Basic Vegetative Phase Research Articles

RFLP mapping of QTLs for photoperiod response in tropical sorghum

Genetic control of flowering time in sorghum was investigated using a recombinant inbred lines population derived from a cross between IS 2807, a slightly photoperiod sensitive tropical caudatum landrace, and IS 7680,a highly photoperiod sensitive tropical guinea landrace. Progenies were sown with their parents at six different dates between 1995 and 1997 in Burkina Faso. Direct field measures and synthetic measures derived from the implementation of a model were used to characterize the photoperiod response. Emphasis was put to identify the most relevant traits to account for Basic Vegetative Phase (BVP) and photoperiod sensitivity sensus stricto. One QTL was detected on Linkage Group (LG) F for the traits related to BVP. Two QTLs were detected on LGs C and H for the traits related to the photoperiod sensitivity sensus stricto. This gives credit to at least partially independent genetic determinisms for those two components of photoperiod response. Evidences for possible orthology of the QTLs detected here with other QTLs and major genes involved in flowering time of sorghum and rice are discussed.

Adapting a photoperiod-sensitive routine to the INTERCOM model for use in West Africa

In West Africa, weeds are the major constraint to rice production. Native African rice Oryza glaberrima, however, is very competitive against weeds and research is ongoing to introgress competitive traits of O. glaberrima into high-yielding O. sativa types (Jones et al 1997). To support this work, the crop-weed competition model INTERCOM (Kropff and van Laar 1993) is being adapted and parameterized to evaluate weed-competitive rice plant types in a prebreeding support project. The accurate prediction of phenology is the first step in applying process-based mechanistic models as tools for rice research and decision support at the site or regional level. Phenology is important in situations in which weeds compete with rice because competitiveness is affected by the partitioning of dry matter to organs and partitioning is driven by phenology. Phenology in INTERCOM is calculated from a thermal time (°C day) approach that assumes a linear developmental rate from plant emergence to flowering and another from flowering to physiological maturity. Rice development to flowering, however, has been shown to respond to both temperature and photoperiod at specific stages. Thus, subphases-a basic vegetative phase (BVP), a photoperiod sensitive phase (PSP), and a panicle formation phase (PFP)- have been identified (Vergara and Chang 1985). Varietal sensitivity to photoperiod modulates the duration of PSP, depending on the positive deviation of daylength from a critical daylength value. These were used to modify the phenology routine in INTERCOM in a way similar to that in ORYZA_1 but allowing for multispecies structure, which is characteristic of INTERCOM.

The influence of photoperiod on barley development

Time to awn emergence and leaf number on the main culm were recorded for 10 barley cultivars grown under a short and long photoperiod after 4 weeks cold treatment at 4°C; the appearance of leaves on the main stem was also recorded at regular intervals. There were differences among the cultivars for photoperiod response and the duration of the basic vegetative phase. Photoperiod response tended to be complementary with basic vegetative phase, as one increased the other decreased and vice versa. Leaf appearance generally did not differ significantly between photoperiod treatments. In the short day, leaf appearance continued for a longer period with more leaves produced on the main stem. Leaf appearance as a function of time was best described by a cubic or a quadratic exponential polynomial function. The absolute rate of leaf appearance (leaves d−1) under short day showed an increase to a maximum followed by a decrease to a minimum and then a further increase. Under long day, three patterns of absolute rate of leaf appearance were evident. There was a rapid increase to a maximum followed by either a rapid or more gradual decline; in several cultivars the pattern was similar to the one seen for the cultivars in the short day treatment, although it was somewhat truncated. The significance of photoperiod response and basic vegetative phase are discussed in relation to crop adaptation and the change in the absolute rate of leaf appearance is discussed in relation to the stage of plant development.

