Trunk Cross-sectional Area Research Articles

Soil amendments influence Pratylenchus penetrans populations, beneficial rhizosphere microorganisms, and growth of newly planted sweet cherry

Replant disease (RD) presents a significant barrier to establishing productive orchards on old orchard soil. Using a field and greenhouse experiment, this study evaluated the influence of agricultural waste compost (AWC) soil amendments, and bark chip mulch (BM) on Pratylenchus penetrans populations and new growth of sweet cherry planted into soil previously used for apple production. Impacts of the treatments on the abundance of rhizosphere microorganisms associated with soil suppressiveness were also evaluated. In the field experiment, fumigation, and preplant incorporation of AWC combined with surface application of BM increased trunk cross-sectional area (TCSA) compared to untreated control plots. Fumigation initially decreased P. penetrans populations in soil, however populations recovered by the end of the first growing season. AWC and BM suppressed P. penetrans populations in roots relative to fumigation or the control. AWC increased the abundance of total bacteria, 2,4-diacetylphloroglucinol-producing (DAPG) bacteria, and pyrrolnitrin-producing (PRN) bacteria in the rhizosphere, relative to fumigation and the control. In the greenhouse experiment, fumigation, AWC, and yard trimmings compost (YTC) increased shoot length of apple and sweet cherry seedlings as well as suppressed P. penetrans populations compared to the control. AWC also increased the abundance of total bacteria, Pseudomonas spp., DAPG+bacteria, and PRN+bacteria relative to fumigation and the control. Overall, composts and BM show potential as alternatives to fumigation for suppression of RD on sweet cherry, with promotion of beneficial rhizosphere microorganisms a possible contributing mechanism in compost-induced soil suppressiveness.

Prohexadione calcium controls shoot growth of pear trees

The aim of this study was to evaluate the effects of prohexadione calcium (PCa) on vegetative growth and production of ‘Carrick’, ‘Packham’s’ and ‘William’s’ pear. The trial was performed at the experimental field of the Federal University of Pelotas, Capão do Leão, RS, Brazil (31º 52’ 00" S; 52º 21’ 24" W), during the growing seasons of 2011 and 2012. Treatments were applied to single-tree replications in a randomized complete block design with four replications as follows: Control (unsprayed), PCa (PCa - 750 g ha-1 i.a.). The application was split in four (187,5g ha-1 a.i. each) and three timings (250g ha-1 a.i. each) in the 2011 and 2012 growing seasons, respectively. The assessed parameters were: shoot length, trunk cross sectional area (TCSA) increment, number of nodes, internode length, pruning weight, number of fruits, average fruit weight, production per tree and return bloom. It was possible to conclude that application of PCa at 750 g. ha-1 a.i satisfactorily controls shoot growth through the reduction of internode length of ‘Carrick’, ‘Packham’s’ and ‘William’s’ pears. Besides, it was observed that return bloom is not negatively affected by PCa. So, this plant growth regulator is a potential management tool to reduce shoot growth and the need for pruning in pear orchards.

Effect of planting densities and varieties on yield and yield associated characters of apple (Malus × dometica) on semi-dwarfing rootstock

Four apple (Malus × domestica Borkh) varieties (Starkrimson, Cooper IV, Red Chief, and Mollies Delicious) were planted at 3 planting densities (1600, 1142 and 952 plants / ha) on semi-dwarf rootstock during 2002-03 and data on yield and growth were recorded after 7 years. Results indicated that maximum mean trunk cross sectional area was registered in Mollies Delicious at all the densities (103.79, 92.61 and 77.06 cm2) and lowest (67.01, 75.65 and 80.33 cm2) in Cooper IV. Largest sized fruit (177.80 g/ fruit) recorded in the S3 (952 tree/ha) and minimum (160.73 g/ fruit) in S1 density (1600 tree/ha). Maximum mean yield and yield efficiency were recorded in Starkrimson and Red Chief and minimum yield and yield efficiency in Cooper IV. Density has a detrimental effect on yield efficiency, it was maximum (0.48 kg/cm2) in S3 and minimum (0.21 cm2) in S1 density. The fruit weight increases with decrease in plant density, fruit size has negative correlation with number of fruit tree. Positive correlation was obtained between yield and yield efficiency (0.999) and planting densities with yield efficiency (0.691).

