The nature and inheritance of sweetness and acidity in the cultivated apple

Summary A survey was made of the sweetness and sourness of the fruits of apple cultivars. Measurements of the concentration of sugars and malic acid in ripe fruits were made and the variation between samples of a cultivar, between cultivars, between years and between cultivars and their tetraploid and colour sports was studied and showed a wide range of variation between cultivars but fairly constant values within cultivars.The study of a number of progenies shows that sweetness and sourness are inherited independently. Sweetness shows a quantitative pattern of inheritance and the progeny mean approximates the mid-parent value. Sourness is controlled by a single gene, with medium and high acidity being dominant to very low, superimposed on a quantitative pattern.The mean sugar and acid concentrations of a progeny and the approximate range of variation can be predicted from the sugar and acid concentrations found in the parents.     

Juvenile period and precocity of apple and pear seedlings

The existence of a genetical relation between the precocity of the parents and the length of the juvenile period of their progeny suggested a similar relation between precocity in the juvenile and in the adult phase of a seedling. This was confirmed in a trial with adult apple and pear seedlings budded on a rootstock. The percentage of trees which flowered in the third year following budding was higher when the juvenile period had been shorter. This relation should be taken into consideration in breeding.     

Juvenile phase and growth of apple and pear seedlings

It was investigated whether and to what extent the duration of the juvenile phase of pear and apple seedlings is related to their vegetative growth. The juvenile phase was defined as the period in years that the seedling remains vegetative; the trunk diameter served as a measure of vegetative vigour. The following observations were made:

1. 1)

   A significant negative correlation exists between the duration of the juvenile phase and the vigour of the seedling (as measured by trunk diameter).

2. 2)

   Environmental conditions with respect to weather, soil and cultural practices which promote or restrict growth, tend to shorten or lengthen the juvenile phase accordingly by their influence on the time required for the attainment of a certain minimum size which at least partly determines the attainment of the flowering condition.

3. 3)

   The weak rootstock M. IX significantly accelerated the onset of flowering of apple seedlings by about 1 1/2 years; this rootstock appears to combine a retarding effect on growth with a specific influence on flowering.

     

Pre-selection of compact mutants induced by X-ray treatment in apple and pear

Summary Mutation breeding of apple and pear started in 1965 using dormant scions which, after irradiation (X-rays), were grafted on rootstocks. The most efficient dose for apple was around 3 krad, for pear between 4.5 and 7 krad. Primarily shoots exhibiting compact traits were selected, defining such shoots as being thicker than normal for their length or shorter than normal for their diameter while having shorter internodes than normal shoots. The selection was carried out on one-season-old shoots of the same trees during three successive seasons, this involved a cut back at the end of the first and second season. The selected compact shoots yielded with apple on average four times more clones with a distinct compact habit than normal appearing shoots; four out of every five clones were found to be stable in both apple and pear. Averaging the results for apple, 7% of the surviving trees produced shoots the clones of which showed compact growth, this was only 0.5% for pear. In all several dozens of such clones were obtained of the apple varieties Golden Delicious, Cox's Orange Pippin, Belle de Boskoop and Tydeman's Early and a few distinct compact and some dwarf clones of Beurré Hardy and Doyenné du Comice.Samenvatting Mutatieveredeling bij appel en peer begon in 1965 met enthout dat, na bestraling, op onderstam werd geënt. De doelmatigste dosering lag bij appel om en nabij 3 krad, bij peer tussen 3, 5 en 7 krad, afhankelijk van het ras. De nadruk viel op de selectie van spur-scheuten cum scheuten met een gedrongen habitus. Zulke scheuten werden gedefiniëerd als scheuten die, afgaande op hun lengte, dikker zijn of, afgaande op hun diameter, korter zijn dan normaal terwijl in beide gevallen de internodiën korter zijn dan bij vergelijkbare normale scheuten.De selectie werd uitgevoerd op éénjarige scheuten van dezelfde geënte bomen gedurende drie achtereenvolgende seizoenen; dit hield in dat na het eerste en het tweede groeiseizoen werd teruggesnoeid. De geselecteerde appelscheuten gaven, na enting, viermaal meer klonen met een uitgesproken gedrongen habitus dan willekeurige normaaluitziende scheuten uit bestraald materiaal. Zowel bij appel als bij peer bleken vier van de vijf klonen stabiel te zijn. Bij appel produceerden gemiddeld 7% van de overlevende bomen klonen met een gedrongen groei, bij peer was dit slechts 0.5%.In totaal werden enige dozijnen klonen met gedrongen of zwakkere groei verkregen bij de appelrassen Golden Delicious, Cox's Orange Pippin, Belle de Boskoop en Tydeman's Early en slechts enkele bij de pererassen Beurré Hardy en Doyenné du Comice.Subcontract Institute for Atomic Sciences in Agriculture (ITAL), Wageningen, the Netherlands.     

