Summer Flush Research Articles

Persian lemon in the Mexican counties of Nayarit and Veracruz: Foliar sampling period for nutritional diagnosis

In Mexico, Nayarit and Veracruz stand out as producers of Persian lemon. Nayarit has a larger surface area with high production potential and a 68% expansion of its cultivated area in the last 10 years. Veracruz has larger planted area and production volume. This investigation was conducted aiming to determine the period of nutritional stability in Persian lemon leaves and define the appropriate time to perform foliar sampling for nutritional diagnosis. In 2017, rainfed orchards were selected in both states. Per orchard, 20 trees were selected, 50 shoots were marked per flow (Nayarit winter and summer, Veracruz winter and spring), and sampled monthly. Soil and foliar nutrient analysis was performed (total nitrogen (N-total) (semi-microKjeldahl digestion), nitrates (NO3) (colorimetry), potassium (K) (atomic absorption), phosphorus (P), sulfur (S), calcium (Ca), magnesium (Mg), copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), (ICP-Optical Coupled Plasma using an ICAP 7200 spectrophotometer (Thermo Scientific®), and boron (B) (colorimetry) (Genesis 20 spectrophotometer (Thermo Scientific®)). Daily predicted values were calculated and the best functions (highest R2, lowest mean square of the error and value of the Mallows coefficient) were chosen. Mathematical derivatives and criteria were calculated to determine the best period for sampling. For Nayarit, the appropriate period for leaf sampling was the summer flush of July 29 to August 18 and from February 8 to March 19 for the winter flush. In Veracruz, it was from April 10 to May 10 for the winter flush and from September 23 to October 8 for the spring flush.

Multi criteria decision making analysis to identify micronutrient deficiencies in Kinnow (Citrus reticulata Blanco)

The soils of South-Western Punjab are alkaline and exhibited widespread nutrient deficiencies. Foliar applications of micronutrients under such circumstances hold great importance. However, micronutrient sprays on Kinnow grown in such soils are limited only to Zn and Mn. Therefore, the response of Kinnow to foliar applications of micronutrient mixture (containing Fe, Zn, Cu, Mn, B, and Mo) was expected. In this viewpoint, studies were carried out during 2015–2019 to see the effect of foliar sprays (0.3 and 0.6%) of non-chelated and EDTA-chelated micronutrient mixtures in Kinnow mandarin. The results were compared with standard practice i.e., 0.3% sprays each of zinc sulfate and manganese sulfate on spring and summer flushes. The data was analyzed in Randomized Block Design, repeated in octuplet. The overall performance of treatments was evaluated using weighted aggregated sum product assessment model (WASPAS). The WASPAS score varied between 0.638–0.649 and 0.194–0.245 in treatments received non-chelated and chelated micronutrient mixtures, respectively, pointing out the superiority of the former. In overall, treatment followed standard practice registered highest WASPAS score and ranked at number 1 among all. Highly significant (p < 0.01) correlation between WASPAS score and leaf Zn, Mn, and Cu concentrations clearly demonstrated the importance of foliar sprays of these micronutrients in the citrus production under the prevailing conditions. The study also suggests that multi criteria decision making analysis holds a key importance in agriculture domain for insightful decision making.

Techniques for Reducing the Abundance of Spring–Summer Flush Shoots in Southern Spanish Orange Orchards

The Mediterranean Basin is the second highest citrus growing region in the world behind China. Citrus trees are known to produce several flush shoots per year, particularly during the spring–summer season. Farmers endeavor to reduce the growth of summer shoots by means of hand pruning, especially those located at the top of the tree, as most of these shoots become vigorous, nutrient consuming, non-productive, and attractive to several pests. Furthermore, hand pruning substantially increases the costs of citrus orchards production. This research was therefore intended to study new different treatments to control spring–summer flush shoots and thus reduce growers’ investments in citrus production. Six different treatments were applied in two experimental and high density orange orchards over two consecutive years: (1) control; (2) topping (mechanical pruning); (3) dichlorprop-p; (4) triclopyr; (5) topping + dichlorprop-p; and (6) topping + triclopyr. The treatment of dichlorprop-p alone reduced the number of summer young shoots in both years. Moreover, these applications did not negatively affect yield or fruit quality. These mechanical methodologies help citrus growers manage the density of flush shoots and reduce hand labor costs in citrus orchards.