Results from 13-year study of cultivar-rootstock combinations in sweet cherry

The study was carried out during the period 1999-2011 at the Institute of Agriculture - Kyustendil, Bulgaria. The growth, reproductive characteristics and fruit quality of 'Van' sweet cherry trees, grafted on clonal rootstocks: 'P-7', 'Karamy', 'Hybrid 2', 'SL-64' and seedlings from 'Vladimir' and 'Mahaleb 20-86' were studied. The trees on 'SL-64' were used as a control. The trees were planted in the spring of 1999 at distances of 5.50×5.0 m, formed in free-growing crowns and grown without irrigation. After thirteen years, the biggest trunk cross-sectional area had the trees grafted on 'Hybrid 2' and the smallest on 'Mahaleb 20-86'. The trees crown volume was reduced by 14.9% for 'Vladimir', 21.4% for 'P-7', 22.6% for 'Hybrid 2', 27.8% for 'Mahaleb 20-86', and 35.9% for 'Karamy', when compared to 'SL-64'. The row strips were not occupied by the trees, which allow optimizing planting distances. 'P-7' had the highest root-suckering ability, followed by 'Vladimir'. Trees grafted on 'Vladimir' had the best vitality, while those on 'Karamy' were with the highest mortality rate. The highest productivity had the trees on 'SL-64' and the lowest on 'Karamy'. Productivity was also good for 'P-7' and 'Vladimir', which was confirmed by the data for yield efficiency and the quantity of fruit 1 m-3 of the crown volume. No significant differences were found in the average weight and fruit size as well as in their chemical composition (dry matter, total sugars and acids) among tested rootstocks.

Impact of Plum pox virus (PPV-D) infection on peach tree growth, productivity and bud cold hardiness

In 2000, the Dideron (D) strain of Plum pox virus (PPV) was detected in commercial peach and nectarine orchards in the Niagara region of Ontario where most of Canada’s stone fruit crops are produced. As part of a disease management research programme, peach (Prunus persica L. Batsch) trees in a commercial orchard at Niagara-on-the-Lake were assayed for PPV annually for 3 years. The orchard consisted of two blocks of the cultivars ‘Allstar’ and ‘Brighton’, of which 4 of 288 and 5 of 252 trees, respectively, were infected with PPV-D. The growth and health of these PPV-infected and non-infected trees were evaluated based on the annual growth rates, vigour (chlorophyll content) and bud winter hardiness. Comparative fruit quantity and quality index values were based on total yield and marketable yield per tree, fruit size and weight, fruit pH, titratable acidity, total soluble solids, flesh firmness, and fruit skin colour. Results from these preliminary studies showed that trees infected with this mild Ontario isolate of PPV produced slightly more fruit of smaller size that ripened earlier than non-infected trees. However, yield efficiencies based on weight of fruit relative to the trunk cross-sectional area did not differ statistically. Screenhouse studies on three graft-inoculated fresh market peach cultivars (‘Babygold’, ‘Catherina’, and ‘Garnet Beauty’) similarly did not demonstrate any differences in growth or fruit production in the second and third year post inoculation, but fruit on infected trees matured somewhat earlier.

