Estimates of genetic variability and heritability for vegetative and reproductive characters of kiwifruit (Actinidia deliciosa)

The results of this study indicated a great deal of genetic variation in a number of characters of horticultural interest in kiwifruit seedling populations, and therefore, a potential to improve kiwifruit by vine selection. High narrow sense heritability was shown for pedicel length(0.62) and flowering duration (0.50) in male vines, and pedicel length (0.67),floral shoot percentage (0.54), leaf length-width ratio (0.64), fruit elongation (0.64) and fruit weight (0.52) in female vines. For these traits, selection of superior seedlings should lead to rapid genetic improvement in these populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Variability and inheritance of flowering time and duration in Actinidia chinensis (kiwifruit)

We investigated the variability and inheritance of flowering in a seedling population of diploid Actinidia chinensis Planch. We found considerable variation in time to reach 50% flowering (D50) and flowering duration (FD). D50 was highly heritable (h ² > 0.85) suggesting that this trait would respond well to selection in this population, whereas FD was greatly affected by the environment (h ² < 0.20). The results also showed that the flowering times of male vines were more sensitive to the environment than those of female vines. However, significant specific combining ability (SCA) effects could be achieved by targeting specific bi-parental combinations for breeding and selection of flowering time. The diversity in flowering traits among males will facilitate the selection of male pollinizers that coincide in flowering time with present or future female cultivars. The possibility of breeding female cultivars with a short flowering period to improve the consistency of fruit maturity at harvest is discussed.     

Fruit and vegetative characteristics of endosperm-derived kiwifruit (Actinidia chinensis F) plants

Summary Four hundred and thirty-eight endosperm-derived plants of kiwifruit (Actinidia chinensis) were observed. The plants were field planted in 1982 and all had flowered annually since 1986. A sample of these plants was assessed for leaf morphology, growth characteristics, flowering, sex expression, chromosome number, and fruit quality characteristics. The chromosome number of the endosperm plants varied from 58 to 146; most were aneuploid. A few triploid plants (2n=3x=87) were obtained; none of these were parthenocarpic. Segregation of sex expression was observed in progeny from one endosperm-derived callus.     

Inheritance of resistance to Pseudomonas syringae pv. actinidiae and genetic correlations with fruit characters in a diploid Actinidia chinensis (kiwifruit) population

Bacterial canker of kiwifruit, caused by a virulent strain of Pseudomonas syringae pv. actinidiae (Psa), has resulted in serious damage to kiwifruit industry worldwide. The variability and inheritance of resistance to Psa and fruit characters in a disconnected factorial mating population of diploid Actinidia chinensis Planch were investigated. Significant variation in all characters was found, and this appeared to be under polygenic control. Results indicated the extent and nature of genetic variation in Psa resistance available in our breeding gene pool. Estimates of narrow-sense heritability were moderate-high to high for Psa resistance, fruit weight, dry matter content (DM) and soluble solids contents (SSC), but low for fruit number per vine. The moderate-high heritability for Psa resistance indicated a genetic control of the observed variation, and selection for Psa resistance could be possible. Psa resistance had a high negative genetic correlation with fruit number per vine, but a moderate positive correlation with fruit weight, DM and SSC. The results implied that yield penalty of Psa resistance might exist in kiwifruit. Thus, selection strategies based on Psa resistance need to take account of its negative correlation with fruit number per vine. Male and female parents useful for improving Psa resistance and fruit characters simultaneously were identified. Two full-sib families were outstanding, as they combined high degrees of resistance to Psa with high yield components and reasonable amounts of DM and SSC.     

