Genetics of yield, quality and shelf life characteristics in tomato under normal and late planting conditions

Seventy nine genotypes of tomato (15 lines, four testers and their 60 F₁ hybrids produced in line × tester fashion) were evaluated under normal (E₁) and late planting (E₂) conditions in the Department of Vegetable Crops, Punjab Agricultural University, Ludhiana, India, to determine the nature of gene action controlling yield, quality and shelf life characteristics and to identify a few good combiner genotypes which may be used in further breeding programmes to extend the fruit availability period of tomato in North Indian plains. The lines were significantly different from testers for most of the characters thereby justifying the choice of testers. Additive gene action was predominant for days to ripening, total yield per plant, marketable yield per plant, number of fruits per plant, average fruit weight, fruit shape index and lycopene in both the environments, whereas non-additive genetic variance predominated in controlling firmness index, number of locules, pericarp thickness, alcohol insoluble solids (AIS), dry matter, total soluble solids (TSS), titratable acidity, TSS:Acid ratio, pH, ascorbic acid and shelf life, under both normal and late planting conditions. The best general combining ability (gca) effects, among females, in respect of yield per plant were shown by Spectrum in E₁ and by LT-42 in E₂. Among the testers, the best gca values in both the environments were possessed by nor-RM-1 for total yield per plant, marketable yield per plant, number of fruits per plant, dry matter and TSS; by rin-RM-2 for firmness index, pericarp thickness and alcohol insoluble solids; by alc-IIHR-2050 for average fruit weight, number of locules and shelf life and by alc-IIHR-2052 for lycopene. The gca of ripening mutants had a nice consonance with their per se performance for most of the characters indicating that additive gene action was operative in these mutants for majority of the traits.     

Inheritance and genetic linkage analysis of a firm-ripening tomato mutant

The tomato cv. ‘Santa Clara’ is widely cultivated among tomato producers in most of the South‐east of Brazil. Recently, some plants of this cultivar were identified with morphological alterations in both vegetative and reproductive organs. These plants showed firm (firme) ripe fruits, slow and delayed ripening. They also had yellow leaves associated with precocious senescence and flowers with pale stigmas. The objective of this work was to determine the genetic model of inheritance for this mutation and to evaluate its effects on shelf life and loss of firmness in mature fruits, as well as analyse the occurrence of genetic relationships between this putative mutant and other pleiotropic mutants. Mutated plants were crossed with the non‐mutant cv. ‘Santa Clara’ and some previously described pleiotropic mutants. Seeds of F₁ and F₂ generations and backcrosses were obtained for the segregation analysis. Morphological characteristics modified by this mutation are governed by a recessive gene with pleiotropic effects. In addition, the test of allelism showed a lack of genetic complementation between the ‘firme’ mutant and lutescent‐2 mapped on chromosome 10. Fruits of the ‘firme’ mutant had a slower rate of softening compared with the cv. ‘Santa Clara’ and its hybrids. The fruit shelf life of the mutant ‘firme’ was significantly superior to the other genotypes. No maternal effect was detected in either qualitative or quantitative characteristics. Based on the data, the mutation ‘firme’ in the cv. ‘Santa Clara’ is located in the region containing the l‐2 locus, which promoted alterations in ripening and post‐harvest physiology of fruits. The mutation ‘firme’ may represent a new allele of the gene lutescent‐2 or a gene linked to physiological events of fruit ripening.     

