Pear mutagenesis: In vitro treatment with gamma-rays and field selection for vegetative form traits

In vitro shoots of four pear (Pyrus communis L.) cultivars, 'Conference', 'Doyenné d'Hiver', 'Passe Crassane' and 'Bartlett', were irradiated with gamma rays (3.5 Gy). Around 1000 microcuttings of each cultivar were treated. After three subcultures, microcuttings from both the irradiated shoots and additional non-irradiated shoots were rooted; plants obtained were used to establish a survey orchard in Ostellato (Ferrara), Italy. For the first 2 years in the field, growth and survival were observed, but no data were collected. Subsequently, field surveys were conducted to characterize the population and identify mutants for vegetative traits. Trees that showed phenotypic evidence of vegetative growth characteristics more desirable than those shown by the overall population and by control plants were selected and measured for three years. Traits used for selection were small tree size, wide branch angle and short internodes. Frequencies of variants with compact habit varied with cultivars from 0.5% to 2.7% of irradiated trees. Effect of mutagenic treatment and efficacy of the selection methods are discussed.     

Farmers' Perceptions on Rice Varieties in Sikasso Region of Mali and their Implications for Rice Breeding

Rice is an important staple food and cash crop. Although many varieties of rice have been developed to date, few are adopted possibly because researchers did not take into account farmers’ preferences and perceptions on varieties during the development process. Because farmers increasingly rely on low-yielding landraces, production fails to meet demand. To provide an understanding of farmers’ preferences for rice cultivars and perceptions on drought stress and management practices as inputs to rice breeding research, this study was conducted in the Sikasso region of Mali in September 2005 using participatory rural appraisal approach. A total number of 125 farmers were randomly selected from 10 villages in three ecologies and interviewed individually and in groups. Results showed that farmers’ preferences, crop management practices and ranking of production constraints differed significantly across ecologies. Whereas farmers in the irrigated ecologies preferred high-yielding, long duration rice varieties, those in the upland and lowland ecologies preferred tall plants of short duration. While upland and lowland farmers preferred red and white long grains, respectively, irrigated ecologies were indifferent about grain colour. Farmers appeared willing to trade-off yield for grain quality and plant height, inconsistent with traditional breeders’ selection criteria. The high preference for tall varieties among farmers in the upland and lowland ecologies also contrasted sharply with the model of dwarf rice varieties responsible for the green revolution in Asia. The implication of these findings for rice breeders is that different plant idiotypes complemented by effective drought management practices should target different ecologies to increase impact.     

Collaborative and consultative participatory plant breeding of rice for the rainfed uplands of eastern India

We describe a participatory plant breeding (PPB) programme in rice for the rainfed uplands of eastern India. Collaborative participation (farmers grew and selected in segregating materials in their fields) and consultative participation (farmers selected among progenies in researchers' plots) were used. The PPB was started with only two crosses and, of these, Kalinga III/IR64 was the most successful and produced two released varieties: Ashoka 200F from collaborative breeding and Ashoka 228 from consultative breeding. Both yielded significantly more than control varieties, including Kalinga III, in research trials and in participatory trials in farmers' fields. Qualitative data from participatory trials was highly informative, statistically analysable, and cheaper to obtain than quantitative data. In low-yielding research-station and on-farm trials the two new upland varieties showed no significant genotype × environment interaction with the check varieties. However, in higher-yielding All India Coordinated Rice Improvement Project trials, both varieties were more adapted to low yielding environments than the national check variety. Farmers liked the varieties for their early maturity, improved lodging resistance, higher fodder and grain yield, long-slender grains and excellent cooking quality. Before certified seed production, farmer groups have produced large quantities of seed that have spread widely through informal channels. The returns from PPB, compared to conventional breeding, were higher because it cost less, the genetic gains per year were higher, and the benefits to farmers were realised earlier. This revised version was published online in August 2006 with corrections to the Cover Date.     

Improving participatory varietal selection processes: participatory varietal selection and the role of informal seed diffusion mechanisms for upland rice in Ghana

This paper considers the process of Participatory Varietal Selection (PVS) and presents approaches and ideas based on PVS activities conducted on upland rice throughout Ghana between 1997 and 2003. In particular the role of informal seed systems in PVS is investigated and implications for PVS design are identified. PVS programmes were conducted in two main agroecological zones, Forest and Savannah, with 1,578 and 1,143 mm of annual rainfall, respectively, and between 40 and 100 varieties tested at each site. In the Savannah zone IR12979-24-1 was officially released and in the Forest zone IDSA 85 was widely accepted by farmers. Two surveys were conducted in an area of the Forest zone to study mechanisms of spread. Here small amounts (1–2 kg) of seed of selected varieties had been given to 94 farmers. In 2002, 37% of 2,289 farmers in communities surveyed had already grown a PVS variety and had obtained seed via informal mechanisms from other farmers, i.e. through gift, exchange or purchase. A modified approach for PVS is presented which enables important issues identified in the paper to be accommodated. These issues include: utilising existing seed spread mechanisms; facilitating formal release of acceptable varieties; assessing post-harvest traits, and; the need for PVS to be an ongoing and sustainable process.     

