Pollen grains of heat tolerant tomato cultivars retain higher carbohydrate concentration under heat stress conditions

Exposure to high temperatures (heat stress) causes reduced yield in tomatoes (Lycopersicon esculentum), mainly by affecting male gametophyte development. Two experiments were conducted where several tomato cultivars were grown under heat stress, in growth chambers (day/night temperatures of 31/25 °C) or in greenhouses (day/night temperatures of 32/26 °C), or under control (day/night temperatures of 28/22 °C) conditions. In heat-sensitive cultivars, heat stress caused a reduction in the number of pollen grains, impaired their viability and germinability, caused reduced fruit set and markedly reduced the numbers of seeds per fruit. In the heat-tolerant cultivars, however, the number and quality of pollen grains, the number of fruits and the number of seeds per fruit were less affected by high temperatures. In all the heat-sensitive cultivars, the heat-stress conditions caused a marked reduction in starch concentration in the developing pollen grains at 3 days before anthesis, and a parallel decrease in the total soluble sugar concentration in the mature pollen, whereas in the four heat-tolerant cultivars tested, starch accumulation at 3 days before anthesis and soluble sugar concentration at anthesis were not affected by heat stress. These results indicate that the carbohydrate content of developing and mature tomato pollen grains may be an important factor in determining pollen quality, and suggest that heat-tolerant cultivars have a mechanism for maintaining the appropriate carbohydrate content under heat stress.     

Effects of shading and thidiazuron + oil treatment on dormancy breaking,blooming and fruit set in apricot in a warm-winter climate

Overcoming dormancy represents one of the major limitations to fruit tree production in warm areas. High temperatures during the chilling period have a negative effect on breaking of dormancy. Shading of trees reduces the incidence of radiation and the temperature. Previous works on shading did not take into account the stage of dormancy. The aim of this work was to evaluate the effects of shading during different periods of endodormancy, in an area having relatively warm winters, and the effects of a treatment of thidiazuron ([TDZ] N-phenyl-N-1,2,3-thiodiazol-5-il-urea) and winter oil, on apricot blooming, fruit set and ripening. The study was carried out during three years which showed marked differences regarding chilling accumulation. Autumn shading did not affect blooming or harvesting. Regarding harvest date, 2–3 days of precocity were achieved by shading during endodormancy, relative to the control. The TDZ + oil treatment increased blooming percentage, made blooming more uniform and brought forward the blooming (by 7–14 days) and ripening (3–8 days) dates. However, pistil abortion percentage was strongly increased by using TDZ and winter oil when there was low chilling accumulation, which led to reduce fruit set percentage. Shading during late endodormancy produced 5 days precocity for the harvest date in the year with lower chill accumulation. Shading of trees during endodormancy and TDZ + oil treatment could be suitable for increasing precocity in warm-winter climates. Significant year-to-year variation has been shown for blooming, pistil abortion, fruit set and fruit/bud percentages. Correlations among these variables are also discussed. Under conditions of marginal chill accumulation, the distribution of chilling during autumn and winter had an important role in the overcoming of dormancy, blooming and fruit set.     

Low temperature storage and in vitro germination of cherimoya (Annona cherimola Mill.) pollen

Due to the protogynous dichogamy of cherimoya and to the absence of proper pollinating vectors, hand-pollination with fresh pollen is a common practice for cherimoya commercial production. In order to optimize the process of hand-pollination, in this work we have studied the conservation of cherimoya pollen at −20, −80 and −196 °C for up to 3 months. In vitro pollen germination of fresh pollen was 57.1% and it was progressively reduced with conservation time at the three temperatures studied reaching a minimum after 3 months of storage of 10.4%, 14.2% and 13.6% at −20, −80 and −196 °C, respectively. Differences in germination among temperatures were only significant during the first 2 weeks of storage. Field pollinations with pollen stored for up to 3 months at the three temperatures show no yield differences compared to pollinations performed with fresh pollen. The results indicate that pollen collected and stored at sub-zero temperatures at the beginning of the cherimoya blooming season can be used along the whole blooming season avoiding the need of collecting fresh pollen daily.     

