Runner Plants Research Articles

Effect of Light Intensity on Rooting and Growth of Hydroponic Strawberry Runner Plants in a LED Plant Factory

To rapidly produce strawberry (Fragaria × ananassa Duch. cv. Benihoppe) transplants from cuttings, suitable light intensities for unrooted runner plants at the rooting stage and rooted runner plants at the seedling stage were determined in a plant factory under LED lighting. At the rooting stage, unrooted runner plants at the 3-leaf stage were hydroponically rooted for 6 days under light intensity of 30, 90, 150, and 210 μmol m−2 s−1, respectively. At the seedling stage, rooted runner plants were hydroponically grown for 18 days under light intensity of 90, 180, 270, and 360 μmol m−2 s−1, respectively. The tube LED lights consisting of white and red LED chips were used as sole light source, and photoperiod was controlled as 16 h d−1. The results showed that the maximum root number (7.7) and longest root length (14.8 cm) of the runner plants were found under 90 μmol m−2 s−1 at the rooting stage. Photosynthetic activity in runner plant leaves under 90 μmol m−2 s−1 were higher than that under 30, 150, and 210 μmol m−2 s−1. Higher light intensity at the range of 90–270 μmol m−2 s−1 increased the stomatal conductance of newly formed leaves of rooted runner plants, thus improving the net photosynthetic rate and growth of rooted runner plants at the seedling stage. The crown diameter, shoot and root dry weights, and root to shoot ratio of rooted runner plants increased by 9.7%, 38.8%, 106.1%, and 48.7%, respectively, when the light intensity increased from 90 to 270 μmol m−2 s−1. However, there was no further improvement of runner plant growth under 360 μmol m−2 s−1. Furthermore, no significant difference of increased dry biomass per mole of photons delivered was found between 180 and 270 μmol m−2 s−1. In consideration of transplant quality and economic balance, light intensity of 90 μmol m−2 s−1 at the rooting stage and 270 μmol m−2 s−1 at the seedling stage were suggested for rapidly producing hydroponic strawberry transplants based on unrooted runner plants in the LED plant factory.

Effects of light intensity and photoperiod on runner plant propagation of hydroponic strawberry transplants under LED lighting

Vegetative propagation of strawberry (Fragaria × ananassa Duch.) in the plant factory with artificial lighting is considered as an effective approach to produce high-quality transplants. In this study, mother plants of ‘Benihoppe’ strawberry were grown hydroponically for 50 d under eight LED lighting treatments by combining four levels of light intensity (200, 250, 300 and 350 mol/(m2·s)) and two photoperiods (12 h/d and 16 h/d). Runner development, growth of runner plants, photon yield and energy yield in runners and runner plants were investigated to evaluate the strawberry propagation efficiency. Results indicated that length of runners decreased linearly with increasing daily light integral (DLI) under each photoperiod and was significantly shorter under photoperiod of 16 h/d. Runner elongation was inhibited by high DLI. Number of runners and runner plants formed by mother plants increased by 38.9% and 33.7%, when DLI increased from 8.6 to 11.5 mol/(m2·d), respectively; however, no further increase was observed when DLI was higher than 11.5 mol/(m2·d). Similar trends were found in crown diameter and biomass of primary and secondary runner plants. Negative impact of high DLI (20.2 mol/(m2·d)) on photosynthetic capacity of runner plants was observed as a decrease in leaf net photosynthetic rate, potential maximum photochemical efficiency of PSII, and chlorophyll content. Furthermore, photon yield and energy yield in runners and runner plants decreased significantly with increasing DLI. Therefore, DLI in a range of 11.5-17.3 mol/(m2·d) is beneficial to improve strawberry propagation efficiency and quality of runner plants, and 11.5 mol/(m2·d) is optimal for the strawberry propagation of runner plants in the LED plant factory because of the higher photon and energy yields. Keywords: hydroponic strawberry, vegetative propagation, daily light integral, photon yield DOI: 10.25165/j.ijabe.20191206.5265 Citation: Zheng J F, He D X, Ji F. Effects of light intensity and photoperiod on runner plant propagation of hydroponic strawberry transplants under LED lighting. Int J Agric & Biol Eng, 2019; 12(6): 26–31.

