Prohexadione Calcium Research Articles

Effect of prohexadione calcium and chlormequat chloride on growth, yield and fruit quality of pear under high density planting

The present experiment was conducted to evaluate the effect of plant bioregulators (PBRs) on vegetative growth, fruit yield and quality of quality of pear cv. Patharnakh trained on Y-trellis system. The foliar applications of prohexadione calcium (100, 200 and 400 ppm) and chlormequat chloride (250, 500 and 1000 ppm) was done on eight-years-old trees at 10 days after full bloom. The control trees were sprayed with water only. Observations on vegetative growth, fruit number/plant, fruit size, fruit quality and leaf nutrients were recorded. Reduction in pruning wood weight without any effect on return bloom was observed with different PBR treatments. Prohexadione calcium (400 ppm) was found most effective in reducing shoot number (70) and internodal length (4.18 cm). This treatment also increased fruit number (83 per tree), fruit size (8.04 cm × 7.51 cm), TSS content (12.33 °Brix), fruit frmness (62.94 N), and reducing sugars content (7.00%); however, the titratable acidity was not affected. As compared to control, fruit yield of pear tree was signifcantly improved (~35%) with the Pro-Ca 400 or 200 ppm treatments. Similarly, higher dose of chlormequat chloride (500 or 1000 ppm) signifcantly reduced the shoot number and intermodal length, and increased fruit yield as compared to control. The PBR treatments reduced the leaf nitrogen content but increased leaf phosphorus and potassium levels.

Bioregulators Induced Modulation of Leaf Physiological Attributes and Severity of Papaya Ring Spot Viral Disease Symptom expression in Papaya

The present study aimed to evaluate the influence of bioregulators on physiological attributes and yield components of TNAU Papaya CO. 8 variety during 2017 - 2018. The study involved two factors viz., growth retardants as factor I and stress tolerance promoting bioregulators as factor II. The treatments involving growth retardants (Factor I) were water spray (G1) as control, 250 ppm of pro hexadione calcium (G2), 500 ppm of mepiquat chloride (G3) and 500 ppm of chlormequat chloride (G4). Similarly, the stress tolerance promoting bioregulators (Factor II) comprised of water spray as control (S1), 100 ppm of methyl jasmonate (S2), 100 ppm of salicylic acid (S3) and 0.6 g/ L of strobilurins (S4). The bioregulators were applied as foliar spray at the fourth and eighth months after transplanting. Initially, growth retardants were sprayed and one week after that, the stress tolerance promoting bioregulators were sprayed. Observations were recorded on number of leaves, leaf area index, leaf gas exchange parameters, papaya ring spot virusdisease incidence and yield components. Among the treatments, higher number of leaves (52.03) were observed in the combination involving 250 ppm of prohexadione calcium and 100 ppm of salicylic acid (G2S3) and leaf area index (2.73) was highly influenced by 500 ppm of chlormequat chloride and 100 ppm of salicylic acid (G4S3). Leaf gas exchange parameters were found to be superior with 250 ppm of prohexadione calcium and 100 ppm of salicylic acid treatment (net photosynthetic rate - 16.46 µmol cm-2 s-1, stomatal conductance - 0.51 mol m-2s-1, transpiration rate - 7.58 mmol m-2s-1) as compared to control. Significant differences were also observed among the treatments for yield and yield components. The fruit yield was significantly improved by the treatment involving 500 ppm of mepiquat chloride and 100 ppm of salicylic acid (G3S3 - 61.76 kg plant-1), indicating the possibility for enhancing papaya yield under field conditions where PRSV is prevalent.

Influence of Bioregulators on Latex Yield and Proteolytic Activity of Papain Extracted from Field-grown TNAU Papaya CO. 8 under the Natural Incidence of Papaya Ring Spot Virus