爱多收液剂对温州蜜柑生长和结果的影响

2000～2001年对爱多收的主要生物学效应进行了详细的研究。结果表明,不管是高产的大年还是低产的小年,1.8％爱多收液剂都能使温州蜜柑发芽提早4～6d,开花提早3～5d,并促进幼果膨大,但对果实后期的膨大没有影响;在低产的2000年能提高前期坐果率20％以上,后期坐果率15％以上,增产9.8％～29.3％,能显著改善品质,而在高产的2001年,这些方面的作用不显著;在增加花量方面,小年效果很明显,大年不明显。证明爱多收增加柑橘的产量主要是通过提高坐果率来达到的。爱多收应在少花的小年使用。     

Effects of low temperatures on sexual reproduction of ‘Tainong 1’ mango (Mangifera indica)

Prevailing ambient temperature during the reproductive phase is one of important factors for seed and fruit set in different plant species. In mango (Mangifera indica L.), natural low temperatures during flowering induced seedless fruits. Here the sexual reproduction process of ‘Tainong 1’ mango at low temperatures (diurnal maximum temperature < 20 °C) was studied. For comparison, we also examined this process at “normal” temperatures (diurnal maximum ranging from 25 to 30 °C, diurnal average temperature > 20 °C). Results showed: natural low temperatures significantly affected pistil and male gametophyte development, resulting in pollen grains with low viability. Meiotic chromosomal irregularities, including univalents, multivalents, laggards, bridges and micronuclei were detected at higher incidences and significantly greater proportions of nucleolus fragmentation and dissolution were detected when temperatures were low. Pollen tube growth was retarded under low temperature stress, either in vivo or in vitro. The virtual absence of sexual reproduction of ‘Tainong 1’ mango at low temperatures appears to be due largely to slow growth of pollen tube in vivo and to a low rate of successful fertilization.     

Sind Pollenspritzungen oder Pollendispenser Alternativen zur herkömmlichen Bestäubung der Apfelbäume durch Bienen?

The efficacy of different methods of applying cv. ‘Golden Delicious‘ pollen to ‘Cox Orange‘ apple trees inside insect-proof cages was investigated: (1) spraying pollen suspended in water directly into the trees while they were in bloom (treatment A); (2) pollen transfer by honeybees (treatment B) or by bumblebees (treatment C), both of which had to pass through a dispenser loaded with cv. ‘Golden Delicious‘ pollen; (3) transfer by honeybees of pollen from cv ‘Golden Delicious‘ trees bearing compatible pollen and maintained in pots within the same cages (treatment D). Naturally pollinated cv. ‘Cox Orange‘ apple trees outside the cages in the orchard served as controls. For methods A–C normal commercially available ‘Golden Delicious‘ pollen was used for hand pollination, and its efficacy was assessed with reference to the amount of fruit that set. The fruit-set at the time of harvesting differed significantly (Nemenyi test) with the different methods of pollination: 1.0% (±2.0) of the blossoms ripened to yield marketable apples after treatment A, 6.1% (±5.2) after treatment B, 4.9% (±4.6) after treatment C, and 20.4% (±11.5) after treatment D, while the corresponding figure for the control trees was 7.3% (±2.8) and that for hand pollination, 41,9%. The low fruit-set after an aqueous suspension of cv. ‘Golden Delicious‘ pollen was sprayed on the test trees shows that this procedure did not result in adequate pollination. The density of pollen grains was determined on filter papers during spraying and was an average of 3 (±2.6, range 0.0–8.6) pollen grains/cm². When the pollen dispensers were used, the fruit-set was lower than on the hand-pollinated control trees. Despite the success of manual pollination with exogenous cv. ‘Golden Delicious‘ pollen, pollen spraying to enhance pollination, as specified in current instructions, cannot be recommended for commercial apple growing in Germany.     