Split application of nutrients improve growth and yield of Huanglongbing‐affected citrus trees

AbstractCitrus production in Florida declined steadily because of Huanglongbing (i.e., HLB, citrus greening) caused by the bacteria Candidatus Liberibacter asiaticus. The objectives of the study were to determine whether leaf tissue nutrient concentration, tree growth, fruit yield, and juice content were improved with split applications of essential nutrients on selected rootstocks on Florida sandy soils. The treatments were arranged in a split‐split plot design where the nitrogen (N) was fertigated in 20 splits and the Ca + Mg nutrients were also split three times coinciding with the spring, summer, and late summer flush seasons on trees budded on two rootstocks of ‘Hamlin’ citrus trees [Citrus sinensis (L.) Osbeck]. A significant difference in leaf N, calcium (Ca), and magnesium (Mg) concentration were detected between rootstocks when trees received the highest N rate and remained within the optimum range of critical nutrition concentration even with the lowest N rate, suggesting a lower N requirement with split N applications. Yet, leaf Mg concentration remained in the minimum range implying a low soil Mg pool. For Ca, Mg, and Ca + Mg treatments, we recorded 1.41×, 1.23×, and 1.23× and 1.22×, 1.26×, and 1.30× greater tree canopy volumes (TCV) on Cleopatra and Swingle rootstocks, respectively, as compared with control trees. Significantly greater fruit yield was detected for trees budded on Cleopatra rootstocks that received either Ca or Ca + Mg treated trees with 59.7 and 63.0 kg tree–1 as compared with the control trees (36.9 kg tree–1), respectively. A magnitude of 1.14× more average fruit weight than control trees was noted for trees budded on Swingle rootstock in response to Mg nutrition. Therefore, the application of essential nutrients has a positive impact to ameliorate tree growth and nutrient deficiency associated with Candidatus Liberibacter asiaticus‐induced problems, thereby improving tree growth and yield.

The Effect of Foliar and Ground-Applied Essential Nutrients on Huanglongbing-Affected Mature Citrus Trees.

The fate of foliar and ground-applied essential nutrients is the least studied topic under citrus greening or Huanglongbing (HLB)-affected citrus, which is inherently suffering from severe root decline because of HLB-associated problems. The objective of this study was to evaluate if ground-applied coupled with foliar spray of essential nutrients can reverse the decline in tree growth and understand the fate of the nutrients in the soil-root-tree interfaces. The treatments were arranged in a split-split plot design in which nitrogen (N) was ground-applied in 20 splits biweekly and Mn, Zn, and B were foliar and /or ground-applied in three splits following the spring, summer, and late summer flush seasons. Soil nutrients in three depths (0–15, 15–30, and 30–45 cm), root, and leaf nutrient concentrations of the essential nutrients, leaf area index (LAI), and tree canopy volume (TCV) data were studied twice (spring and summer) for two years. A significantly higher soil NH4-N and NO3-N concentrations were detected in the topsoil depth than the two lower soil depths (15–30 and 30–45 cm) indicating lesser nutrient leaching as trees received moderate (224 kg ha−1) N rate. Except for soil zinc (Zn) concentration, all the nutrient concentrations were significantly higher in the topsoil (0–15 cm), compared with two lower soil depths indicating that Zn was intricate by changes in soil environmental conditions, root acquisition, and/or leaching to lower soil depth. Leaf N concentration significantly increased over time following seasonal environmental fluctuations, tree growth, and development. Thus, leaf N concentration remained above the optimum nutrient range implying lower N requirement under irrigation scheduling with SmartIrrigation, an App used to determine the daily irrigation duration to meet tree water requirement and split fertigation techniques. Root Manganese (Mn) and Zn concentrations were significantly higher in the root tissues of the treated than the control trees and translocated to the leaves accordingly. Meanwhile, a significantly higher LAI for trees budded on Swingle (Swc) rootstock however, larger TCV for trees budded on Volkameriana (Volk) rootstocks. The trees had significantly larger TCV when the trees received a moderate N rate during early study years and under foliar 9 kg ha−1 coupled with the ground 9 kg ha−1 Mn and Zn treatments during the late study years. Therefore, split ground application of 224 kg ha−1 of N, foliar applied 9 kg ha−1 coupled with ground-applied 9 kg ha−1 Mn and Zn were the suggested rates to sustain the essential leaf nutrient concentration within the optimum ranges and improve the deterioration of vegetative growth associated with HLB-induced problems of citrus trees.