PRODUCTIVE PERFORMANCE OF ‘FUJI’ APPLE TREES ON ‘JM’ SERIES ROOTSTOCKS, IN SÃO JOAQUIM/SC

ABSTRACT Worldwide, research has developed new apple rootstocks that induce higher yields, pest resistance and adaptation to different climatic and soil conditions. Thus, the performance of these new rootstocks in the conditions of the main regions that grow apples should be investigated. The objective of this study was to evaluate the performance of ‘Fuji’ trees on different rootstocks of JM series and M.7 in the region of São Joaquim, SC. The experiment was performed from 2010 to 2015. Plant material consisted on the cultivar Fuji grafted on the rootstocks JM.2, JM.3, JM.5, JM.7, JM.8 and M.7, planted as single axis trees in the winter of 2002, and spaced at 5 x 1.5m. Trees were trained in a central-leader system and arranged in a randomized complete block design with four replicates. The number of fruits per tree, production per tree, yield, yield efficiency, fruit weigh, and trunk cross sectional area were evaluated. The results showed that the yield of ‘Fuji’ apple trees is greater with the rootstocks JM.3, JM.7, JM.8, and M.7. The rootstocks JM.2, JM.5, JM.7 and JM.8 induce similar vigor as M.7. The results also show that fruit weight is little affected by rootstock.

Horticultural performance of 23 Sicilian olive genotypes in hedgerow systems: Vegetative growth, productive potential and oil quality

The super high density (SHD) model is a new olive growing system characterized by earlier and higher yields, fully mechanized harvesting and reduced orchard management costs. Until recently all commercial SHD orchards were planted primarily with three varieties: ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’. To increase variety diversity, broaden available olive oil chemical and organoleptic profiles, and olive oils for marketing, minor local varieties should be evaluated for adaptability to the SHD system. This study compares multiple Sicilian native genotypes to the three current cultivars ‘Arbequina’, ‘Arbosana’ and ‘Koroneiki’. The cumulative fruit and oil production, trunk-cross section area, canopy volume, alternate bearing behavior and oil quality were evaluated in a SHD system. Among the standard cultivars ‘Koroneiki’ had significantly higher and ‘Arbequina’ average productivity respectively compared to earlier reports and was chosen as the reference for evaluating the performance of the Sicilian genotypes. Many of the genotypes investigated had olive and oil yields equal to or higher than ‘Arbequina’; ‘Abunara’ and ‘ADE’ had very high productivity. ‘Abunara’ produced a medium-high quality oil. The ‘KALAT’ selection had high productivity and low vigor, and therefore high productive efficiency. However, the oil polyphenols were low. The ‘Cerasuola’ and ‘Piricuddara’ cultivars had good productivity and a very high quality oils. These results confirm the need to evaluate and preserve local genetic resources as a strategy for improving SHD olive management and increasing olive cultivar and oil diversity.

Prohexadione calcium on shoot growth of 'Starkrimson' pear trees

Abstract: The objective of this work was to evaluate the fruiting and vegetative growth of 'Starkrimson' pear in response to the application of prohexadione calcium (P-Ca). P-Ca (250 mg L-1) was sprayed to scaffold limbs and to whole trees in commercial orchards. A randomized complete block design was used to minimize declivity effects. Vegetative growth (length and number of shoots, increment in limb and trunk cross-sectional area, number of nodes, and internode length), production (fruit number, yield, yield efficiency, and fruit size), and return bloom were evaluated from 2010 to 2013. P-Ca efficiently controlled shoot growth in all growing seasons, when applied early in the season, due to the reduction in internode length. Production was not negatively affected by the application of P-Ca in all years and at both sites, and fruit size and return bloom were not reduced. Fruit quality attributes were also little affected by P-Ca, except for total soluble solids content, which was lower than that of the control. This shows that P-Ca is efficient to manage tree vigor in high-density 'Starkrimson' pear orchards.

Performance of apricot varieties/genotypes in north western Himalayan region of India

A long term experiment (2010-11 to 2014-15) was performed to evaluate the morphological and qualitative traits of apricot varieties/genotypes under north western Himalayan region of India. There were ten varieties/genotypes (CITH-Apricot-01, CITH-Apricot-02, CITH-Apricot-03, Communis, Erani, Afghani, Balcota, CITH-Apricot-09, Chinese apricot, Tokpopa Nimu ) were evaluated under RCBD with three replications. The results of five year pooled data indicated that maximum average Trunk Cross Sectional Area (TCSA) (168.03 cm2) was recorded in the variety Communis. Maximum fruit weight (80.03 g) and yield (113.87 kg/tree) were recorded in CITH-Apricot-01. The productivity efficiency (1.21 kg cm-2 TCSA) was noted in CITH-Apricot-02. The fruit stone ratio 21.62 was recorded in Afghani variety. The highest TSS (25.070 Brix) was estimated in CITH-Apricot-09. Acidity was noticed maximum in the variety Chinese apricot. The total sugar and non reducing sugar were manifested maximum in the apricot genotype Tokpopa Nimu and reducing sugar (8.9%) was recorded in CITH-Apricot-09 under the north western Himalayan region of India.SAARC J. Agri., 14(2): 107-116 (2016)

