Impact of field-scale nighttime air temperatures during kernel development on rice milling quality

Recent research has shown that elevated nighttime air temperatures (NTATs) may contribute to increased chalk and reduced milling quality. The objective of this study was to develop a method to quantify the effects of elevated NTATs on chalk formation and peak head rice yield (pHRY) in field-grown rice cultivars. To do so, 95th percentiles of NTAT frequencies (NT₉₅) occurring during reproductive (R) stages of Bengal, Jupiter, Cypress, LaGrue, Wells, and XL723 cultivars were correlated with chalk levels and pHRYs observed during the 2007 through 2009 harvest seasons. Chalk levels were strongly correlated with NT₉₅ during the R7 and R8 stages for all cultivars, except Bengal. Peak HRYs of Cypress, LaGrue, Wells, and XL723 were linearly and inversely related to NT₉₅ occurring during the R8 stage, while pHRYs of Bengal and Jupiter showed no significant correlations with this percentile at any R-stage. Although strong correlations of chalk levels and pHRYs with NT₉₅ were observed during the R8 stage of cultivar development, it is speculated that rice plants classified in this stage actually exhibit many kernels that lag in development and exist in the R6 and R7 grain-filling stages, where elevated NTATs are thought to have deleterious effects on chalk levels and milling quality.     

Genetic analyses of heading date of Japonica rice cultivars from Northeast China

Northeast regions of China (38–55°N latitude) play an important role in Japonica rice planting. Heading dates of 10 Japonica rice cultivars native to the Northeast of China were investigated and their sensitivities to photoperiod and temperature were analyzed. The results showed that these Japonica rice cultivars were insensitive to photoperiod but strongly sensitive to temperature, i.e. a high temperature can markedly shorten the heading date. Genetic analyses were conducted on these 10 cultivars using a set of heading date tester lines. All these Japonica cultivars carried a dominant early heading gene Ef-1, and most of these cultivars carried the photoperiod insensitivity allele e₁, and two types of alleles were presented at the Se-1 locus, including recessive photoperiod insensitivity gene Se-1^e and dominant strong photoperiod-sensitivity (PS) gene Se-1ⁿ. The PS of these cultivars carrying E₁ or Se-1ⁿ can be repressed or weakened by Ef-1 and the recessive allele hd2 they carried. These results provided a reasonable explanation to the adaptability of Japonica rice to the high latitude environment of the Northeast China, and could be useful for breeding new cultivars well adapted to the high latitude regions and expanding the rice cultivation range.     

Irrigated cotton in the tropical dry season. III: Impact of temperature,cultivar and sowing date on fibre quality

Depending on sowing month, temperatures during boll growth in the tropical dry season are potentially sub- or supra optimal for the fibre quality parameters length and strength. The aims of this research were to: (1) measure the effect of sowing date on the quality of fibre from cotton grown during the dry season as this was not known; (2) use the range in temperature created by varying sowing date in the dry season, to derive relationships with gin turnout, the fibre quality parameters length, strength and micronaire. Over three seasons, two Gossypium hirsutum (upland) cultivars and one Gossypium barbadense cultivar were sown from March to June at the Ord River (15.5°S), Western Australia. For the highest yielding sowing months of March and April, fibre length and strength were at or below market preference due to relatively low temperatures and solar radiation during early fibre development. Fibre micronaire achieved market preference at all sowing months due to favourable late season temperatures and radiation. It is likely that current G. barbadense cultivars will have short fibre when grown in the dry season. For fibre length and gin turnout quadratic responses (p < 0.05) to weighted minimum temperature were fitted for each cultivar, where the optimum minimum temperature was 18–20 and 16–17 °C, respectively. The cultivar differences in fibre properties observed here suggest that wider screening may identify G. hirsutum cultivars with suitable fibre length and strength in the dry season. It was demonstrated by weighting of temperatures for the contribution of the cohort of bolls pollinated each day; the variation in crop fibre quality and gin turnout in the field due to temperature can be predicted.     