Inheritance of shelf life and other quality traits of tomato fruit estimated from F<Subscript>1</Subscript>’s,F<Subscript>2</Subscript>’s and backcross generations derived from standard cultivar, <Emphasis Type="Italic">nor</Emphasis> homozygote and wild cherry tomato

A tomato cultivar with high quality fruit and a long shelf life is a main goal in tomato breeding and it would be achieved using wild germplasm. The objective of this work was to explore the inheritance for fruit quality traits, especially fruit shelf life, in three tomato crosses using a standard Argentinean cultivar (Ca, cv ‘Caimanta’), a ripening mutant (nor, homozygous for the nor gene) of Solanum lycopersicum, and a wild cherry type (Ce, LA1385 of S. lycopersicum var. cerasiforme). The wild parent had a shorter fruit shelf life than the mutant genotype but higher than Ca. When the Ce genotype was analyzed in hybrid combination, the F₁ (Ca×Ce) was similar to the wild genotype for shelf life whereas the F₁ (nor × Ce) had a longer shelf life. Both F₁ crosses and backcrosses to the cherry type genotype had significantly lower fruit weight than the cultivated genotypes but higher than the cherry type parent. In the F₂ analysis, it was found that the inheritance underlying quality traits is complex since non allelic interactions were detected. A significant additive genetic variance was found for fruit shelf life as well as for other fruit quality traits in each cross. The genetic parameters analyzed by mean values and variances in parental, F₁ and F₂ and backcross generations indicated that the cross between the normal ripening cultivar and LA1385 of S. lycopersicum var. cerasiforme offers the best possibility to obtain long shelf life tomato genotypes with good fruit quality.     

Inheritance and linkage relationship of scent in rice

Summary The inheritance of scent in rice and linkage relationship of genes governing scent with those controlling leaf sheath colour, ripening hull colour and apiculus pigmentation were studied in a cross between Pankaj (nonscented) and Kalabhat (scented) rice cultivars. The scent was identified by leaf analysis.Two dominant complementary genes Sk ₁ and Sk ₂ were found to be responsible for controlling scent. Either of the genes produce mild scent, the presence of both Sk ₁ and Sk ₂ is necessary for production of parental type scent. The genes were independent of other genes controlling leaf sheath colour, ripening hull colour and apiculus pigmentation.     

Rosetted siblings in F2 of a cross in pomegranate (Punica granatum L.) can be useful model for rosetting investigations

Environmentally and developmentally controlled rosette formation is welldocumented in certain crop species. But this report describes a geneticallyinduced rosetting observed in pomegranate (Punica granatum L.).Rosette genotypes were detected at a frequency of 0.12 in the F₂ familiesof cv. Ganesh and a recessive rosette mutant clone of cv. Kabul Yellow. Therosetted seedlings had leaves almost touching the ground at emergence, whichwere closely set on a thick, compressed stem with narrow inter-nodes andinactive subapical meristem. They were similar in some certain respects tothe naturally occurring rosetting noticed in lettuce, spinach and lisianthus.The occurrence of rosette type was attributed to a recessive mutant gene ofKabul Yellow and was ascribed the gene symbol rg (rosette growth) whichwas found to alter a host of morphological traits in rosette siblings innursery and field. The foliage colour, pink of Ganesh and yellow of KabulYellow, served as visual marker in distinguishing segregating progeny intopink/yellow normal and rosette types in the nursery. A monogenic segregationin F₂ for pink and yellow was evident both in normal and rosette siblings.When a single gene mutation for rosetting was considered a large portion ofthe rosette progeny in F₂ was found missing. This has been explained on thebasis of two conditional lethal genes operating in rosette individuals.Moreover, the F₂ and BC₁ seeds had very low seed fertility indicatingthat F₁ possibly carried heavy load of lethal genes. On transplantation,the rosette mutants started to grow tall and erect, like spinach, but had acompact habit with restricted branching and exhibited early leaf senescence,leaving a crown of bushy growth at the tip of almost naked, brittle shoots.Rosettes differed significantly from normal siblings for all the morphologicalcharacteristics studied. The normal progenies flowered and set fruits within13 months, the rosette ones almost failed to do so even after growing for 38months, although they showed relatively loose rosetting than in the nursery.However, one seedling produced 3 small flowers with rudimentary ovary.Moreover, it was observed that the rosette plants had a tendency to regressto normal state, since 9 out of the 31 rosette progeny produced axilary shootsthat had normal stem and leaf attributes. The individuals with both normal androsette shoots should serve the same purpose in research work, as do perfect isogeniclines. Based on the frequency at which the normal shoots appeared the role ofcryptic transposable elements (TEs) was suspected rather than back mutation.Rosette siblings with altered morphology reported here can be secured inabundant number along with the contrasting normal siblings by raising theF₂, which provide a good opportunity to gain an insight in the control ofvarious plant developmental processes. Besides, it can be viewed as a valuablemodel system for fundamental research on physiological, biochemical andmolecular genetical bases of rosetting in crop plants.     