Effect of distance from early flowering pollinizers ‘Maypole’ and ‘Dolgo’ on ‘Fiji’ fruit set

An apple orchard consisting of a single cultivar under the condition of natural pollination must have suitable pollinizers such as Crab apples to ensure stable fruit production. We selected ‘Maypole’ and ‘Dolgo’ as pollinizers for the cultivar ‘Fuji’, and investigated the rate of fruit and seeds in ‘Fuji’ fruits produced by pollen of the pollinizers. We developed a method for tracing pollen flow based on the leaf color of progeny and S-RNase allele of ‘Maypole’, and on Simple Sequence Repeat (SSR) analyses of ‘Maypole’ and ‘Dolgo’. These were powerful tools for determining the distance insects (mainly Osmia cornifrons) carry pollen from the pollinizers to ‘Fuji’. Although the fruit set of ‘Fuji’ apples was not reduced with increasing distance between ‘Fuji’ apple trees and pollinizers (probably due to pollen flow from other commercial cultivars planted outside the area), the rate of ‘Fuji’ apple fruit produced by the pollen of the pollinizers decreased with increasing distance. The rate of fruit produced by the pollinizers was 84% and 77% when ‘Fuji’ was 2.5 m from ‘Maypole’ and ‘Dolgo’, respectively, and 71% and 64% when ‘Fuji’ was 5 m from ‘Maypole’ and ‘Dolgo’, respectively, but was reduced to 47% and 39% when ‘Fuji’ was 10 m from ‘Maypole’ and ‘Dolgo’, respectively. However, the spacing could cause reduced fruit size, and require extra fruit thinning for producing large fruits. It could also cause reduction of the yield for increasing the planting area of pollinizers. We recommend that pollinizers should be planted not more than 10 m from ‘Fuji’.     

Improving pollination of almond (Amygdalus communis L., Rosaceae) using electrostatic techniques

Summary

Supplementary pollination of almond using electrostatic techniques was tested in a three year study (1996–1998) in Northern Israel. We used an electrostatic pollination device and tested its effects on fruitlet set, fruit set, yield weight and nut weight. We also tested its ability to pollinate flowers on the tree from the distal to the proximal part of the branches. We found that when individual branches were pollinated, fruitlet set was in accordance with the expected deposition rate of pollen grains on the stigma: electrostatic 1 open pollination > non-electrostatic + open pollination + open pollination > electrostatic pollination > non-electrostatic pollination > spontaneous self pollination. Fruit set results showed the same pattern but were not as precise. Electrostatic pollination of individual trees resulted in an insignificant increase in pollen germinability on the stigma. The highest germinability was on the distal part of the branch and the lowest was on the proximal part of the branch, in all pollination treatments. Electrostatic pollination increased yield as compared with non-electrostatic and open pollination. Nut weight, however, decreased slightly with increased yield. We suggest that electrostatic pollination can be an important method for pollen supplementation in almond orchards when honeybee pollination is insuf®cient and when the trees can withstand the added portion of nuts, resulting from improved pollination.     

The Effect of Distance From Pollinizer Varieties on the Fruit Set of Apple,Pear and Sweet-Cherry Trees

In a dwarf-pyramid apple orchard, rows of Cox’s Orange Pippin adjacent to rows of Janies Grieve had greater initial and final fruit sets than rows between other Cox rows. Flowers on the south sides of trees tended to have a greater set of fruit than those on the north sides.

In a sweet-cherry orchard containing a block of five rows of Early Rivers with pollinizer rows on each side, most fruit was set on the two outside rows and least in the centre row. Trees in the outside rows set more fruit on their sides facing the pollinizers than on their far sides. In another sweet-cherry orchard, Frogmore trees set more fruit on their south sides than on the other parts.

In a dwarf pyramid orchard of Comice, the trees with one graft of Conference (every tenth tree) set more fruit than trees without a graft. However, the fruit set on Conference dwarf and standard trees (two orchards of each) did not differ with their distance from pollinizers.     