Comparison of Physicochemical Properties of the Grains between Old- and New-Types of Rice Cultivars in Japan

Abstract

The physicochemical properties of the grains of 16 old- and 21 new-type rice cultivars in Japan were investigated in 1995 and 1996. Among the old- and new-type cultivars, we found a similar pattern of varietal differences in physicochemical properties in both years, and in both the fields with and without nitrogen fertilizer applied. Between the two types, no significant differences in the mean protein and amylose contents in the rice grain were observed. The old-type rice cultivars tended to be lower in mean maximum viscosity and breakdown values than the new- type cultivars, although the difference was not significant. Cooked rice of the old-type cultivars tended to be higher in mean hardness/adhesion ratio (H/-H) and hardness/adhesiveness ratio (H/A₃) than that of the new -type cultivars. The physicochemical properties which showed superior values in the standard partial regression coefficients against the taste of cooked rice were the protein content, breakdown value and H/-H. These, physico-chemical properties can be efficient indicators for evaluating the taste of cooked rice. The coefficient of parentage of each cultivar to cultivar Koshihikari showed tight negative correlations with amylose content, H/-H and H/A₃, and tight positive correlations with maximum viscosity and breakdown values. The coefficients showed a loose positive correlation with protein content. However, Sasanishiki, Domannaka, Chiyonishiki, Nakate shinsenbon and Rikuu 132 were superior in their physicochemical indicators, in spite of their small coefficients of parentage to Koshihikari. This suggests that a highly palatable cultivar that is widely different from Koshihikari can be developed by utilizing genetic resources with superior physicochemical indicators.     

Effect of soaking temperature on commingled rice properties

Parboiling involves soaking, steaming, and drying, and soaking is important in achieving desired parboiled rice properties. This study investigated the effects of soaking temperature and commingling on rice properties prior to steaming. Rough rice of four cultivars (Taggart, CL151, XL753, and CL XL745) and their combinations at 1:1 wt ratio were soaked at 65, 70 or 75 °C for 3 h, and dried. Both soaking temperature and difference in onset gelatinization temperature (T_o) of individual cultivars in commingled rice affected milling and physicochemical properties. The head brown rice yield was greater when the soaking temperature was below but close to the T_o for individual rice cultivars, but became difficult to predict for commingled rice. Commingled rice consisting of high T_o rice cultivars required higher soaking temperatures to reduce chalkiness during soaking. The color attributes of commingled rice was predominately affected by the cultivar that exhibited the most change. The gelatinization properties were governed by the low-T_o cultivar, whereas the pasting properties were more influenced by the high-T_o cultivar for the commingled rice. Therefore, using commingled rice with a wide range of gelatinization temperature as a feedstock may lead to inconsistent quality of parboiled rice.     

Introgression of Gene for Non-Pollen Type Thermo-Sensitive Genic Male Sterility to Thai Rice Cultivars

For the two-line hybrid rice system, pol en sterility is regulated by recessive gene that responds to temperature. The recessive gene controlling thermo-sensitive genetic male sterility （TGMS） is expressed when the plants are grown in conditions with higher or lower critical temperatures. To transfer tgms gene（s） control ing TGMS to Thai rice cultivars by backcross breeding method, a male sterile line was used as a donor parent while Thai rice cultivars ChaiNat 1, PathumThani 1, and SuphanBuri 1 were used as recurrent parents. The BC2F2 lines were developed from backcrossing and selfing. Moreover, the simple sequence repeat （SSR） markers were developed for identifying tgms gene and the linked marker was used for assisting selection in backcrossing. The identification lines were confirmed by pol en observation. The results showed the success of introgression of the tgms gene into Thai rice cultivars. These lines will be tested for combining ability and used as female parent in hybrid rice production in Thailand.     

Heat-tolerant rice cultivars retain grain appearance quality under free-air CO2 enrichment

Background

Heat-tolerant rice cultivars have been developed as a countermeasure to poor grain appearance quality under high temperatures. Recent studies showed that elevated CO₂ concentrations (E-[CO₂]) also reduce grain quality. To determine whether heat-tolerant cultivars also tolerate E-[CO₂], we conducted a free-air CO₂ enrichment (FACE) experiment with 12 rice cultivars differing in heat tolerance.