Growth and Flower Bud Induction in Strawberry ‘Sulhyang’ Runner Plant as Affected by Exogenous Application of Benzyladenine, Gibberellic Acid, and Salicylic Acid

Strawberry (Fragaria × ananassa) is one of the most important and popular fruit crops in the world, and ‘Sulhyang’ is one of the principal cultivars cultivated in the Republic of Korea for the domestic market. The growth and flower induction in strawberry is the process which influences directly on fruit bearing and yield of this crop. In this study, effect of benzyladenine (BA), gibberellic acid (GA3), and salicylic acid (SA) on growth and flower bud induction in strawberry ‘Sulhyang’ was investigated. The 3-week-old runner plants, grown in 21-cell propagation trays, were potted and cultivated in growth chambers with 25oC/15oC (day/night) temperatures, 70% relative humidity (RH), and light intensity of 300 μmol·m-2·s-1 photosynthetic photon flux density (PPFD) provided by white light emitting diodes (LEDs). The runner plants were treated with one of three concentrations, 0 (control), 100, and 200 mg·L-1 of BA, GA3, or SA solution. The chemicals were sprayed two times on leaves of runner plants at an interval of two weeks. After 9 weeks the results showed that the application of all chemicals caused reduction of root length and chlorophyll (SPAD) content as compared to the control. The lowest chlorophyll (SPAD) content was recorded in plants treated with GA3. However, the treatment of 200 mg·L-1 GA3 promoted leaf area, leaf fresh weight, and plant fresh weight. The greatest flower induction (85%) and number of inflorescences (4.3 inflorescences per plant) were observed in the treatment of 200 mg·L-1 SA, followed by 100 mg·L-1 SA. Overall, results suggest that foliar application of GA3 solution could accelerate plant growth, while foliar application of SA solution could induce hastened flowering. Further studies may be needed to find out the relationship between GA3 and SA solutions treated in a combination, and the molecular mechanism involved in those responses observed.

Prohexadione-Calcium Application during Vegetative Growth Affects Growth of Mother Plants, Runners, and Runner Plants of Maehyang Strawberry

Strawberry (Fragaria × ananassa Duch.) is an important horticultural crop that is vegetatively propagated using runner plants. To achieve massive production of runner plants, it is important to transfer the assimilation products of the mother plant to the runner plants, and not to the runner itself. Application of prohexadione–calcium (Pro–Ca), a plant growth retardant with few side effects, to strawberry is effective in inhibiting transport of assimilates to runners. This study aimed to determine the optimum application method and concentration of Pro–Ca on the growth characteristics of mother plants, runners, and runner plants for the propagation of strawberry in nurseries. Pro–Ca was applied at the rate of 0, 50, 100, 150, or 200 mg·L−1 (35 mL per plant) to plants via foliar spray or drenching under greenhouse conditions at 30 days after transplantation. Petiole lengths of mother plants were measured 15 weeks after treatment; growth was suppressed at the higher concentrations of Pro–Ca regardless of the application method. However, the crown diameter was not significantly affected by the application method or Pro–Ca concentration. The number of runners was 7.0 to 8.2, with no significant difference across treatments. Runner length was shorter at higher concentrations of Pro–Ca, especially in the 200 mg·L−1 drench treatment. However, fresh weight (FW) and dry weights (DW) of runners in the 50 mg·L−1 Pro–Ca drench treatments were higher than controls. Foliar spray and drench treatments were more effective for runner plant production than the control; a greater number of runner plants were produced with the 100 and 150 mg·L−1 Pro–Ca foliar spray treatment and the 50 and 100 mg·L−1 drench treatment. The FW and DW of the first runner plant was not significantly different in all treatments, but DW of the second runner plant, and FW and DW of the third runner plant were greatest in the 50 mg·L−1 Pro–Ca drench treatment. These results suggested that growth and production of runner plants of Maehyang strawberry were greatest under the 50 mg·L−1 Pro–Ca drench treatment.