Development of a hemp (Cannabis sativa L.) simulation model 2.The flowering response of two hemp cultivars to photoperiod

The duration from sowing to flowering is an important determinant of fibre yield potential in hemp, since maximum stem yield occurs shortly after flowering. As a short-day plant, daylength has a key influence on the timing of flowering in hemp. This paper reports on studies into the effect of photoperiod on the thermal time duration from sowing to flowering for 2 hemp cultivars, and develops parameters to enable simulation of post-emergent phenology in the hemp model described in the final paper of this series. The hemp model divides the post-emergent period into a vegetative phase that ends at floral initiation, aflower development phase (FDP) between flower initiation and appearance, and a short phase between first flower appearance and harvest maturity (male anthesis). The vegetative phase is further divided into a temperature-dependent basic vegetative phase (BVP) and a daylength-dependent photoperiod induced phase (PIP). For a short-day plant, the duration of PIP is assumed to be zero degree days at daylengths below a base or maximum optimum photoperiod (MOP). Daylengths in excess of the MOP lead to an increase in thermal time within PIP, the duration of which is determined by a genotype’s photoperiod sensitivity (PS). Two hemp genotypes, Kompolti and Futura 77, were exposed to 6 different photoperiod regimes ranging from 8 to 16 h in a growth chamber. Thermal time durations from emergence to flower initiation and first flower formation (harvest) were calculated from thermograph plots. The flowering responses for the 2 cultivars were typical for a short-day plant, with flowering occurring rapidly in daylengths less than about 14 h and with increasing delay at longer photoperiods. With the exception of a longer thermal time duration from flower formation to harvest maturity in the case of Kompolti, the 2 cultivars had similar values for the key phenology parameters. Respectively, for Futura and Kompolti: BVP was 383˚Cd and 390˚Cd, MOP was 14 h and 13.8 h, PS was 266˚Cd/h and 252˚Cd/h, and FDP was 76.8˚Cd and 80.2˚Cd.

Modelling photoperiod and temperature responses of flowering in quinoa ( Chenopodium quinoa Willd.)

Two modelling approaches were used to quantify photoperiod and temperature responses of time from emergence to visible flower buds in nine quinoa ( Chenopodium quinoa Willd.) cultivars. The first, non-interactive model, considers temperature and photoperiod responses as independent, and the threshold photoperiod, critical photoperiod, and base temperatures as constants. The second, interactive model, considers these attributes as variable, and allows for interaction between photoperiod and temperature responses. Controlled-environment experiments with a factorial combination of temperature and photoperiod provided information on responses, and data from field experiments were utilized in tests of the predictive capacity of the models. The two models were very similar in their goodness of fit and predictive capacity, but testing revealed that some assumptions about the interactive model were not fulfilled, whereas the non-interactive model is more consistent with the data. Both the models failed to predict dates of visible flower buds when average temperatures during the phase were >20°C; it is proposed that interaction between irradiance receipt and high temperature in controlled environments result in lower optimum temperatures there than in the field. Differences between field data and predicted values were eliminated when predictions were recalculated assuming no optimum for the temperature response. All nine cultivars examined are short-day plants. A juvenile sub-phase was observed in the six cultivars for which it was tested; and its duration was negatively associated with the latitude of origin of the lines ( R 2 = 0.9, p < 0.05). Photoperiod sensitivity was negatively associated with the latitude of origin of the lines ( R 2 = 0.55, p < 0.05) and positively associated with duration of the basic vegetative phase (minimal time between emergence and visible flower buds) ( R 2 = 0.55, p < 0.05) using the non-interactive model. Photoperiod and temperature response parameters were not significantly associated with the latitude of origin for the interactive model ( p > 0.05).

