Inheritance of temperature sensitivity of the photoperiod response in common bean (Phaseolus vulgaris L.)

Summary Photoperiod response of flowering in common bean (Phaseolus vulgaris L.) is thought to be controlled by the genes Ppd and Hr. However, cultivars also vary in the degree that cooler temperatures reduces their sensitivity to photoperiod. To examine the inheritance of this temperature sensitivity, crosses of cvs. Gordo x de Celaya and Flor de Mayo × Rojo 70 were evaluated at two sites differing in mean temperature and using 12.5-h natural photoperiod or 18-h artificially extended photoperiod. Under 18-h photoperiod at the warmer site, Palmira, no plants of the parents or of the F₂ populations flowered, confirming that the parents were sensitive to photoperiod. Under 12.5-h photoperiod at the cooler site, Popayan, the parents for each cross flowered at similar dates and no segregation for days to flower was observed. However, under 18-h photoperiod, de Celaya and Rojo 70 and the F₁ populations did not flower within 100 days after planting, while the F₂ and F₃ populations showed segregation that was consistent with single gene inheritance, late flowering being dominant. Late flowering at Popayan under 18-h photoperiod indicates a lack of temperature sensitivity, so temperature insensitivity of the photoperiod response was dominant to sensitivity. The name Tip, for temperature insensitivity of photoperiod response, is proposed for this gene, with the recessive form of this gene conditioning earlier flowering at cooler temperatures with long daylengths. It is recognized that the observed segregation patterns could represent the effect of multiple alleles at the Ppd or Hr loci, and studies are proposed to test this possibility with molecular markers and recombinant inbred lines.     

Sources and inheritance of earliness in tropically adapted indeterminate common bean

Summary Nineteen early maturing, indeterminate common bean parents were crossed with a tester line of normal maturity. All parents, F₁ hybrids, F₂'s, and backcross generations were evaluated at CIAT-Palmira, Colombia. All 19F₁ populations flowered and matured almost as early as the respective early parent (mean of 61 vs 59 days). The F₂ populations were slightly less early (63 days), but were still earlier than the mean of the two parents (65 days). Additive effects for days to maturity were usually larger than dominance or interaction effects. Narrow sense heritability for days to flower and maturity were high (greater than 0.67), while heritabilities of absolute and relative duration of pod filling were low (0.17 to 0.50). Also, our data indicated that for each day of increase in earliness, yield potential will decrease 74 kg/ha.     

Inheritance of two components of early maturity in groundnut (Arachis hypogaea L.)

Summary Knowledge of inheritance of early maturity or its components is important to groundnut breeders in developing short-duration cultivars. This study was conducted to determine the inheritance of two components of early maturity: days to first flower from sowing, and days to accumulation of 25 flowers from the appearance of first flower, using three groundnut genotypes. Two early-maturing (Chico and Gangapuri) and one late-maturing (M 13) genotypes were crossed in all possible combinations, including reciprocals. The parents, F₁, F₂, F₃, and backcross populations were evaluated for days to first flower from sowing, and for days to accumulation of 25 flowers. The data suggest that days to first flower in the crosses studied is governed by a single gene with additive gene action. Chico and Gangapuri possess the same allele for this component of earliness. Three independent genes with complete dominance at each locus appear to control the days to accumulation of 25 flowers. In crosses between late (M 13) and early (Chico or Gangapuri) parents, a segregation pattern suggesting dominant-recessive epistasis (13 late:3 early) was observed for this component. Segregation in the F₂ generation (1 late:15 early) of both early parents (Chico x Gangapuri) indicated that the genes for early accumulation of flowers in these two parents are at different loci.Submitted as ICRISAT J.A. No. 1557.     