Extended Supplementation of Nutrient Solution for Runner Plant Production Improved the Growth of Runner Plants and Enhanced the Reproduction Rate and Quality of ‘Maehyang’ Strawberry Fruits

This study aimed to investigate the optimum supply period of nutrient solution for the growth of runner plants as well as the flowering, fruit quality, and yield of ‘Maehyang’ strawberry. The runner plants separated from the mother plants were divided into 5 groups, each receiving a supply period treatment of watering (W) and nutrient solution (N) [control (W40), combination of W and N: W20 + N20, W25 + N15, W30 + N10, and W35 + N5]. The EC and pH were 0.6 dS·m-1 and 6.5, respectively. The treated runner plants were transplanted to the strawberry growing pots filled with a commercial growing medium on September 13, 2017 and managed with EC 0.6 to 1.2 dS·m-1 strawberry nutrient solution. Growth characteristics and mineral elements of the runner plants were measured at 40 days after treatment. The crown diameter, fresh weight of shoot, and the leaf area were significantly higher in the W20 + N20 group. The P, Mg, S, and Fe contents in the runner plant leaves significantly increased in the W20 + N20 and the W25 + N15 groups. In addition, the C/N ratio was 7.81% higher in the W20 + N20 group than in groups that had received other treatments. The budding ratio and flowering of primary and secondary inflorescences in the W20 + N20 group were approximately 3 to 9 days faster compared to the control. The fruit characteristics, such as weight, length, diameter, firmness, soluble solids content, and acidity, were not significantly different across the groups. The total number of fruits and marketable fruit yield showed positive results in the W20 + N20 group during the total harvest period. The results indicate that the supply period of nutrient solution has a direct impact on the growth of runner plants of ‘Maehyang’ strawberry, and may also affect parameters of reproductive growth, such as flowering response and fruit yield after transplanting.

PGR and Its Application Method Affect Number and Length of Runners Produced in ‘Maehyang’ and ‘Sulhyang’ Strawberries

Vegetative propagation using runner plants is an important method to expand the cultivation area for the strawberry (Fragaria × ananassa Duch.). However, excessively long runners need an increased total amount of nutrients and energy to receive elongation from mother plants, which may lead to poor growth or reduced output. The use of plant growth regulators (PGRs) is an adoptable way to solve such problems. The objectives of this experiment were to study the effects of PGRs and their application methods on the growth and development of runners, runner plants, and mother plants, and also to find effective ways to control the number and length of runners without harmful side effects. Chlormequat chloride (CCC), 6-benzylaminopurine (BA), and ethephon (ETH) at a concentration of 100 mg·L−1 were applied via three different methods: injection into crowns, medium drench, and foliar spray. The results showed that BA injection into crowns was the most effective combination among all treatments, which prominently shortened the length of runners and increased the number of runners and leaves on a single plant. Furthermore, plants with BA solution injection tended to produce stronger runners with higher fresh and dry weights, without affecting the health states of mother plants. The ETH solution seemed to have toxic effects on plants, by leading many dead leaves and weak runners, and increased activities of antioxidant enzymes. Other than the injection method, the other two application methods of the CCC solution did not significantly affect the growth and development of both cultivars. Runner plants grown for 30 days were not affected by any treatments, and they were in similar conditions. Overall, BA injection into crowns is recommended for controlling the number and length of strawberry runners.

Effects of light intensity and photoperiod on runner plant propagation of hydroponic strawberry transplants under LED lighting