Flower and fruit characters in a kiwifruit hermaphrodite

The dioecious genus Actinidia includes the kiwifruit, A. deliciosa. Currently, the kiwifruit industry is based predominantly on a single female cultivar, 'Hayward', with up to 13% of the orchard canopy in commercial blocks in New Zealand consisting of unfruitful males vines, necessary as pollinizers. The development of hermaphrodite cultivars became a possibility with the identification of inconstant males, which carry a mixture of staminate flowers and bisexual flowers, the latter developing into small fruits containing seeds. This paper describes a hermaphrodite vine, obtained as a rare variant among the progeny from a cross between 'Hayward' and an inconstant (fruiting) male. Testing of pollen from all flowers in one season and measurement of fruit characters after self-setting demonstrated this seedling is completely hermaphroditic, carrying only bisexual flowers, with no restriction on selfing. Although it does not have commercial potential, it will be used as a parent. Perceived benefits from the development of hermaphrodite cultivars include increased productivity, improved pollination, simplified vine management and therefore substantial cost savings. This revised version was published online in July 2006 with corrections to the Cover Date.     

Manova and discriminant analyses of phenotypic data as a guide for parent selection in kiwifruit (Actinidia deliciosa) breeding

Evaluation of seedling populations assists in identifying those plants most desirable as parents for a breeding programme. A multivariate analysis of variance (Manova) showed that the seedling populations from 6 kiwifruit (Actinidia deliciosa) crosses differed in their overall merit. Discriminant functions were then used to identify the characters most powerful in distinguishing between populations. The populations were placed in order of their function scores which represent overall merit, and the superior populations were determined. The results showed that `Bruno' was a superior female parent for the production of seedlings with high discriminant function scores for floriferousness (male offspring)and productivity and high vitamin C content (female offspring). One male parent D-1-20 was consistently superior to D-1-6 the other male parent. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of tree and fruit characters in progenies from crosses of sweet cherry (Prunus avium L.) cultivars

Summary Approximately 1000 seedlings from 20 combinations crossed in 1979, 1980 and 1981 (Theiler-Hedtrich 1985a) were tested for several characters: fruit set (yield), fruit size, fruit colour, formation of abscission layer and bleeding after fruit removal from fruit stalks, bacterial canker resistance, flowering and harvesting time. From progeny of crosses with Stella as pollinator, 56% (Vittoria × Stella) and 46% (Schüttler × Stella) of the seedlings were self-compatible, of which 14 were high yielding with good fruit size and quality. From the data recorded it can be concluded:fruit set is a recessive character; only 5 to 20% of very good yielding seedlings were obtained in different progeny, even if the parental plants were both very good croppers.Fruit juice and skin colour was in most progenies ‘black’ even if they were from combinations with ‘white’ varieties, e.g., Merton Glory or Schüttler. Only from the combination Schiittler (‘white’) × Stella (‘black’), 50% of the seedlings were ‘white’; Stella therefore is heterozygous for the character of fruit juice and skin colour.Fruit size is evenly distributed in progeny with respect to the fruit size of their parent plants.Abscission layer formation and non-bleeding is a genetically complex character. In combinations where both parent plants formed fruits with complete abscission layers and which were not bleeding after fruit removal from the stalk, this character was inherited only to 50% (Vittoria × Schüttler) or 85% (Vittoria × Frühe von der Weid) in the progeny. For the genetical control of this character further studies are necessary.Bacterial canker susceptibility was evenly distributed in seedlings from all combinations even if the highly resistant cv. Vittoria was used as one parent plant, thereby not confirming the expected results of a higher proportion of resistant seedlings from combinations with Vittoria.Flowering and harvest time of the seedlings from different combinations was within the range of the parent plants. Only in the combination of Vittoria × Stella (mid-to late-ripening season) one seedling out of 99 was found to form ripe fruits two weeks earlier than the parental plants. From the seedlings tested 40 have been chosen for further evaluation or genetical studies.     

