster, monogerm, multigerm, seed production, seed stalk.

INTRODUCTION

Red beet (Beta vulgaris L.) is a biennial vegetable cultivated in temperate areas of North America, the Middle East, parts of Asia, and Europe [4]. Poland, producing about 298,000 tons of red beet roots a year, is a European leader in terms of the growing area and the amount of production, as well the level of consumption [2].

Modern agriculture requires seeds of the highest quality that are needed in order to be able to perform precision sowing. However, the majority of red beet cultivars still form multigerm clusters that produce several seedlings, which requires thinning them by hand. Thus, the current red beet breeding program is aimed at creating monogerm cultivars. The seed production of beet is difficult because it is cross-pollinated whose pollen can be carried by the wind from a distance of 20 km [4]. Therefore, the generative development of beet is often carried out in plastic tunnels that facilitate the proper isolation of plants at the stage of flowering [10].

The current study on red beet is mainly based on the vegetative growth stage, thus still little research concerns the evaluation of the factors that determine the yield and quality of the seeds [8]. Based on the available previous research on the generative growth of red beet [7, 9, 10, 14, 15] and sugar beet [1, 5, 11–13], one can conclude that the morphology of seed plants as well as the yield and quality of seeds are dependent on both the cultivars/lines characteristics and the growing conditions.

The aim of the study was to evaluate the impact of both cultivars/lines characteristics and growing method on red beet seed plant morphology, as well as on the yield and quality of clusters. The comparison of 16 lines and cultivars grown simultaneously in the field and under plastic tunnels determined the suitability of using tunnels during the red beet generative development. The results of the experiment will be useful in red beet seed production both hybrid and open-pollination cultivars, especially with the trait of cluster monogermity.

MATERIAL AND METHODS

The study was performed between 2010–2013 at the Experimental Field of the Unit of Genetics, Plant Breeding and Seed Science at Prusy near Krakow, southern Poland. The plant material consisted of 16 lines and cultivars of red beet (Beta vulgaris L.): three monogerm (279 A and B, AR79 A and B, W411 A and B) and three multigerm (218 A and B, 357 A and B, 391 A and B) cytoplasmic male sterile pairs of breeding lines A and their respective maintainer fertile lines B, as well four commercial cultivars, one monogerm (‘Patryk’) and three multigerm (‘Astar’ F1, ‘Okrągły C.’, ‘Polglob’ F1).

The field experiment was managed according to standard crop management practices recommended for red beet under Polish conditions. The experiment was conducted as a randomized complete block with three replications under open field conditions and under four plastic tunnels, each 24 m2. At the beginning of April seven stecklings of each line and cultivar were planted in rows spaced 50 cm apart with a space of 25 cm between plants.

The harvesting of ripened seed stalks began in early August and continued until the end of September. Seed plant collection started when the clusters at the base of each branch were brown. The data obtained during harvesting includes the height (cm) of the highest shoot of each plant. Subsequently the seed stalk structure type was determined according to Janas and Grzesik [8]. Each plant was assigned to one of three morphological types, so the percentage of ‘single’, ‘bush’, and ‘bush with main stem’ seed stalks types was calculated. For bush and bush with main stem plants, the number of shoots was also counted.

The seed stalks were dried for a week, after which the clusters were hand-threshed and then air-dried for four weeks at a temperature of 20–25ºC. Subsequently the cluster yield (g) per plant was evaluated. The 1000-cluster weight (g) and germination capacity were measured according to ISTA recommendations [3, 6]. The mean germination time (MGT), assessed in four replications, each consisting of 100 clusters taken at random, was calculated according to the following formula: MGT = Σ (T × G) / F, where T = the day of germination, G = the number of germinated clusters (with 2 mm radicle emergence) on the counting day and F = the final number of germinated clusters. Statistical analysis was conducted using the STATISTICA software (version 9). The data from the study in the years of the experiment were comparable, so they were subjected to a general analysis of variance (ANOVA) as the mean. The significant differences for all of the tested features were calculated using the Duncan test at a significance level of p ≤ 0.05.