Results

The percentage of undamaged grains of five standard cultivars (Akitakomachi, Kinuhikari, Koshihikari, Matsuribare, Nipponbare) averaged 61.7% in the ambient [CO₂] (AMB) plot and 51.7% in the FACE plot, whereas that of heat-tolerant cultivars (Eminokizuna, Wa2398, Kanto 257, Toyama 80, Mineharuka, Kanto 259, Saikai 290) averaged 73.5% in AMB and 71.3% in FACE. This resulted in a significant [CO₂] by cultivar interaction. The percentage of white-base or white-back grains increased from 8.4% in AMB to 17.1% in FACE in the sensitive cultivars, but from only 2.1% in AMB to only 4.4% in FACE in the heat-tolerant cultivars.

Conclusion

Heat-tolerant cultivars retained their grain appearance quality at E-[CO₂] under present air temperatures. Further improvements in appearance quality under present conditions will be needed to achieve improvements under E-[CO₂], because E-[CO₂] will likely lower the threshold temperature for heat stress.     

Super Rice Cropping Will Enhance Rice Yield and Reduce CH4 Emission： A Case Study in Nanjing,China

A pot experiment was performed to learn the differences in plant productivity and OH4 emission between two rice cultivars, super rice variety Ningjing 1 and traditional variety Zhendao 11, which were currently commercially appUed in Nanjing, China. Similar seasonal changes of CH4 emission fluxes and soil solution CH4 contents were found between the tested cultivars. Although there was no significant difference in plant biomass production between the cultivars, the grain yield of Ningjing 1 was significantly higher by 35.0% （P 〈 0.05） than that of Zhendao 11, whereas the total CH4 emission from Ningjing 1 was 35.2% lower （P 〈 0.05）. The main difference in the amounts of CH4 emission between the cultivars occurred in the period from the tillering stage to the heading stage. The biomass-scaled and yield-scaled CH4 emissions were respectively 3.8 and 5.2 mg/g for Ningjing 1, significantly lower than those for Zhendao 11 （7.4 and 12.8 mg/g, respectively）. According to the relationships between the plant growth characteristics and the CH4 emission, a stronger root system contributed mainly to the lower CH4 emission of Ningjing 1, as compared with Zhendao 11. Our results demonstrated that super rice has advantages not only in grain productivity but also in CH4 emission mitigation. Further expansion of super rice cropping will enhance rice yield and reduce greenhouse gas emission in China.     

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.     

Identification of novel glutelin subunits and a comparison of glutelin composition between japonica and indica rice (Oryza sativa L.)

Glutelin, a major protein in rice grains, is encoded by a multigene family. However, its protein composition is not well characterised. Here, we identified and characterised two novel glutelin subunits, GluBX and GluC. The individual glutelin subunits of japonica cv. Nipponbare and indica cv. 93-11 rice were analysed using 2-dimensional gel electrophoresis, LC–MS/MS, and Western blotting. Comparison of the glutelin profiles between three japonica and three indica cultivars indicated two distinct subunits (GluA-1 and GluA-3 isomers) and a distinction in the subunit composition (notably GluA-3 and Lys-rich GluB-1 components) of these two subspecies. Sequence alignment revealed different nutritional (Lys residues) and functional (Cys residues) characteristics between the type-A and type-B glutelin subfamilies. We also analysed amino acid and total protein contents of the grains in thirty-five cultivars, and we demonstrated that the Lys-rich glutelin composition of indica cultivars is superior to that of japonica cultivars. The Lys-rich and Cys-poor GluBX subunit is a native protein and is a high nutritional protein in grains. Our combined approaches for the identification of glutelin subunits have revealed the nutritional characteristics of individual subunits in rice, and this knowledge will provide new insights for improving grain quality during rice breeding.     