Local adjustment method for field experiments. 2. Application in experiments with and without replications

Summary Presented are the results of an application of the local adjustment Field-method in the analysis of the real field experiments without replications and in experiments with pseudo- and random replications. It was found that the local adjustment allowed a more precise estimation of the real values of genotypes in all kinds of experiments over a wide interval of spatial heterogeneity. The results obtained indicate that by simply using up to 5 random replications the decrease of the spatial effects is inadequate for fields with medium and high soil heterogeneity or with unsuccessful randomization. The Field-method which has sufficient precision in evaluating spatial heterogeneity, considerably increases the reliability of estimates in experiments even with a small number of replications or with unsuccessful randomization. Therefore, for all field experiments that have fulfilled the necessary requirements the Field-method is recommended as an obligatory statistical procedure for a prior data analysis as it allows an accurate estimation of the real character expression of genotypes, as well as the random variance in experiments without replication and the parameters of ANOVA in ones with pseudo- and random replications.     

Local adjustment method for field experiments. 1. The method and its examination by computer simulation

Summary The modification of the nearest neighbour method for using various size plots in field trials has been developed and the results of testing its validity by computer simulation are presented. It was found that the Field-S variant of this method using a square pilot area is the best for fields with a low and medium spatial heterogeneity. The Field-L variant using the least quantity of neighbours, offers advantages for fields with a medium and high spatial effect. The optimal values of the controlling coefficients of these variants were computed to allow for the calculation of the environmental indices over a wide interval of spatial heterogeneity with sufficient accuracy. For this reason, this local adjustment method is recommended as an obligatory statistical procedure for a prior data analysis of any field experiments that have fulfilled the necessary requirements. The original Field and CRBSD programs using the local adjustment method developed have been created for IBM-compatible personal computers.     

Construction and characterization of 3-S Lines, an alternative population for mapping studies in rice (Oryza sativa L.)

Most traits of agronomic importance in rice are quantitative in nature and are controlled by polygenes, called quantitative trait loci (QTL). Understanding the nature and effect of QTLs are important for rice breeding to achieve higher yield and stability. Single segment substitution lines (SSSLs or 3-S Lines) were developed through simple sequence repeats (SSR) marker-facilitated backcrossing methods for Hua-Jing-Xian 74 (HJX74) with the donor segment from six elite germplasm and was characterized. Complete genome survey was carried out with 258 polymorphic SSR markers. Polymorphism of the donors with the recurrent parent varied between 32.98 and 60.73% with an average of 47.81%. Japonica donors were more polymorphic than indica donors. Number of substitution segments per plant decreased with the advancement of backcross generations. In BC₂F_1, BC₃F₁, BC₃F₂ and BC₃F₃ the average number of substitution segment per plant were 12.5, 5.98, 1.69 and 1.46, respectively. Average size of substitution segments also decreased with the number of times plants were backcrossed and selfed. In BC₂F₁, BC₃F₁, BC₃F₂ and BC₃F_3, average size of the segments was 25.43, 22.38, 20.78 and 18.15 cM, respectively. The rate of reduction of segment size was more in backcross (11.99%) than selfing (7.15%) generations. Percent recovery of recurrent parent genome in BC₂F₁, BC₃F₁, BC₃F₂ and BC₃F₃ was 82.24, 92.55, 98.04 and 98.52%, respectively. A total of 111 SSSLs comprising of 43 unique types were developed in BC₃F₂ and BC₃F₃. The estimated length of the segments in SSSLs ranged from 2.00 to 64.80 cM with an average of 21.75 cM, and 6.05 to 48.90 cM with an average of 20.95 cM in BC₃F₂ and BC₃F₃, respectively. Total length of all substitution segments was 2367.5 cM that covered 704.50 cM (39.25%) of the entire rice genome. Effective development and successful utilization of 3-S Lines for analysis of QTLs and mapping of genes established the suitability of the SSR marker facilitated backcross breeding approach for 3-S Lines development and its utilization.     