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.     

Inheritance of resistance to fruit rot (Phytophthora parasiticaDast.) in tomato (Lycopersicon esculentum Mill.)

Summary Fruit rot disease caused by Phytophthora parasiticaDast. is a limiting factor in tomato production in Himachal Pradesh. 30 to 60 per cent fruits are damaged by this disease. Crosses were made between EC 54725 (Lycopersicon pimpinellifolium), a small tyuited type, resistant to fruit rot and four highly susceptible tomato commercial cultivars (Gola, Sioux, S12, and Lalmani). Studies of F₁'s, F₂'s and back crosses indicated that EC 54725 carries a dominant gene imparting resistance to fruit rot.     

Genetics of novel corolla colours in periwinkle

Inheritance of a novel corolla colour in periwinkle [Catharanthus roseus (L) G. Don], viz. magenta, was studied by crossing an accession MJ, possessing this corolla colour, with cultivar Nirmal, possessing white corolla. The accession MJ was also crossed with another accession OR, possessing another novel corolla colour, viz. orange-red, to determine the relationship between genes governing magenta corolla and orange-red corolla. The F₁ plants of the cross MJ× Nirmal had pink corolla and red eye. In the F₂ generation, five kinds of corolla colours were observed: (i) pink corolla and red eye, (ii) rose corolla and red eye, (iii) magenta corolla and red eye, (iv) white corolla and red eye and (v) white corolla. The observed frequencies of the five kinds of plants fitted a ratio of 144:27:9:12:64. The progeny of the backcross, F₁ × MJ, segregated into three kinds of plants, (i) pink corolla and red eye, (ii) rose corolla and red eye and (iii) magenta corolla and red eye, in the ratio of 2:1:1, while the backcross, F₁ × Nirmal, segregated into two kinds of plants, (i) pink corolla and red eye and (ii) white corolla, in the ratio of 1:1. Two new genes (proposed symbols O^m and J) appeared to be involved in the determination of magenta and rose corolla colours. Interaction between four independent genes R, W, O^m and J, appeared to explain the observed segregation in the cross MJ × Nirmal. The F₁ plants of the cross MJ × OR had scarlet-red corolla and red eye. The segregation data of F₂ and backcross generations suggested that genes governing orange-red corolla and magenta corolla were allelic to each other. Two new and non-parental corolla colours viz., rose corolla and scarlet-red corolla, were observed in the progeny of the crosses of the present study.     

Inheritance of seed colour in Brassica campestris L. and breeding for yellow-seeded B. napus L.

Summary Seed colour inheritance was studied in five yellow-seeded and one black-seeded B. campestris accessions. Diallel crosses between the yellow-seeded types indicated that the four var. yellow sarson accessions of Indian origin had the same genotype for seed colour but were different from the Swedish yellow-seeded breeding line. Black seed colour was dominant over yellow. The segregation patterns for seed colour in F₂ (Including reciprocals) and BC₁ (backcross of F₁ to the yellow-seeded parent) indicated that the black seed colour was conditioned by a single dominant gene. Seed colour was mainly controlled by the maternal genotype but influenced by the interplay between the maternal and endosperm and/or embryonic genotypes. For developing yellow-seeded B. napus genotypes, resynthesized B. napus lines containing genes for yellow seed (Chen et al., 1988) were crossed with B. napus of yellow/brown seeds, or with yellow-seeded B. carinata. Yellow-seeded F₂ plants were found in the crosses that involved the B. napus breeding line. However, this yellow-seeded character did not breed true up to F₄. Crosses between a yellow-seeded F₃ plant and a monogenomically controlled black-seeded B. napus line of resynthesized origin revealed that the black-seeded trait in the B. alboglabra genome was possibly governed by two independently dominant genes with duplicated effect. Crossability between the resynthesized B. napus lines as female and B. carinata as male was fairly high. The sterility of the F₁ plants prevented further breeding progress for developing yellow-seeded B. napus by this strategy.     