Allelic relationships of genes controlling number of flowers per axis in chickpea

Genetic variation for number of flowers per axis in chickpea (Cicer arietinum L.) includes single-flower, double-flower, triple-flower and multi-flower traits. A double-flowered (DF) line ICC 4929, a triple-flowered (TF) line IPC 99-18 and a multi-flowered (MF) line JGM 7 were intercrossed in all possible combinations and flowering behavior of parents, F₁s and F₂s was studied to establish allelic relationships, penetrance and expressivity of genes controlling number of flowers per axis in chickpea. The F₁ from ICC 4929 (DF) × IPC 99-18 (TF) cross were double-flowered, whereas F₁ from ICC 4929 (DF) × JGM 7 (MF) and IPC 99-18 (TF) × JGM 7 (MF) crosses were single-flowered. The F₂ from ICC 4929 (DF) × IPC 99-18 (TF) cross gave a good fit to a 3:1 ratio for double-flowered and triple-flowered plants. The F₂ from ICC 4929 (DF) × JGM 7 (MF) cross segregated in a ratio of 9:3:3:1 for single-flowered, double-flowered, multi-flowered and double-multi-flowered plants. The F₂ from IPC 99-18 (TF) × JGM 7 (MF) cross segregated in a ratio of 9:3:4 for single-flowered, triple-flowered and multi-flowered plants. The results clearly established that two loci control number of flowers per axis in chickpea. The double-flower and triple-flower traits are controlled by a single-locus (Sfl) and the allele for double-flowered trait (sfl ^d ) is dominant over the allele for triple-flower trait (sfl ^t ). The three alleles at the Sfl locus has the dominance relationship Sfl > sfl ^d > sfl ^t . The multi-flower trait is controlled by a different gene (cym). Single-flowered plants have dominant alleles at both the loci (Sfl_ Cym_). The double-flower, the triple-flower and the multi-flower traits showed complete penetrance, but variable expressivity. The expressivity was 96.3% for double-flower and 76.4% for double-pod in ICC 4929, 81.2% for triple-flower and 0.0% for triple-pod in IPC 99-18, and 51.3% for multi-flower and 24.7% for multi-pod in JGM 7. Average number of flowers per axis and average number of pods per axis were higher in JGM 7 than double-flowered line ICC 4929 and triple-flowered line IPC 99-18. The results of this study will help in development of breeding strategies for exploitation of these flowering and podding traits in chickpea improvement.     

A gene producing one to nine flowers per flowering node in chickpea

Chickpea (Cicer arietinum L.) has a racemose type of inflorescence and at each axis of the raceme usually one or two and rarely three flowers are borne. Plants producing 3 to 9 flowers, arranged in acymose inflorescence, at many axis of the raceme, were identified in F₂ of an interspecific cross ICC 5783 (C. arietinum) × ICCW 9 (C. reticulatum)in which both the parents involved were single-flowered. A spontaneous mutation in one of the two parents or in the F₁was suspected. However, the possibility for establishment of a rare recombination of two interacting recessive genes could not be ruled out. The number of pods set varied from 0 to 5 in each cyme. Inheritance studies indicated that a single recessive gene, designated cym, is responsible for cymose inflorescence. The allelic relationship of cym with sfl, a gene for double-flowered trait, was studied from a cross involving multi flowered plants and the double-flowered line ICC 4929. Thecym gene was not allelic to sfl, suggesting that two loci control the number of flowers per peduncle in chickpea. The cym locus segregated independently of the locus sfl, ifc (inhibitor of flower color) and blv (bronze leave). This revised version was published online in August 2006 with corrections to the Cover Date.     

Methods for the Selection of Low-Temperature Tolerant Mutants of Chrysanthemum morifolium Ramat. by Using Irradiated Cell Suspension Cultures

In order to improve mutant selection procedures, 5000 plantlets were regenerated in three different harvests (flush A, B and C) from X-irradiated (15 and 20 Gy) and non-irradiated cell suspensions of Chrysanthemum morifolium cv. ‘Parliament’. After screening under suboptimal energy condition (12°C greenhouse temperature, winter low-light), a total of 95 early flowering plants were selected. These plants flowered at least as early as a low-temperature tolerant (LTT) mutant E₂, used as a reference. The percentage of early flowering variants was highest among plants obtained from calli, X-irradiated with 15 Gy and regenerating relatively late (flush B). It appeared that the applied selection method (e.q. harvest) had a large impact on the number of early plants obtained.     