Rice crop duration and leaf appearance rate in a variable thermal environment. II. Comparison of genotypes

Rice crop duration in tropical-arid, irrigated environments, such as the Sahel, varies strongly among seasons and years. For rice double-cropping systems, cultivars are needed that have a stable duration under variable daylengths and temperatures. No efficient selection tools are currently available to screen for comparatively thermo- and photoperiod-insensitive cultivars, and little is known about the genetic diversity of rice in this respect. A previous study presented a model that disaggregates photothermal effects on rice phenology for the different crop development stages and the two main factors, daylength and temperature. The present study characterizes differences in the photothermal response of 18 rice lines for three major phases of their development, namely, germination, the appearance of early leaves, and the induction phase (IP) between the end of the basic vegetative phase (BVP) and panicle initiation (PI). A field experiment was conducted at Ndiaye in Senegal, using 11 staggered sowing dates at 15 day intervals. Three check cultivars were replicated four times per date, and the others were not replicated. Phenological observations included leaf tip appearance rates on a daily basis, and heading and flowering dates. Water and air temperatures were also monitored. The duration from seed soaking to the appearance of the first leaf depended linearly on water temperature, with a base temperature of about 8°C. No differences were observed among lines. The appearance rate of the first to the fourth leaf had an optimum temperature ( T opt) between 22°C and 25°C, with significant differences between lines. Lines with low T opt had high maximal leaf appearance rates during seedling stage. The quantitatively most important component of the seasonal variability of crop duration was IP, which depended on temperature and photoperiod. Photoperiodic and temperature effects were disaggregated using an empirically based model leaf appearance (LAP), which, by way of parametrization, helped quantify genotypic differences. The photothermal differences between lines were associated with adaptation to specific seasons. Lines such as IR13240-108-2-2-3, which is adapted to several seasons, were comparatively insensitive to photoperiod and temperature. That line also had a low T opt and a high Leaf Appearance. In conclusion, screening for temperature-insensitive leaf appearance rates may be promising for rice breeding for arid, irrigated environments. Selection for combined low thermal and photoperiod sensitivity, however, would be impractical on an experimental basis, and would therefore require genetic markers.

Rice crop duration and leaf appearance rate in a variable thermal environment.: I. Development of an empirically based model

Variable crop duration is a major constraint to rice double cropping in arid irrigated environments, such as the Sahel. Photoperiodism and low air and water temperatures during the cool season are the major causes of variability, and cultivars are needed whose photothermal response provides a more stable crop duration. A previous study analyzed cultivar photothermal constants on the basis of progress to flowering. The present study sought to identify, on the basis of leaf appearance rates, the phenological stages that are most sensitive photothermally, and to explore technical options to screen germplasm for stable crop duration. Three Oryza sativa, indica-type rice cultivars (Jaya, IKP, IR64) were sown in the field at 15-day intervals during the dry season of 1995 (11 sowing dates) and 1996 (5 sowing dates) in Ndiaye, Senegal, under full irrigation and wide spacing to reduce microclimate variability. Mean daily water temperature ( T w) varied from 13 to 35°C. After seed soaking, the rate at which the first leaf ( L 1) appeared was linearly related with T w, with a base temperature ( T base) of about 10°C. Appearance rates of the subsequent three leaves ( L 2– L 4) had a similar T base, and presented a distinct temperature optimum ( T opt) at about 23°C, beyond which development rates decreased. Errors were too large to determine differences among cultivars in thermal constants. No significant temperature response was observed for the leaf appearances between L 5 to the flag leaf ( L 12 to L 20). Crop duration to flowering varied by 45 (IR64) and 63 days (Jaya). These variations were associated with highly variable leaf numbers in all cultivars, including photoperiod-insensitive IKP. One-third of the variable duration was hypothesized to be due to a variable basic vegetative phase (BVP), caused by variable germination and leaf appearance rates, and two-thirds to variable duration of panicle induction after BVP. Water temperature was the main determinant of both sources of variability. A simulation model, describing these temperature and photoperiod effects on leaf number, growth duration and leaf appearance rates, was developed using the 1995 data, and satisfactorily validated with the 1996 data. The model was used to identify phenological-stage and cultivar-specific causes of variable crop duration.

Geographical Variation in Heading Photoperiodic Sensitivity of Echinochloa oryzicola Vasing.