Environmental variables influence the developmental stages of the citrus leafminer, infestation level and mined leaves physiological response of Kinnow mandarin

Climate change has not only exacerbated abiotic stress, but has also rendered external conditions more feasible for pests to spread and infest citrus fruit. Citrus leafminer (Phyllocnistis citrella) is a potential pest that directly feeds the newly sprouted leaves and twigs of all three spring, summer and autumn flushes. Increasing temperatures in spring and autumn, leafminer accrued more heat units or developmental degree days to accelerate the biological stages of its life-cycle, thereby increasing the pressure of infestation. Present work was conducted at three different environmental conditions in Sargodha, Toba Tek Singh (TTS) and Vehari districts of the Punjab province, Pakistan; all three experimental sites were located in different agro-ecological zones. More infestation was recorded in all three flushes at TTS and Vehari than in Sargodha. Overall, more damage was observed due to higher temperatures in TTS and Vehari than in Sargodha. After May–June heat stress, spontaneous vegetative growth continued from July to November, produced newly spouted tender leaves for feeding the leafminer larvae, and was seen more in TTS and Vehari. Leafminer larva prefers to enter young and tender leaves with a maximum entrance in leaves up to 1 cm2 in size while observing no entrance above 3 cm2 of leaf size. Physiological response of leaves primarily attributed to chlorophyll and carotenoid contents, both of which were recorded lower in the mined leaves, thereby reducing leaf photosynthetic activity. Similarly, lower levels of polyphenols and antioxidant activity were also recorded in the mined leaves. The on-tree age of mined leaves of three vegetative flushes of Kinnow plant was also less counted than non-mined leaves. Climate change has affected vegetative phenology and become feasible for pests due to extemporaneous leaf growth, particularly leafminer, and eventually causes economic loss by supplying low carbohydrates either to hanging fruits or next-season crops.

Study of seasonal variation in total polyphenol content in fresh leaves of tea [Camellia sinensis (L.) Kuntze

Experiment was conducted in the year 2018 and 2019 with an aim to study the variation in total polyphenol content in fresh green leaves of Camellia sinensis (L.) Kuntze var. assamica grown in Kangra Valley of Himachal Pradesh. The samples were collected at an interval of 14 days during three plucking seasons viz. April-June(Summer flush),July-August (Monsoon flush) and September- October (Back end flush). Samples of fresh green shoots collected in the 1st week of June recorded significantly highest total polyphenols (240.154g/kg) but was at par with the total polyphenols obtained in the samples of fresh green shoots collected in the 3rd week of May (237.136g/kg) during 2018. The fresh green shoots collected in 1st week of September recorded significantly lower TP than the rest of the treatments except the TP obtained from the fresh green shoots collected in the 3rd week of September,1st week of October,3rd week of October and 3rd week of July.

Seasonality of fine root dynamics and activity of root and shoot vascular cambium in a Quercus ilex L. forest (Italy)

We investigated the effects of seasonal changes in soil moisture and temperature on the morphological growth traits of fine roots (<2 mm in diameter) and vascular cambium activity of stems and coarse roots in a mature Quercus ilex L. stand in the South of Italy. Fine roots were sampled by a soil core method, and cambium tissues were carefully collected by hammer and chisel. Mean annual fine root mass and length were 115 g m−2 (live 45 g m−2; dead 70 g m−2) and 471 m m−2 (live 244 m m−2, dead 227 m m−2), respectively. Mean diameter size of fine root necromass was higher than for fine root biomass. Mean specific root length (SRL) was 6.8 m g−1 and turnover rate was 3 year−1. Fine root traits displayed a complex pattern related to season. In particular, biomass and length peaked in summer and late autumn. The summer maximum was characterized by an increase of the thinner part of the root population (smallest diameter size and highest SRL) and was mainly driven by soil temperature. Our results suggest that Q. ilex adopted an intensive strategy modifying the root length per unit mass, channelling carbon preferentially into the production of very fine roots. This allowed trees to exploit transient periods of low soil water content by accessing a greater soil volume and thereby facilitating nutrient and water uptake. The autumn maximum was characterized by an increase in mean diameter size of the fine root population (largest mean diameter size and lowest SRL). Thus, once precipitation sufficiently recharged soil moisture, it is reasonable to state that in addition to trees producing new roots, their percentage of very fine roots that did not die after the summer flush continued their growth in a radial pattern to function for starch storage. Shoot and root cambial activity strongly varied during the season from the winter minimum (4.8 shoot and 4.7 root cambial cell number) to three- and two-fold higher values measured during the summer maximum, and higher values but of lesser magnitude measured in autumn. Periods of cambial activity significantly matched fine root phenology. Matching these growth traits with soil temperature and water content within a natural stand of Q. ilex enables this species to survive the typically dry summer in the Mediterranean area, which is likely to become drier and longer given the increase in temperature expected this century.

