Adaptation to low/high input cultivation

Summary Many aeas of world, particular those where agriculture is largely practiced by resource-poor farmers with little or no use of external inputs, have not benefitted from the spectacular yield increases achieved by the combination of modern breeding technologies and use of inputs. The paper argues that because breeding is mostly conducted in presence of high inputs, it has systematically missed the opportunity to exploit genetic differences at low levels of inputs. Many studies show that these differences do exist, particularly in the case of fertilizers, and that these differences can only be identified is selection is conducted under the target level of inputs. Although this was predicted by theory more than 40 years ago, and has been supported by a large body of experimental data, very few breeders select in sub-optimal or stress conditions. The most common justification is the high environmental variation, and hence the lower heritability expected in low input conditions. While this is not supported by experimental evidence, the paper shows that in the case of a typical crop grown in low-input and climatically marginal conditions such as barley, genetic gains are possible by using locally adapted germplasm and by selecting in the target environment. Similar conclusions, in relation to the use of a low-input selection environment, have been reached recently in maize. It is concluded that the best avenue to a sustainable increase of agricultural production in low-input agricultural systems is through locally based breeding programs.     

Relationship between barley grain yield measured in low- and high-yielding environments

Summary The paper addresses the general question of identifying the optimum environment for selection in plant breeding programs for low input agricultural systems. After defining low-yielding and high-yielding environments based on the average grain yield of large numbers of barley genotypes in different cropping seasons, we examined: 1) the phenotypic relationships between the highest yielding genotypes in low- and high-yielding environments, and 2) the genetic correlation coefficients between grain yield in low- and high-yielding environments. The results indicate that the alleles controlling high grain yield in low-yielding conditions are at least partially different from those controlling high grain yield in high-yielding conditions. Therefore, selection in high-yielding environments is expected to produce a negative response or no response in low-yielding environments. This may explain why crop varieties bred under high-yielding conditions failed to have an impact in low-yielding agricultural systems. The results may be extrapolated to systems where environmental concern suggests a reduction of inputs by raising the question of whether crop breeding programs based on selection under high inputs are likely to generate the right type of germplasm for an environmentally friendly agriculture.     

Choice of selection strategy in breeding barley for stress environments

To determine the optimum selection environment for barley (Hordeum vulgare L.) targeted at low-input, stress environment, barley lines were selected for high yield under stress (YS), high yield under non-stress (YNS), or average yield in stress and non-stress conditions (YA) during three breeding cycles (cohorts) of three years each. The lines were then tested in a total of 21 year-location combinations with average grain yields ranging from 0.35 to 4.86 t ha^-1. Yield under stress of the YS lines was between 27% and 54% higher than that of the YNS lines, with the top YS lines yielding under stress between 16% and 30% more than the top YNS lines. Realized heritability was between 0.35 and 0.67 when selection was conducted under stress and was significant in all three cohorts. By contrast, selection under non-stress gave a significant response in only one cohort, and its efficiency in improving yield under stress was significantly lower than selection under stress. The best YNS line ranked only 19th for yield under stress. The highest-yielding lines under stress were not only selected under stress, but were also landraces collected in very dry areas (< 250 mm total annual rainfall). This confirms earlier findings and supports the idea that the most effective way to improve productivity of crops grown in less-favored areas is to use locally adapted germplasm and select in the target environment(s). This revised version was published online in July 2006 with corrections to the Cover Date.     

Environment of selection and type of germplasm in barley breeding for low-yielding conditions

Summary Thee groups consisting of 332, 243 and 280 barley breeding lines (entries) of known selection history were evaluated in 10, 9 and 8 environments, respectively, to determine the relationship between grain yield in low yielding (LYE) or high yielding (HYE) environment, and selection history and type of germplasm. One cycle of selection in LYE produced on average five times more entries outyielding the best check in LYE than selection in HYE. A retrospective analysis indicated that the highest yielding lines in LYE were lower yielding (15%–28%) in HYE when compared with the best check, and by 20% and 38% compared with the best entries in HYE. In contrast, the highest yielding lines in HYE were lower yielding (4%–33%) in LYE when compared with the best check, and by 33% and 40% when compared with the best entries in LYE. The highest yielding lines in LYE did not differ consistently from the highest yielding lines in HYE for a number of morphological and developmental traits including days to heading. This suggests there are many paths to high yield in LYE and that analytical breeding based on individual traits may not be appropriate for variable environments. Only 0.07% of the highest yielding entries in LYE was selected for high yield in HYE conditions confirming previous results indicating that selection for high yield in HYE is an inefficient strategy for improving yield in low yielding conditions. This frequency is 28 times lower than the frequency of high yielding entries in LYE selected from landraces or crosses with landraces in low yielding conditions. The results imply that the most cost-effective strategy for barley breeding in low yielding conditions is to select repeatedly in low yielding conditions and to include adapted germplasm (landraces) in the breeding material.     

A methodological study on participatory barley breeding II. Response to selection

Farmer participation is increasingly seen as a key to develop technologies which are more relevant to farmers' communities. In plant breeding, farmer participation is seen as key to increase the probability of adoption of new varieties. This paper addresses the issue of selection efficiency in participatory plant breeding by testing the effect of selection environment and of who did the selection in one cropping season (1997) on the performance of the selected lines in the following cropping season (1998). Selection environment had a larger effect on response to selection than who did the selection, confirming the importance of decentralized selection. Selections made by the breeder and the farmers in 1997, differed in 1998 for a number of traits, but seldom for grain yield. When the difference for grain yield was significant, breeder's selection was more effective on station, while farmers' selection was more effective in farmers' fields. The results of this study indicate that it is possible to organize a plant breeding program with the objective of adapting crops to a multitude of both physical and socio-economic environments: such a breeding program will, at the same time, increase productivity and stability, enhance biodiversity and produce environmentally friendly cultivars. This revised version was published online in July 2006 with corrections to the Cover Date.     