Vegetative propagation of strawberry (Fragaria × ananassa Duch.) in the plant factory with artificial lighting is considered as an effective approach to produce high-quality transplants. In this study, mother plants of ‘Benihoppe’ strawberry were grown hydroponically for 50 d under eight LED lighting treatments by combining four levels of light intensity (200, 250, 300 and 350 mol/(m2·s)) and two photoperiods (12 h/d and 16 h/d). Runner development, growth of runner plants, photon yield and energy yield in runners and runner plants were investigated to evaluate the strawberry propagation efficiency. Results indicated that length of runners decreased linearly with increasing daily light integral (DLI) under each photoperiod and was significantly shorter under photoperiod of 16 h/d. Runner elongation was inhibited by high DLI. Number of runners and runner plants formed by mother plants increased by 38.9% and 33.7%, when DLI increased from 8.6 to 11.5 mol/(m2·d), respectively; however, no further increase was observed when DLI was higher than 11.5 mol/(m2·d). Similar trends were found in crown diameter and biomass of primary and secondary runner plants. Negative impact of high DLI (20.2 mol/(m2·d)) on photosynthetic capacity of runner plants was observed as a decrease in leaf net photosynthetic rate, potential maximum photochemical efficiency of PSII, and chlorophyll content. Furthermore, photon yield and energy yield in runners and runner plants decreased significantly with increasing DLI. Therefore, DLI in a range of 11.5-17.3 mol/(m2·d) is beneficial to improve strawberry propagation efficiency and quality of runner plants, and 11.5 mol/(m2·d) is optimal for the strawberry propagation of runner plants in the LED plant factory because of the higher photon and energy yields. Keywords: hydroponic strawberry, vegetative propagation, daily light integral, photon yield DOI: 10.25165/j.ijabe.20191206.5265 Citation: Zheng J F, He D X, Ji F. Effects of light intensity and photoperiod on runner plant propagation of hydroponic strawberry transplants under LED lighting. Int J Agric & Biol Eng, 2019; 12(6): 26–31.

Effects of light intensity and photoperiod on runner plant propagation of hydroponic strawberry transplants under LED lighting

Vegetative propagation of strawberry (Fragaria × ananassa Duch.) in the plant factory with artificial lighting is considered as an effective approach to produce high-quality transplants. In this study, mother plants of ‘Benihoppe’ strawberry were grown hydroponically for 50 d under eight LED lighting treatments by combining four levels of light intensity (200, 250, 300 and 350 mol/(m2·s)) and two photoperiods (12 h/d and 16 h/d). Runner development, growth of runner plants, photon yield and energy yield in runners and runner plants were investigated to evaluate the strawberry propagation efficiency. Results indicated that length of runners decreased linearly with increasing daily light integral (DLI) under each photoperiod and was significantly shorter under photoperiod of 16 h/d. Runner elongation was inhibited by high DLI. Number of runners and runner plants formed by mother plants increased by 38.9% and 33.7%, when DLI increased from 8.6 to 11.5 mol/(m2·d), respectively; however, no further increase was observed when DLI was higher than 11.5 mol/(m2·d). Similar trends were found in crown diameter and biomass of primary and secondary runner plants. Negative impact of high DLI (20.2 mol/(m2·d)) on photosynthetic capacity of runner plants was observed as a decrease in leaf net photosynthetic rate, potential maximum photochemical efficiency of PSII, and chlorophyll content. Furthermore, photon yield and energy yield in runners and runner plants decreased significantly with increasing DLI. Therefore, DLI in a range of 11.5-17.3 mol/(m2·d) is beneficial to improve strawberry propagation efficiency and quality of runner plants, and 11.5 mol/(m2·d) is optimal for the strawberry propagation of runner plants in the LED plant factory because of the higher photon and energy yields. Keywords: hydroponic strawberry, vegetative propagation, daily light integral, photon yield DOI: 10.25165/j.ijabe.20191206.5265 Citation: Zheng J F, He D X, Ji F. Effects of light intensity and photoperiod on runner plant propagation of hydroponic strawberry transplants under LED lighting. Int J Agric & Biol Eng, 2019; 12(6): 26–31.

Effect of secondary metabolites in lemon balm on anthracnose control in strawberry

In strawberry cultivation, anthracnose caused by Colletotrichum gloeosporioides is difficult to control in the major strawberry-producing regions of Japan, and has caused great losses in nurseries and during fruit production. The antifungal functions of herbs of the family Lamiaceae have been exploited in medical and food applications. However, the antifungal effect of Lamiaceae herbs on plant diseases remains unclear. In this study, the antifungal effect of the Lamiaceae herb lemon balm (Melissa officinalis L.) on anthracnose and changes in antioxidative ability in strawberry plants were investigated. Strawberry (Fragaria × ananassa Duch. 'Tochiotome') runner plants were treated twice with a shoot extract (2%) of lemon balm. The plants were then inoculated with 10 mL C. gloeosporioides (10(5) conidia mL(-1)). The incidence and severity of symptoms of anthracnose were alleviated in strawberry plants by the application of a shoot extract of lemon balm. No difference was observed in dry weight of shoots and roots between treatments. On the other hand, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ascorbic acid content increased in lemon-balm-treated plants. From these findings, lemon balm extract shows an anthracnose-suppressant effect in strawberry plants.