Low temperature-induced sterility in rice: Evidence for the effects of temperature before panicle initiation

Spikelet sterility of rice (Oryza sativa L.) results from low temperatures during panicle development. However, this temperature alone cannot fully explain the fluctuations in sterility observed in the field, since the susceptibility of rice plants to low temperature often changes according to its physiological status during sensitive stages. In the present study, we examined whether temperatures before the panicle initiation stage (PI) influence the plant's susceptibility to sterility during panicle development. To test this, we conducted a 2-year pot study and an analysis of field data using a model of cooling degree-days (CDD). In the pot study, the air temperature (T_a) and water temperature (T_w) were controlled independently for 3 weeks during the vegetative growth stage before PI. After PI, the plants were submerged in a cool water bath at a critical temperature of 19.5 °C to induce floral sterility. We found that low T_w during vegetative growth significantly increased the sterility. Low T_a during vegetative growth also significantly increased the sterility, but this effect was diminished by warm T_w even at low T_a. There was a close and negative correlation between sterility and T_w during vegetative growth. In the analysis of field data, we introduced CDD using temperatures below a threshold level of 20 °C to represent the magnitude of the exposure to low temperature from PI to the heading stage. Data of T_a was used for this analysis because data of T_w was scare. The CDD model was applied to 77 independent data sets collected at nine Agricultural Research Centers during four typical cool summers (1980, 1988, 1993, and 2003) in northern Japan. Year-to-year variations in sterility at one site were roughly accounted for by the variations in CDD, but large deviations were observed among the years. The deviations were related to T_a averaged over the 30-day period before PI. For a similar level of CDD, the lower the T_a before PI, the greater the sterility. Similar deviations were observed in the between-site relationships between sterility and CDD, and these deviations were related with the T_a before PI. These results suggest that temperatures before PI, and especially T_w, change the susceptibility of a rice plant to low temperatures during panicle development.     

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 (L₁) appeared was linearly related with T_w, with a base temperature (T_base) of about 10°C. Appearance rates of the subsequent three leaves (L₂–L₄) 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 L₅ to the flag leaf (L₁₂ to L₂₀). 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.     

Genotypic Diversity of Cross-Tolerance to Oxidative and Drought Stresses in Rice Seedlings Evaluated by the Maximum Quantum Yield of Photosystem II and Membrane Stability

Abstract

The genotypic variation of oxidative damage under oxidative and drought stresses was evaluated for a total of 67 rice cultivars consisting of 61 from the rice diversity research set of germplasm and 6 high-yielding varieties. The maximum quantum yield of photosystem II (F_v/F_m) and the membrane stability index (MSI) were measured to assess the oxidative damage induced by methyl viologen (MV) for oxidative stress and polyethylene glycol (PEG) for drought stress. Considerable variations in F_v/F_m and MSI among the cultivars in MV treatment indicated the existence of genotypic diversity in the susceptibility to oxidative damage. The weak relationships of F_v/F_m and MSI between MV and PEG treatment suggested that mechanisms other than oxidative stress tolerance affected the genotypic diversity of oxidative damage in PEG treatment. We used principal component analysis to quantify the cross-tolerance to oxidative damage under MV and PEG treatments: cross-tolerance was higher in cultivars in the japonica group than in the indica groups and higher in the improved cultivars than in the landraces. These results suggest that genotypic diversity of cross-tolerance is related to adaptation to the ecosystem where the genotypes originated and that the characteristics responsible for the tolerance to oxidative damage have been selected during breeding for improved grain yield.     

高温胁迫下水稻产量的高光谱估测研究

为了定量分析不同生育期冠层反射光谱参数与水稻产量及产量构成要素的相互关系,确定能够准确预测高温胁迫下水稻籽粒产量的敏感光谱参数,通过盆栽试验,测定了孕穗期4种温度胁迫处理后的2个水稻品种不同生育期冠层高光谱反射率以及成熟后的理论产量、实际产量、穗数、每穗粒数、千粒重、穗长、穗干质量和结实率。结果表明,相对于蜡熟期的光谱参数,抽穗期和灌浆期的光谱参数与理论产量、实际产量、穗数、每穗粒数、千粒重、穗长、穗干质量以及结实率的相关性都较高,均达到显著水平。此两个时期可以作为预测水稻产量的关键时期。其中,差值植被指数DVI[810,A(450,560,680)]、垂直植被指数PVI(810,680)、红边幅值Dλred和红边峰值面积可以同时预测成熟水稻的理论产量和实际产量。而差值植被指数DVI(810,450)和DVI(810,560)、垂直植被指数PVI(810,680)和Dλred可以同时预测成熟水稻的穗数、每穗粒数和千粒重。相对于灌浆期的模型,抽穗期的模型能较可靠地监测水稻产量。     