Inheritance and selection of some fruit characters of apple. I. Inheritance of low and high acidity

Summary Fruit acidity as such appears to be gouverned by a single major gene, low acidity being a recessive character. The additional genetic variation is explainable by the additive gene action model. This mode of inheritance causes the pH distribution of seedlings in progenies to shift with a higher mid-parent pH towards more low-acid cum sweet (pH 3.8) and fewer high-acid cum sour (pH 2.9) seedlings or vice versa with a lower midparent pH. As a result, in crosses between heterozygotes (Mama) the total proportion of undesirable seedlings -low plus high-acid ones-, remains similar, irrespective of the mid-parent pH. This proportion constituted about one third of the seedlings. A same proportion, but of mainly sour plants, was found in crosses between relatively acid homozygotes (Mama) or between these and similar heterozygotes. It was less than one quarter if the heterozygous partner was medium-acid and a few percentages only when both the homozygous and heterozygous partner were medium-acid. Choosing parents in the absence of information, chances are that the very large majority of the medium-acid types are heterozygotes, that among the relatively acid ones one in two is homozygous and that the odds to find homozygotes among the sour types are probably best. Attention was drawn to the importance of a high sugar content — which is quantitatively inherited — in parents with a relatively low pH to increase the chances of selecting seedlings with a good sugar/acid ratio.     

Inheritance of firmness in raw cucumber (Cucumis sativus L.) fruit

Summary Inheritance of raw cucumber fruit texture (Magness-Taylor Fruit Pressure Tester firmness) was investigated over a 4-year period from 1971–1974. Results from 2 separate but related experiments suggested that firmness was quantitatively inherited with sufficient additive effects to permit gain from selection. In a selection study within 4 F₂ populations derived from crosses between firm (Chipper and Gy3) and soft (Mincu and Green F) fruit type cultivars, variation among and within F₃ and F₄ families was significant but overall family means were not significantly higher than the high parent in any of the 4 crosses. Narrow sense heritability estimates for fruit texture were 0.80 in the Mincu × Chipper population and 0.77 in the Green F × Chipper, Mincu × Gy3, and Gy3 × Green F crosses. In a separate experiment, generation means analysis was used to assess the mode of gene action in 2 crosses: Green F × Chipper, and Gy3 × Green F. Additive genetic effects accounted for 98.8% and 99.3% of the total genetic variation within each cross, respectively.Scientific Journal Series Paper No. 9794.     

Inheritance of early blight resistance in diploid potatoes

Early blight (Alternatia solani) is a fungal disease in hot and humid environments, which causes leaf, stem and tuber lesions. Early blight resistance should be incorporated into potato cultivars because the fungicide spraying is an expensive solution for developing countries. The diploid cultivated species Solanum tuberosum group Phureja and group Stenotomum are sources of resistance alleles. The elucidation of the inheritance for early blight resistance must help to decide what could be the best breeding procedure to improve this diploid germplasm and transfer the resistance to the tetraploid level. Three experiments were carried out under controlled and field conditions to determine the heritability of this trait using nested and diallel mating designs with haploid, species and haploid-species hybrids. The narrow-sense heritability estimates were relatively high (0.64–0.78). This means that additivity was the most important type of gene action for determining resistance to early blight at the diploid level. The results suggested that diploid parents showing highest levels of resistance, throughout the cycle of disease development, can be used in 4x×2x crosses to obtain resistant tetraploid progenies to this fungal disease.     

Inheritance and selection of some fruit characters of apple. II. The relation between leaf and fruit pH as a basis for preselection

Summary The leaf pH of two year old apple seedlings was found to be sufficiently related to the fruit pH, measured when the seedlings were six to seven years old, to serve as a basis for pre-selection. Discarding all seedlings with an above average leaf pH (40% of the total) eliminated the majority (74%) of seedling with low-acid cum sweet fruits. The method was not effective for reducing the proportion of seedlings with high-acid cum sour fruits.     

Methods for evaluating fruit characters and incorporation in a final index in the Norwegian pear breeding programme

Summary In the Norwegian pear breeding programme selection is based on evaluation of 20 fruit samples together with field observations of precocity, productivity and resistance to biotic and abiotic factors. Fruit weight is recorded in grams, and then transformed to a scale of 20 gram classes. Appearance, shelf life and flavour are recorded on a 0 to 9 scale, and observations of shelf life and flavour are made at 4 defined intervals following ripening at 20 °C. The final index is made by summarizing the scores of fruit size and appearance, mean score of internal breakdown, mean score of flavour, maximum score of flavour and scores of precocity, productivity and resistance. All parameters, except mean flavour, are given a weighting of one, mean fruit flavour is given a weighting of 2. Data for 160 seedlings evaluated in 1992 is presented.     