The inheritance of days to flowering in broccoli (Brassica oleracea var. italica)

Summary Crosses between an early flowering inbred broccoli (Brassica oleracea L. var. italica) HS140 and four later maturing inbred lines, S301, S310, s318, and S258, were studied to determine the inheritance of earliness as expressed by days to first open flower. Mean days to first flower for F₁ and F₂ were almost identical, and were close to the mean of the two parents in three crosses, indicating additive inheritance. In the cross HS140×S258, for which no F₁ plants were available, the F₂ mean was closer to the mean of the early parent, but this was likely due to a distortion of the data caused by the very late maturation of S258, the latest maturing parent in the study. Frequency distribution for parents and progenies supported the conclusions from parent and progeny mean values and indicated that days to maturity is a quantitative character, with mostly additive inheritance.Oregon Agricultural Experiment Station Technical Paper No. 7578.     

Problems in breeding the legume Indigofera spicata for tropical pastures

A survey of I. spicata introductions showed the majority to be tetraploid perennials and similar to each other with red stems, strongly stoloniferous habit, and poor seeding ability. The rest were green stemmed annuals or biennials which were either diploid or tetraploid and which were free seeding and almost non-stoloniferous.Crosses were attempted using several green stemmed introductions as the female parents with a representative red stemmed one as the male. The ploidy of a diploid parent was raised with colchicine treatment before crossing. F₁ seed was obtained in all crosses except in that involving the induced tetraploid. The F₁ generations were sterile except for one cross from which a small quantity of F₂ seed was obtained. A high degree of sterility was maintained in the F₂ and F₃ generations but fertile F₃ selections produced mostly fertile progeny. The sterility could be followed by the percentage stained pollen and appeared to be controlled by genetic factors.Normal types of distribution of the phenotypic classes for yield and stoloniferous development were obtained for the F₃ population which contained 26.3 per cent perennial plants. Two F₃ lines were obtained which combined the desirable characters of the two parents.The effect of temperature and photoperiod on all introductions used as parents and the two promising lines was investigated in a phytotron. All types flowered at both the 8 hour and 16 hour photoperiods and temperatures 27°/22°C and 30°/25°C favoured flowering. The better flowering of the green stemmed parent had apparently been transferred to the selected F₃ lines. The highest plant dry weights occurred at 30°/25°C and the effect of photoperiod on yield was reversed as the temperature increased.     

Successful interspecific hybridization between Cucumis sativus L. and C. hystrix Chakr.

Interspecific F₁ hybrids were obtained from a cross between Cucumis sativus L. (2n = 2x = 14) and C. hystrix Chakr. (2n = 2x = 24). Controlled crossing resulted in fruit containing embryos which were excised and rescued on a Murashige and Skoog solid medium. A total of 59 vigorous plants were obtained from a fruit containing 159 embryos (37.3% regeneration rate). Hybrid plants were morphologically uniform. The multiple branching habit, densely brown hairs (especially on corolla and pistil), orange-yellow collora, and ovate fruit of F₁ hybrid plants were similar to that of the C. hystrix paternal parent. While appearance of the first pistillate flower was more similar to that of C. sativus maternal parent than to C. hystrix, staminate flower appearance was mid-parent in occurence. The diameter and internode length of stem, shape and size of leaves and flowers were intermediate when compared to the parents. An elongated green, trilobate style/stigma which was not apparent in either parent was observed in staminate flowers of F₁ plants. Similarly, the style/stigma of pistillate flower of F₁ plants were longger when compared to their parents. The brown pubescence observed on pistillate flowers of the F₁ and C. hystrix was not observed on the C. sativus parent. The somatic chromosome number of F₁ plants was 19. Two morphologically distinct groups of chromosomes were observed in the F₁ hybrid; 7 relatively large chromosomes characteristic of C. sativus, and 12 smaller chromosomes characteristic of C. hystrix. Analysis of malate dehydrogenase isozyme banding patterns provided additional comfirmation of hybridity. Reciprocal crossing of F₁ plants to either parent and self-crossing indicated that the hybrids were male and female sterile. This revised version was published online in July 2006 with corrections to the Cover Date.     