Effects of regulated deficit irrigation on physiology, yield and fruit quality in apricot trees under Mediterranean conditions

Scarce water resources mainly in arid and semi-arid areas have caused an increasing interest for applying irrigation protocols aiming to reduce water spends. The effects of regulated deficit irrigation (RDI) on the performance of apricot trees (Prunus armeniaca L. cv. “Búlida”) were assessed in Murcia (SE Spain), during three consecutive growing seasons (2008-2010). The hypothesis was that RDI would not restrict yield but increase fruit quality while saving water. Two irrigation treatments were established: i) control, irrigated to fully satisfy crop water requirements (100% ETc) and ii) RDI, that reduced the amount of applied water to: a) 40% of ETc at flowering and stage I of fruit growth; b) 60% of ETc during the stage II of fruit growth and c) 50% and 25% of ETc during the late postharvest period (from 60 days after harvest). Stem water potential, gas exchanges, trunk cross-sectional area (TCSA), fruit diameter, yield and fruit quality traits were determined. Vegetative growth was decreased by the use of RDI (12% less TCSA on average for the three years), whereas yield was unaffected. In addition, some qualitative characteristics of the fruits, such as the level of soluble solids, sweetness/acidity relation and fruit colour, were improved by the use of RDI. These results and average water savings of approximately 30%, lead us to conclude that RDI strategies are a possible solution for irrigation management in areas with water shortages, such as arid and semi-arid environments.

Tree architecture influenced productivity and quality attributes in apple under HDP

The present experiment was conducted to develop efficient tree architecture in apple under high densityplanting systems. In this trial vertical axis tree and cordon tree architecture were validated first time in Indiaviewing the success in horticultural advanced countries. Maximum annual extension growth (102.34 cm), trunkcross sectional area (23.66 cm2), the highest yield per tree (10.92 kg), yield per hectare (84.63 t/ha) and yield efficiency (0.45 kg/cm2) were recorded in cultivar Coe Red Fuji under vertical axis tree architecture. Maximum fruitweight was observed in cultivar Coe Red Fuji under cordon tree architecture (167.14 h). The red colour intensitywas recorded maximum (a*) (20.16) in cultivar Coe Red Fuji under vertical axis tree architecture, while, maximum yellow colour intensity (b*) (28.44) were found in Granny Smith fruits under same architecture. Cultivar Coe RedFuji has excelled on the overall vegetative growth, yield and quality attributes under HDP in vertical axis system.

Growth and productivity characteristics of Japanese plum cultivars

Growth and productivity characteristics including: initial and final fruit set, yield per tree, trunk cross-sectional area, yield efficiency and fruit weight were studied in ten cultivars of Japanese plums in the Belgrade area for the period of three years (2013-2015). Initial fruit set ranged from 5.6 to 44.4%, and the final fruit set from 2.6 to 23.36%. The high yield per tree (over 10 kg) was obtained in cultivars ?Obilnaja? and ?Morettini 355?, whereas the low yield (under 5 kg) was obtained in cultivars ?Strival?, ?Black Amber?, ?Early Angeleno? and ?Autumn Giant?. The lowest vigor was observed in the cultivar ?Golden Plum?, and the highest in the cultivar ?Strival?. The majority of cultivars had a very large fruit (over 50 g). The yield was strongly positively correlated with initial and final fruit set (r = 0.84**; r = 0.92**, respectively). Fruit weight was moderately negatively correlated with initial and final fruit set (r = -0.67*; r = -0.63*, respectively).