Coagulable protein in potato: Screening method and prospects for breeding

Summary From tubers of 34 varieties of Solanum tuberosum, extracts were prepared and analysed for crude protein and coagulable protein by the Kjeldahl method. Content of coagulable protein was 0.37–1.24%. From the same material, juice was prepared with a juice centrifuge and analysed for coagulable protein by the Kjeldahl and microbiuret method. The average amount of coagulable protein in the juice was 81.8% of the total coagulable protein. The correlation coefficient between coagulable protein in the juice and total coagulable protein was 0.956. The correlation coefficient between Kjeldahl and microbiuret data for coagulable protein in the juice was 0.956. Analysis of tuber juice by the microbiuret method is recommended as a rapid screening technique for coagulable protein.Relationships between protein data of the 34 varieties and earliness, yield and content of dry matter were analysed statistically. Content of coagulable protein in fresh material correlated with content of dry matter (rs=–0.756), yield of fresh potatoes (r=–0.615) and earliness (r=–0.361) but not significantly with yield of dry matter (rs=–0.309). Coagulable protein in dry matter correlated with fresh yield (r=–0.525), but not significantly with content of dry matter (r=–0.260), yield of dry matter (r=–0.131) and earliness (r=–0.054). Path coefficient analysis showed that 67% of the variation in coagulable protein in fresh material was statistically determined by earliness, content of dry matter, fresh yield and content of uncoagulable protein in fresh material, whereas only 34% of the variation in content of coagulable protein in dry matter was determined by these components. A high content of coagulable protein in fresh or dry matter can be combined with early maturity and with high yield of dry matter. Coagulable protein in dry matter seems to be a more suitable criterion of selection than coagulable protein in fresh material.     

Confirming a major QTL and finding additional loci responsible for field resistance to brown spot (Bipolaris oryzae) in rice

Brown spot is a devastating rice disease. Quantitative resistance has been observed in local varieties (e.g., ‘Tadukan’), but no economically useful resistant variety has been bred. Using quantitative trait locus (QTL) analysis of recombinant inbred lines (RILs) from ‘Tadukan’ (resistant) × ‘Hinohikari’ (susceptible), we previously found three QTLs (qBS2, qBS9, and qBS11) that conferred resistance in seedlings in a greenhouse. To confirm their effect, the parents and later generations of RILs were transplanted into paddy fields where brown spot severely occurred. Three new resistance QTLs (qBSfR1, qBSfR4, and qBSfR11) were detected on chromosomes 1, 4, and 11, respectively. The ‘Tadukan’ alleles at qBSfR1 and qBSfR11 and the ‘Hinohikari’ allele at qBSfR4 increased resistance. The major QTL qBSfR11 coincided with qBS11 from the previous study, whereas qBSfR1 and qBSfR4 were new but neither qBS2 nor qBS9 were detected. To verify the qBSfR1 and qBSfR11 ‘Tadukan’ resistance alleles, near-isogenic lines (NILs) with one or both QTLs in a susceptible background (‘Koshihikari’) were evaluated under field conditions. NILs with qBSfR11 acquired significant field resistance; those with qBSfR1 did not. This confirms the effectiveness of qBSfR11. Genetic markers flanking qBSfR11 will be powerful tools for marker-assisted selection to improve brown spot resistance.     

Biochemical, molecular, and cytogenetic technologies for characterizing 1RS in wheat: A review

Chromosome arm 1RS of rye ( Secale cereale L.), when transferred to wheat ( Triticum sp.), significantly influences variety performance, because it carries genes for resistance to disease and insect pathogens. Inserted into wheat, 1RS also promotes haploid production, affects end-product quality, and sometimes affects yield. Therefore, its detection by breeders and geneticists is important. The entire 1RS arm is present in chromosome substitutions and in Robertsonian translocations involving chromosomes 1A, 1B, or 1D of wheat. In recombinant lines, a segment of 1RS has been exchanged with a segment of a group-1 wheat chromosome. Determining the wheat chromosome arm involved in a translocation, the source of rye chromatin, and the amount of 1RS chromatin introduced is necessary for a complete characterization of the introgressed segment. Biochemical, molecular, and cytogenetic technologies are described which enable such a characterization of 1RS in wheat. Examples of using gel electrophoresis, high-performance liquid chromatography, monoclonal antibodies, rye-specific molecular probes, RFLP and PCR assays, chromosome banding, in situ hybridization, and flow cytometry are provided. A comparison of these technologies is made and the advantages and disadvantages of each technology are discussed relative to modern wheat breeding efforts. This revised version was published online in July 2006 with corrections to the Cover Date.     