Photoperiodic sensitivity in heading of Echinochloa oryzicola Vasing., an obligate weed in flooded rice, was determined with 20 strains originally collected in nine countries from 7°S to 44°N. Plants of the strains were grown under 12, 14 and 16-hr photoperiods at 25°C and the days to heading after sowing were recorded to classify them in photoperiod sensitivity by the duration of the basic vegetative phase (BVP) and photosensitive phase (PSP). The strains originally collected in the temperate region above 30°N were classified into those with either weak or strong sensitivity. A geographical cline was apparent among them and the strains from higher latitude exhibited heading earlier under 14-hr photoperiod. All of the seven strains from the subtropical and tropical regions below 30°N had a PSP of less than 30 days and were classified among those with photoperiod insensitivity. It is likely that this trait of E. oryzicola is advantageous for its wider adaptability in diverse rice cropping systems in these regions.

Photoperiodically Sensitive and Insensitive Phases of Preflowering Development in Rice

The time interval between sowing and flowering in rice (Oryza sativa L.) comprises three successive phases: a basic vegetative phase (BVP), a photoperiod‐sensitive phase (PSP), and a post‐PSP phase (PPP). The objective of this study was to estimate the length of the three phases in diverse rice cultivars to provide the basis for accurately predicting rice flowering dates. In greenhouse experiments, plants of 20 cultivars were transferred from short day (SD) (10 h d−1) long day (LD) (12.5 or 14 h d−1) or from LD to at various tim es aft er sowing. The duration of BVP varied greatly among cultivars ranging from 16.7 to 45.4 d. The indica cultivars exhibited an apparently longer BVP than the japonica cuitivars. The duration of PPP also varied among cultivars, from 18.0 to 37.2 d. For all cultivars, the length of the intervening PSP was shorter under SD conditions (3.6–24.1 d) than under LD conditions (10.5–76.5 d); the difference in PSP between SD and LD depended on the photoperiod sensitivity of the cultivar. The PSP under both SD and LD conditions did not necessarily end at panicle initiation (PI), but, on average, 4 to 5 d after PI. This study confirms the necessity to divide the entire preflowering period into the three phases for modeling purposes. Further studies are needed to elucidate the phenomenoinn some cultivars of a significant delay of flowering by early SD‐to‐LD transfers before PI.

Climatic determinants of irrigated rice performance in the Sahel — I. Photothermal and micro-climatic responses of flowering

In the Sahel, variable crop duration of irrigated rice poses serious timing problems for intensification of production. Photothermal effects on phenology have been studied to develop simulation tools for breeding and cropping systems research. Forty-nine genotypes were planted at monthly intervals in various rice-garden trials. Environment variability among seasons, sites and within the crop canopy was characterized to develop a field-based, photothermal model for flowering. Basic concepts were summation of heat units and a linear thermal response of development rate having upper (Topt) and lower (Tbase) response limits. Photoperiodism was modeled by a slope constant (CPP) and a basic vegetative phase (BVP). Photoperiodism and transplanting shock acted as modifiers of heat requirements (Tsum), thereby having greater effects on duration at low than at high temperatures. Tbase, Topt, Tsum, BVP and CPP were considered genotypic constants and calibrated by optimization. Daily input temperature for the model was the physiologically relevant temperature Tphys at the shoot apex. Tphys depended on apex submergence, water temperature and diurnal temperature patterns. Diurnal temperature segments exceeding the Tbase-Topt range were disregarded. Mean water temperature was below air temperature, particularly at high leaf area index and on dry days. Mean air temperature was closer to the minimum than to the maximum when amplitudes were high or days short. Minimum temperatures below 18°C at booting stage resulted in near total spikelet sterility and a specific delay in heading. The model was validated for a site thermally different from the site of calibration.