VEGETATIVE AND PRODUCTIVE RESPONSES OF ORGANIC APPLE (Malus domestica L.) TO FOSSILIZED RED GUANO AND A CONTROLLED-RELEASE FERTILIZER

Fossilized red guano and organic controlled-release fertilizers are among the N fertilizers that can be used in organic production. There is little information about the impacts of these fertilizers on the vegetative growth, fruit yield and quality, and mineral contents in fruits. The objective of this study was to assess the responses of increasing levels of N fertilization with fossilized red guano and a controlled-release fertilizer (Fertil®) on the vegetative growth, fruit yield, quality and mineral composition of ‘Granny Smith’ apples grown under organic management. Treatments included the application of increasing levels of N fertilization (100, 120 and 170 kg N ha-1) applied 50% during early spring and 50% during early summer. In general, trees with higher levels of N fertilizationshowed greater terminal shoot length and trunk cross-sectional area (TCSA) than those of the control treatment. Yield ranged from 60.0 to 62.0 kg tree-1, as well as fruit mineral concentration and ratios were not affected by the treatments. Leaf mineral concentrations were affected only in the case of N. Bitter pit incidence was low (1.4 in a scale 1-4), and therefore not statistically significant. Both fertilizers proved effective in enhancing vegetative growth compared to the control. Fertilizer applications did not affect tree cropping, fruit firmness, TSS, starch index, fruit ground color and incidence of physiological disorders.

Productivity of apricot cultivars of medium late and late maturity in the Belgrade area

Characteristics of productivity and growth (yield per tree, trunk crosssectional area, yield efficiency and fruit weight) were studied in 30 apricot cultivars of medium late and late maturity in the Belgrade area during the six-year period (2009?2014). The cultivar ?Hungarian Best? was used as a control for comparison. The period of study was divided into initial bearing (trees aged three to four years) and full bearing (trees aged five to eight years). Significant differences in yield between cultivars and years were found. An average yield in the period of initial bearing ranged from 0.6 to 6.4 kg per tree, and in the period of full bearing from 4.5 to 18.4 kg per tree. Compared to the control cultivar, significantly higher yield was obtained in 11 cultivars. Adverse weather conditions resulted in a significant reduction in yield in two out of six years of study. Cumulative yield efficiency varied from 0.10 to 0.85 kg/cm2 and in 13 cultivars it was significantly higher compared to the control cultivar. Fruit weight ranged from 26.6 to 81.1 g. Compared to the control, fruit weight was significantly higher in nine cultivars, and significantly lower in ten cultivars. On the basis of high yield and large fruit size, introduced cultivars ?Roxana?, ?Mary de Cenad? and ?Silvercot? as well as domestic cultivars ?Novosadska Rodna?, ?NS-4? and ?NS-6? can be recommended for growing in the Belgrade area.

Efecto de la combinación Adara-M2624 y otros siete portainjertos sobre las características del dosel de dos variedades de cerezo

Se estudió la influencia de los portainjertos SL64, MxM60, MxM14, CAB6P, Weiroot 13, GiSeLa® 5 y GiSeLa® 6 y Adara-Mariana 2624, sobre el comportamiento vegetativo de las variedades de cerezo Bing y Celeste, durante 9 años después de la injertación, en las condiciones agroclimáticas locales. El diseño experimental fue por bloques completos al azar, con seis repeticiones de cuatro plantas por unidad experimental. Las variables fueron: área de sección trasversal de la variedad (AST), relación AST variedad-filtro, altura, volumen de dosel, índice de vigor y densidad de sierpes. El tamaño del dosel fue influido principalmente por el portainjerto y, en menor medida, por la variedad e interacción. En las condiciones del ensayo, SL64 fue el más vigoroso, seguido por MxM60 como vigoroso. Los MxM14, CAB6P y Adara-M2624 fueron semivigorosos; W13, semienanizante; G6, enanizante y G5, muy enanizante. GiSeLa® 5, GiSeLa® 6 y Weirrot 13 mantuvieron el VDct por debajo del máximo disponible, mientras que el de MxM14 y Adara-Mariana 2624 fue controlado sólo con poda. La variedad Bing fue más vigorosa que Celeste. Las combinaciones de portainjertos muy enanizantes con variedades de vigor medio resultaron en árboles demasiado débiles, y viceversa, plantas con excesivo vigor. Los W13, CAB6P y Adara-M2624 formaron sierpes.