Growth and propagation rate of strawberry transplants produced in a plant factory with artificial lighting as affected by separation time from stock plants

The suitable size of runner plants based on separation time from their stock plants was determined to maximize propagation rate of strawberry transplants using autotrophic transplant propagation method, a novel propagation method in a plant factory with artificial lighting for transplant production (T-PFAL). When runner tips with unfolded bracts were fixed on a growing medium to generate runner plants, the first true leaf, a runner, and roots of the runner plants appeared 6–10 days after fixing the runner tips (DAF), and their shoot and root dry weights significantly increased 6 and 10 DAF, respectively. The top/root ratio was the greatest 10 DAF. The net photosynthetic rate of runner plants 9, 11, and 13 DAF decreased after separation, while that at 15, 17, and 19 DAF did not. The runner plants separated from their stock plants 15, 20, and 25 DAF were successfully grown until 30 DAF; however, those 10 DAF was not. At 30 DAF, the root dry weight of the runner plants separated from the stock plants 15 DAF was smaller than that of the runner plants separated 20, 25, and 30 DAF, whereas the dry weights of leaves and runners were not significantly different. The use of small stock plants could reduce the required timescale from placing stock plants to produce new runner plants, but there was no significant difference in the timescales when the runner plants were separated 15 or 20 DAF due to the relatively insufficient growth of runner plants separated 15 DAF. These results indicate that runner plants separated 20 DAF, with two true leaves and a 5-mm crown diameter, would be suitable stock plants for the autotrophic transplant propagation method in a T-PFAL for strawberry propagation.

Growth of Runner Plants Grown in a Plant Factory as Affected by Light Intensity and Container Volume

Growth of Runner Plants Grown in a Plant Factory as Affected by Light Intensity and Container Volume

Over-expression of EjLFY-1 Leads to an Early Flowering Habit in Strawberry (Fragaria × ananassa) and Its Asexual Progeny.

As a master regulator involved in flower development, LEAFY-like gene has been demonstrated to play a key role in the flowering process regulation of angiosperms. Expression analysis of EjLFY-1, a LEAFY (LFY) homolog of loquat (Eriobotrya japonica Lindl.), indicated its participation in the regulation of flowering in loquat. To verify its function and potential value in the genetic engineering to shorten the juvenile phase, ectopic expression of EjLFY-1 in strawberry (Fragaria × ananassa) was achieved using Agrobacterium-mediated gene transfer of a plant expression vector with the loquat EjLFY-1 gene driven by the CaMV 35S promoter. Totally 59 plantlets were verified to be the transformants. The presence, expression and integration of EjLFY-1 in the transformants were assessed by PCR, quantitative real-time PCR and Southern blot, respectively. Constitutive expression of EjLFY-1 in strawberry accelerated the flowering process in strawberry with the shorten necessary period for flowering induction, development of flower and fruit set. While vegetative growth habits of the transformants in the first cropping season were consistent with the WT ones. Meanwhile, both the flowers and fruits of the transformants were also as same as those of the WT ones. Furthermore, the early-flowering habit was maintained in their asexual progeny, the runner plants. While with continuous asexual propagation, the clones showed a more strengthen early-flowering phenotype, such as the reduced vegetative growth and the abnormal floral organs in individual plantlets. These results demonstrated the function of this gene and at the same time provided us new insights into the utilization potential of such genes in the genetic engineering of perennial fruits.

Epidemiological Significance of Crown Rot in the Fruiting Field in Relation to Colletotrichum gloeosporioides Infection of Strawberry Nursery Plants.