Reduction of apple tree height (Malus domestica Borkh) cv. Ultra Red Gala/MM111 does not decrease fruit yield and quality

In Chile, like in other countries, a high percentage of apple (Malus domestica Borkh) orchards are grafted on vigorous or semi-vigorous rootstocks. The need to decrease the amount of labor involved and increase efficiency has motivated this study on the effect of reducing the height of cv. Ultra Red Gala/MM111 trees in a commercial orchard in the Maule Region of Chile. Apple trees were planted in 2003, and their tree heights were adjusted to 2.5, 3.0 and 3.6 m prior to blooming in 2006. The reduction of plant height from 3.6 m to 2.5 m determined a significant reduction in canopy volume (26% and 29% in 2007/2008 and 2008/2009, respectively), but no differences were detected in leaf area index (LAI) and the photosynthetic active radiation (PAR) transmitted through the canopy. However, a higher proportion of the canopies of the shorter trees had over 30% of incident PAR, the threshold for the production of good fruit quality and flower-bud differentiation. There were no differences in fruit production among plant heights, accumulating 131 tonnes ha⁻¹ in the three growing seasons. Over the three seasons, the shortest plants (2.5 m) required 19, 57 and 42% less labor time at harvest, respectively, than the plants maintained at a height of 3.6 m. There were no evident differences in fruit quality among the treatments; flesh firmness varied between 73.0 and 74.0 N, soluble solids between 11.6 and 12.6°Brix, mean weight between 180 and 200 g, and the percentage of red coloring exceeded 59% of the Premium fruit in the three growing seasons. Our results suggest that it is possible to manage plants with reduced height on semi-vigorous rootstocks and thus reduce the time necessary for harvesting, without affecting fruit yield and quality.     

Response of evergreen perennial tree crops to gibberellic acid is crop load-dependent. I: GA3 increases the yield of commercially valuable ‘Nules’ Clementine Mandarin fruit only in the off-crop year of an alternate bearing orchard

Worldwide, gibberellic acid (GA₃) is used routinely to increase fruit number and size of seedless mandarins. The efficacy of seven combinations of GA₃ concentrations and application times to maximize total yield and yield of commercially valuable fruit (diameter 57.2–76.2 mm) of ‘Nules’ Clementine mandarin (Citrus reticulata Blanco) was determined in a commercial orchard. GA₃ applied during the period of intense flower abscission failed to reduce the total number of abscised flowers in both the light off- and heavy on-bloom years. No GA₃ treatment reduced fruit abscission when trees were setting the low yield off-crop. However, all trees receiving GA₃ in the high yield on-crop year had fewer abscised fruit than untreated control trees (P = 0.0188) and GA₃ applied 10 days after 75% petal fall and in July increased the number of fruit retained on tagged branches >20% compared to control trees (P = 0.0005). Maximum air temperature was not related to flower or fruit abscission. In the off-crop year (548 fruit per untreated control tree), it was necessary to apply 15 or 25 mg L⁻¹ GA₃ at 60% bloom, 90% bloom, 75% petal fall and 10 days after 75% petal fall to significantly increase the number of fruit per tree and yield of commercially valuable fruit (kilograms and number per tree) (P < 0.0001) above that of control trees, with no reduction in total kilograms per tree. In the following on-crop year, it was better not to apply GA₃: no treatment increased total yield or fruit size and five of seven GA₃ treatments tested reduced total yield as kilograms and number of fruit per tree (P = 0.0003). The results provide strong evidence that GA₃ efficacy is crop load-dependent and dictate that crop load should be considered when using GA₃ to increase fruit set or fruit size of mandarins.     

苹果园树下铺设园艺地布及行间种草技术研究

连续4年对苹果园树下铺设园艺地布和行间种草进行观测,结果表明,此项技术增加土壤含水量、增加有机质含量、强壮树体、增加中短枝量,对提高果实产量和品质效果明显,应在生产中推广应用。     

Sensitive stages of fruit and seed development of chili pepper (Capsicum annuum L. var. Shishito) exposed to high-temperature stress