The Effects of Rootstocks and Training Systems on the Early Performance of ‘0900 Ziraat’ Sweet Cherry

The effects of three rootstocks (‘Gisela 5’, ‘Gisela 6’ and ‘MaxMa 14’) and three training systems (Spanish bush, Steep leader and Vogel central leader) on early performance of ‘0900 Ziraat’ sweet cherry were compared. There have been significant differences among both rootstocks and training systems in terms of tree heights. At the end of the fourth year, while the height of the trees grafted on ‘Gisela 5’ was 238.3 cm, those grafted on ‘MaxMa 14’ reached 266.4 cm in height. While the shortest tree height was obtained from Spanish bush system, heights of the trees in Steep leader and Vogel central leader training systems were found to be at similar levels. ‘Gisela’ 5 had lower trunk cross section area (TCSA) than ‘Gisela 6’ and ‘MaxMa 14’ rootstocks. Among three systems, trees trained to Steep leader had the highest TCSA, followed by Spanish bush and Vogel central leader. Interactions were found between rootstock and training system for yield and yield efficiency. On ‘Gisela 6’, cumulative yield of Vogel central leader system (17.0 g/tree) was significantly higher than Spanish bush (14.8 g/tree) and Steep leader (12.6 g/tree). On the other hand, on ‘MaxMa 14’, there were not significant differences in cumulative yield per tree among training systems. On ‘Gisela 5’ and ‘Gisela 6’, the highest yield efficiency were observed in trees trained as Vogel central leader. Yield efficiency of Vogel central leader (0.49 kg cm-²) was two time higher than those of Spanish bush (0.29 kg cm-²) and Steep leader (0.26 kg cm-²) on ‘Gisela 6’. The weight of fruits from trees grafted on ‘Gisela 5’ was lower than those from trees on ‘Gisela 6’ and ‘MaxMa 14’. In the fourth year, while the average fruit weight was 5.86 g on ‘Gisela 5’, it was 6.00 and 6.25 g on ‘Gisela 6’ and ‘MaxMa 14’ rootstocks respectively.

Yield efficiency for nine apple cultivars grafted on two rootstocks

ABSTRACT: Currently, using smaller trees is one of the most important trends in apple cultivation. It is expected that reduced size plants produce lower amount of fruit, but with high yield and yield efficiency. The aim of this study was to evaluate the yield efficiency (YE) of nine apple tree cultivars, grafted on two rootstocks, from the second to the seventh year after planting. The YE indexes oscillated from one to the other year, regardless of rootstock. Correlations between YE and yield per tree and between YE and trunk cross sectional area (TCSA) confirmed that efficiency can be increased by the production increment or by the plant's vigor reduction. The usefulness of cumulative YE (ƩYE) is highlighted to compare apple tree cultivars after the third year of production. The highest ƩYE indexes were observed for 'Royal Gala' and 'Baigent', on M-9 rootstock, and for 'Gala Real' and 'Maxi-Gala', on Marubakaido/M-9 rootstock.

Genetic base-broadening of cacao for precocity and cropping efficiency

AbstractIntroduction of clones from genetic groups that are underrepresented in the pedigree of commercial cacao varieties in West Africa represents an important aspect of cacao improvement strategy of broadening the genetic base to overcome current yield stagnation of the crop. The objective of the present study was to determine the combining abilities of more recently introduced cacao clones for yield and cropping efficiency in the early bearing years. Seven recently introduced clones were crossed as males to five clones commonly used in the seed gardens in Ghana using a North Carolina II design. The 35 F1varieties and one commercial variety were evaluated in the field from June 2010 to March 2015 for four traits: increase in trunk cross-sectional area in the juvenile, and in the pod-bearing phases, bean yield and cropping efficiency. Though both GCA and SCA variances were significant for all traits, the ratios of GCA:SCA were much smaller than unity, indicating the importance of non-additive effects in the control of the traits. Among the set of clones therefore, prediction of F1variety performance cannot be based on the GCA orper se(average) performance of the clones. Six varieties were more precocious, and eight had higher cropping efficiencies than the standard variety. Bean yields ranged from 0.74 to 1.05 t/ha/year in the fourth and fifth years after planting among the top six varieties. The study provides evidence of the large potential for productivity increase through the use of cacao clones beyond Pound's early introductions into West Africa.