Genetic variation of the control of flowering in kenaf with emphasis on the ambiphotoperiodic response of cultivar Guatemala 4

Days to flower of six kenaf ( Hibiscus cannabinus) cultivars (Guatemala 4, Guatemala 51, Everglades 71, CPI 72226, CPI 72246 and CPI 72247) were examined over a range of environments and planting dates. The latitudes of the locations ranged from 17°15′S to 34°33′S. The response of flowering to planting date and location varied with the cultivar. Four of the cultivars (Everglades 71, CPI 72226, 72246, 72247) flowered at all locations and planting dates after the longest day of summer. A short day flowering model, whereby thermal time to flower increases with lengthening photoperiods up to a critical photoperiod which inhibited flowering, was fitted to the data. This model was able to explain more than 84% of the variation in the observed thermal time to flower for the four cultivars at a range of independent locations. There were genetic differences in the parameters such as critical photoperiod and basic vegetative phase among these cultivars. The remaining two cultivars (Guatemala 4 and Guatemala 51) flowered during the long days of summer at locations more southerly than 19°31′S. The short day response, described above, was not adequate to explain this flowering response at lower latitudes. An alternative response named an ambiphotoperiodic response, that has been recorded in other species, was recognised for these cultivars. A simulation model based on the ambiphotoperiodic response of these cultivars explained 92 and 99% of the variation respectively in thermal time to flower at all locations.

A simulation model of kenaf for assisting fibre industry planning in northern Australia. I. General introduction and phenological model

The feasibility of utilizing kenaf (Hibiscus cannabinus L.) as a fibre crop and potential source of paper pulp is being investigated. This paper is the first in a series which develops and validates a simulation model of kenaf, and applies it to assessing the potential for dryland production in regions of tropical Australia. The duration from sowing to flowering is an important determinant of fibre yield in kenaf. Accordingly, the effect of temperature and photoperiod on the phenology of kenaf was examined. Data were collated from sowing-date experiments on kenaf cultivars Guatemala 4 and Everglades 71 at six locations in tropical Australia, ranging in latitude from 12� 54'S. to 19� 32'S. Data from one site, Kununurra, W.A. (15� 39'S.), was used to develop a model which described the duration from sowing to flowering in kenaf based on four stages: (1) sowing to emergence; (2) emergence to the end of the basic vegetative phase (BVP); (3) a photoperiod-induced phase (PIP) which ends at floral initiation; and (4) a flower development phase (FDP). Both kenaf cultivars responded as qualitative short-day plants where flowering did not occur above a critical photoperiod of 12.9 h. Assuming a base photoperiod of 12.0 h, the thermal time required to complete the BVP for the two cultivars was similar. However, photoperiod sensitivity during PIP, and the thermal time required for FDP, were greater for Guatemala 4 than for Everglades 71. Validation of the model against independently observed data for both cultivars at other sites resulted in close predictions in the thermal time required for flowering. This phenological model for kenaf can be used to assess the effect of sowing date on phenology at different locations in tropical environments, and is a key component of a crop growth simulation model to assess the environmental constraints to productivity in these regions.

Photoperiod response characteristics of alfalfa (Medicago sativa L.) cultivars

Ten cultivars of alfalfa (Medicago sativa L.) were exposed to low temperatures for varying times and to a series of photoperiods in controlled environment cabinets to determine vernalization and photoperiod responses. There was a reduction in time of 2–16 d from emergence to flowering for vernalization treatments. Vernalization treatments of less than 1 d or greater than 28 d had similar numbers of days from emergence to flowering. The photoperiod response characteristics included the basic vegetative phase (BVP), which is a juvenile phase that must be completed before the plant is responsive to photoperiod, the maximal optimal photoperiod (MOP), the photoperiod beyond which flowering occurs in a constant number of days, and photoperiod sensitivity, the number of days delay in flowering per hour increase in photoperiod. Anik and Vernal comprised a group with the longest BVP, 29.0 d; a group of six cultivars had a mean BVP of 27.6 d, and Maris Kabul and Saranac had the shortest BVP, 25.6 d. The MOP was greatest for Beaver (19 h), shortest for Vernal (17.7 h) and intermediate for the remaining cultivars (18.3 h). Alfalfa was confirmed as a long-day plant, because the time to flowering decreased as photoperiod was lengthened. This results in negative photoperiod sensitivity values. Anik, with a photoperiod sensitivity of −20.50 d h−1, was different from the rest of the cultivars, with a photoperiod sensitivity ranging from −8.51 to −5.08 d h−1. These results demonstrate that alfalfa photoperiod response is consistent with the general response observed for annual long-day species of crop plants and suggest that legume breeders may be able to incorporate specific photoperiod characteristics into alfalfa cultivars in order to optimize harvest dates. Key words: Daylength, development, flowering