The sensitivity of developmental stages to high temperature was investigated in chili pepper (Capsicum annuum L. var. Shishito). Plants were subjected to heat stress (38/30 °C day/night) immediately after anthesis for 5 or 10 days, or from 10 to 30 days after anthesis (DAA), from 30 DAA until harvest of the seeds, or immediately after anthesis until harvest of the seeds. Control plants were grown at 30/22 °C (day/night). Exposure to high temperature (heat stress) during different periods of development after anthesis adversely affected fruit growth, seed yield, and seed quality in chili pepper. Heat stress for the whole period after anthesis, and from 30 DAA until harvest reduced the growth period of chili fruits by 15 and 10 days, respectively. Heat stress from 10 to 30 DAA reduced fruit width and fruit weight. The early stage of seed development from anthesis until 10 DAA was sensitive to high temperature, which affected fruit length, fruit weight and seed set. Applying high temperatures to plants for 10 DAA increased the proportion of abnormal seeds per fruit. High temperatures from 10 DAA until 30 DAA inhibited carbohydrate accumulation and adversely affected seed germinability and vigor. These results suggest that the stage of development at which chili peppers are exposed to high temperatures is an important factor in fruit and seed growth and in seed quality.     

Growth,yield and fruit quality of ‘Marisol’ clementine grown on four rootstocks in Egypt

To evaluate the most appropriate rootstocks for mandarin production in Egypt, vegetative growth, yield and fruit quality of ‘Marisol’ clementine (as newly introduced cultivar in Egypt) grafted on Sour orange (the common rootstock), Cleopatra mandarin, Carrizo citrange and ‘Swingle’ citrumelo were evaluated under the Egyptian conditions during 2004/2005 and 2005/2006 seasons. Trees were grown in a private farm at ‘Wady El-Mullak’ region, Ismailia Governorate (Latitude, 30°36′ N; longitude, 32°14′ E; Altitude, 10 m above sea level).     

Light penetration,growth, and fruit productivity in ‘Fuji’ apple trees trained to four growing systems

The study was conducted to document the range in soil nutrients, trunk and shoot growth, leaf characteristics and nutrient content, flower bud characteristics, yield, fruit quality, disease occurrence, light penetration, and shoot bark color in a 15-year-old ‘Fuji’ apple (Malus × domestica Borkh.) orchard on M.26 rootstocks trained to four growing systems. SS trees naturally growing had greater width and volume than the LT lightly heading, MLT heavily heading, and S trees thinning and bending. LT trees had more upward terminal shoots at old branches, large numbers of lateral shoots, and longer total shoot length. Leaf [N], [P], and [K] were the lowest for the MLT trees. SS and S trees had greater flower bud density and fruit yield, but LT trees had poor fruit color and less soluble solids and firmness. Percent light penetration into the canopy was the highest with the S system but not different from MLT or SS. The lowest was for the LT system, however, it was not statistically different from MLT or SS.     

Developmental problems in over-winter off-season longan fruit. I: Effect of temperatures

Fruit development was investigated in the field in over-winter off-season (bloomed in late November) and on-season (bloomed in mid April) longans (Dimocarpus longan Lour. cv. Chuliang) in 2004–2005 and 2007–2008 crops, and in potted trees grown in phytotrons set at cold (15/10 °C, day/night, simulating winter) or warm temperatures (28/23 °C, day/night) in 2008. Development of fruit in both on-season and off-season longans could be divided into two stages based on the pattern of fresh weight increase. Stage I was characterized by the slow fruit growth, and Stage II by rapid fruit growth with aril expansion. Off-season longan had a longer period of fruit development than on-season longan, chiefly due to a longer Stage I. The development of off-season fruit, especially in Stage I, was exposed to low and abruptly fluctuating temperatures. In contrast, the temperatures during on-season fruit growth were warmer and less fluctuating. Off-season fruit were smaller with a significantly higher fruit drop. Intensive fruit drop did not occur during cold period until temperature had risen. Fruit cracking in off-season longan was severe (27.6%) in 2004–2005 with a dry and cold winter, but negligible in 2007–2008 with a wet and cold winter. In phytotron experiment, trees exposed to the cold temperature regime during early fruit development produced significantly smaller fruit compared to those exposed to the warm temperature regime (6.2 g vs 7.3 g), while there was no significant difference in fruit drop rate and cracking incidence. The results suggested temperatures lower than 15 °C were stressful for the growth of young fruit and reduced the growth potential and thus fruit size. Severe fruit drop in over-winter off-season longan might be associated with stressful cold plus abrupt temperature fluctuations, while severe fruit cracking in over-winter off-season longan might be related to cold and dry weather in the winter.     