Genetics of flower colour in China aster (Callistephus chinensis (L.) Nees)

Summary The genetics of flower colours violet, blue, deep pink, pink, light pink, creamy white and white was investigated in 17 cross combinations involving 10 parents in China aster (Callistephus chinensis (L.) Nees). Violet was dominant over all other colours; blue was dominant over creamy white; deep pink was dominant over pink and white, but incompletely dominant over light pink and pink was dominant over light pink and white. Four genes C, R, B and P were found to govern these different flower colours. The gene P had a dominant allele P^D and a recessive allele p.Contribution No. 146/88 of the Indian Institute of Horticultural Research, Bangalore 56080, India.     

Inheritance of fruit colour in a wild Russian red raspberry seedling

Summary A new gene, i, from a self-incompatible wild Russian Rubus idaeus seedling is described. The gene i interacts with the fruit colour gene T, Tii plants having apricot instead of red fruits, and spines, leaves and stems pigmented to varying degrees. A deficit of apricot-fruited seedlings in progenies segregating for i could be explained by linkage between i and the self-incompatibility S locus with a crossover value of approximately 26.7%.Segregations for spine colour in crosses and backcrosses of the Russian seedling with two green-spined (ttII) raspberries selected for their yellow fruit colour, showed that both the latter carried the spine colour intensifier gene P. This suggests that earlier authors were incorrect in attributing the apricot fruit colour developed by some tt plants to a pleiotropic effect of P.     

Heritability of fruit shape in pears

Heritabilities for each of three different height and width ratios describing fruit shape were estimated from measurements on a population of seedlings comprising 17 families of European and Asian pear parentage in the Hort Research pear cultivar breeding programme. In families with European cultivars as parents, the pyriform curvature in the upper, or stem end, half of the fruit was also quantified and heritabilities estimated. Heritabilities were computed using parent-offspring regression and from consideration of the variance components. Heritabilities estimated from parent-offspring regression were generally high and higher than those estimated from variance component analysis, although within the limits of error. Heritability estimates for the height: maximum width ratio were > 0.5 by both methods of estimation indicating that fairly rapid genetic gain could be expected. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of siliqua characters in Indian colza I. Locule number and siliqua position

Summary F₁, F₂, BC₁ and BC₂ generations, involving bilocular and tetralocular siliquae and with upright and pendent siliqua position, were studied with their parents. The segregation pattern in these generations indicated that number of locules is monogenically governed with the allel for bilocular type (VV-two valved pods) showing complete dominance over tetralocular (vv). Upright siliqua position is governed by two dominant genes (Up₁ Up₁ Up₂ Up₂) and pendent by two recessive genes (up₁ up₁ up₂ up₂). However, in absence of even a single dominant gene it give rise to a third type of siliqua position i.e. parallel.     

Genetic variance of six agronomic characters in three lentil (Lens culinaris Medic) crosses

Summary Three lentil (Lens culinaris Medic) crosses (cross 1 = Chilean × PI 297784; cross 2 = Tekoa × PI 212611; cross 3 = Precoz × PI 212611) were advanced in a hierarchal design from the F₂ generation to the F₅ generation and tested in replicated field experiments. The purpose was to estimate the genotypic variances and covariances for several characters and to partition these into components due to additive, dominance, and additive × additive variances.Additive genetic variance was the major component of variance in cross 2 for all characters, except plant height and seed weight. Unexpectedly, estimates of dominance variance appeared to be high in crosses 1 and 3. Estimates of the additive × additive component seemed very small in all three populations. The dominance variance component estimates were consistently high for plant height in the three crosses and for seed weight in crosses 2 and 3. Where parental means were close, additive variance estimates were often low and in many cases negative. The unexpected high ratio of dominance variance to additive variance indicated that dominance variance was important in the crosses we studied.Cooperative investigations of Agricultural Research Service, US Department of Agriculture and the College of Agriculture, Washington State University, Pullman, Washington 99164, Work sponsored by Fellowship from Univ. of Jordan, Amman, Jordan. Scientific paper no. 5825.Formerly: Department of Agronomy and Soils, Washington State University, Pullman, WA., USA. Presently: Department of Plant Production and Plant Protection, University of Jordan, Amman, Jordan.Statistical Services, Washington State University, Pullman, WA 99164, USA.US Department of Agriculture, Agricultural Research Service, Washington State University, Pullman WA 99164, USA.     