Temperature and Photoperiod Effects Mediated by the Sorghum Maturity Genes

A more complete understanding of the role of photoperiod and temperature in the genetic control of flowering in sorghum (Sorghum bicolor L. Moench) will allow breeders greater flexibility in making crosses among widely differing maturity types and will also contribute to the understanding of regional adaptation requirements. The objective of this study was to characterize the photoperiodic responses of 10 sorghum lines with all known combinations of the sorghum maturity genes Ma1, Ma2, and Ma3. Twenty growth chamber trials were conducted to examine photoperiods between 11 and 15 h at 0.5‐h intervals and to examine the influence of mean daily temperature as well as the range of day/night temperature. Compared with other genotypes, the recessive maR3 allele resulted in a reduction of 3.1 leaves in the basic vegetative phase (BVP‐Ieaf number under favorable photoperiods) and also eliminated photoperiod sensitivity. There was little influence of Ma2 or Ma3 genes on BVP. The dominant Ma1 allele conferred increased photoperiod sensitivity (4.5 leaves/h) compared to homozygous ma1, condition (1.4 leaves/h). There were no significant differences detected in the Maximum Optimal Photoperiod, which was about 12 h. The Ma2 gene was implicated in a photoperiod ✕ temperature interaction, although the exact role was not clear. The dominant allele of Ma3 increased the phyllochron (leaf development rate) by about 0.2 d/leaf. Thus, the developmental response of sorghum to photoperiod and temperature involves the complementation of effects from these maturity genes.

Vernalization and photoperiodic responses of selected chromosome substitution lines derived from 'Rescue', 'Cadet', and 'Cypress' wheats

The vernalization responses of 'Rescue', 'Cadet', 'Cypress', and selected chromosome substitution lines derived from these cultivars were measured by comparing days to ear emergence of vernalized and unvernalized plants under 24- and 16-h photoperiods. The genotype of 'Cadet' appears to be Vrn1Vrni1, vrn4vrn4, vrnxvrnx (where vrnx is an unidentified locus), and of 'Rescue' vrn1vrn1, Vrn3Vrn3, Vrn4Vrn4. 'Cypress' appears to carry Vrn4 and one or both of vrn1, and vrn3. Although some minor photoperiod responses were observed, no loci involved in major photoperiod responses were detected on chromosomes 5A, 4B, and 5B in 'Rescue' or 'Cadet' or on chromosome 5B in 'Cypress'. However, the duration of the basic vegetative phase appears to be controlled by a locus or loci on chromosome 5B, and chromosomes 5A and 4B may be involved in minor photoperiodic responses.Key words: Triticum aestivum, vernalization, photoperiod responses.

Varietal variations in basic vegetative phase and photosensitive phase among Japanese native cultivars of rice.

