Identification and overcoming barriers between Brassica rapa L. em. Metzg. and B. nigra (L.) Koch crosses for the resynthesis of B. juncea (L.) Czern.

Brassica juncea (2n = 36, AABB) is an amphidiploid derived from its diploid progenitor species B. rapa (2n = 20, AA) and B. nigra (2n = 16, BB). Resynthesis of B. juncea by exploiting the wider gene pool of the present day diploids offers a powerful tool for obtaining novel genetic variation. Hybridization between the two species is difficult because of the presence of crossability barriers. Barriers to hybridization were identified using Aniline Blue Fluorescence (ABF) method. Crosses were classified as having pre- or post-fertilization barriers based on whether less than or more than one per cent ovules showed pollen tube entry. Of the 23 crosses studied, seven crosses all with B. rapa as the female parent showed pre-fertilization barriers. Only 0 to 0.3 per cent ovules were fertilized in these crosses. The remaining 16 crosses, four with B. rapa as the female parent and 12 with B. nigra as the female parent, showed post-fertilization barriers. In crosses with pre-fertilization barriers use of bud pollination and stump pollination ensured or increased fertilization. These two simple techniques were used in combination with ovary-ovule culture to ensure recovery of hybrids. In crosses with post-fertilization barriers, ovary-ovule culture alone helped to obtain hybrids. Hybrids were obtained at higher frequency with the use of direct ovule culture compared to ovary-ovule culture. The F₁ plants obtained in vitro were multiplied on MS medium + 2 mg/l Kn + 0.2 mg/l IAA. These F₁ plants were confirmed as true hybrids through morphology, leaf isozymes and cytology. In all 17 hybrids were obtained of which three were amphidiploids.     

A new yam bean (Pachyrhizus spp.) interspecific hybrid

The yam bean (Pachyrhizus spp.) is a legume tuber / root crop locally grown in Central America, South America and Asia. The tuber is usually consumed raw for its refreshing taste and high moisture content. A recently found P. tuberosus type from a small ecogeographic region in the tropical lowlands of Peru has a high tuber dry matter content and this so-called Chuin-Type is consumed like manioc. This study was conducted to determine the possibility to use the Chuin-Type as a source to incorporate high dry matter into the remaining yam bean gene pool. Three P. tuberosus (Chuin) accessions were crossed with 15 P. ahipa accessions from the Andean highlands resulting in six successful interspecific hybridisations. Successful crosses were confirmed by morphological and agronomical traits as well as multivariate statistics. All hybrid plants were fertile and vigorous. Owing to the fertility and vigour of interspecific hybrids it is assumed that a hybrid between P. tuberosus and P. ahipa might already evolved in the area of origin and that interspecific hybridisation is appropriate to improve the tuber dry matter content in the yam bean which might give the crop new forms of food and processing use.     

Agricultural potential of Mediterranean grain and forage legumes: Key differences between and within Vicia species in terms of phenology, yield, and agronomy give insight into plant adaptation to semi-arid environments

