Preliminary Evaluation Results of New Plum Cultivars in a Dense Planting
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Preliminary evaluation results of new plum cultivars in a dense planting J. Blažek, I. Pištěková Research and Breeding Institute of Pomology Holovousy, Holovousy, Czech Republic ABSTRACT: Sixteen new plum cultivars mostly bred in Germany were tested together with several standards in a high density experimental orchard established at Holovousy in the spring of 2004 with spacing 5 × 1.5 m. Trees were trained as spindles on St. Julian A rootstock. In the orchard the following characteristics were evaluated: tree vigour based upon measuring of trunk-cross section area and canopy volume, yields, time of flowering, time of fruit ripening and basic parameters of fruit quality. The highest yields and precocity of fruiting were recorded on cultivars Tophit, Jojo, Elena, and President, whereas the least productive were Ruth Gerstetter, Anna Späth, and Topgigant Plus. Cultivars Katinka, Jojo, Topper, and Empress had the highest values of yield efficiency whilst the lowest ones were recorded on Topgigant Plus and Anna Späth. All evaluated cultivars were characterized by mean start of fruit ripening and length of harvest period. Topgigant Plus had the largest fruits (mean 75.9 g) followed by Bluefre, Empress and Tophit, whereas the smallest ones were recorded in Katinka, Gabrovská and Valjevka. The highest scores for fruit quality were given to Hanita, Tophit and Presenta. New cultivar Tophit was the most remarkable regarding all evaluated character- istics including its time of ripening that would prolong the season of commercially grown fresh fruit cultivars for use in the Czech Republic. Keywords: plum; cultivars; tree vigour; time of ripening; yields; fruit size; fruit quality In the Czech Republic, like in most European Hartmann, Petruschke 2002; Blažek 2007). In countries, plums were grown until practically the Europe a majority of new plum and prune cultivars end of the last century in traditional orchards of have been bred in Germany thanks to two exten- standard or semi-standard trees planted in densi- sive breeding programmes at the universities in ties between 100 and 400 per ha. Economically im- Hohenheim and Geisenheim (Hartmann 1998, portant yields typically began in the 6th year after 2007; Jacob 1999, 2002a,b, 2007). New interest- planting or later. Selected clones of Domestic Prune ing cultivars of the species have also been bred and Green Gage, then Stanley, with some tolerance in Bulgaria (Vitanova et al. 2007) and in Serbia to Plum pox virus, and since eighties also Čačanska (Nenadović-Mratinić et al. 2007). A range of lepotica or Čačanska najbolja were predominately the new cultivars from these institutions and oth- planted there. The production was mainly harvest- ers bred in USA or Canada were recommended for ed mechanically by shakers and used for processing use or for testing in new systems of plum growing or drying. In the last 15 years increase in demands (Hodun et al. 1998; Grzyb, Rozpara 2000; Hart- for fresh plums for direct consumption contributed mann, Fischer 2003). to establishing a new more intensive type of plum In the Czech Republic the first experimental or- orchards with earlier cropping to supply fruits of chard with several new cultivars on two rootstocks better quality for this intended purpose (Blažek, in a dense spacing was established at Holovousy Kneifel 2005). 1998. In that testing cultivars Valor and Empress In most current Prunus domestica L. breeding had the best performance of tree growth, bearing programmes throughout the world, attention has habit and fruit size, indicating their suitability for focussed on improvement of fruit quality, prolong- the modern types of plum orchards (Blažek et al. ing of the harvest season and on resistance or toler- 2004, 2006). Utilizing this experience, the second ance to Plum pox virus (Okie, Weinberger 1996; experimental orchard of this type was established Supported by the Ministry of Agriculture of the Czech Republic, Project No. QH81235. HORT. SCI. (PRAGUE), 36, 2009 (2): 45–54 45 at Holovousy into which mainly new plum cultivars eter PR 101) and by organoleptic assessment of from Germany were planted together with several several characteristics using a 1–9 rating scale in standard ones like President that in some extend which 9 corresponds to the best performance. The had been previously used for renovation of plum total fruit quality comprised both appearance and orchards also in this country. The present paper re- “eating quality” (taste, firmness etc.) expressed by ports on the results obtained from the first three a single number. Fruit samples during harvest time years of fruiting of the orchards. of each cultivar were taken repeatedly in interval 3 to 5 days (usually 3 or 4 times) for determining MATERIAL AND METHODS the length of its harvest period. Ripening dates were referenced to the number of days after the rip- The experimental orchard was established dur- ening date of Ruth Gerstetter for comparison of the ing autumn 2004 at Holovousy. One year old