The cultivation of papaya for both fruits and commercial papain extraction drastically suffers often due to the devastating incidence of papaya ringspot virus disease. The present study aimed to find out whether the papain yield and quality are influenced when bioregulators are applied to manage papaya ring spot virus (PRSV) incidence or as a measure to limit the height of the crop in TNAU Papaya CO.8 variety grown in the open field with the natural incidence of PRSV. Three growth retardants [250 ppm of prohexadione calcium (G2), 500 ppm of mepiquat chloride (G3) and 500 ppm of chlormequat chloride (G4)] and three stress tolerance promoting bioregulators [100 ppm of methyl jasmonate (S2), 100 ppm of salicylic acid (S3) and 0.6 g/ l of strobilurins (S4)] were employed in the study. Water spray (G1 and S1) was kept as control. The treatments were imposed at 4th and 8th months after planting. The growth retardants were initially sprayed and, in the subsequentweek ,the stress tolerance promoting bioregulators were sprayed as per the recommended doses. Among the combinations tried, spraying 250 ppm of prohexadione calcium followed by water spray (G2S1) a week later recorded the lowest plant height (140.79 cm) at the time of fruiting. The treatment combination G 2S2 involving 250 ppm of prohexadione calcium and 100 ppm of methyl jasmonate registered a higher number of fruits (42.17). The combination of 250 ppm of prohexadione calcium along with 100 ppm of salicylic acid (G2S3) was found to be the most effective combination to manage PRSV without compromising papain production and to enhance the proteolytic activity significantly (44378.36 TU g-1) as compared to other combinations. The treatment combination of 500 ppm of mepiquat chloride and 100 ppm of salicylic acid (G3S3) favored higher dry latex yield apart from a significant reduction in PRSV symptoms. Both these treatment combinations (G2S3 and G 3S3) merit due consideration in PRSV management for commercial fruit and papain production in papaya

The Dwarfing Effects of Different Plant Growth Retardants on Magnolia wufengensis L.Y. Ma et L. R. Wang

The effects of varieties, concentrations, and number of applications of plant growth retardants (PGRs) on the morphological, physiological, and endogenous hormones of Magnolia wufengensis L.Y. Ma et L. R. Wang were assessed to obtain the most suitable dwarfing protocol for M. wufengensis and to provide theoretical support and technical guidance for the cultivation and promotion of this species. One-year-old M. wufengensis ‘Jiaohong No. 2’ grafted seedlings served as the experimental materials. In the first part of the experiment, three PGRs (uniconazole, paclobutrazol, prohexadione calcium), three concentrations (500, 1000, 1500 ppm), and three applications (one, three, and five applications) were applied in dwarfing experiments to perform L9 (34) orthogonal tests. In the second part of the study, dwarfing experiments were supplemented with different high uniconazole concentrations (0, 1500, 2000, 2500 ppm). Spraying 1500 ppm uniconazole five times achieved the best M. wufengensis dwarfing effect, related indicators of M. wufengensis under this treatment were better than other treatment combinations. Here, M. wufengensis plant height, internode length, scion diameter, and node number were significantly reduced by 56.9%, 62.6%, 72.8%, and 74.4%, respectively, compared with the control group. This treatment increased superoxide dismutase (SOD) activity by 66.0%, peroxidase (POD) activity by 85.0%, soluble protein contents by 43.3%, and soluble sugar contents by 27.6%, and reduced malondialdehyde (MDA) contents by 32.1% in leaves of M. wufengensis compared with the control. The stress resistance of M. wufengensis was enhanced. The treatment also reduced gibberellin (GA3) levels by 73.0%, auxin (IAA) by 58.0%, and zeatin (ZT) by 70.6%, and increased (abscisic acid) ABA by 98.1% in the leaves of M. wufengensis. The uniconazole supplementation experiment also showed that 1500 ppm was the optimal uniconazole concentration. The leaves exhibited abnormalities such as crinkling or adhesion when 2000 or 2500 ppm was applied. Given the importance of morphological indicators and dwarfing for the ornamental value of M. wufengensis, the optimal dwarfing treatment for M. wufengensis was spraying 1500 ppm uniconazole five times.