Variance component analysis of plant architectural traits and fruit yield in melon

Summary  A cross was made between a unique highly branched, early flowering line, U. S. Department of Agriculture (USDA) 846-1 (P_1; 7 to 11 lateral branches), and ‘Topmark’ (P₂; 2 to 4 lateral branches), a U.S. Western Shipping melon, to produce an array of 119 F₃ families. Subsequently, a genetic analysis was conducted at Arlington and Hancock, Wisconsin in 2001 to evaluate the segregating progeny for factors likely involved in yield-formation, including days to anthesis, percentage of plants with early pistillate flowering, primary branch number, fruit number and weight per plant, average weight per fruit, percentage of plants with predominantly crown fruit set, and percentage of plants with early maturing fruit. Although, genotype × environment (G × E) interactions were important for some traits (e.g., fruit number and fruit weight), considerable additive and/or dominance variance was detected for all traits. This research provides critical data associated with highly branched melon germplasm including trait correlations and heritabilies (broad- and narrow-sense ranged between 0.28 and 0.91) that used judiciously will allow the development high yielding melon cultivars with early, basally concentrated fruit suitable for once-over or machine harvesting operations.     

Pollination, Fertilization and Seed Development in Inbred Lines and F1 Hybrids of Spring Faba Beans (Vicia faba L.)

When the flowers are not disturbed, the yield of F₁ hybrids of faba beans normally exceeds that in their inbred parents. The basis of this “heterotic autofertility” was investigated by examining flowers for pollination and fertilization throughout the flowering season and assessing the distribution of seeds and pods on mature plants. Six inbred lines and seven of their F₁ hybrids were grown without protection from bee visitation, and their autofertility was estimated’ by comparing their fertilization with that of cytoplasmic male-sterile line. The first direct evidence was obtained that heterotic autofertility acts by increasing; the proportion of flowers which were pollinated and fertilized. The autofertility was not perfect, especially in a closed-flower hybrid, as many ovules remained unfertilized. Several factors contributed to the number of seeds per pod in F₁ hybrids, being superior to parental means: (1) more ovules per flower, (2) greater fertilization of the basal ovules, (3) reduced abortion of the apical ovules and (4) greater overall maturation ovules.     

Dominance of bush growth habit in spaghetti squash (Cucurbita pepo)

Summary Bush and vine habit accessions and their reciprocal F₁s of spaghetti squash (Cucurbita pepo) were compared for various vegetative and reproductive characteristics. Bush habit was dominant to vine. Vine plants produced more leaves, longer internodes, and more male flowers than did bush and F₁ plants. Pistillate flowers developed at lower nodes in bush and F₁ plants than in vine plants. Vine plants produced as much or more vegetative matter than did bush and F₁ plants, but bush and F₁ plants produced more fruits and greater yields than did vine plants.     