The days to heading of 93 native rice cultivars collected from various locations in Japan weret examined under a short-day (30°C phytotoron, in winter, natural day-length), and a long-day (a paddy field, in summer, natural day-length and temperature) condition. From the clata, varietal variations in the periods of basic vegetative phase (BVP) as shown, by days to heading in shortday condition and in photosensitive phase (PSP) as shown by the difference in days to heading between longday and shortday conclitions were surveyed, so as to learn about the mode of differentiation of early-maturing cultivars in Japan. The cultivars tested were divisible into two groups with a long (75-90r days) and a short (38-75 days) BVP. Among the cultivars with short BVPs, the distribution of PSP, varying from O to 72 days, was trimodal. Among those from areas north of 32N in latitude, PSP decreasecl with increasing latitude of collection site. But no cor-relation between PSP and latitude was found among cultivars from the southwest islands. The early-maturing cultivars (with short BVP and short PSP) distributed throughout Japan alt*nough they were infrequent. The pattern of distribution of native rice cultivars vvith varying BVP and PSP periods seems to reflect the variations in environrnental condition anc'i cropping system under which they have been cultivated so far.

VERNALIZATION AND PHOTOPERIOD RESPONSE CHARACTERISTICS OF A RECIPROCAL SUBSTITUTION SERIES OF RESCUE AND CADET HARD RED SPRING WHEAT

A reciprocal substitution series between Rescue and Cadet hard red spring wheats was used to identify chromosomal differences for vernalization response, basic vegetative phase, and photoperiod sensitivity. A greenhouse technique was used to provide estimates of these variables. Genes affecting vernalization were found on chromosomes 2A, 5A and 5B. Chromosomes 2A and 5B also affected the length of the basic vegetative phase. A gene on chromosome 3B affected photoperiod sensitivity.Key words: Day length, Triticum aestivum L., basic vegetative phase

The genetic control of basic vegetative phase in early-maturing native rice varieties of Japan.

既報(佐藤・林 1985)で述べた感光相(PSP)が短かく基本栄養生長期間(BVP)も短かい早生品種群に属する日本の在来イネ品種について，到穂日数の温度反応(感温性)および基本栄養生長期間(BVP)の品種間差異とその遺伝様式を調べた.供試した早生24品種は，生育期間中の温度が高いほど到穂日数が減少し温度反応を示したが，その品種間差は小さかった.早生品種群内には到穂日数がさらに短かいもの，やや長いものの2群が存在した.BVPの長さを支配するEf-1b遺伝子との相同性検定の結果，多くの早生品種はEf-1b遺伝子とこの作用を強める複数の変更遺伝子をもつと推定されたが，一部の品種はEf-1b以外の早生遺伝子をもつと考えられた.Ef-1b遺伝子は，北海道から鹿児島に至る日本の各地に分布した.これらのことから北部日本の早生品種は必ずしもイネの北進の過程で自然淘汰の結果分化したとは限らず，むしろイネの日本への伝播の初期にすでに分化していた早生品種が選抜されて北上したと考えるほうがよいと結論された.

Effect of Temperature on Rice Growth and Development under the Controlled Environment. - With special reference to effect of temperature on the length of the period of Basic Vegetative Phase and Various growth characteristic of rice plants -

Effect of Temperature on Rice Growth and Development under the Controlled Environment. - With special reference to effect of temperature on the length of the period of Basic Vegetative Phase and Various growth characteristic of rice plants -

Monogenic Control of Basic Vegetative Phase and Photoperiod-sensitive Phase in Rice

Lm which belongs to the linkage group I is one of the primary loci controlling heading time of cultivated rice and is also associated with photoperiod sensitivity. The effects of alleles of the Lm locus on two phases of the vegetative growth duration, the basic vegetative phase and the photoperiod-sensitive phase, were analysed by growing two isogenic lines with Lme and Lmu allelles under natural and controlled daylengths. Heterozygotes (Lme/Lmu) were maintained during 15 generations Lrom F1 through BC4F11 in the cross between the Malaysian cultivar Morak Sepilai and the Japanese cultivar Fujisaka 5, which was used as the recurrent parent for the successive four backcrosses. Fujisaka 5 and Morak Sepilai transmitted the early-maturing allele Lme and the late-maturing allele Lmu to their hybrid progenies, respectively.