trees characteristics from different years. All data were of twenty-three cultivars grafted on the rootstock statistically evaluated by an analysis of variance. St. Julien A were planted in a spacing 5 m between the rows and 1.5 m between trees within the row RESULTS mostly in 3 replications per 3 trees in each. The only exception in this scheme were 7 new cultivars from Tree vigour Germany (Top 2000, Topfirst, Topfive, Topgigant Plus, Topper, Topstar Plus, and Toptaste) which This characteristic was expressed by cross sec- because of lack of source material only 3 trees each tional area and canopy volume calculated upon were available after summer budding. For every measuring of trees after growing season 2008. replication of cultivar and rootstock 3 trees were Their mean values and spans for each cultivar are planted. Cultivars Ruth Gerstetter and Anna Späth given in Table 1. The most vigorous were trees of were used in this experiment as standards for com- cultivar Tophit which were nearly double in size parison of time of ripening. compared with trees of least vigour cultivar Top- Climatic conditions of Holovousy are character- per. Besides Tophit, trees of cultivars Tegera and ized by the average annual temperature of 8.1°C Elena were significantly more vigorous than the and the average annual rainfall of 650 mm. The soil average, whereas significantly weaker growth than was medium loam sandy with rather deep culti- average was displayed in cultivars Topfirst, Topstar vated layer on gravely substrate. The orchard was Plus, Katinka and Top 2000. The remainder were of located at the altitude of 280 m a.s.l. Experimental medium vigour and mostly these cultivars were not trees were trained as spindles using strong wooden significantly different from one another. stakes as supports. No irrigation was applied in the orchard. Clean strips were kept under trees by Yields and yield efficiency contact herbicides whereas frequently cut sod was kept in alleys between tree rows. Fertilizers were The highest total yield for the first 3 years of applied according to soil analyses. Spraying treat- cropping (19.5 kg) was noted for trees of cultivar ments against pests and diseases were conducted Tophit. Its yield was nearly 3 times higher than to- according to the recommendations used for com- tal yield of the least cropping trees of Ruth Gerstet- mercial orchards. ter (Table 2). With Tophit in 2008 (in the third year The following records were taken annually: trunk of cropping) 13.8 kg of fruits per tree were har- circumference (for calculation of trunk cross-sec- vested, corresponding to the yield 18.4 t/ha. Nearly tion area), canopy diameter (in two opposite direc- the same total yields like Tophit were observed tions), canopy height and fruit yield per tree. The for cultivars Jojo (19.3 kg) and Empress (19.1 kg). date when harvest ripening started was estimated Likewise total yield of standard cultivar President for each cultivar considering typical colouring of did not differ significantly from these values. On the majority of fruits, strength of fruit stem attach- the other hand the lowest total yields after stan- ment and taste of fruit samples. On that date sam- dard Ruth Gerstetter were also recorded on trees of ples of 50 fruits were taken at random from each Anna Späth and Topgigant Plus. Considering yields replication. in the first year of cropping, cultivars Tophit, Presi- Fruit samples were individually assessed for dent and Jojo were the most precocious, whereas mean fruit weight, flesh firmness (based on the In- Anna Späth, Oneida and Gabrovská the least. stron measuring of 10 fruits), soluble solids content The highest yield efficiencies in 2007 were recorded (in juice of fruits measured by digital refractom- in cultivars Katinka and Topper which were closely 46 HORT. SCI. (PRAGUE), 36, 2009 (2): 45–54 Table 1. Vigour of trees after the season 2008 expressed in the trunk-cross section area and canopy volume Trunk-cross section area (cm2) Canopy volume (m3) Cultivar mean % of total min. max. mean % of total min. max. Anna Späth 25.1 96 22.6 28.3 2.8 86 2.8 3.1 Bluefre 27.6 106 22.2 29.6 3.6 110 3.4 3.9 Elena 31.9 123 28.7 32.5 3.9 121 3.5 4.2 Empress 29.3 113 26.9 30.5 3.7 114 3.5 3.9 Gabrovská 26.5 102 23.3 29.2 3.2 99 2.8 3.6 Hanita 29.2 112 25.3 34.5 3.5 106 3.2 3.8 Jojo 23.9 92 19.2 28.3 2.9 90 2.7 3.3 Katinka 23.3 89 19.6 26.0 2.7 83 2.5 2.9 Oneida 29.3 113 24.4 34.0 3.8 118 3.6 4.1 Presenta 25.9 99 19.5 30.6 3.0 92 2.6 3.4 President 29.6 114 26.2 30.7 3.7 113 3.4 4.0 Ruth Gerstetter 23.9 92 17.6 26.3 3.0 92 2.6 3.3 Tegera 32.4 125 27.3 32.8 4.0 124 3.7 4.2 Top 2000 23.1 89 17.5 26.5 2.9 89 2.6 3.3 Topfirst 20.4 79 17.5 22.8 2.5 77 2.2 2.9 Topfive 23.8 92 19.6 27.2 3.2 99 2.9 3.6 Topgigant Plus 24.5 94 19.8 29.6 3.3 102 3.0 3.5 Tophit 33.3 128 29.6 38.2 4.1 127 3.7 4.4 Topper 17.6 68 16.0 20.2 2.2 69 1.7 2.5 Topstar Plus 22.8 88 17.8 27.7 2.7 83 2.4 3.0 Toptaste 23.5 90 19.3 26.8 3.0 92 2.5 3.4 Valjevka 27.8 107 25.1 30.5 3.5 107 3.2 3.7 Valor 25.7 99 22.2 30.2 3.3 102 3.0 3.8 Total mean 26.11 100 3.25 100 LSD (P = 0.05) 4.15 0.47 followed by Top 2000 and Valor.