Inheritance of nut and kernel traits in almond (Prunus amygdalus Batsch)

Summary An almond breeding program was initiated in 1966 to develop improved cultivars for arid conditions with irrigation. Nut and kernel traits were evaluated for almond parents and progenies. Highly significant parent/progeny correlation coefficients (0.7–0.9) were found for shell hardness, percentage of kernel, in-shell (nut) and kernel weight, kernel length and width, as well as kernel color and outer shell retention.Double kernels and kernel thickness had low parent/progeny correlation coefficients. Shell hardness and percent kernel were highly correlated, as were shell hardness and outer shell retention, percent kernel and outer shell retention, and kernel width and nut weight.All but two of the evaluated traits (kernel thickness and percent doubles) appear to be highly heritable with mostly additive gene action, although some degree of dominance appeared to be involved in percent kernel, shell hardness and percent doubles.Contribution No. 185-E from Agricultural Research Organization, Israel.     

Inheritance of seed size in cowpea (Vigna unguiculata (L.) Walp.)

Summary The inheritance of seed weight in cowpea was examined in a field planting of the parents, reciprocal F₁s, F₂s and backcrosses to both parents of a cross between TVu 1977-OD (small seeded) and ACC 70002 (large).Seed weight was inherited quantitatively and small seed was partially domiminant to large seed size. Gene action was predominantly additive but dominance and additive × additive epistatic effects were also significant.Broad and narrow sense heritabilities were 85.1±5.3% and 75.4±18.6% respectively. The minimum number of loci involved in the inheritance of seed size was eight, and each gene pair contributed up to 1.02 g increase to seed weight. The estimate of genetic advance from F₂ to F₃ generations with 5% selection intensity was 3.58 g.International Institute of Tropical Agriculture, Semi-Arid Food Grain Research and Development Project/National Cowpea Improvement Program, B.P. 1783, Ouagadougou, Upper Volta.Department of Primary Industries, Hermitage Research Station, Warwick 4370, Queensland, Australia.International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), ICRISAT Center, Patancheru, P.O. 502 324, A.P., India.     

Inheritance,heritability and breeding behaviour of three sources of resistance to Septoria tritici in wheat

Summary We examined the inheritance, heritability, and breeding behaviour of resistance to Septoria tritict in the spring wheat cultivars Seabreeze, Veranopolis, and IAS-20 in crosses to the susceptible Australian spring cultivar Gamenya. Resistance in Seabreeze was higher than that in Veranopolis and IAS-20. Inheritance of resistance in Seabreeze seems to be determined by at least three recessive genes. Resistance in Veranopolis and IAS-20 might be due to a single gene. Similarity of inheritance patterns and breeding behaviour of the resistance from Veranopolis and IAS-20 and the common ancestry of these two cultivars suggest that they may carry the same gene. Standard unit heritabilities of Septoria scores, as measured by correlation of F₂ plant with F₃ family mean data, were high (57–68%). Parent offspring genetic correlations confirmed previously reported associations between resistance and lateness and resistance and tall plant height, but correlations were not sufficiently high to be a major obstacle to selection. Resistance in Veranopolis and IAS-20 were easily recovered in first backcrosses while that in Sea breeze was more difficult to recover.Contribution from the Department of Agriculture Western Australia.