EMS Induction of Early Flowering Mutants in Spring Rape (Brassica napus)

Studies were undertaken to induce early flowering mutants by ethyl methanesulphonate (EMS) treatments of Brassica napus seeds. EMS treatments for 12 h of a highly inbred B. napus line TBS had adverse effects on M¹ plant development and fertility only when concentrations were greater than 1%. However, an EMS concentration of 1.5% did not reduce M₁ plant fertility to an extent which significantly reduced production of M₂ seeds. Genetic changes induced by EMS treatment and affecting flowering time were of three main types: (1) Changes within a polygenic system reflected by increased variation in flowering time among M₂ families. As the increase in variation was due primarily to a higher frequency of later flowering plants, these polygenic changes would be of little value in developing better-adapted cultivars. (2) Induction of a recessive mutation at a major gene locus which caused M₃ plants homozygous for the mutant gene to flower at least 20 days earlier than the parental line TB8. (3) Induction of a dominant mutation at a major gene locus which affects flowering time by causing a substantial reduction in vernalization requirement. M₂ plants carrying the mutant gene flowered as early as 59 days before the parental line. These major gene mutations could be rapidly exploited in the development of agronomically superior cultivars for short-season, lower rainfall environments in Western Australia.     

Inheritance of bolting tendency in lettuce Lactuca sativa L.

Resistance to early flowering is an important attribute of lettuce cultivars adapted to tropical conditions. Lettuce cultivars may vary widely in the number of days necessary from sowing to inflorescence formation and flowering. In this paper, we report on the polygenic inheritance of the number of days to flowering in two crosses among contrasting lettuce cultivars – Vitória × Brasil-303 and Babá × Elisa. F₁ and F₂ seed were obtained for each cross, and used to estimate broad sense heritabilities. F₃ families were obtained from randonly sampled F₂ plants, and used to estimate narrow sense heritabilities based on parent-offspring regression. Trials were carried out in plastic greenhouses in Campos dos Goytacazes, in the Northern part of the State of Rio de Janeiro, Brazil. Broad and narrow sense heritabilities for days to first anthesis were 0.737 and 0.489 for the cross Vitória × Brasil-303, and 0.818 and 0.481 respectively, for the cross Babá × Elisa. In both crosses, both early and late-flowering transgressive segregants were obtained. Genetic gains based on selection of late flowering transgressive segregants in the F₂'s were estimated to be 10.2 days in Vitória × Brasil-303 cross, and 8.7 days in the Babá × Elisa cross. This revised version was published online in August 2006 with corrections to the Cover Date.     

Genetic analysis of the response to day length in rice

Summary Inheritance of time-to-flowering, plant height, tiller number, spikelet number and flag leaf area was studied under day lengths of 10 and 14 hours in a diallel cross of six rice varieties. Early flowering was dominant to late in both environments but the varieties flowering early in one environment were late flowering in the other. Analysis of F₁ and F₂ data from the cross of Heenati-310 x IR-8 suggested a digenic control of early flowering in short days with complementary interaction. It is considered that while relatively few genes control time-to-flowering in rice a previous proposal that separate genes for time-to-flowering and photoperiod sensitivity exist is unnecessary on present evidence. Whereas culm length, tiller number and flag leaf area were increased by longer days, the number of spikelets per panicle was reduced. The length of the panicle was little affected by changing environment, and throughout certain characters and varieties, such as tiller number in I-geo-tze, were more stable than others. Varietal crosses of Heenati-310 x IR-8 and Tainan x MI-273(m) appeared to give high yield potential.     

Flowering time in oil flax can be influenced by microgametophytic selection

The effect of selection for pollen competitive ability in F₁hybrids on days to flowering and some other morphological traits was studied in oil flax. Various intensity of selection on the rate of pollen tube growth was ensured by the change of the time intervals from pollination to the deletion of a part of the style. In the experimental variants the upper half of the style of F₁hybrids was cut off at 40, 60, and 120 minutes, in the control styles being native. It was shown that F₂ population structure essentialy changed for some morphological traits independence of competition intensity between the microgametophytes. The percentage of early flowering genotypes increased with shortening the period from pollination till style excision. In the treatment where styles were cut off 40 min after pollination the frequency of early flowering plants was highest while the frequency of those plants in 120 min treatment approached the control. Moreover, some treatments considerably influenced the phenotypic ratio in the F₂ population for such traits as petal colour and number of side shoots. It is concluded that a positive relationship exists between pollen competitive ability and early flowering in oil flax. The approach based on selection of fast growing pollen tubes that increases the frequency of early flowering plants could be used in oil flax breeding for early ripeness. This revised version was published online in July 2006 with corrections to the Cover Date.     