In order to identify key adaptive traits which affect productivity in Mediterranean grain and forage legumes and simultaneously determine the agricultural potential of a wide range of Vicia species, germplasm collected from the wild throughout the eastern Mediterranean was grown under semi-arid conditions in Tel Hadya, Syria (313 mm growing season rainfall). These included species currently in use in Mediterranean agriculture, such as V. sativa L., as well as those more widely used in the past-such as V. ervilia L., but also a broad selection from Section Narbonensis (B. Fedtsch. ex Radzhi) Maxted, including V. narbonensis L, V. johannis Tamamsch., V. hyaeniscyamus Mout., V. serratifolia Jacq., and V. kalakhensis Khattab et al. V. faba, a near relative of the taxa in Section Narbonensis, was included as a domesticated control. Where applicable, a representative range of subspecies was used. Accessions were chosen from a wide range of habitats in terms of latitude (31.02–40.72 decimal^o), longitude (27.1–43.17 decimal^o), altitude (20–1510 m), rainfall (180–1700 mm/yr) and soil depth (5–50 cm) in order to maximise diversity within species. Agricultural potential was determined by measuring seed, hay and biological yield, as well as agronomic traits such as harvest index, standing crop height, and seed size. The comparative influence of phenology and key agronomic traits such as plant habit and seed size on productivity varied tremendously between species, depending on their reproductive strategies. In V. sativa and V. ervilia, the smaller seed species which rely on long vegetative phases and growing seasons to accumulate sufficient biomass to set seed, and in which there was comparatively little agronomic variation, phenology had a large impact on yield. In early emerging taxa such as V. ervilia and V. s. subsp. sativa, with built-in long vegetative phases and growing seasons, seed yield was negatively correlated with flower ing (r = –0.86 to –0.88), whereas the opposite was the case for later emerging taxa such as V. s. subsp. nigra (L.) Ehrh. (r = 0.95). Within V. narbonensis and relatives, the larger seeded Vicia species which rely on more conservative reproductive strategies where high seedling vigour associated with large seeds enables the species to enter reproductive phases relatively early, phenology had a much smaller impact on yield than did variation of key traits such as seed weight, plant habit and pod shattering. Among the undomesticated germplasm harvest indices ranged from 0.09–0.31, hay yields from 0.1–3.4 t/ha, seed yield from 0–2.0 t/ha, and dry matter at maturity from 1.6–6.5 t/ha. Sub-specific taxonomy was crucial in determining agronomic potential. V. narbonensis var. aegyptiaca Kornhuber ex Asch. et Schweinf. showed the most potential, combining an upright habit, large seeds (212 mg) and tendency to retain intact pods after maturity, with the highest yield, harvest index and crop height of all the wild Vicia species. V. sativa subsp. sativa, V. ervilia and V. narbonensis var. narbonensis were less productive, but still showed agricultural potential. The smaller seeded V. narbonensis, var. affinis, var. jordanica H. Schäf. and var. salmonea (Mout.) H. Schäf., and their close relatives V. johannis, V. hyaeniscyamus, V. serratifolia and V. kalakhensis have little to offer Mediterranean agriculture on the basis of poor agronomy.     

Polymorphism of high molecular weight glutenin subunits in three species of Aegilops

A collection of 136 accessions of Aegilops umbellulata (39), Ae. comosa (75) and Ae. markgrafii (22) was analysed for high-molecular-weight (HMW) glutenin subunits composition. The homogeneity of the accessions was studied and 55.1% of the collection was homogeneous for HMW glutenin subunits (29 Ae. umbellulata, 33 Ae. comosa and 14 Ae. markgrafii). The HMW glutenin subunits of Ae. umbellulata are encoded by the Glu-U1 locus; in Ae. comosa results showed that this proteins are encoded at the 1M chromosome, and the locus was named Glu-M1. In Ae. markgrafii it was assumed that HMW glutenin subunits were encoded by an homoeologous locus and it was named Glu-C1. All the accessions of Ae. umbellulata and Ae. markgrafii expressed both, x-type and y-type subunits. Among the Ae. comosa accessions, only one expressed an x-type subunit alone. All the accessions of Ae. umbellulata and some of Ae. comosa had x-type glutenins of higher molecular weights than those commonly present in bread wheat. A total of 8 alleles were detected at the Glu-U1 locus, 11 at the Glu-M1 and 4 at the Glu-C1. The new HMW glutenin variation found in this work suggests their possible utilisation in breeding for wheat quality.     