Influence of Prohexadione Calcium Rate on Growth and Yield of Peanut (Arachis hypogaea)

ABSTRACT Prohexadione calcium, a plant growth regulator, is commonly used on virginia market type peanut (Arachis hypogaea L.) cultivars to manage excessive vine growth and improve digging efficiency. However, use of prohexadione calcium on runner market type cultivars has been minimal. The objective of this research was to evaluate prohexadione calcium on virginia and runner market type peanut cultivars at multiple rates in small-plot (17 site years) and on-farm (5 site years) experiments. Applications of prohexadione calcium were at the manufacturer's recommended use rate of 140 g a.i./ha (1x), 105 g a.i /ha (0.75x), and 70 g a.i /ha (0.5x) rates. A non-treated control was also included in all experiments. Cultivar and treatment responses were evaluated based on mainstem height, yield, total sound mature kernels, and return on investment. Plants treated with prohexadione calcium had greater row definition based on a 1-10 row visibility rating scale. Plant main stem heights were often shortened when prohexadione calcium was applied compared to the control, although response varied by location and by year. Average mainstem heights were 26 cm for non-treated plots and 23 cm for prohexadione calcium treated plots across all virginia market type small plot experiments. Prohexadione calcium did not significantly increase yield at any rate in any small plot experiments regardless of rate. Reduced rates of prohexadione calcium significantly increased yield in all the large on-farm experiments compared to the control. Yield increases ranged from 453 to 731 kg/ha for all prohexadione calcium treatments compared to the control across all large plot on-farm experiments. The greatest return on investment was the 0.75x rate resulting in an increase in revenue of $210 ha−1. With an increase in yield and return on investment in all large plot on-farm experiments and not in small plot experiments no matter the market type, it is assumed that the growth and yield response to prohexadione calcium may be more pronounced where soil variability is greater, affecting growth, digging, and yield potential. Prohexadione calcium can be beneficial in virginia market type and runner market type peanut cultivars to decrease vine growth and increase yield.

Respostas a aplicação de concentrações de prohexadione cálcio em amora-preta (Rubus spp.) cv. Tupy

O objetivo deste trabalho foi avaliar os efeitos da aplicação de diferentes concentrações de prohexadione cálcio na prorrogação do período de colheita e nos atributos físico-químicos de frutos de amoreira preta da cultivar Tupy. Os tratamentos foram constituídos de quatro concentrações de prohexadione cálcio (PCa) (100; 200; 400; 800 mg.L-1), além de um tratamento testemunha sem aplicação. Foram avaliados os dias decorridos após a aplicação (DAP), massa média dos frutos, sólidos solúveis, acidez titulável e cor: luminosidade (L*), ângulo hue (ºHue), cromaticidade (C*). A PCa estende o período de colheitas dos frutos de amora-preta em decorrência do aumento das concentrações aplicadas, doses elevadas de PCa diminuem a massa média de frutos e aumentam o teor de sólidos solúveis. Quanto aos parâmetros de cor, os frutos tendem ao vermelho (ºHue), com aumento dos valores de luminosidade (L*) e intensidade da cor (C*).

Productive behavior of strawberry from potted seedlings produced with application of prohexadione calcium in soilless cultivation

Use of national strawberry seedlings, produced in a system without soil, is an alternative to reduce the dependence of producers on using imported seedlings. The objective of this work was to evaluate the effect of applying different concentrations of prohexadione calcium (ProCa) in the growth control of strawberry seedlings and the productive behavior after planting these seedlings. The experiment was carried out in a greenhouse, with a 4 x 2 factorial scheme, four concentrations of prohexadione calcium (0, 150, 300 and 600 mg L-1) and two cultivars (Aromas and Camarosa). In the seedling phase, a completely randomized design was used, with 4 replications, with the experimental unit consisting of 12 seedlings. In the post-planting phase, a completely randomized design was used, with 5 replications and the experimental unit consisted of 4 plants. In the seedlings, the following were evaluated: number of leaves, crown diameter, petiole length, leaf area, chlorophyll content and dry matter of the aerial part. The parameters evaluated in the strawberry plants were: full bloom and fruiting, number of fruits per plant, average fruit weight, total fruit weight, length and diameter of fruit, dry weight of leaves and crowns. The application of 150, 300 and 600 mg L-1 of ProCa decreased the leaf area and petiole length for both cultivars, thus reduced the vegetative growth of the seedlings. On the other hand the chlorophyll a, b and total contents were increased in relation to the absence of ProCa for the two cultivars evaluated. The ProCa concentrations did not influence the number of fruits and the fruit mass per plant, and the results were related to the cultivar factor, where the cv Camarosa had the higher values.