Strigolactones restore vegetative and reproductive developments in Huanglongbing (HLB) affected, greenhouse-grown citrus trees by modulating carbohydrate distribution

Abstract Two-year-old greenhouse-grown Huanglongbing (HLB)-affected and healthy ‘Hamlin’ sweet orange (Citrus sinensis L. Osbeck) trees were spray treated with 10 μM strigolactone (SL) during the floral induction period (November 2016 and January 2017), and the flowering and fruit-setting period (April and June of 2017). Trees were grouped in four treatments: SL-treated HLB-affected trees; untreated HLB-affected trees; SL-treated healthy trees, and healthy control trees. Strigolactone application on HLB-affected trees during floral induction accelerated and augmented reproductive growth by inducing a 2.3-fold increase in flower bearing branches and an average of 2.6-fold increase in flowers per tree within two months from application. On the contrary, the same trees produced 31% less vegetative branches, 55% less flower bearing branches and 85% fewer flowers than HLB trees during the spring flush (April 2017). For the entire season, the number of fruit was higher in HLB + SL trees compared to untreated HLB-affected trees. Strigolactone application on healthy trees increased sucrose and starch content in mature leaves by 26% and 166%, respectively, with a 47% increase in the number of flowers compared to untreated trees. Strigolactone application during the flowering and fruit-setting period induced additional summer flush. The results of iodine staining and analytical observations demonstrated a decline in starch content in leaves and an increase in roots of SL-treated HLB-affected trees. We conclude that strigolactone ameliorates the effect of HLB by balancing vegetative and reproductive developmental response in HLB-affected citrus trees through the partitioning of stored carbohydrate.

Chloride and carbonate salinity tolerance in Mimusops zeyheri seedlings during summer and winter shoot flushes

ABSTRACTShoot flushes alternate with root flushes and the evergreen red milkwood (Mimusops zeyheri Sond.) fruit tree has winter (May–July) and summer (October-December) shoot flushes in southern hemisphere. Fruit of this plant contain high vitamin C and the tree is being researched and bred for arid inland southern Africa regions. Climate change predictions suggested that by 2030 the regions would experience high temperatures (>45°C), recurrent floods and repeated droughts, which are associated with increased salinity challenges. The objective of this study was to determine the degree of salt tolerance in M. zeyheri seedlings to chloride and carbonate salinity during summer and winter shoot flushes under microplot conditions. Treatments, comprising untreated control, NaCl, KCl, CaCl2 and Na2CO3 each at 1.0 molar (M) solutions, were applied weekly for eight weeks. During both seasons, CaCl2 and Na2CO3 salinity had significant effects on soil pH and EC. During summer, salt types increased (106%–253%) dry shoot mass and reduced (53%–79%) root/shoot ratio. During winter, Na2CO3 salinity increased (114%) dry shoot mass, but the effects were not different to those induced by NaCl and CaCl2 salinity. All other plant growth variables were not affected by salt type. Salt type had significant effects on assimilation of selected nutrient elements in leaf tissues of M. zeyheri seedlings during winter. Sodium chloride did not have significant effects on nutrient elements, whereas KCl, CaCl2 and Na2CO3 significantly affected selected macronutrient elements and Zn. In conclusion, effects of chloride and carbonate salinity on M. zeyheri seedlings were both season- and salt type-specific, with seedlings displaying some degree of salt tolerance to chloride and carbonate salinity.