Genetic diversity among <Emphasis Type="Italic">Jatropha</Emphasis> species as revealed by RAPD markers

The genus Jatropha is native of tropical America with more than 200 species that are widely distributed in tropics with a promise for use as an oil crop for biodiesel. This investigation was carried out to assess the genetic diversity of 12 Jatropha species based on random amplified polymorphic DNA markers. From 26 random primers used, 18 primers gave reproducible amplification banding patterns of 112 polymorphic bands out of 134 bands scored accounting for 80.2% polymorphism across the genotypes. Three primers viz., OPA 4, OPF 11, and OPD 14 generated 100% polymorphic patterns. The polymorphic information content was highest for the primer OPD 14 (0.50) followed by the primers OPF 11 and OPAD 11 (0.48). Jaccard’s coefficient of similarity varied from 0.00 to 0.85, indicative of high level of genetic variation among the genotypes studied. UPGMA cluster analysis indicated three distinct clusters, one comprising all accessions of J. curcas L., while second included six species viz., J. ramanadensis Ramam., J. gossypiifolia L., J. podagrica Hook., J. tanjorensis J. L. Ellis et Saroja J. villosa Wight and J. integerrima Jacq. J. glandulifera Roxb. remained distinct and formed third cluster indicating its higher genetic distinctness from other species. The overall grouping pattern of clustering corresponds well with principal component analysis confirming patterns of genetic diversity observed among the species. The result provides valid guidelines for collection, conservation and characterization of Jatropha genetic resources.     

Diversity of native rice (Oryza Poaceae:) species of Costa Rica

We found several populations of wild Oryza species in the lowlands of Costa Rica. The plants showed extensive morphological variation, suggesting the presence of several species. In the morphologic study, 33 traits were scored for plants of all the species. A principal component analysis revealed the significant morphological separation of the different species. The analyses indicated that there are three species, O. grandi­glumis, O. latifolia and O. glumaepatula. Two putative hybrid types were found, both significantly differing in their morphology from the known species and intermediate at several traits. O. grandi­glumis is a new record for Costa Rican flora. Its main population is located in Caño Negro Wildlife Refuge, Los Chiles, Alajuela. O. latifolia is distributed throughout the lowlands of the country and the plants of the Atlantic slope are significantly bigger in general habit than those of the Guanacaste area. During this study a population of O. glumaepatula of hundreds of thousands of plants was discovered in the Medio Queso River wetland, Los Chiles, Alajuela. This population is the most important source of genes for cultivar's improvement from the primary gene pool of rice in Costa Rica. The small ligule and the wide flag leaf characteristic of the two CCDD species separated them from the AA diploid O. glumaepatula. Seed size, ligule size, number of branches in the panicle, plant height and sterile lemma length are all bigger in O. grandi­glumis, and influenced the second factor that separated the CCDD species in two discrete clusters. The species found offer great possibilities for the improvement of rice cultivars and they should be thoroughly studied and appropriately protected.     

Characterization of Intergeneric Hybrids of Saccharum using Molecular Markers

The potential use of RAPD markers in identifying genuine intergeneric hybrids of Saccharum was examined in 12 hybrids of Saccharum with Erianthus spp., Sorghum bicolor and Zea mays. In the three groups of hybrids examined, RAPD markers could precisely identify the true hybrids of Saccharum officinarum × Sorghum bicolor and Saccharum officinarum × Zea mays. Though Erianthus had a very distinct RAPD profile and as many as 107 Erianthus-specific bands were identified, a decisive profile that can identify all the hybrids could not be obtained. The strong molecular differentiation between S.officinarum and Erianthus was not adequately resolved in the RAPD profiles of their hybrid progenies which suggest that more refined molecular techniques will be required for the characterization of Saccharum–Erianthus hybrids.     

Production of Intergeneric Hybrids Between <Emphasis Type="Italic">Sinapis alba</Emphasis> and <Emphasis Type="Italic">Brassica carinata</Emphasis>

Reciprocal crosses were made between Brassica carinata and its related species Sinapis alba. Pollen germination studies indicated the presence post-fertilization barriers in both ways. Sequential ovary–ovule culture helped to realize the intergeneric hybrids from the cross S. alba × B. carinata. The F₁ obtained was confirmed as a hybrid based on morphology, cytology and isozyme studies. The hybrid was backcrossed to its male parent and obtained BC₁ seeds, which were used to raise BC₁ generation. The BC₁ generation plants were further backcrossed to B. carinata in order to develop alloplasmic lines.     