Anthracnose crown rot (ACR), caused by Colletotrichum gloeosporioides, is a serious disease of strawberry (Fragaria × ananassa) in the southeastern United States, and there is a need to determine the link between nursery and fruiting-field disease risk. A 2-year study in 2007, repeated in 2008, was conducted at the North Carolina State University Horticultural Crops Research Station, Clinton, using 'Chandler', the most popular cultivar in North Carolina and one that is highly susceptible to ACR. Mother plants in a summer nursery were inoculated midseason with three pathogenic strains of C. gloeosporioides at an incidence level of 0, 5, 10, or 25%. Asymptomatic runner plants were selected at maturity (85 to 88 days after inoculation) from the nursery in early to mid-October from within a 0.5-m (inner) or 0.5- to 1.0-m (outer) radius around inoculated mother plants and planted into a plasticulture fruiting field system, with fruit harvest in April to June the following spring. Plants collected from the 25%-inner treatment had the greatest area under the disease progress curve (AUDPC) values, with a terminal ACR-related plant mortality of 32 and 20% by the end of fruit harvest and marketable yield losses of 30.5 and 30.2% in 2007-08 (Yr1) and 2008-09 (Yr2) seasons, respectively. All treatments increased AUDPC values compared with noninoculated treatments except the 10%-outer (O) and 5%-O treatments in Yr1 and Yr2, respectively. Marketable yield decreased 291.6 kg/ha for every percent increase in inoculum level (i.e., 0 to 25%, R2 = 0.696, P = 0.001). Levels of quiescent infection (QI) incidence (percentage of sampled leaves) assessed 25 to 28 days before digging runner plants also directly affected yield. For example, yield decreased 131.0 kg/ha for every percent increase in QI incidence in mother plants (R2 = 0.744, P = 0.001). Immersion of plants in fungicide solutions prior to planting decreased AUDPC values and improved plant stand by 7 to 11% but did not affect marketable yield compared with controls. This study provides results that can enable nursery and fruit growers to assess risk and implement mitigation measures to limit nursery plant and fruit yield losses.

Potential Inoculum Sources and Incidence of Strawberry Soilborne Pathogens in Spain

The decline and death of strawberry plants in Spanish fruit production fields have mainly been attributed to the soilborne pathogens Macrophomina phaseolina, Phytophthora cactorum, and Fusarium spp. Inoculum sources of M. phaseolina and P. cactorum, and the incidence all three genera, were investigated in nurseries and fruit production fields over three consecutive seasons. M. phaseolina inoculum sources consisted of fumigated preplant fruit production soils (50%) and fumigated nursery soils (47%), although the pathogen could not be detected in nursery mother and runner plants. P. cactorum inoculum sources included nursery (20%) and preplant fruit production (17%) fumigated soils, and nursery runner plants (up to 15%). In fruit production plants, the average incidence of M. phaseolina and P. cactorum were 4.2 and 3.7%, respectively. Fusarium spp. inoculum sources could not be accessed extensively due to the lack of effective quantitative real-time PCR assays. Limited testing of nursery plants showed that Fusarium oxysporum f. sp. fragariae (Fof) was absent. In field production plants and soil, F. solani was the main pathogenic Fusarium spp., with Fof only identified once in a fruit production plant. Ineffectively fumigated soils in nurseries and production fields, along with infected runner plants, can be inoculum sources of soilborne strawberry pathogens in Spain.

Functional growth analysis of ‘Sonata’ strawberry plants grown under controlled temperature and daylength conditions

In order to investigate the relationship between environmental conditions and vegetative growth and reproductive development in the strawberry, freshly rooted runner plants of the cultivar ‘Sonata’ were grown in a phytotron at temperatures of 12, 18 and 24°C and photoperiods of 10h short day (SD) and 20h long day (LD) for 31d and harvested at 10d intervals. Plant dry weight and leaf area increases were exponential versus time, giving a linear regression with the natural log (ln). This rendered the relative growth rate (RGR) constant over time at each environmental condition. Over the entire 31d growth period, the RGR increased linearly with increasing temperature across the range of temperatures with a further 10–13% enhancement by LD. A maximum RGR value of 0.077g/g/d was determined in LD at 24°C. Increases in the RGR was driven by a combined increase in net assimilation rate (NAR) and leaf area ratio (LAR) and was associated with an increased allocation of dry matter production into leaves and less into crowns and roots. Because of this, the shoot/root ratio increased consistently with increasing temperature and photoperiod, which was also associated with a significant increase in the tissue C/N concentration ratio. Low temperature promoted starch accumulation markedly in all parts of the plants, with a further enhancement by LD conditions, while the concentrations of soluble sugars were less affected by the climatic environment. Forcing of plants exposed to the various growth conditions for 31d showed that all plants at 12 and 18°C and 80% of those at 24°C had initiated flowers in SD, whereas none had initiated flowers in LD regardless of temperature conditions. All these results demonstrate an opposite environmental relationship between vegetative growth and reproductive development in the strawberry.