RESULTS AND DISCUSSION

The main objective of the experiment was to evaluate the influence of both growing method and the cultivars/lines characteristics on red beet seed stalk architecture as well as the yield and quality of clusters. It was noted that seed stalk height, the number of shoots and the percentage of bushes with main stem plants, which are the most preferred from the viewpoint of seed production, remained at a similar level both in the plastic tunnels as well as in the field (Tab. 1). Significant differences between plants grown in the field and in the tunnels were seen only in a fraction of single and bush seed stalks. However, in the study carried out by Michalik and Kozak [10], red beet seed plants grown in plastic tunnels were considerably higher and bushier than plants grown in the field. The effect of cultivars/lines characteristics on the presently examined seed stalk morphological features was clear. In half of the tested lines and cultivars the height of plants grown both in the field and in the tunnels was comparable. Ten of the 16 tested objects formed a similar number of shoots in both growing methods. In addition, the plant structure of the individual cultivars and lines grown in tunnels as well as in the field was highly comparable. Michalik [9], Michalik and Kozak [10], Apostolides and Goulas [1] and Jagosz [7], testing different sugar and red beet cultivars and breeding lines, also reported the strong impact of genotype on the construction of seed stalks. Comparing the presently tested lines and cultivars, generally, a similar frequency of the occurrence of particular morphological types of plants was observed. Jagosz [7] also noted similar seed plant construction within the tested red beet lines and cultivars. However, in both the present study and in the study by Jagosz [7], the seed stalks of the lines were much lower, but they produced more shoots than the cultivars. Currently, the lines A and B formed seed plants with a similar structure and height, as well as a similar number of shoots. A strong resemblance of lines A and B in plant construction also was noted by Jagosz [7]. Nevertheless, Michalik and Kozak [10] found quite a large variation in bush plant number within lines A and B. In most of the monogerm lines, a tendency to form higher plants with more shoots and a higher percentage of bushes with main stem seed stalks was noted when compared to the average for the lines.

According to Michalik and Kozak [10], the seed plants cultivated in tunnels yielded much better than those in the field. Presently, there was no clear impact of growing method on the yield or the 1000-cluster weight (Tab. 2). In contrast, the clusters collected in the field germinated faster, but their germination capacity was lower than clusters harvested in the tunnels. The strong impact of cultivars/lines characteristics on the cluster yield of different beet cultivars and breeding lines was reported by Michalik [9], Michalik and Kozak [10], Apostolides and Goulas [1] and Jagosz [7]. The currently tested cultivars and most of the lines yielded at the same level and presented similar 1000-cluster weights in both growing conditions, which points towards the strong influence of cultivars/lines characteristics on these features. The studied cultivars produced much higher cluster yield and resulted in better germination than the lines. Michalik and Kozak [10] and Jagosz [7] also noted better yielding, while Michalik [9] and Jagosz [7] recorded a higher germination capacity of cultivars than lines. According to Michalik [9], the current study also confirm that the mean 1000-cluster weight was higher in the cultivars than the lines. However, Jagosz [7], comparing lines and cultivars, found similar values of 1000-cluster weights. The MGT of the lines was longer than that of the cultivars, both presently as well as in the research by Jagosz [7]. In the current experiment as well as in studies published by Michalik [9], Michalik and Kozak [10] and Jagosz [7], lines A and B mostly presented comparable values of clusters yield and quality traits. Compared to the average for the lines, two-thirds of the monogerm lines produced very high cluster yield, while the yield of the other lines were lower by half. However, this did not affect the 1000-cluster weight, which was proportionally lower in all of the monogerm objects.

The results indicate that most of the morphological features of red beet seed stalks as well as the yield and quality traits of clusters are largely by cultivars/lines characteristics conditioned, thereby are scarcely modified by growing methods. The majority of the objects tested at the same time in the field and under plastic tunnels presented comparable values of the studied features. Thus, it was concluded that the cultivation of seed plants in the tunnel, which provides high protection against undesirable pollination, can be used in the generative stage of the seed production of mono- and multigerm cultivars of red beet.

CONCLUSIONS

1. Most of the genotypes grown at the same time in the field and under plastic tunnels presented comparable values of the studied characteristics of the seed stalk architecture and the yield and quality of clusters.
2. The seed stalk height, the number of shoots and the percentage of bushes with main stem plants, were comparable in both growing methods.
3. The method of cultivation had no effect on the yield and the 1000-cluster weight.
4. The clusters collected in the tunnels germinated slower but resulted in higher germination capacity than the clusters harvested in the field.

ACKNOWLEDGEMENTS

This work was supported by the Ministry of Agriculture and Rural Development. Project No. HOR hn 801-22/12 and HOR hn 10-13.

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Accepted for print: 19.11.2015

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