Inheritance of Seed Shattering in Lolium temulentum and L. persicum Hybrids

Lolium temulentum and L. persicum are non-crop species found in wheat and barley fields. L. temulentum has non-shattering seeds like the associated grain crops, whereas L. persicum seeds shatter after maturity. We analyzed the inheritance mode of shattering tendency by comparing the F₂ of L. temulentum and L. persicum hybrids. The selfed progeny of L. temulentum and L. persicum exhibited typical non-shattering (1.6% shattering) and shattering phenotypes (70.8%), respectively. F₁ hybrids of L. temulentum×L. persicum and its reciprocals were of the shattering phenotype (71.4% and 63.8%, respectively), indicating that shattering is dominant to non-shattering. When the phenotype ratio was assumed to be 15 shattering: 1 non-shattering, the χ² value for F₂ segregation was not significant at the 5% level, and the reciprocal effect was not detected. This indicates that the non-shattering tendency is controlled by two recessive genes. The two-gene inheritance model of shattering tendency suggests that harvest is the selector for seed shattering in cultivated fields, thus the alternative tendency for non-shattering seeds of L. temulentum or shattering of L. persicum would be better adapted to cultivated fields.     

Transpiration and canopy conductance at two slope positions in a Japanese cedar forest watershed

Plant–soil system patterns and processes along a slope are among the greatest causes of uncertainty in estimating watershed-scale transpiration (E). Tree-to-tree and radial variations in xylem sap flux density (F_d), in addition to tree biometrics, were measured over a 2-year period (2005–2006) in two slope stand positions. The areas of interest consisted of an upper slope plot (UP) and a lower slope plot (LP) in a Japanese cedar (Cryptomeria japonica D. Don) forest watershed and the environmental controls of stand E for each plot were compared. Canopy stand E (E_C) and canopy stomatal conductance (G_C) in the UP were less than those in the LP during the growing season, while those in the UP were greater than those in the LP over winter. In addition, mean stand F_d (J_S) in the UP was greater than that in the LP over winter, but J_S values were similar in the UP and LP except in the winter, which allows us to extrapolate watershed-scale E based on J_S estimated from F_d measurements of a partial stand in the watershed. However, this relationship contains a bias and differed between 2005 and 2006. Although there were significant differences in soil moisture conditions between the UP and LP in both years, a systematic relationship between the similarity in J_S and soil moisture conditions was not found. The bias was due to a tendency for J_S in the LP to be greater than that in the UP in 2006. This tendency was amplified because J_S in the LP was greater than that in the UP around an atmospheric humidity deficit (D) of 1–1.5 kPa and frequencies of this D range were higher in 2006 than in 2005. The greater J_S in the LP at D  1–1.5 kPa could be explained by the difference in the response of G_C to D between the UP and LP. Our results suggest this to be the cause of the similarity in J_S values for the UP and LP and for the occasional abortion of its similarity. However, even when the bias or the occasional deviation is disregarded, the error in estimating stand E from a partial stand is so small that it is comparable to an F_d measurement error. For example, the error when using only the LP was 6.6% for stand E.     