A genetic study of growth characters and yield characters of oilseed rape

Summary Analysis of single plants in parental, F₁ and F₂ populations of three crosses of oilseed rape indicated cytoplasmic effects in F₁ or F₂ generations for most of the observed characters. There was evidence of dominance for early flowering and early maturity. Heterosis was exhibited for yield and yield components. The heritabilities for the characters under study were generally very low.     

Inheritance of duration from sowing to first flowering in pigeonpea

Duration from sowing to flowering is the most important trait influencing adaptation in pigeon pea (Cajanus cajan), but the inheritance of this trait has not been elucidated clearly. Crosses were made between two early (60 to 70d) and one late (160 to 170d) flowering pigeonpea genotype and F₁, F₂ and BC₁ populations produced. These populations, comprising 60 to 100 parents, 30 F₁, 400F₂ and 40 to 50 BC₁ plants, were grown under natural (mean13.4 hd^-1) and artificially extended (to 15 hd^-1) daylength and duration from sowing to first flowering recorded. Genetic analysis of the segregation ratios, supported by Chi-square tests, indicated that the duration from sowing to flowering in each of the crosses was controlled by two genes assorting independently and with predominantly additive quantitative effects. The segregation patterns were most clearly defined in the 15 hd^-1 daylength. This revised version was published online in July 2006 with corrections to the Cover Date.     

Inheritance of plant elongation ability at seedling stage in rice

Summary In a comparison of methods to study inheritance of plant elongation ability, 15-, 20-, 25-, 30-, and 35-day-old F₂ populations of a cross between Baisbish (floating variety) and IR42 (nonelongating semidwarf modern variety) of rice, (Oryza sativa L.) were subjected to 65 cm water depth for 7 days. Frequency distribution of plant height before and after submergence was obtained. Bimodal curves in 15-, 20- and 25-day-old populations gave good fits to 9:7 elongating: nonelongating plants, suggesting that elongation was due to two dominant complementary genes. Segregation in the 30-day-old population was not clear-cut. A seedling age of 20 days was subsequently chosen for further studies.Two F₂'s involving floating rice and a nonelongating semidwarf; four F₂'s involving floating rice and an elongating semidwarf; and two F₂'s involving elongating and nonelongating semidwarf parents were studied with 20-day-old seedlings in the same way. Floating rice combinations with nonelongating semidwarf parents as well as with elongating semidwarf parents segregated into 9:7 elongating: nonelongating ratio. It is possible that because elongating and nonelongating dwarf parents did not differ much in elongation ability at seedling age, their combination with floating rice parents provided similar segregation. The F₂ distributions for height in elongating and nonelongating dwarf cross combinations were continuous with one peak.Genetic constitution of parents proposed are Sd1 Sd1 El El for floating parents, sd1 sd1 El El for semidwarf elongating, and sd1 sd1 el el for dwarf nonelongating.     

Heterosis and epistasis in rapeseed estimated from generation means

Summary Heterosis and epistasis in spring oilseed rape (Brassica napus L.) was analysed by comparing generation means for ten agronomic traits. Parents, F₂, F₃ and F₆ generations of four crosses with Swedish and French material were investigated. The F₂ was 11% higher in yield, earlier in flowering time, and slightly later in maturation when compared with the parents. Randomly derived single seed descent lines had an 8% lower yield, were later flowering and maturing than the parents in F₆. This poorer average performance of recombinant lines is explained by the loss of favourable epistatic interactions present in the parents.