Organic varieties for cauliflowers and cabbages in Brittany: from genetic resources to participatory plant breeding

Plant breeding for organic agriculture (OA) was stimulated when it came under the European Organic Agriculture Regulation (2092/91) in 2004. In Brittany, the need for specific varieties for organic farming arose early for the Brassica species because of the unsuitability of most of the modern varieties to the principles of OA. Moreover, the private sector of plant breeding finds it economically difficult to satisfy the demands of OA. The aim of the present study is to provide varieties and seed for organic farmers for two vegetable Brassica crops, and to show how genetic resources can contribute to this purpose in the framework of a Participatory Plant Breeding (PPB) programme. The emergence of PPB in Brittany is the result of several concomitant and favourable circumstances: the will of the professionals (represented by IBB, Inter Bio Bretagne), their organization (an experimental station, the PAIS, Plateforme Agrobiologique d’IBB à Suscinio), the research initiative in INRA and the availability of genetic resources. From genetic resource observations, our experience showed several breeding situations: reviving a traditional activity (Roscoff cauliflower and local cabbages), extending tradition (autumn cauliflower), diversifying production by new introductions (coloured cauliflowers), and creating new forms of population varieties (broccoli and coloured cauliflowers). Farmers have taken charge of population breeding by mass selection and the PAIS, with INRA scientific support, has taken up innovative selection and the improvement of varieties completing the farmers’ initiatives. The PAIS remained the central point for information and for providing the seed for trials. Seed production will be managed in a collective way. Until now, the exchange of seed remained an experimental dimension of PPB. French seed legislation represents a limitation on the development of seed exchange by PPB.     

Breeding for yield stability in unpredictable environments: single traits,interaction between traits,and architecture of genotypes

Summary Attempts to identify individual traits to use as an indirect measure for grain yield have shown some degree of success in environments where crop yields are affected by no stress or only by predictable stresses. However, analytical breeding has been largely unsuccessful in the case of a) stressful environments characterized by low yields due to high variability in the frequency, timing, duration and severity of a number of climatic stresses, and b) breeding programs where the major objective is greater yield stability defined as a reduction in the frequency of crop failures. Experimental evidence suggests that, when environmental variability is high due to unpredictable differences in frequency, timing and severity of various climatic stresses, each time different combinations of several traits are likely to confer drought resistance. Interaction among traits in determining overall crop response to variable stresses is expected to occasionally enhance the importance of a specific trait in a specific stress situation. In this context it becomes difficult to consider drought resistance as a character with its own identity in terms of inheritance.Assessment and verification of traits based on the use of isogenic lines tends to oversimplify the interactions between traits, as the approach provides information on the effect of a specific trait only in a specific genetic background.At the population level of organisation, the dilemma between selection for individual traits and specific combinations of traits can be translated into the dilemma between selection for individual genotypes and specific combinations of genotypes. The evidence that natural selection under stress conditions has not been able to identify either a single trait or a single genotype with a given adapted architecture of traits, is discussed in relation to germplasm development philosophies to stabilize yield in unpredictably stressed environments.     

The need for characterisation and evaluation of germplasm: kiwifruit as an example

Genetic diversity provides the raw material for breeding and plant improvement. Breeders of plant species that have little or no history of improvement tend to make the greatest use of collections of raw or unimproved germplasm. Kiwifruit (Actinidia) are one such crop in that they have been subjected to little selection pressure and are still very similar to plants in the wild. To take advantage of the diversity in the genus Actinidia, breeders need to know the extent of the diversity and also need to be able to identify the plants with which they are working. Voucher specimens should be prepared for all plants used in experimental studies. A good understanding of the reproductive biology of Actinidia should facilitate incorporation of wild germplasm into kiwifruit breeding programmes. The HortResearch Actinidia collection has already proved its worth with the development of valuable new kiwifruit cultivars.     

Natural variation within the genus Beta and its possible use for breeding sugar beet: A review

Summary Sugar beet is a relatively young crop, which supposedly has a narrow genetic base. Natural variation occurring in primitive beet varieties and in wild Beta species has been used for breeding sugar beet. This paper reviews information on desirable characteristics in Beta germplasm and the attempts made for the introgression of such characters into commercial breeding material. After an introduction on the availability of germplasm and the possibilities of hybridisation, attention is focussed on the mating system (especially male sterility), on morphological and physiological characteristics, including yield and sugar content, and on resistances to diseases and pests.     