Genetic resources in apple,pear and vineyard peach populations in former Yugoslavia

Summary During the period 1988–90, several germplasm collecting trips were made to all republics of former Yugoslavia. A total of 56 old apple cultivars, many of which are represented in up to 5 types, 38 old pear cultivars and 367 genotypes of vineyard peaches were collected. The availability of so much genetic and genotypic wealth made it possible to start apple disease resistance breeding and peach cultivar and rootstock breeding programmes.     

Pre-determination of survival rate of apple and pear scions after X-ray treatment

Summary A simple method is described which makes it possible to pre-determine the survival rate of dormant scions of woody crops such as apple and pear after X-ray treatment.During early spring irradiated scions were kept on water in a warm glasshouse and the buds were left to sprout. It appeared that the relation between X-ray dose and percentage of buds surviving on the scions after 3–4 weeks was similar to the relation between dose and the percentage of irradiated grafts surviving after two growing seasons in the field. In sofar the dose at which 50% survival occurs is presumed to be the most efficient one, the method enables speedy determination of the most effective dose of X-ray treatment.     

Precocity and productivity of propagated apple and pear seedlings as dependent on the juvenile period

Summary Adult apple and pear seedlings varying in juvenile period were propagated on rootstocks. They were subsequently found to be more precocious and more productive when the juvenile period had been shorter. In view of the significant relation between vigour measured by stem diameter) and precocity of both seedlings and propagated trees, it is possible to pre-select for the potentially more precocious seedlings on the basis of vigour.Samenvatting De vruchtbaarheid van vegetatief vermeerderde appel- en peerzaailingen in verband met hun jeugdperiode Reeds vruchtdragende appel- en perezaailingen, waarvan de voormalige jeugdperiode sterk varieerde, werden op onderstam geoculeerd. Het bleek dat de bomen gemiddeld vroeger vruchtbaar en productiever waren naarmate de voormalige jeugdperiode korter was geweest.De al eerder geconstateerde relatie tussen groeikracht en jeugdperiode (kortere jeugdperiode naarmate de bommen dikker zijn), bleek ook na vermeerdering te bestaan, d.w.z. de dikkere bomen bloeiden eerder dan de dunnere. Daar deze samenhang erfelijk bepaald is, biedt dit de mogelijkheid om de potentieel vroeg-vruchtbare zaailingen reeds in het kwekerijstadium op basis van groeikracht te selecteren.     

The performance of double or mixed pollinations with compatible and self-incompatible or incongruous pollen of pear and apple

Summary Six pear and five apple trials were carried out to ascertain the outcome of combinations of compatible pollen (C) with self (S) or incongruous pollen (I) as to the pollination index (PI=seeds/pollinated flower). The PI of the mixture C+I (1:5) was consistently depressed as compared to that of the control C. The results of the double pollinations S/C and I/C were affected by the temperature at pollination; their PI's at <15°C were twice as high as those at >15°C, being well above and below the PI of C in the former and latter case respectively. The opposite was true for the C/S combination, the PI of which increased with the pollination temperature; the PI of C/I did not differ much from the PI of C, irrespective of temperature. The conclusion was reached that the interaction previously and presently found between compatible and self-incompatible pollen also exists to a fair extent between compatible and incongruous pollen. However, in pear neither the mentor nor the pioneer pollen technique proved to aid its hybridization with apple, the formation of self seed was not observed either. In apple the production of apple × pear hybrids was likewise doubtful, but the double pollinations S/C and C/S formed 4–10% self seed.     

The interaction between compatible and self-incompatible pollen of apple and pear as influcenced by their ratio in the pollen cloud

Summary The production of self-seed was investigated in apple and pear with the aid of viable and compatible mentor/ pioneer pollen in relation to the proportion of self-imcompatible pollen present in the pollen cloud.Treatments consisted of mixtures of compatible and self-incompatible pollen at ratios of 1:1, 1:2 and 1:9 applied once or twice or followed by self-pollination. Selfing only, whether once or twice, produced virtually no fruits or seeds, while mixed pollinations did. Generally, fruit set tended to decrease and the self-seed to increase with increasing amounts of self pollen in the pollinations.The pioncer-pollen method (compatible in advance of self pollen) appeared more effective than the mentor pollen method (compatible and self pollen mixed). The use of viable instead of dead mentor/pioneer pollen causes competition for the ovules with the self pollen, but has the advantage that, in addition to some self-seed, other seeds are formed which, e.g. in apple, are necessary to keep the fruits on the tree until harvest.Fruit set was moderately reduced at ratios of compatible pollen to self pollen not exceeding 1:9 with pear and 1:5 with apple which constitute maximal ratios in practice as regards pollinator trees: trees of the main cultivar. In fruit orchards and probably in nature with other species, the interaction between compatible and self pollen may result in more self-seed, and so suggests that inbreeding played a greater part in the evolution of self-incompatible species, than the meager results of articial self-pollination imply.     