Desempenho agronômico da videira ‘Cabernet Sauvignon’ submetida a diferentes épocas de aplicação e concentrações de Prohexadiona de Cálcio

Devido à falta de informações consistentes em relação a aplicação de Prohexadiona de Cálcio em videira, tem-se como objetivo deste trabalho avaliar o efeito de diferentes épocas de aplicação e concentrações de Prohexadiona de Cálcio no desempenho vitícola da cultivar Cabernet Sauvignon cultivada em regiões de altitude elevada de Santa Catarina. O presente estudo foi realizado durante a safra 2014/2015. As aplicações ocorrem em diferentes épocas e concentrações, sendo subdividas na inflorescência separada, plena florada e 15 dias após a plena florada. Realizaram-se avaliações vegeto-produtivas: área foliar, produtividade, relação área foliar/produção, crescimento de ramo, e parâmetros: pH, acidez total, sólidos solúveis, polifenóis totais, e arquitetura de cacho. A aplicação de Prohexadiona de Cálcio na concentração de 250 mg L-1, realizada na fase de plena florada aumentou em 23% a produtividade da cultivar Cabernet Sauvignon. Este aumento da produtividade esteve relacionado com a maior massa de cacho e com o maior número de bagas por cacho. A Prohexadiona de Cálcio aplicada na fase de inflorescência separada reduz o crescimento dos ramos. Porém devido as condições de excesso de vigor do vinhedo, a redução no crescimento não eliminou a necessidade da realização do desponte dos ramos. Houve redução na massa da baga da cultivar Cabernet Sauvignon com a aplicação de Prohexadiona de Cálcio, característica positiva na elaboração de vinhos tintos. A aplicação de Prohexadiona de Cálcio nas concentrações e épocas utilizadas não influenciaram na maturação tecnológica (Sólidos solúveis, Acidez e pH) da uva Cabernet Sauvignon.

Managing vigor of blackberry with prohexadione calcium: effects on primocane and floricane development

Managing vigor of blackberry with prohexadione calcium: effects on primocane and floricane development

Techniques to modify cluster architecture and their effect on the viticultural performance of the Sauvignon Blanc cultivar

Abstract: The objective of this work was to evaluate the effect of different techniques to modify grape cluster architecture on the incidence and severity of botrytis bunch rot, as well as on the viticultural performance of the 'Sauvignon Blanc' grapevine (Vitis vinifera). Associated with fungicides, four treatments were tested: control, 30 ppm gibberellic acid sprayed at full bloom, 1,000 ppm prohexadione calcium sprayed at full bloom, and berry thinning at the stage of beginning of berry touch. The experiment was carried out in the 2015, 2016, and 2017 vintages. Clusters were treated with fungicides during the stages of full bloom, beginning of berry touch, veraison, and around 15 days before harvest. Berry thinning does not cause losses in the yield and quality of 'Sauvignon Blanc', and, despite having little effect on cluster architecture, is effective in reducing the incidence and severity of Botrytis cinerea. Prohexadione calcium improves grape phenolic maturation, is effective in reducing the incidence and severity of B. cinerea, and reduces cluster compactness by decreasing berry diameter. The application of gibberellic acid spray at full bloom is not recommended because it decreases yield and bud fertility and increases berry susceptibility to B. cinerea infection.

Reducing Preharvest Bolting in Open-field-grown Cilantro (Coriandrum sativum L. cv. Santo) through Use of Growth Regulators

Cilantro (Coriandrum sativum L.), also called coriander, is an herbaceous, annual plant that is cultivated worldwide for its leaves and seeds. Cilantro has a strong propensity to bolt quickly in hot weather and under long-day (LD) conditions, which affects the flavor and renders the crop unmarketable. High incidence of preharvest bolting in open-field production can cause significant economic loss. The phytohormone gibberellic acid (GA) regulates stem elongation and floral initiation in many LD rosette plants. In pilot experiments, we found that GA induced bolting in greenhouse-grown cilantro and that plant growth regulators (PGRs) with anti-GA activity can delay this process. We then explored the effects of different GA inhibitors on reducing the incidence of bolting in cilantro grown in a commercial open-field environment. Four field trials were conducted on a commercial farm near Clewiston in Florida between Fall 2016 and Spring 2018. Different growth regulators were applied at different times, ranging from 5 to 8 weeks after seeding (WAS), and plants were harvested 2 to 3 weeks thereafter. Applications of GA inhibitors significantly reduced the incidence of bolting in three of the four trials, but the extent depended on the type of inhibitor used. The results from one trial were inconclusive due to changes in weather that prevented bolting in the entire field. Overall, plots treated with prohexadione calcium and paclobutrazol were most effective and reduced bolting by up to 78%. Applying the PGRs at 5 and 6 WAS was more effective than at 7 or 8 WAS.