Habitat selection, diet and food availability of European Golden Plover Pluvialis apricaria chicks in Swedish Lapland

Fennoscandian alpine tundra habitats support large numbers of breeding waders, but relatively little is known about their breeding ecology despite the fact that this habitat is threatened by climate change. We studied habitat selection, diet and prey availability of European (Eurasian) Golden Plover Pluvialis apricaria chicks at the Vindelfjällen Nature Reserve, Ammarnäs, Sweden. Information from 22 chicks tracked using radio‐transmitters was analysed. By analysing 149 faecal samples, four main prey taxa were identified, Coleoptera (40%), Bibionidae (31%), Hymenoptera (13%) and Tipulidae (10%). We found that chicks switched from feeding on Tipulidae to feeding on Bibionidae as they grew, and that this switch coincided with a shift from the use of the habitat where Tipulidae were abundant (alpine meadow/heathland) to the use of the habitat were Bibionidae were abundant (Willow shrub). Although chicks track food availability to some extent, the link between prey availability and habitat use was not perfect, indicating that additional factors other than food abundance, such as shelter from predators, determine habitat selection. Bibionidae are an important prey for Golden Plover chicks as it is the only prey group that has a late summer flush in abundance, in contrast to the general decline of total arthropod biomass during the chick‐rearing period. However, Bibionidae imagoes only occurred in 2011 and were virtually absent in 2013, which relates to the species’ ecology with 2‐ to 5‐year cycles in mass occurrence. Extreme annual variation in an essential food source such as Bibionidae imagoes might have an important effect on the condition and survival of Golden Plover chicks, an important subject for future studies. The foraging conditions for Golden Plover chicks in Fennoscandia appear to be different to those in the UK, where the chicks rely mainly on a Tipulidae flush only.

Liquid Organic Fertilizers for Sustainable Agriculture: Nutrient Uptake of Organic versus Mineral Fertilizers in Citrus Trees.

The main objective of this study was to compare the performance of two liquid organic fertilizers, an animal and a plant-based fertilizer, with mineral fertilization on citrus trees. The source of the fertilizer (mineral or organic) had significant effect in the nutritional status of the organic and conventionally managed mandarins. Nutrient uptake, vegetative growth, carbohydrate synthesis and soil characteristics were analyzed. Results showed that plants fertilized with animal based liquid fertilizers exhibited higher total biomass with a more profuse development of new developing organs (leaves and fibrous roots). Liquid organic fertilization resulted in an increased uptake of macro and micronutrients compared to mineral fertilized trees. Moreover, organic fertilization positively affected the carbohydrate content (fructose, glucose and sucrose) mainly in summer flush leaves. Liquid organic fertilization also resulted in an increase of soil organic matter content. Animal-based fertilizer, due to intrinsic composition, increased total tree biomass and carbohydrate leaves content, and led to lower soil nitrate concentration and higher P and Mg exchangeable in soil extract compared to vegetal-based fertilizer. Therefore, liquid organic fertilizers could be used as an alternative to traditional mineral fertilization in drip irrigated citrus trees.

Physiological and phenological responses of Protea ‘Pink Ice’ to elevated temperatures

Rising temperatures associated with global climate change may alter the physiology and phenology of Protea species and cultivars. Protea species are assumed to be well adapted to warm summers characteristic of their natural Mediterranean-type habitat, but their plasticity in responding to higher growth temperatures is not known. Using infrared lamps, a greenhouse-based temperature gradient was constructed, with temperatures ranging from ambient to ambient+3.1°C. Potted plants of Protea ‘Pink Ice’ (P. compacta R. Br×P. susannae Phill.) were grown at five positions along this gradient for 12 months under irrigation. Simultaneously, a field verification experiment in a nearby commercial ‘Pink Ice’ orchard was conducted under ambient temperature and ambient+2.9°C. Increased sclerophylly (leaf dry weight per unit area) with increasing temperature indicated leaf structural changes. While leaf area based gas exchange (net CO2 assimilation rate, stomatal conductance and dark respiration rate) did not differ across the temperature gradient, leaf weight based CO2 assimilation rate and dark respiration rate decreased significantly towards the upper end of the temperature range. The optimum temperature for net CO2 assimilation rate (Topt) showed seasonal adjustments, but increased in response to experimental warming only in the field experiment. Significant temperature elevation resulted in an earlier onset of spring bud break, but warming extended inflorescence initiation from the spring flush to the summer flush, leading to delayed flowering. Aboveground biomass allocation shifted from inflorescences to leaves and to a lesser degree to stems, with elevated temperatures, whereas root growth was stimulated in the middle of the warming range. The results of this study suggest that elevated temperature may prolong the vegetative growth period in some Protea cultivars where water is not limiting, at the expense of flower production. This could have significant economic and marketing consequences for commercial cut flower production systems. The findings are also of significance to ecologists studying the responses of Proteaceae to climate change.