A comparison of apple and pear seedlings with reference to the juvenile period I. Seedling growth and yield

Summary Several thousand apple and pear seedlings of many progenies were studied in connection with their juvenile period (J.P.). The initially significant inverse relation between the vigour (stem diameter) and the J.P. of the seedlings became insignificant as the trees grew older, due to a retardation of growth occurring when the seedlings become generative. This relation can be used effectively in pre-selecting for vigour in the nursery. Cumulative yields were higher when the J.P. was shorter, but there was no evident link between the J.P. and annual yield in full bearing, that is to say, precocity and preductivity are not directly connected. Better growing conditions and pre-selection have shortened the mean progeny J.P. of either crop by three years since the 1950's. Generally, the pear seedlings appear to grow faster, to become generative slower and to yield lower than comparable apple seedlings. The mean J.P. of apple and pear progenies averaged 4.2 and 6.0 years respectively. The difference between apple and pear may be attributable to a greater selection pressure on both precocity and productivity with apple than with pear.This possibly also led to a smaller tree in the productive phase on the assumption that tree size at first flowering-small at a short, large at a long J.P.-expresses reproductive efficiency and as such is reflected in the size of the adult tree.Also presented at the Juvenility Symposium held at West-Berlin, November 1976.     

Pollen and pollination experiments. III. The viability of apple and pear pollen as affected by irradiation and storage

Summary Apple and pear pollen was irradiated with doses of 0, 50, 100, 250 and 500 krad (gamma rays) and stored at 4°C and 0–10% r.h. From the in-vitro germination percentages an average LD 50 dose of about 220 krad was estimated. For both irradiated and untreated pollen a close and corresponding lineair relationship existed between germination percentage and pollen tube growth.Irradiated pollen was much more sensitive to dry storage conditions than untreated pollen, resulting in less germination and more bursting. Apparently, irradiation caused the pollen cell membrane to lose its flexibility faster than normal. Rehydration of dry-stored, irradiated pollen in water-saturated air restored germination percentages up to their initial levels. The importance of this procedure in germination trials is stressed.     

A comparison of apple and pear seedlings with reference to the juvenile period. II. Mode of inheritance

Summary Analysis of two incomplete half-diallel schemes of crosses, involving 22 apple and 33 pear progenies with 2500 and 5400 seedlings respectively, showed a highly significant GCA and an insignificant SCA variance for the juvenile period (J.P.). This indicates that the inheritance of the J.P. is of an additive nature, a mode of inheritance which is a function of the inheritance of a complex of factors governing growth. The mean J.P. of apple progenies varied between 3.4 and 5.0 years, that of pear progenies between 4.7 and 7.0 years. The implications for breeding are discussed.Also presented at the Juvenility Symposium held at West-Berlin, November 1976.     

Daily photosynthetic radiation use efficiency for apple and pear leaves: Seasonal changes and estimation of canopy net carbon exchange rate

The estimation of whole canopy carbon assimilation rate using the relationship between daily net CO₂ assimilation rate (A_n) and daily incident photosynthetically active radiation (PAR) for individual leaves within the canopy has been considered an alternative to whole canopy gas exchange measurements. This relationship has been reported as being linear, but it has been explored only between the end of active shoot growth and harvest and in few species. Apple (Malus domestica) trees were used to study the seasonal changes in the relationship between daily A_n and incident PAR in individual leaves during the growing season of 2007 and this was done for pear (Pyrus communis) trees in 2008. Fifty leaves exposed to different light environments within the canopy of a given tree were selected. For each leaf seven times a day incident PAR and A_n was measured. Daily incident PAR and A_n was estimated by integrating instantaneous values. The relationship between daily A_n and daily incident PAR within the canopy had different patterns depending on the time of the season. It was always curvilinear early and late in the season, but tended to be more linear between the end of active shoot and harvest (mid-season). The initial slope and curvature of the relationship changed during the season and both were significantly related to daily PAR above the canopy. Whole canopy net carbon exchange rate was estimated considering canopy intercepted PAR and the relationship between daily A_n and incident PAR in individual leaves. The values were similar to those reported in the literature during mid-season. Estimated whole canopy net carbon exchange rate varied substantially after harvest, depending on whether a linear or curvilinear response of daily A_n to PAR for individual leaves within the canopy was considered. We showed that apple and pear whole canopy net carbon exchange rate can be estimated during mid-season, which is the most relevant phase for tree fruit production, using the following parameters: photosynthetic rate of well exposed leaves, daily pattern of incident photosynthetically active radiation (PAR), daily integral of PAR intercepted by the canopy and leaf area     