Effect of far-red light, temperature, and plant age on morphological changes and induction of flowering of a ‘June-bearing’ strawberry

The main purpose of this study was to investigate the effects of supplementary far-red light on floral induction in the strawberry (Fragaria × ananassa Duch.). The plants were grown in summer conditions with natural daylight and an end-of-day far-red (EOD FR; 735 nm) light treatment. In experiments 1 and 2, the plants were exposed to EOD FR for 0, 2, 4, and 6 h daily for 8, 16, 24, and 32 days in July and August. In experiment 3, plants aged 8-, 10-, and 12-weeks old were treated with 32 daily cycles of EOD FR for 6 h. The plants exposed to high temperatures in July did not flower, although their morphological traits were altered by EOD FR. In the cooler temperatures of August, besides significant morphological changes, plants exposed to 6 h of EOD FR for 32 daily cycles produced flowers. The last experiment revealed a significant induction of flowering in the 12-week-old runner plants, which was absent in the younger plants. These results clearly demonstrate the effect of EOD FR treatment duration, temperature, and plant age on morphological traits and flowering. It can be concluded that flowering in 12-week old and older ‘Paros’ strawberries can be induced by 32 daily cycles of 735 nm far-red light in August and September.

Post-harvest chemical manipulation in strawberry regeneration under Jammu sub-tropics

The present investigation on postharvest chemical manipulation in strawberry (Fragaria × ananassa Duch.) regeneration under Jammu sub-tropics was carried out to standardize the dose and time of application of chemicals for optimising the runner production. Application of plant growth regulators enhanced the runner production in strawberry cultivar Chandler under Jammu sub-tropics. The maximum number of runners/mother plant (13.53), number of trains/mother plant (4.10), number of runners/train (3.30), plant spread per mother plant (34.02 cm), plant spread per runner plant (10.83 cm), number of leaves per mother plant (22) and number of leaves per runner plants (7.29) of strawberry cv. Chandler was recorded with the application of 300 ppm GA3 + 150 ppm BA. The maximum plant height per mother plant (23.29 cm), plant height per runner (10.88 cm), petiole length per mother plant (19.1 cm), petiole length per runner plant (10.70 cm) and root length per runner plant (5.90 cm) were recorded under application of GA3 100 ppm. Whereas, control treatment recorded the maximum crown diameter (6.92 mm), crown weight (0.66 g) and leaf area (16.57). The findings indicated that the application of GA3 (300 ppm) + BA (150 ppm) enhanced the regeneration capacity of strawberry runners under Jammu sub-tropics.

English

The response of ‘Ventana’, an early flowering cultivar, and ‘Camarosa’, an intermediate flowering cultivar, to nursery late-season nitrogen (N) applications and digging date were studied in strawberry (Fragaria x ananassa Duch). Two experiments were conducted. In the first experiment, runner plants dug on September 20 and October 11 from a high-latitude nursery in California, were established in growth chambers set at 25°/15oC day/night temperature, 12-h photoperiod, and grown for 90 days. Compared to the first experiment, in the second experiment plants received extra N (foliar-applied) in the nursery in late summer, and runner plants were not grown in GC but in open field (Irvine, California). In the second experiment, runner plants were dug on Sept 20 and Oct 2. In both experiments, plants dug in September were exposed to ~100 chilling units (CU: hours ≤7.2°C) and plants dug in October were exposed to ~300 CU. As a result, October-dug plants had greater crown and root dry weight, and greater concentration of starch and total nonstructural carbohydrates (TNC) in leaves, crowns and roots, compared to September-dug plants. In control plants, from September to October, root TNC concentration increased in ‘Camarosa’ from ~6% to ~11%, and in ‘Ventana’ from ~14% to ~21%, and leaf N concentration ranged from 1.47 to 1.81% in ‘Camarosa’, and from 1.60 to 1.96% in ‘Ventana’. Late-summer N applications increased plant N concentration and early-season yields. Late-summer nursery N applications reduced dead leaf biomass (DLB) and dead leaf area (DLA) in both cultivars, although ‘Ventana’ had lower DLB and DLA than ‘Camarosa’. ‘Ventana’ had a greater leaf number and flowered earlier, and had greater early fruit production than ‘Camarosa’. The genetic earliness of ‘Ventana’ would be correlated with the potential of the plant for accumulation of higher initial levels of leaf N and root TNC, and for having greater leaf longevity, compared to ‘Camarosa’. Key words: Fragaria x ananassa Duch., foliar urea, carbohydrates, chilling, plant maturity, early flowering cultivars.