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.

Investigation and Prevention of Cork Spot Disorder in ‘Akizuki’ Pear (Pyrus pyrifolia Nakai)

‘Akizuki’ (Pyrus pyrifolia Nakai) is a dominant Asian pear cultivar with gradually increasing cultivation area in Shandong province. However, this cultivar is found susceptible to cork spot disorder in recent years. In this study, we explored the physiological-biochemical mechanism of cork spot disorder in pear fruit, and investigated the effectiveness of spraying calcium (Ca), boron (B) solution or prohexadione calcium (P-Ca) on cork spot incidence. Cork spotted fruit had the characteristics of significantly larger fruit size with shorter fruit pedicels. Compared with normal fruit, cork spotted fruit had lower content of total soluble solids, soluble and reducing sugar, and vitamin C. In addition, cork spotted fruit accumulated much higher levels of N and Mg, and lower levels of K and P. However, Ca deficiency was not observed in cork spotted fruit, on the contrary, we determined high concentrations of Ca and free Ca2+ in disordered fruit. At the same time, the ratios of K/Ca, Mg/Ca, and (K+Mg)/Ca were significantly lower in cork spotted fruit as compared with normal fruit. Among all treatments, spraying with 3500 times dilution of P-Ca at 15-day intervals from 30 to 90 days after full bloom showed promise for reducing cork spot incidence in ‘Akizuki’ pear without affecting fruit quality attributes. This research herein reveals the physiological-biochemical characteristic of cork spot disorder, and implicates P-Ca as a potential tool to reduce cork spot incidence in Asian pear cultivar Akizuki.

Photosynthetic pigments and vigour of rice (Oryza sativa L.) seedlings as affected by kinetin and prohexadione-calcium

In the present study effects of exogenous application of Kinetin (Kn @ 10, 20 and 40 mg/l) and Prohexadione calcium (BX-112 @ 5, 10 and 20 mg/l) were studied on rice (Oryza sativa L.) cultivars viz PB-2, PB-3 and PUSA 112. Different levels of Kn and BX-112 were applied to seedlings, five days after sowing (DAS). The content of photosynthetic pigments (total chlorophyll) was recorded at fourteen DAS stage, furthermore application of Kn significantly improved it in selected cultivars with more percent increase at 7 DAS. The content of accessory pigments (carotenoids) was recorded higher in both Kn as well as BX-112 treated sets. Kn application promoted vigour of rice seedlings in the selected cultivars with more pronounced effect in treatments involving higher concentration of Kn. BX-112 decreased both the vigour and relative growth rate (RGR) that led to reduction in growth of seedlings of all the three cultivars. This study revealed that though both Kn and BX-112 improved accumulation of photosynthetic pigments yet Kn application promoted growth and vigour of the seedlingswhile BX-112displayed an inhibitory effect on vigour of rice seedling.

Concentration and periods of application of prohexadione calcium in the growth of strawberry seedlings

For strawberry cultivation in Brazil, producers are dependent on imported seedlings. An alternative strategy to reduce this dependence is the use of seedlings obtained from nursery plants grown in a protected environment. However, as these seedlings are produced in the summer and planted at the end of this season or the spring of the following year, it is necessary to control growth to reduce the energy costs of the plants. The objective of this study was to evaluate the effect of different concentrations and periods of application of proexadione calcium (ProCa) on growth control of strawberry seedlings. The experiment was carried out in a greenhouse with seedlings of the cultivars ‘Aromas’ and ‘Camarosa’, produced by rooting stolons and kept in polystyrene trays of 72 cells in a substrate of carbonized rice husk. The experimental design was completely randomized, with a 4 × 2 factorial scheme (4 concentrations of ProCa: 0, 100, 200, and 400 mg L-1 × 2 periods of application: at 20 and 30 days after the planting period of rooting stolon). Plant survival, crown diameter, petiole length, total leaf area, specific leaf area, chlorophyll concentration, and dry mass of the crown and shoot were evaluated. The application of ProCa at 20 days after the planting period of the rooting stolon at the concentrations of 200 and 400 mg L-1 favored the reduction of petiole length in plants of ‘Aromas’ strawberry and total leaf aerial in ‘Camarosa’ strawberry. The application of ProCa from the concentration of 100 mg L-1 reduced the vegetative growth of ‘Aromas’ and ‘Camarosa’ strawberry seedlings cultivated in substrate.