Identification of the Appropriate Leaf Sampling Period for Nutrient Analysis in ‘Hass’ Avocado

This research was carried out from 2004 to 2005 in two commercial ‘Hass’ avocado orchards cultivated under rainfed conditions in a hot subhumid climate of the state of Nayarit, Mexico. The objectives of this study were to: 1) establish the patterns in nutrient concentrations during the lifespan of winter and summer vegetative flush leaves; and 2) validate a methodology based on mathematical functions to identify the appropriate period for leaf sampling to diagnose plant nutrition in avocado considering its two major vegetative flushes. Leaf samples were taken monthly for each vegetative flush, starting when leaf length was 5 cm or greater and concluding at leaf abscission. Starting at vegetative budbreak, winter and summer leaves lived 12.5 and 7.8 months, respectively. Summer flush leaves grew faster and attained greater length than winter leaves. A mathematical model based on the concentration of macro- and micronutrients through the lifespan of avocado leaves was evaluated. This model was used to determine the period when nutrient concentrations became stable and, consequently, to identify the proper leaf sampling period. For the ‘Hass’ avocado in Nayarit, the period for sampling winter flush leaves corresponded to 6.6- to 7.9-month-old leaves (4 Sept. to 13 Oct.). For summer leaves the optimum period was shorter and occurred when leaves were 3.9 to 4.9 months old (5 Dec. to 5 Jan.). The procedure and sampling time obtained here should be tested in other regions.

Phloem Production in Huanglongbing-affected Citrus Trees

Citrus greening disease [Huanglongbing (HLB)] is the most significant and widespread threat to the citrus industry in recent history. A bacterium [Candidatus Liberibacter asiaticus (CLas)] vectored by the Asian citrus psyllid is the presumed causal agent of the disease, which results in the collapse of phloem tissue, leading to decreased productivity, chlorotic leaves, and bitter, misshapen fruit. Once infected, trees never fully recover and there currently is no cure, although foliar nutrient sprays and intensive irrigation appear to slow tree decline in some situations. Despite phloem necrosis in older tissue, new vegetative and reproductive growth occurs. Our current understanding of phloem collapse in citrus resulting from HLB is based on anatomical reports of trees in different stages of decline and does not explain the persistence of growth. Here, we present data that show new phloem cells are produced during the periodic flushes of vegetative growth and their subsequent collapse and plugging over a 6-month period. Cellular activity within the cambium and the ray parenchyma was diminished in HLB-affected petioles, suggesting an important link in the carbohydrate transport pathway is missing. Because of the short window of time during which the phloem appears healthy, the weeks immediately before and after the spring and summer flush are of critical importance for the management of citrus health.

DETERMINATION OF FOLIAR SAMPLING CONDITIONS AND STANDARD LEAF NUTRIENT LEVELS TO ASSESS MINERAL STATUS OF LOQUAT TREE

Loquat [Eriobotrya japonica (Thunb.) Lindl.] is a minor fruit-tree species which is grown commercially in the Mediterranean region. Given the current increase in loquat cultivation, there is a need to define basic crop-management procedures in order to obtain high yields and optimal fruit quality. The aim of this work was to develop a routine for loquat farmers to follow, in order to know the nutritional status of trees in order to establish a rational fertilization regime, and to correct nutrient deficiencies as soon as possible. This paper reports three experiments aimed at establishing: 1) leaf type, 2) time of leaf sampling and 3) the standard leaf nutrient levels as a function of maximum yield. Results indicate that the summer flush leaves could be the most representative of nutritional status. Thus, the most appropriate time to sample leaves for analysis is in summer (beginning of August to the end of September), taking mature 3–4 month old leaves.