生物炭对强酸性茶园土壤酸度的改良效果研究

利用盆栽试验研究了施用石灰和不同用量生物炭对强酸性茶园土壤酸度的调控效果。结果表明：施用生物炭和石灰处理均可显著提高茶园土壤pH值。5~20 g/kg生物炭施用量处理土壤的pH值低于施用石灰处理,但当生物炭用量大于40 g/kg时土壤pH值显著高于石灰处理,说明在强酸性条件下,低用量生物炭处理在调节土壤pH值的效果不如石灰。施用生物炭处理土壤阳离子交换量比施用石灰处理提高了0.98%~8.67%,盐基饱和度提高0.85%~40.90%,土壤交换性钙、镁、钾和钠含量分别提高1.70%~11.36%、32.79%~80.52%、76.47%~1744.12%和4.93%~57.48%,说明施用生物黑炭比施用石灰可增强土壤对酸的缓冲性能。     

A single recessive gene for stem sweetness in sorghum

Summary The inheritance of stemsweetness in sorghum has followed a qualitative pattern, non-sweet being monogenically dominant over sweet. Hence sweetness was controlled by a single recessive gene. A maternal effect was not involved for the expression of sweetness.     

Incompatibility and resistance to woolly apple aphid in apple

The study investigated the reported linkage of the locus for resistance to woolly apple aphid with the locus for incompatibility. Apple seedlings from the cross ‘Northern Spy’(heterozygous for resistance) בTotem’(susceptible) were scored for resistance, and for incompatibility genotype, by analysis of stylar ribonucleases, and for Got‐1, the isoenzyme marker for incompatibility. Cosegregation analysis provided no evidence that the loci for resistance and incompatibility are linked. Two rootstock cultivars,‘M9’and ‘Merton 789′, which in early work had been reported to give poor set in crosses with ‘Northern Spy’, were found to have the same incompatibility genotype as ‘Northern Spy’, namely S₁S₃.‘M4’and ‘Irish Peach’, two other cultivars that had given poor set when crossed on to ‘Northern Spy’, appeared to be homozygous at the incompatibility locus and to have the genotypes S₃S₃ and S₁S₁, respectively.     

Browning disorders in pear fruit

Disorders occurring during long-term storage of pears can cause economic loss, especially when disordered fruit cannot be distinguished externally from sound fruit. A typical category of disorders in pear fruit is related to internal browning of the flesh and the presence of cavities. In this review, information which appeared in the literature in the last decade has been integrated into a generic model for the development of storage-related browning disorders in pear. In this model it is assumed that browning disorders are caused by an imbalance between oxidative and reductive processes due to metabolic gas gradients inside the fruit, leading to an accumulation of reactive oxygen species. The latter may induce loss of membrane integrity which becomes macroscopically visible through the enzymatic oxidation of phenolic compounds to brown coloured polymers. The development of disorders during postharvest ripening and storage of fruit also depends on a range of preharvest factors such as climate conditions and crop load. Methods to evaluate the incidence of browning disorders nondestructively have been reviewed.     

过碳酰胺对红壤pH、活性铝含量及玉米幼苗生长的影响

过碳酰胺是一种新型精细化工品,也是一种新型氮肥,在国外已得到广泛的应用和开发,而中国对其开发和应用刚刚起步。研究了南方3种酸性土壤中施入过碳酰胺后,对土壤pH值变化、铝元素活性及玉米幼苗生长的影响。静态试验结果表明：对3种酸性红壤施用不同浓度过碳酰胺,其pH值在短期内都随着施入过碳酰胺浓度的增大而急剧上升,交换性铝含量随着施用过碳酰胺浓度的增大而急剧下降。动态试验表明,施用过碳酰胺后,土壤pH值上升的现象是短期的,pH值达到最大值后缓慢下降,而土壤中铝元素的有效性与土壤pH的变化趋势呈显著负相关。植物实验表明,短期内,经过碳酰胺处理的玉米幼苗主根明显缩短,侧根生长受到抑制,并且其玉米铝毒明显重于不经过碳酰胺处理的玉米,被玉米吸收的铝主要分布在玉米的地下部分（即根内）,只有较少的铝被转移到地上部分。