The 5S rRNA gene diversity in the genus <Emphasis Type="Italic">Secale</Emphasis> and determination of its closest haplomes

We analyzed 127 rDNA sequences (5S DNA units) obtained from 23 seed accession samples from more or less 10 taxa in wild and cultivated rye, genus Secale L. The sequences fell into two known groups, here assigned to two unit classes, viz. long R1 and short R1 (designations to reflect on R haplome of rye). The different taxa could not be fully differentiated based on the 5S DNA units. We searched for 5S DNA sequences from known unit classes most closely similar to the long R1 and the short R1. One set with the long R1 unit class contained sequences of the long P1 unit class from Agropyron (P haplome) and from Kengyilia (StYP haplome), long J1 from Thinopyrum (J haplome), whereas the set with the short R1 included the long S1 from Pseudoroegneria (St haplome) and Kengyilia (StYP haplome), the short J1 from Thinopyrum (J haplome) and the short V1 from Dasypyrum (V haplome). Each of the two sets was analyzed separately by maximum likelihood (ML) phylogenetic analysis from which we were able to infer that the 5S DNA units of Secale differentiated in a non-clock fashion and followed the HKY substitution model in the gene tree with the long R1 unit class and the HKY + G in the gene tree with the short R1 unit class. A complementary Bayesian analysis yielded identical tree topologies to the ML ones for each of the two sequence sets. In the tree with the long R1 units the long P1 and long J1 unit classes were closest to the long R1 unit class, whereas in the tree with the short R1 units the long S1 and short J1 unit classes were closest to the short R1 unit class, indicating possibly a close relationship between the St, J and R haplomes.     

Conservation of the genetic variation of Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L.) in synthetic hexaploid wheats (T. turgidum L. s.lat. x T. tauschii; 2n=6x=42, AABBDD) and its potential utilization for wheat improvement

Triticum tauschii (Coss.) Schmalh. (Aegilops squarrosa auct. non L., 2n=2x=14, DD genome) with its diverse range of accessions and distribution provides a unique opportunity for exploiting novel genetic variability for wheat (T. aestivum L.) improvement associated with biotic/abiotic stress factors. From our working collection of 490 T. tauschii accessions we have so far produced 430 different synthetic hexaploids (2n=6x=42, AABBDD) resulting from the chromosome doubling of Triticum turgidum L. s. lat. x T. tauschii F₁ hybrids (each synthetic involving a different T. tauschii accession). We present here our results on hybrid production, plantlet regeneration, cytology, colchicine induced doubling of the 2n=3x=21 chromosome F1 hybrids, seed increase of the doubled progeny and screening for a biotic stress; Cochliobolus sativus Ito and Kuribay (syn. Helminthosporium sativum Pamm. King and Bakke); of 250 of these synthetic hexaploid (2n=6x=42) amphiploids. Application of the direct crossing methodology involving susceptible T. aestivum cultivars with resistant T. tauschii accessions is also alluded to.     

Effect of nitrogen application on the A N value of soil

Pot experiments were conducted with two soils, from Rottenhaus and Seibersdorf in Austria, to ascertain whether the rate of fertilizer N application and the test crop would influence the amount of N available in the soil as assessed by the A-value method. ¹⁵N-labelled fertilizer was applied at rates of 10, 25, 40, 60, and 100 mg N kg^-1 soil, corresponding approximately to 20, 50, 80, 120 and 200 kg N ha^-1 respectively, and two crop species, barley (Hordeum vulgareL.) and non-nodulating soybean (Glycine max L.) were used to determine the soil A _N value under the various fertilizer regimes. The results showed that the Rottenhaus soil had a higher A _N value than the Seibersdorf soil, suggesting that the former was more fertile than the latter. The A _N values of both soils were significantly affected by the level of N application. When grown in the same soil, the two test crops showed significantly different fertilizer use efficiency and per cent N derived from fertilizer when the rate of N application exceeded 20 kg ha^-1. Thus, the A _N value as determined by the two test crops differed significantly for the same soil when the rate of N application was greater than 20 kg/ha. The difference was greater when the soil fertility level was high. The dependence of the A _N value on the level of N application and the species of crop seriously compromises the suitability of this method for determining plant-associated N₂ fixation. Hence, considerable caution is required when using this method to estimate plant-associated N₂ fixation.     