Responses of Intermediate Wheatgrass to Plant Growth Regulators and Nitrogen Fertilizer

Core Ideas Trinexapac‐ethyl reduces height and lodging in wheatgrass.Trinexapac‐ethyl increased grain yield when lodging risk was high.Prohexanedione calcium had no effect on wheatgrass.Trinexapac‐ethyl can reduce risk of yield losses due to lodging. Intermediate wheatgrass (Thinopyrum intermedium; IWG), a new perennial grain crop, has the potential to provide ecosystem services while producing food‐grade grain; however, productivity is currently limited by high rates of lodging. Trinexapac‐ethyl (TE) and prohexadione‐calcium (PC) are widely used plant growth regulators (PGRs) for mitigating lodging and improving seed yield in other grass crops. Our objectives were to determine the effects of the PGRs PC and TE, PGR application rate, and nitrogen (N) fertilizer rate (0, 40, 80 kg N ha−1) on IWG lodging, height, and grain and biomass yields. Experiments were initiated in first‐ and third‐year stands at St. Paul and Rosemount, MN. Few effects of PC on IWG height, lodging, or yields were observed, while TE consistently reduced plant height by 10 to 20% and lodging by up to 20% in a year with high lodging risk. Application of TE to IWG at the recommended rate (437 g a.i. ha−1) or higher rates increased grain yields by 65 to 100% when lodging incidence was high, but did not affect grain yields in years with lower lodging risk. While a negative correlation between lodging and grain yields was observed, nitrogen fertilizer affected IWG grain and biomass yields in only one of five site‐years, and there was no interaction between N fertilizer and PGR effects on IWG. Nonetheless, the PGR TE demonstrated the potential to reduce plant height and lodging, thereby increasing IWG yield potential.

Pre-harvest spray application of prohexadione-calcium and paclobutrazol improves rind colour and regulates fruit quality in M7 Navel oranges

Abstract Sweet orange (Citrus sinensis L. Osbeck) cv. ‘M7’ Navel exhibits poor flavedo colour at harvest in Western Australia. Gibberellins are known to retard fruit colour development in citrus fruit, therefore the efficacy of different concentrations and timings of spray applications of two inhibitors of gibberellin biosynthesis such as prohexadione calcium (Pro-Ca) and paclobutrazol (PBZ) on flavedo colour development and fruit quality was investigated. The effects of an aqueous solution containing different concentration of Pro-Ca (200, 400, 600, 800, 1200, 1600 or 2000 mg L−1), and PBZ (100, 250, 500, 1000, 1500 and 2000 mg L−1) sprayed at 6 or 3 weeks before anticipated harvest (WBAH) on flavedo colour development particularly from yellow to deep orange and on the fruit quality were investigated during 2015 and 2016. Unsprayed trees were kept as control. The spray application of Pro-Ca (800 mg L−1) resulted in decreased hue angle (h°) (57.5), and increased citrus colour index (CCI) (10.2) and, total carotenoid levels (38.3 mg kg−1) in the flavedo during 2015. Furthermore, Pro-Ca (600 or 800 mg L−1) showed enhanced levels of total carotenoids (39.2 and 38.3 mg kg−1) respectively, during 2015. In 2016, a single spray application Pro-Ca (1200 mg L−1) at 3 WBAH exhibited reduced h° (56.6) and increased CCI (10.7), and levels of total carotenoids (36.8 mg kg−1) as compared to the control. Additionally, a single spray application of Pro-Ca (800, 1200 or 1600 mg L−1) was able to increase total carotenoids in the flavedo (32.7, 36.8 or 33.1 mg kg−1) respectively. In 2016, Pro-Ca (800 mg L−1) exhibited increased SSC (13.0%) and reduced TA (1.08%) in the fruit juice. A single spray application of PBZ (1000 mg L−1) at 6 WBAH significantly reduced h° (56.7) and increased CCI (10.6) and levels of total carotenoids in the flavedo (42.6 mg kg−1). However, a single spray application of PBZ (1500 mg L−1) at 3 WBAH showed lower h° (55.4) and enhanced CCI (11.2) and level of total carotenoids (47.1 mg kg−1) in the flavedo during 2016. In conclusion, pre-harvest spray application of Pro-Ca (800 and 1200 mg L−1) applied at 6 and 3 WBAH respectively enhanced fruit colour. A single pre-harvest spray application of PBZ (1000 and 1500 mg L−1) applied at 6 and 3 WBAH respectively improved fruit colour in early maturing ‘M7’ Navel.