Presence of Gene Del in Wild Species of the Genus Lycopersicon Mill.

The carotene composition of the fruits of F₁ hybrids between Lycopersicon esculentum Mill. — cv. 1/D (genotype Del⁺Dd⁺) and wild species of genus Lycopersicon with various fruit pigmentation — red, orange, and green — has been investigated. The results reveal that the red and orange-fruited species carry the recessive allele Del⁺, while the green-fruited species carry a δ-carotene gene which is identical or similar in action to the dominant gene Del. The test of allelism that has been carried out proves that the δ-carotene gene from Lycopersicon pennellii Corr. is allelic to gene Del.     

Heterosis and heritability in crosses among Asian and Ethiopian parents of hot pepper genotypes

Hot pepper is the most important worldwide grown and consumed spice and vegetable crop. Though hybrid breeding has been proposed for genetic improvement in the crop, but there is lack of information on heterosis in crosses among crop genotypes in Ethiopia. Twelve genotypes (nine Asian and three Ethiopian parents) of hot pepper were crossed in 2003 cropping season in a half-diallel fashion to fit Griffing’s fixed effect model analysis. An open field experiment was conducted in 2004/2005 to investigate heterosis for fourteen traits in 66 F₁ hybrids grown together with their 12 selfed parents. Highly significant genotypic differences were observed for all the traits except for leaf area. Variance component due to specific combining ability (dominance) were larger than that due to general combining ability (additive) for each of the studied traits with few exceptions. Broad sense heritability (H _b²) for fruit traits were more than 60% and with wide gap from narrow sense heritability (h _n²) for most of the important traits like number of fruit per plant (H _b² = 88.3% and h _n² = 46.0%), days to maturity (H _b² = 87.2% and h _n² = 23.1%) and dry fruit yield per plant (H _b² = 72.6% and h _n² = 14.6%). Maximum heterosis over mid-parent and better-parent, and economic superiority of hybrid over standard check were recorded, respectively for dry fruit yield per plant (163.8, 161.8 and 92.1%), number of fruits per plant (104.4, 79.6 and 136.4%) and days to maturity (−29.8, −31.5 and −23.6%). These observations suggested a possibility of utilizing dominance genetic potentiality available in diverse genotypes of the crop by heterosis breeding for improving hot pepper to the extent of better economic return compared to the current commercial cultivar under production in the country. Low narrow sense versus very high broad sense heritability for days to maturity and dry fruit yield per plant could be a sign for achievability of earliness and high fruit yield using heterosis in hot pepper. The maximum heterobeltiosis were recorded either from F₁s obtained from Ethiopian and Asian crosses or from within Asian crosses, suggesting the possibility of maximizing heterosis by considering genetically diverse parental genotypes. The manifestation of highest heterosis in hybrids from among Asian lines indicated existence of genetic diversity among Asian genotypes and the potentiality for improvement of hot pepper using genotypes from different regions of the world along with elite inbred lines from local cultivars.     

Mode of inheritance of Alcobaca,a tomato fruit-ripening mutant

Summary Alcobaca, an abnormally ripening tomato mutant, was crossed with the normal cultivar Rutgers. Examination of F₁, F₂ and BC₁ populations indicated that a single recessive gene controls the mutant phenotype. No maternal effect was detected.     