Initial Inoculum and Spatial Dispersal of Colletotrichum gloeosporioides, the Causal Agent of Strawberry Anthracnose Crown Rot.

Anthracnose crown rot (ACR), caused by Colletotrichum gloeosporioides, is a serious disease of strawberry (Fragaria × ananassa) in nurseries and fruiting fields in the southeastern United States. This study was conducted to determine the potential of alternative hosts for initial inoculum source and spread that causes ACR in strawberry nurseries. Results indicated that Parthenocissus quinquefolia is a noncultivated host of C. gloeosporioides in North Carolina and may serve as an initial inoculum source for planting material. Sources of inoculum data were complemented with a 2-year study of disease incidence and spread in simulated nursery production experiments. Sixty days after inoculation of the mother plants in the nursery, three different inoculation levels showed a significant positive correlation (r = 0.78, P < 0.004) with the quiescent infection (QI) incidence on the runner or daughter plants at the end of the nursery production cycle. Runner plant counts from different proportion of mother plants' inoculation treatments indicated that runner plant production was negatively and significantly (P < 0.001) affected by C. gloeosporioides. Infected tips used to produce transplants destined for fruit production resulted in 29.3 and 16.8% mortality in plug trays in 2007 and 2008, respectively. Tracking foliar QI incidence that resulted from dispersal of inoculum from an introduced point source in the nursery showed a sharp decline at 1 m and beyond from the inoculation focus. Although the exponential model (R2 = 0.92 to 0.94) had slightly higher coefficients of determination than the modified power law (R2 = 0.89 to 0.90), residual plots indicated that the modified power law model fit the disease gradient data better than the exponential model in both years. Results from our dispersal study indicated that rogueing of infected plants within a 4-m radius of infection foci would reduce the risk of transferring infected runner plants from the nursery to the fruiting field.

STUDY ON FLOWER BUD MORPHOLOGICAL DIFFERENTIATION OF 'TIANXIANG' STRAWBERRY

Flower bud differentiation is very important for the yield and quality of strawberry fruit. In order to identify flower bud development, the paraffin section method was adopted to observe the morphological differentiation of apical meristems of ‘Tianxiang’ strawberry (Fragaria A— ananassa Duch.) runner plants in Beijing, 2009. The results showed that top flower bud differentiation lasted for about 44 days, might be divided into seven stages. On 15 September, the buds came into the primary differentiation stage, the apical points became semi-circular, broader, and nearly 70% of the buds started differentiation on 20 September. Then the inflorescence primordia were visible on the apical points, and about 60% of the buds went into the inflorescence primordium differentiation stage on 25 September. Thereafter, the sepal primordia appeared at the base of inflorescence primordia, 60% of the buds were in the sepal primordium differentiation stage by 1 October. On 6 October, in about 90% of the buds the petal primordia could be seen inside of sepal primordial. About 10 d later, the stamen primordia developed in around 80% of the buds. On 22 October, the pistil primordia appeared on the surface of the receptacles. The main pistil primordium differentiation stage was from 22 to 29 October, and about 70% of the buds had finished their pistil primordium differentiation on 29 October. At the end of sampling on 29 October, the secondary buds were mainly in the stamen primordium differentiation stage, and the tertiary buds were mainly in the petal primordium differentiation stage. Our results provided the details of flower bud development in ‘Tianxiang’ strawberry in Beijing, which will contribute to its production and management.