Response of prohexadione calcium and paclobutrazol on growth and physio-chemical characteristics of pear cv. Clapp's Favorite

The present investigation was conducted to study the response of growth retardants on pear cv. Clapp's Favorite during the year 2015–2016. The experiment was laid out with thirteen treatments replicated thrice on 12 year-old-trees with uniform vigour and health under uniform cultural practices. The treatment comprises of single spray and double spray of growth retardants (prohexadione calcium @ 100, 200 and 300 ppm and paclobutrazol @ 100, 200 and 300 ppm). The first spray of growth retardants was applied at petal fall stage and second spray was four weeks after first spray. The plants sprayed twice with prohexadione calcium @ 200 ppm (T9S2) recorded minimum annual shoot extension growth (16.92 cm), internodal length (1.82 cm) and leaf area (22.20 cm2) along with increase in fruit set (18.34%) and minimum fruit drop (32.45%). Increased fruit yield (51.24 kg), yield efficiency (4.08) and following year return bloom (24.04%) was noticed in T9S2 treatment. Prohexadione calcium sprayed twice @ 200 ppm (T9S2) also increased fruit weight (82.85 g), TSS (13.21%) and total sugars (10.23%) closely followed by the double spray of prohexadione calcium @ 300 ppm sprayed twice which was also effective in enhancing the fruit firmness (6.15 kg/cm2) followed by treatment T12S2 i.e. paclobutrazol @ 200 ppm double spray (6.07 kg/cm2). Double spray of prohexadione calcium @ 200 ppm was effective in reducing the vegetative characters and increasing yield and fruit quality characters.

Prohexadione‐Calcium Rate and Timing Effects on Alfalfa Interseeded into Silage Corn

Core Ideas Higher prohexadione rates of 0.5 to 1 kg a.i. ha–1 enhanced interseeded alfalfa establishment and yield under stressful establishment conditions.Prohexadione application to 15 vs. 25 cm tall alfalfa seedlings provided similar improvements in alfalfa stand density and yield.Interseeding alfalfa increased overall corn+alfalfa forage production by 12%. Prohexadione‐calcium (PHD) can enhance establishment of alfalfa (Medicago sativa L.) interseeded into silage corn (Zea mays L.), but optimal application rates and timing for this growth regulator are unknown. Two experiments examined how single or split applications of 0.25 to 1.0 kg a.i. ha−1 of PHD applied to 15 or 25 cm tall glyphosate‐resistant alfalfa seedlings influenced growth, stand density, and yield of alfalfa and corn compared to untreated controls. The PHD treatments reduced seedling top growth by 13 to 32% and increased stand density of alfalfa by 19 to 81% in three out of four locations and alfalfa dry matter yield by 4 to 23% in two out of four locations the following year. Alfalfa responses were not consistently influenced by the rate and timing of PHD application, but higher rates proved advantageous under conditions that impaired alfalfa seedling survival under corn. Application of PHD on alfalfa had little or no effect on corn heights and yields. Corn population and alfalfa seeding rates influenced corn silage yield and alfalfa stand counts in at least one location, but these factors had little effect on crop responses to PHD. Combined 2‐yr yields of corn followed by alfalfa were 12% greater for the interseeding system than for solo‐seeded corn followed by spring seeded alfalfa. Overall, a single application of 0.5 to 1.0 kg a.i. ha−1 of PHD on 15 to 25 cm tall alfalfa proved effective for improving stand density and occasionally first year yield of glyphosate‐resistant alfalfa.

Influence of rootstock on response of ‘Golden Delicious’ apple trees to applications of prohexadione calcium

Influence of rootstock on response of ‘Golden Delicious’ apple trees to applications of prohexadione calcium