Research Progress on Heat Stress of Rice at Flowering Stage

Global warming has caused frequent occurrence of heat stress at the flowering stage of single-season rice in the Yangtze River region of China, which results in declines of spikelet fertility and yield in rice. Rice flowering stage is the most sensitive period to high temperatures, and therefore, the key for heat stress happening is the flowering stage coinciding with high temperature, which causes spikelet fertility decreasing in heat-sensitive varieties, and is the major factor for heat injury differences among various rice planting regions. With the development of rice breeding, temperature indexes for heat stress has been converted from daily maximum temperature of 35 °C to 38 °C with the stress duration of more than 3 d. During the flowering stage, anther dehiscence inhibition and low pollen shedding onto the stigma are two main reasons for spikelet fertility reduction under high temperatures. At panicle initiation stage, high temperatures aggravate spikelet degeneration, and destroy floral organ development. Various types of rice varieties coexist in production, and indica-japonica hybrid rice demonstrates the highest heat resistance in general, followed by indica and japonica rice varieties. In production, avoiding high temperature is the main strategy of preventing heat stress, and planting suitable cultivars and adjustment of sowing date are the most effective measures. Irrigation is an effective real-time cultivation measure to decline the canopy temperature during the rice flowering stage. We suggested that further study should be focused on exploring heat injury differences among different rice variety types, and innovating rice-planting methods according to planting system changes in rice planting regions with extreme heat stress. Meanwhile, high temperature monitor and warning systems should be improved to achieve optimal heat stress management efficiencies.     

Performance of diverse upland rice cultivars in low and high soil fertility conditions in West Africa

Traditional tropical japonica (Oryza sativa) and Oryza glaberrima cultivars are typically grown in low-input, subsistence production systems in the uplands of West Africa by resource-poor farmers. In these systems, low soil fertility (LF), which is generally associated with lower organic carbon content, and N and P availability, is one of the major constraints to rice productivity. Thus, cultivars adapted to LF are needed for the food security of farmers, who would otherwise be solely reliant on nutrient inputs to increase productivity. This study evaluated the performance of six diverse cultivars grown in LF and high soil fertility (HF) conditions with supplemental irrigation over two seasons. Average grain yield across all cultivars in LF was 54% of that in HF (156 vs. 340 g m⁻²). Three improved indica rice cultivars and CG 14 (O. glaberrima) out-yielded Morobérékan (traditional tropical japonica) and WAB450-IBP-38-HB (progeny from interspecific hybridization of tropical japonica and O. glaberrima) in LF (181 vs. 105 g m⁻² on average). The high grain yield in LF was the result of large spikelet number m⁻² due to superior tillering ability and high harvest index rather than biomass production. The high-yielding cultivars in LF consistently had lower leaf chlorophyll content and higher specific leaf area during the period from the early vegetative stage through the reproductive stage. Among them, two indica cultivars (B6144F-MR-6-0-0 and IR 55423-01) were also high yielding in HF. The use of improved indica cultivars adapted to LF, but also with input-responsiveness, appears to offer an attractive and economical approach to improving upland rice productivity and widening genetic diversity in this region.     