Inheritance of resistance to four cucurbit viruses in Cucurbita moschata

Cucurbita moschata cv. Nigerian Local has been used as a source of resistance to Zucchini yellow mosaic virus (ZYMV), Watermelon mosaic virus (WMV), Papaya ringspot virus W (PRSV-W) and Cucumber mosaic virus (CMV) in breeding both Cucurbita moschata and Cucurbita pepo. We used the F₁, F₂ and BC₁ generations derived from the cross C.-moschata cv. Waltham Butternut × Nigerian Local to study the inheritance of resistance to each of the viruses. We confirmed monogenic dominant resistance to ZYMV previously attributed to Zym, and we report monogenic dominant resistance to WMV and CMV which we propose to designate Wmv and Cmv, respectively. A single recessive gene, which we propose to designate prv, controls resistance to PRSV. DNA samples were extracted from a Waltham Butternut BC₁ F₁ population screened with ZYMV and analyzed using randomly amplified polymorphic DNA markers. No RAPD markers linked to ZYMV resistance were found. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reciprocal cross differences in a 6×6 diallel set of groundnut (Arachis hypogaea L.) in the F1 generation

Summary Reciprocal cross differences were studied in a 6×6 diallel full set comprising of thirty hybrid combinations of groundnut in the F₁ generation.Reciprocal cross differences were observed for growth habit in four pairs of crosses, for leaf colour, flower colour and stem pigmentation in two pairs of crosses each. It was observed that the inheritance of flower colour, stem pigmentation and testa colour which exhibited different shades of purple colour was likely to be governed by pleiotropic gene(s). Among the quantitative characters significantly positive reciprocal effects were observed in different crosses for number of mature pods per plant, weight of pods per plant and shelling percent. Marked reciprocal cross differences were observed for pod and kernel characters like pod filling, pod beak, pod constriction and testa colour.     

Synthesis and preliminary characterization of a new species (amphidiploid) in Cucumis

A successful interspecific hybridization between cucumber (Cucumis sativus L., 2n = 14) and a wild it Cucumis species, C. hystrix Chakr. (2n = 24) was made via embryo rescue. Hybrid plants (2n = 19; 7 from cucumber and 12 from C. hystrix) were sterile, but morphologically uniform. Self-pollination and backcrossing of F₁ hybrid plants to either parent confirmed presence of both male- and female-sterility that were likely caused by lack of homology and improper pairing during meiosis. While the multiple-branching habit, densely brown hairs (on corolla and pistil), orange-yellow corolla, and ovate fruit of F₁ hybrid plants were similar to that of the C. hystrix parent, the appearance of the first pistillate flower was more similar to that of C. sativus parent. The diameter and internode length of the stem, and the shape and size of leaves and flowers were intermediate when compared to the parents. The chromosome number in the hybrid was doubled through somaclonal variation during embryo culture and regeneration process to restore the fertility. Pollen grains were released and fruits with viable seeds matured on fertile, synthetic amphidiploid plants. The results from flow cytometry indicated that, on average, 7.3% of the morphologically unique regenerants had the 4C DNA content of 2.35 pg relative to the 2C DNA content of the original F₁ hybrid at 1.17 pg and, therefore, were likely chromosome-doubled F₁ hybrids (2n = 38). Nutrition alanalysis indicated that the synthetic species had higher protein (0.78%)and mineral (0.35%) content compared to the normal pickling cucumber(0.62% and 0.27%, respectively), and could be considered a new Cucumis crop having a special place in the future agriculture. Preliminarily evaluation indicates that C. hystrix possesses a high level of root-knot nematode resistance, and that this resistance is partially expressed in the interspecific F₁ and chromosome-doubled F₁. This and the fact that the fruit morphology of the fertile amphidiploid differs during the growing season (e.g., short and long fruit) suggest that it could be useful in broadening the germplasm base of cucumber. This revised version was published online in July 2006 with corrections to the Cover Date.     