Influence of reference trees on N2-fixation estimates inLeucaena leucocephala andAcacia albida using15N-labelling techniques

Summary We examined the suitability of four reference crops, i.e., two non-fixing trees,Cassia siamea andEucalyptus grandis, and two uninoculated fixing trees,Leucaena leucocephala andAcacia albida, for measuring fixed N₂ fixed in inoculatedL. leucocephala andA. albida grown for 36 weeks in pots. The¹⁵N isotope-dilution (involving the addition of equal amounts of labelled N fertilizer to the non-fixing and the fixing plants) and theA-value (with different amounts of labelled N fertilizer added to the fixing and the non-fixing crops) methods were used. The isotope dilution approach gave several large negative estimates of fixed N₂ inA. albida. Positive and similar values of fixed N₂ were measured in all four reference crops using theA-value approach. ForL. leucocephala the isotope-dilution approach gave different estimates of fixed N₂, with the different reference crops; the uninoculated N₂-fixing crops indicated significantly less fixed N₂ than the non-fixing reference crops. Similar values for N₂ fixed inL. leucocephala were obtained using the two non-fixing trees, either by the isotope-dilution or theA-value method. On average,A. albida derived about twice as much N from fertilizer asL. leucocephala. In both species, the atom %¹⁵N excess declined by about 50% in successive harvests.     

Brassica sect.Brassica (Brassicaceae)

Summary An extensive crossing program including 10 wild taxa and 23 accessions representing 6 major cultivated forms and landraces of theBrassica oleracea group was carried out. Data for crossability, germination, viability, fertility inF ₁ andF ₂ were studied as well as the meiotic chromosomal pairing inF ₁ hybrids in some combinations. The fertility of hybrids between all cultivated forms and wild populations ofB. oleracea was high and it was concluded that all, including the Chinese endemicalboglabra form, belong to the same biological species. Among the other species,B. macrocarpa, B. montana, andB. rupestris had the lowest andB. cretica the highest fertility values in crosses with cultivated forms. The crossing data do not give any further information as to the genetic differentiation ofB. oleracea during the course of domestication. Introgression between wild and cultivated forms has probably occurred frequently. All members of theB. oleracea cytodeme belong to the primary and secondary gene pools of the 18 chromosomic crops and are as such of great importance for breeding purposes.     

Production and analysis of reciprocal hybrids between <Emphasis Type="Italic">Asparagus officinalis</Emphasis> L. and <Emphasis Type="Italic">A. schoberioides</Emphasis> Kunth

The genus Asparagus (Asparagaceae) encompasses 100–300 species, including the important vegetable crop, A. officinalis (garden asparagus). Previous attempts to hybridize garden asparagus with A. densiflorus (Kunth) Jessop, with the aim of introducing disease resistance, were unsuccessful because of the failure of endosperm development. In the present study, reciprocal interspecific hybrids between garden asparagus and A. schoberioides Kunth were generated by hand pollination. The F1 hybrids were analyzed by using both morphological and molecular techniques. This is the first report describing the production of an interspecific hybrid between garden asparagus at the diploid level (2n = 2x = 20) and its diploid (2n = 2x = 20) wild relative, A. schoberioides. Morphological characteristics of candidate hybrids were a mixture of those found in the parents, and cytological and RFLP analyses confirmed that morphologically intermediate plants were indeed diploid hybrids of those two species. In other words, post-zygotic isolation is not complete between phylogenetically distinct these two species. Our results suggest that other Asparagus species may be capable of hybridizing with A. officinalis and that introducing wild characters through interspecific hybridization may offer advantages for breeding for novel traits. Takuro Ito and Toshinori Ochiai authors are contributed equally to this work     