The Effect of Distance from Pollinizer Varieties on the Fruit Set on Trees in Plum and Apple Orchards

The fruit set on plum trees decreased greatly with increase in distance from pollinizer trees, and less so with increase in distance from honey-bee colonies. Trees adjacent to pollinizers had a greater set on the sides facing the pollinizers than on their far sides. Parts of trees touching “ bouquets ” had a greater set than parts without bouquets.

In an apple orchard with main variety and pollinizer trees in separate blocks, the fruit set was greater on the main variety trees adjacent to the pollinizers than on trees farther away. In an apple orchard with a pollinizer tree as every third tree in every third row, main variety trees had a greater fruit set, more seeds per fruit, and more carpels with seeds per fruit, on the sides near to their adjacent pollinizers than on their far sides. The fruit set, number of seeds per fruit, and number of carpels with seed per fruit, were greater the nearer the trees were to the adjacent pollinizer.

These results are discussed in relation to the foraging behaviour of honey-bees and to methods of arranging pollinizer and main variety trees in orchards.     

基于图像处理技术的柑桔园估产系统研制

通过利用柑桔园代表性植株成熟期普通数码照片,运用计算机图像处理、图形识别、智能推衍等技术识别植株挂果数,建立柑桔园产量估算模型,进而对拟测产目标果园取样单株进行图像分析处理,估算出单株产量和单位面积产量,最终实现果园产量的准确估算.     

Fruit set and quality of loquats (Eriobotrya japonica) as effected by pollinations under sub-humid Mediterranean

A field experiment was conducted during 2005 and 2006 growing seasons at Ras Munif (32°22′N, 35°45′E), Ajloun, Jordan, to evaluate different pollination treatments and their effects on fruit set and quality of loquat fruit grown under Mediterranean conditions. Open, supplemental, rain, and covered pollination treatments were imposed on the selected trees. Results showed that under supplemental and open-pollination, extremely higher fruit set was obtained compared with rain and covered treatments. In spite of a heavy crop load, fruits obtained under open and supplemental pollination were also heavier and larger, this could be partly due to a significant increase in seeds and flesh weight. Sugar content was good for both open and supplemental pollination. Wind plays little or no role in loquat pollination process. Loquat flowers attracted very limited number of bee visitors, A. mellifera, Anthophora albigena and Xylocopa violocea of family Apidae and Halictus quadricinctus of family Halictidae were recorded the only loquat flower visitors. They showed a variation in their visiting time but loquat flowers attracted the highest rate and number during the mid of the day.     

Rain effect on pollen–stigma adhesion and fertilization in almond

The fact that rainy weather negatively affects production in almond is well-known by growers. However, as far as we know, no previous study has been carried out in this species to determine if the rain is able to wash off pollen grains from the stigma surface and consequently affect fertilization efficiency. To answer this question, flowers of the self-compatible almond cultivar ‘Antoñeta’ were emasculated on branches of trees in the field, pollinated by hand with pollen of the cultivar ‘Marcona’, and sprayed with water to simulate the rain effect at 4, 8, 24 and 48 h after pollination. A control for which no treatment was applied was also included in the assay. Seven days after spraying the flowers, the number of germinated pollen grains on the stigma was recorded in 10 pistils for each treatment by fluorescent microscopic observation. In addition, for each treatment the initial and final fruit set were determined at 30 and 60 days after pollination, respectively. The following year additional assays were performed in the field and in the laboratory in order to complete the study with earlier treatment times. Thus, an assay of rain simulation in the field at 0 and 2 h, and other consisting on immersing a branch with flowers and shaking it in a water container in the laboratory at 0, 30, 60 and 120 min after pollination were performed. One sample more was immersed, shaken, then pollinated and again immersed and shaken. The results from field assays showed that adhesion of pollen grains to the stigma was very quick and strong, and the treatments did not significantly affect pollen–stigma adhesion and subsequent fruit set. On the other hand, laboratory results showed that all washing treatments decreased the number of germinated pollen grains on the stigma, mainly when the flowers were immersed before pollination. In conclusion, the results showed that the simulated rain was not able to completely wash off pollen grains from the stigma surface, although it seems to affect adhesion in forthcoming pollinations.