Evaluating the potential for farmer and plant breeder collaboration: A case study of farmer maize selection in Oaxaca, Mexico

Formal plant breeders could contribute much to collaboration with farmers for improving crop varieties for local use. To do so outside researchers must have some understanding of local selection practices and their impact on crop populations in terms of the genetic theory underlying plant breeding. In this research we integrated methods from social and biological sciences to better understand selection and its consequences from farmers' perspectives but based on the concepts used by plant breeders. Among the households we worked with, farmers' selection practices were not always effective yet they understood the reasons for this and had no expectations for response to selection in some traits given the methods available to them. Farmers' statements, practices and genetic perceptions regarding selection and the genetic response of their maize populations to their selection indicate selection objectives different than may be typically assumed, suggesting a role for plant breeder collaboration with farmers. This revised version was published online in July 2006 with corrections to the Cover Date.     

高本衔接一体化教学标准的研制与实践——以食品专业为例

以职业教育高本衔接的现实需求为出发点,准确定位制定系统化培养食品领域高技术技能型人才的专业标准和课程标准,既是我国食品行业发展的需要,也是构建现代职业教育体系和职业教育人才培养类型转变的教育发展的必然需求。     

Varietal differences in perennial ryegrass for nitrogen use efficiency in leaf growth following defoliation: performance in flowing solution culture and its relationship to yield under simulated grazing in the field

Varietal differences in rates of NO₃ uptake and remobilization of nitrogen (N) during a cycle of severe defoliation and regrowth were assessed in perennial ryegrass (Lolium perenne L.) varieties Ba11778, Aberelan, Talbot and Gator. Plants were grown in flowing solution culture for 34 days, prior to a 30 d treatment period, including 21 d of regrowth. Net uptake of NO₃ was measured continuously from solutions maintained automatically at 10 mmol m^-3NO₃.¹⁵ N-labelled NO_{3 3} was supplied to the plants in situ for either 21 h immediately prior to defoliation, or for 7-11 days afterwards, to measure remobilization of N from roots and stubble into the regrowing leaves. The four varieties differed only slightly in total dry matter production over 30 d, but varied substantially in post-defoliation specific growth rate by the leaf fraction. Gator was the lowest ( 0.11 g g^-1 d^-1), Ba11778 the highest ( 0.15 g g^-1 d^-1) and Aberelan and Talbot intermediate in leaf regrowth rate. Varieties did not vary significantly in shoot: root dry weight ratio, but the rate of NO₃ uptake per unit of leaf fresh weight during regrowth was 27% lower in Ba11778 than in Gator. Leaves of Ba11778 and Aberelan had a lower organic N concentration in the dry matter at the end of the regrowth period than Talbot, which, in turn, had a lower concentration than Gator. Varieties differed in amount of leaf dry matter produced per unit of N absorbed by the plants after defoliation, the values (g g^-1 N) being Ba11778 (22.6 ), Aberelan (20.7), Talbot (18.3) and Gator (16.7). More N was remobilized from the roots than from the stubble after defoliation. There were no significant differences among varieties in the amount and rate of N remobilization following defoliation. In earlier field experiments employing frequent cutting to simulate grazing, Ba11778 and Aberelan yielded at least 10% more dry matter annually than Talbot which, in turn, outyielded the amenity variety Gator by a similar amount. Thus the present results are consistent with the hypothesis that the efficiency of N use in leaf growth is an important factor determining genetic variation in productivity under frequent defoliation in the field when the herbage produced consists primarily of leaf. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identification of near-isogenic lines: an innovative approach,validated for root and shoot morphological characters in a mapping population of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L.)

Near-isogenic lines (NILs) constitute valuable tools in genetic investigations and plant breeding programs. Conventional methods for developing these are time consuming and tedious. An innovative method for identifying NILs is proposed and validated. The method involves computation of simple correlation coefficients of all possible pairs of genotypes within a mapping population using molecular marker data, and phenotypic characterization of those pairs with very high positive correlation. The pairs having both genomic and phenotypic similarity except for a single trait are considered as NILs. This strategy was tested with a doubled haploid mapping population involving CT9993 and IR62266. This population was saturated with 315 markers and comprised 154 lines. The pairs showing very high correlation coefficients (0.70–0.97) and differing for less than 10% of the markers were considered as Genotypically Closely Related Pairs (GCRPs). Graphical genotyping was employed to visualize the genome of the closely related lines. A total of 39 such pairs were subjected to rigorous evaluation for root and shoot morphological traits in two contrasting moisture regimes. Four GCRPs under well-watered condition and ten GCRPs under low moisture stress condition are statistically significant for a single phenotypic trait and are considered as NILs for their respective traits and would be the valuable materials for genetic studies. Mapped QTLs and candidate genes were employed to explain the probable cause of phenotypic difference in NILs.