Residual effects of low oxygen storage of mature green fruit on ripening processes and ester biosynthesis during ripening in bananas

Mature green banana (Musa sapientum L. cv. Cavendish) fruit were stored in 0.5%, 2%, or 21% O₂ for 7 days at 20 °C before ripening was initiated by ethylene. Residual effects of low O₂ storage in mature green fruit on ripening and ester biosynthesis in fruit were investigated during ripening for up to 6 d at 20 °C. Concentrations of ethanol in mature green fruit did not change during storage in both 21% and 2% O₂ atmospheres, but increased in fruit stored in 0.5% O₂. The activities of alcohol dehydrogenase (ADH) in 2% and 21% O₂ atmospheres remained very low throughout the storage period, but significantly increased with 0.5% O₂. After transferring fruit to regular air and trigging ripening with ethylene, yellowing of peel, fruit softening and hydrolysis of starch in fruit stored in low O₂ atmospheres were slower than in the control. Fruit stored in low O₂ also showed a delayed onset of the climacteric peak. The activities of ADH were lower in the low O₂ stored fruit than in the control fruit. Productions of ethyl acetate, isoamyl acetate, and isobutyl acetate were remarkably suppressed by low O₂ storage. Alcohol acetyltransferase activity increased gradually with storage time in all treatments, being significantly lower in fruit with low O₂ pretreatments. The results indicate that low O₂ plus room temperature storage can extend storage life of bananas with the sacrifice of a low production of ester volatiles.     

Importance of sepals in fruit and seed development in linseed (Linum usitatissimum L.)

Summary The green sepals in linseed (Linum usitatissimum L.) persist till almost the time of fruit ripening. Since the plant retains very few leaves and the fruits are better exposed to receive sunlight, the green sepals may be important in fruit and seed development. Influence of the removal of 0, 1, 3 and 5 sepals on the day of anthesis, 7, 15 and 25 days after anthesis on fruit and seed development was examined. Excision of all the fine sepals on the day of anthesis stopped fruit and seed development in the varieties M 10 and NP (RR) 45 but in Mukta the reduction was about 55%. Removal of three sepals also decreased fruit growth in Mukta and NP (RR) 45. The effect of removal of sepals was more pronounced on the number of seeds per fruit than on seed weight. Sepals fixed ¹⁴CO₂ and translocated ¹⁴C to seeds. However, the ¹⁴CO₂ fixation was maximum at early stages of fruit development, whereas a higher percentage of the fixed ¹⁴C was translocated at later stages of growth. It is suggested that the sepal size in linseed could be a useful selection criterion.     

Morphological and physiological characters affecting flower drop and fruit set of tomatoes at high temperatures

Summary Seven tomato cultivars and lines were studied under high temperature conditions. Fruit set varied between 77.3% in the heat tolerant cv. Hotset, 62% in cv. Gamad and 16.3% in the most sensitive cv. Hosen-Eilon. The characters contributing to low fruit set were bud drop, splitting of the antheridial cone, style exsertion and reduction of the quantity and/or functionality of the gametes. Employing the above characters as criteria for selection, fruit set of an F₄ line, phenotypically similar to the sensitive parent, was improved to 63.1%. Improved fruit set, 87.6%, was also obtained in an F₁ hybrid between Hotset and Gamad. The importance is discussed of various easily recognizable flower components contributing to satisfactory fruit set under high temperatures and their possible use in breeding is elaborated.     

Some notes on the association between fruit dimensions and fruit weight in Capsicum annuum L.

Summary Previous reports on the inheritance of fruit dimensions in Capsicum suggested two contradictory views: independent inheritance of individual dimensions vs inheritance of a shape index, i.e., length/width ratio.The F₂ of a cross between parent lines that differed in fruit size and weight but had similar shape indices exhibited intermediate dominance in fruit weight and in fruit width for small size. The correlation between fruit shape (as measured by the length to width ratio) and fruit weight in the F₂ was small and not significantly different from zero. The two variables, fruit width and fruit length, accounted for 90% of the variation in fruit weight. Apparently one can select for fruit weight in the F₂ independently of fruit shape.