Rhizosphere Aeration Improves Nitrogen Transformation in Soil,and Nitrogen Absorption and Accumulation in Rice Plants

Two rice cultivars (Xiushui 09 and Chunyou 84) were used to evaluate the effects of various soil oxygen (O₂) conditions on soil nitrogen (N) transformation, absorption and accumulation in rice plants. The treatments were continuous flooding (CF), continuous flooding and aeration (CFA), and alternate wetting and drying (AWD). The results showed that the AWD and CFA treatments improved soil N transformation, rice growth, and N absorption and accumulation. Soil NO₃^– content, nitrification activity and ammonia-oxidising bacteria abundance, leaf area, nitrate reductase activity, and N absorption and accumulation in rice all increased in both cultivars. However, soil microbial biomass carbon and pH did not significantly change during the whole period of rice growth. Correlation analysis revealed a significant positive correlation between the nitrification activity and ammonia-oxidising bacteria abundance, and both of them significantly increased as the total N accumulation in rice increased. Our results indicated that improved soil O₂ conditions led to changing soil N cycling and contributed to increases in N absorption and accumulation by rice in paddy fields.     

Cardinal temperatures variability within a tropical japonica rice diversity panel

Air temperature is one of the most critical climatic factors controlling rice growth, development, and production in current and future climatic scenarii predicting increasingly frequent situations of extreme and/or fluctuating temperatures. With its large spectrum of geographical origins and cropping areas, one can credit tropical japonica rice subspecies of a probable genetic diversity of its response to air temperature, which is of major interest for the breeding of better adapted rice varieties. A panel of 195 rice accessions (175 japonica plus 20 reference cultivars) was studied in controlled environment to estimate cardinal (base, optimum, and maximum) temperatures based on the monitoring of the elongation rate (LERmax) of the sixth leaf on the main stem in response to six fixed thermal treatments ranging from 16 to 35 °C. A dedicated statistical framework was elaborated for estimating LERmax, cardinal temperature and related uncertainties. Developed statistical framework enhanced the precision of cardinal temperatures estimated compared to previously reported methods, especially for base temperature. Maximum temperature was trickier to estimate and will require further studies. A significant genotypic variability for base and optimal temperature was pointed out, suggesting tropical japonica subspecies represents a relevant genetic pool to breed for rice genotypes adapted to various thermal situations. These results also suggested that using genotype-dependent cardinal temperature values should enhance the way crop growth models account for genotype?×?environment interactions hence their predictive value in current and future climatic conditions.     

Comparison of predictions of baking volume using large deformation rheological properties

Three large deformation rheological tests, the Kieffer dough extensibility system, the D/R dough inflation system and the 2 g mixograph test, were carried out on doughs made from a large number of winter wheat lines and cultivars grown in Poland. These lines and cultivars represented a broad spread in baking performance in order to assess their suitability as predictors of baking volume. The parameters most closely associated with baking volume were strain hardening index, bubble failure strain, and mixograph bandwidth at 10 min. Simple correlations with baking volume indicate that bubble failure strain and strain hardening index give the highest correlations, whilst the use of best subsets regression, which selects the best combination of parameters, gave increased correlations with R²=0.865 for dough inflation parameters, R²=0.842 for Kieffer parameters and R²=0.760 for mixograph parameters.     

Thermal time requirements for the development of green pea (Pisum sativum L.)

The purpose of this investigation was to quantify, for crop modelling purposes, temperature response functions of various developmental stages of several green pea (Pisum sativum L.) cultivars. Cardinal temperatures, namely the base (T_b), optimum (T_m) and maximum temperature (T_x), for various developmental stages, were also determined. Below T_b and above T_x, development rates were zero and at T_m development proceeded at the maximum rate. Developmental stages were monitored in both controlled environments and field trials. No significant differences were found between cultivars regarding optimum temperatures for 50% germination. A T_b of 0°C, T_m of 29°C and T_x of 40°C for germination represents a good summary of the results. For the emergence, vegetative and reproductive stages, a T_b of 3°C, T_m of 28°C and T_x value of 38°C are appropriate. In the field, the crops required approximately 100°C d for emergence, 260°C d to reach the four-leaf stage, 380°C d till the seven-leaf stage and 730°C d to reach the 14-leaf stage. Thermal time requirements from sowing to flowering ranged from 770°C d to 890°C d for different cultivars, and from sowing to maturity (tenderometer reading of 130) from 1370°C d to 1450°C d.