Tree vigour and yield of plum grown under high density planting system

During the second through sixth growing seasons, under the environmental conditions of Cacak (Serbia), tree vigour, yield (kg tree-1 and t ha-1), yield efficiency, biennial bearing index and fruit weight were studied in five plum cultivars ('Cacanska Rana, 'Cacanska Lepotica', 'Cacanska Najbolja', 'Cacanska Rodna' and 'Stanley') grafted on myrobalan (Prunus cerasifera Ehrh.) seedlings. Trees were planted at a spacing of 4×2 m (1,250 trees ha-1). Five-year results showed that the final tree vigour, expressed as trunk cross-sectional area (TCSA), was the lowest in 'Cacanska Lepotica' (39.9 cm2) and the highest in 'Cacanska Rana' (75.0 cm2) and 'Cacanska Najbolja' (82.9 cm2). 'Cacanska Rodna' and 'Cacanska Najbolja' gave their first yields as early as the second year (1.08 and 1.47 kg tree-1, respectively), whereas the first significant yields in all cultivars were obtained in the third year. Cumulative yield was the lowest in 'Cacanska Rana' (30.75 kg tree-1 and 38.44 t ha-1), somewhat higher in 'Cacanska Najbolja', 'Cacanska Lepotica' and 'Stanley' (43.86, 60.37 and 73.40 t ha-1, respectively), and the highest in 'Cacanska Rodna' (66.36 kg tree-1 and 82.95 t ha-1). However, 'Cacanska Rodna' had the highest biennial bearing index (0.61), whereas the other cultivars exhibited a moderate or poor biennial bearing habit during the experimental years. The lowest biennial bearing index was recorded in 'Cacanska Lepotica' (0.13). Yield efficiency was the lowest in 'Cacanska Rana' (0.12 kg cm-2) and highest in 'Cacanska Rodna' (0.41 kg cm-2). The average fruit weight was in agreement with cultivar-specific traits, and ranged from 27.4 g in 4Cacanska Rodna' to 51.8 g in 'Cacanska Rana'.

Biological and economic qualities of some apple hybrids

Six apple hybrids created at the Institute of Agriculture, Kyustendil (Bulgaria) were tested in 2012-2014. The trees were grafted on 'MM 106' rootstock and planted in the spring of 1998 at a distance 4.5×2.5 m. The trial was established in five replications (1 tree replication-1). The flowering period, ripening time, tree growth, yield, morphometric (fruit weight and dimensions) and chemical properties (soluble solids, total sugars and titratable acids content) were determined. The earliest bloom was observed in hybrid 1/16 ('Winesap' × 'Erwin Baur') - April 10, and the latest in hybrid 1/38 ('Prima × Cooper 4') - April 16. The weakest growth (trunk cross-section area) had the trees of hybrid 1/21 ('Spartan' × 'Prima') and the strongest the trees of hybrid 1/38. Fruit ripened between September 21 and 25, respectively, for hybrid 1/20 ('Winesap' × 'Erwin Baur') and hybrid 1/36 ('Prima' × 'Cooper 4'). Hybrids 1/23 ('Spartan' × 'Prima') and 1/16 produced the highest average yields (22.8 and 22.7 kg tree-1, respectively). The fruits of hybrid 1/20 were the largest (197.3 g). Average soluble solids were between 11.7 and 13.6%, total sugars ranged from 6.7 to 7.7% and titratable acids from 0.15 to 0.76%.