宁夏盐池县不同荒漠化治理措施植物群落稳定性分析

分析不同荒漠化治理措施下植物群落的稳定性,可以为制定防沙治沙对策和措施提供基础数据。以植物α-多样性指数（Shannon-Wiener指数Sw、Simpson指数SD、群落均匀度指数Jsw和Js）和β-多样性指数（相似性系数Cs）、生物量变动系数为指标,从空间和时间2个尺度上分析宁夏盐池县不同荒漠化治理措施下的植物群落稳定性。结果表明：从α-多样性一群落稳定性分析,退耕还林措施下的植物多样性指数和群落均匀度指数较高,人工封育各指数年际间波动较小;从β-多样性一群落稳定性分析,人工封育措施下的植物群落相似性系数较大,且各年间波动较小,群落最稳定,退耕还林地次之;从功能指标分析,人工封育措施下的各年生物量值最高,退耕还林措施下的生物量波动最小。     

Oleaster (var. sylvestris) and subsp. cuspidata are suitable genetic resources for improvement of the olive (Olea europaea subsp. europaea var. europaea)

The olive belongs to Olea, a complex genus and to a species with six subspecies. Subsp. europaea includes both the cultivated olive and the oleaster, the wild ancestor of the olive. Little is known on the phenotype of fruits from subsp. cuspidata. We aimed to compare europaea and cuspidata trees for oil content and composition and to verify whether natural hybrids may exist between the two subspecies. Specimens were from Kenya and putative natural hybrids between cuspidata and europaea were from Stellenbosch (South Africa). Cultivar and oleaster trees were sampled in France (continental and Corsica), Italy (Continental and Sardinia) and Tunisia. We have examined the fruit (drupe) structure between subsp. cuspidata and europaea and extracted oil from the pulp, seed and total drupe. Comparison for oil content was made between the cultivated olive and the oleaster and some cuspidata trees from Kenya. A few of cuspidata individuals from Botanical gardens do not enable phenotyping for oil content and composition. Oil composition analyses were performed for the main fatty acids to compare the three taxa. We used microsatellite markers at 11 loci to compute genetic distances between cuspidata, oleaster and cultivar trees and to reveal eventual hybrids. The SSR polymorphisms were huge between the two subspecies and they revealed that putative hybrids were true hybrids sampled around olive orchards. The whole comparison of oil content shows that olive cultivars display higher oil content than the subsp. cuspidata and that the oleaster trees are intermediate, whereas for oil composition of the drupe, cuspidata from Kenya shows less oleic acid than europaea. However, the cuspidata trees show seed oil composition similarities with the other two taxa. The discussion deals with possible reasons to explain the differences and of the possible uses of these taxa for breeding both the olive and brown olive. H. Hannachi and H. Sommerlatte have equal contribution in the article.     

遗传算法率定参照作物腾发量相关参数的研究

用气象资料计算参照作物腾发量(ET0)的方法需要各种气象(候)和物理参数,净辐射是其中的重要数据之一,而专业测量净辐射的设备在农业气象站里很少安装。为解决计算ET0时缺少太阳净辐射(Rn)测量值这一实际问题,该文采用浑善达克沙地东南缘南沙梁草甸草原区气象站观测的气象资料,用遗传算法模型对联合国粮农组织56号文本(FAO56)推荐值(as和bs)进行率定,计算了对应夏半年(4—9月)和冬半年(1—3月和10—12月)的太阳净辐射和参照作物腾发量,并将率定前后的模拟太阳辐射进行对比分析,用残差估计指数法对该方法模拟的参照作物腾发量模拟精度进行了分析。结果表明:在缺少太阳净辐射测量值的地区,采用FAO56参数(as和bs)推荐值与遗传算法模型率定参数(as和bs)相比,净辐射年内变化趋势一致,采用率定后参数计算的净辐射相对更不稳定,波动更大,但能有效提高参照作物腾发量计算精度。误差较大的模拟值均出现在降雨日前后,降雨虽然并未直接出现在Penman-Monteith公式中,但是降雨必然会对湿度和温度等气象条件造成一定影响,而as和bs是受湿度等因素影响而变化的,其深层次的原因有待进一步分析。