Late 20th century warming in a coastal horticultural region and its effects on tree phenology

Temperature records (1963–2009) from Alstonville, northern New South Wales, Australia, were examined for long-term trends using two methods: annual smoothing using a sine curve; and temperature-based phenological models applied to different parts of the year. Both methods indicated strong seasonality in warming, with winters increasing by 1.5°C over the period, but summers largely unchanged. Estimates of spring custard apple flower development time decreased by c. 13 days (20%) from 1963/64–2008/09; estimates of autumn litchi flush development decreased by c. 8 days (7%); estimates of winter macadamia flush development decreased by c. 17 days (12%) but summer flush development was not affected; and estimates of mango fruit development decreased by c. 12–16 days (7–8%) depending on variety.

VALIDACIÓN DE MODELOS DE PREDICCIÓN DEL DESARROLLO FLORAL DEL AGUACATE ‘HASS’ DESARROLLADOSPARA NAYARIT, EN VARIOS CLIMAS DE MICHOACÁN

Using records of environmental temperature and floral development obtained from 1998 to 2006 in a semiwarm subhumid climate of the state of Nayarit, five floral development prediction models for winter and summer shoots of eHassf avocado were developed. The study was conducted to test prediction models generated in Nayarit for their capacity to predict the floral development on winter, spring and summer shoots of eHassf avocado originally cultivated in the climates of the avocado producer region of the state of Michoacan. The prediction model summerDFA.19 developed in Nayarit showed a strong capacity to predict floral development on summer shoots (R2 = 0.94), in a data set from four climates of Michoacan which accounted for 85 % of the avocado producer region: warm subhumid Aw1(w), semiwarm subhumid (A)C(w0)(w), semiwarm subhumid (A)C(w1)(w) + (A)C(w2)(w), and temperate subhumid C(w2)(w). Other prediction models tested did not predict floral development on winter, spring or summer flush shoots in any of the studied climates.

Genetic variation in seasonal growth patterns in radiata pine in Galicia (northern Spain)

Shoot elongation patterns in 2 and 3-year-old Pinus radiata seedlings were monitored twice a month during 2003 and once a month during 2004 in three progeny tests in northern Spain. Fifty-eight half-sib families were studied. Several annual growth parameters were measured in each seedling: initiation, termination and duration of height growth and number of new buds formed each year. Total height, internode length and frost resistance were also measured in each seedling. The variation in these traits among families and sites was studied, as well as the effects of environmental parameters (temperature and rainfall) on growth phenology patterns. The extent to which bud phenology is genetically controlled and related to growth traits was examined. Families differed significantly in total summer shoot growth and number of summer flushes (lammas growth). The number of cycles produced per year ranged from one to four. Monocyclic families grew throughout the year, whereas polycyclic families grew episodically, depending on rainfall. Heritabilities within sites were moderate and very similar between years and sites for the dates of bud burst and the number of new buds formed. Bud burst was positively genetically correlated with seedling height. Thus, selection for greater growth is expected to delay bud burst. The number of new buds formed each year was negatively correlated with height and internode length, which means that monocyclic families were taller with longer internodes than polycyclic families. Thus, selection for faster stem growth in young progeny tests is expected to increase the length of internodes in the next generation, to reduce the number of flushes per year and to delay the bud burst date, thereby avoiding late spring frost damage.

FLORAL DEVELOPMENT OF ‘HASS’ AVOCADO UNDER SEMIWARM CLIMATE. PART I. INFLUENCE OF SHOOT AGE AND FRUIT LOAD

A multiyear research (1998 to 2006) was undertaken with the goal of developing field management tools to improve the productivity of ‘Hass’ avocado orchards in the semiwarm climate of Nayarit. The objectives were: a) to quantify the effect of ambient temperature on floral development of ‘Hass’, and b) to develop and validate prediction models to prognosticate critical stages of floral phenology. Floral development of ‘Hass’ was related to ambient temperature and mathematically modeled. Floral development on shoots of the winter flush was correlated to chilling days accumulated (CDA) at temperatures £ 21 °C, as well as the accumulated intervals between daily maximum and minimum temperatures (ACINT). In the case of summer flush shoots, they were associated to CDA with temperatures £ 19 °C, £ 20 °C and the ACINT. Two floral development prediction models ere obtained for winter shoots, winterCDA £ 21 (R2 = 0.99) and winterACINT (R2 = 0.96). In the case of summer flush shoots three prediction models were developed, summerCDA £ 19, summerCDA £ 20 and summerINTAC, all of them with R2 = 0.99.