Utilization of exotic germplasm in Nordic barley breeding and its consequences for adaptation

Summary Utilization of exotic germplasm is one way to broaden genetic variation in breeding populations. This approach has recently been adopted in Sweden and Finland, where experimental barley populations has been established for research and pre-breeding purposes. The aim of the project is threefold: (1) to increase overall genetic diversity of Nordic barley breeding material; (2) to develop breeding material which possesses a high level of resistance for various barley diseases; and (3) to study effects of exotic germplasm on adaptation and agronomic performance. Both the Finnish and the Swedish barley populations include the same exotic material i.e. unadapted landraces from different parts of Asia and wild barley (Hordeum vulgare ssp. spontaneum) accessions. Locally adapted high-yielding barley lines were included in the populations. The establishment of these populations involved six crossing generations in order to promote recombination and enhance the break-up of linkage blocks. The paper discusses the third aim of the project. Studies on agronomic performance and adaptation showed that (1) agronomically valuable genotypes can be constructed through recombination using exotic germplasm for Nordic conditions, (2) that incorporation of exotic material is most successful when made in a local genetic base and (3) that exotic germplasm has an effect on adaptation.     

Farmer participation in barley breeding in Syria, Morocco and Tunisia

The paper describes experiments on farmer participation in plant breeding conducted in three countries (Morocco, Syria and Tunisia) on barley, which is the predominant annual rainfed crop in the most marginal areas of these countries. Trials with different types and number of breeding material were planted both on research stations and in farmers' fields. Selection was done by professional breeders and farmers and data were gathered on breeders' and farmers' selection criteria and selection efficiency. The trials reflected the situation of the crop in the three countries, with high yields on station, low yields in some of the most marginal farmers' fields, and poor correlations between research stations and farmers' fields, as well as between farmers' fields. Grain yield was by far the most commonly used selection criterion by the farmers. However, farmers also made a widespread use of selection criteria not normally used by breeders such as grain filling and straw yield, as well as other characteristics of the straw (color) and of the leaves because of the importance of the crop as source of animal feed. A major difference between the selection criteria used by breeders and farmers was disease resistance, almost entirely neglected by the latter. Farmer selection was effective in identifying some of the highest yielding lines in the farmers' own fields and also in those cases where they performed selection on station. The coincidence between entries selected by the breeder and the farmers was high in Morocco but very low in Syria and Tunisia. There were substantial differences between the lines selected by the breeders on station and those selected by farmers in their fields. In Syria, decentralized-participatory selection was significantly more efficient in identifying the highest yielding entries in farmers' fields than any other selection strategy. This work demonstrates that it is possible to organize a plant breeding program so that farmers become major actors in the selection of new cultivars. This revised version was published online in August 2006 with corrections to the Cover Date.     

Specific adaptation of barley varieties in different locations in Ethiopia

Barley is one of the most important cereal crops grown for the livelihoods of the poor farmers of Tigray region in northern Ethiopia. As many low input and marginal environments it has benefited less from the yield increases achieved by modern breeding. This has been largely attributed due to genotype × environment intraction (GEI). To investigate the causes of GEI, ten barley varieties including local checks (two farmers developed varieties, four modern varieties and three rare local varieties) were tested over 21 environments. Participatory methods were applied to sample an adequate number of environments spanning the regional diversity. The yielding ability and stability of the varieties was graphically depicted by GGE and PLSR biplot. There were two major groups of environments, the central and northern highlands, the latter with less rainfall and poorer soils. Rainfall per month and total nitrogen level were the environmental variables that differentiated these two groups. In Tigray, rainfall in June and July were negatively correlated with yield, reflecting waterlogging problems. The different varieties were either specifically or widely adapted across the two environments. The variety ‘Himblil’, originating in Tigray, was the highest yielding and also most stable in the region of origin. However, it was inferior to improved varieties (Shege and Dimtu) at high yield levels. The association of earliness with grain yield indicates that the trait can be effectively manipulated within the existing materials. We recommend breeding for drought/water logging resistance based on selection in the target environment as the best strategy to provide stable and high yielding varieties for Tigray.     

Yield stability and adaptation of Nordic barleys

Summary Grain yield was studied in a collection of 220 Nordic barley lines at diverse locations in the Nordic countries. Two-row (2r) and six-row (6r) lines differed very significantly in reaction to the growing conditions within and between the two locations, Svalöv (in southern Sweden) and Højbakkegård (in Denmark). This difference was also highly significant at Viikki (in Finland), but not at As (in Norway) or between Viikki and As. Genotype × location (GL) and genotype × year (GY) variance components were used to estimate phenotypic yield stability by Shukla's stability variance (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiaabo8adaahaa% WcbeqaaiaabkdaaaGcdaWgaaqcbaCaaiaabMgaaSqabaaaaa!3B73!\[{\text{\sigma }}^{\text{2}} _{\text{i}} \]). Only 7 lines did not contribute significantly to GL- and GY-interactions, and their yield levels were 7–27% lower than that of the highest yielding line (5057 kg/ha). Estimates of GL- and GY-stability parameters were not significantly correlated. Neither responsiveness, measured by the regression coefficient (b _i ), nor phenotypic yield stability, measured by the deviations from regression (Tai's _i ) were correlated with yield. Pedigree studies showed that both b _i and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0dh9WrFfpC0xh9vqqj-hEeeu0xXdbba9frFj0-OqFf% ea0dXdd9vqaq-JfrVkFHe9pgea0dXdar-Jb9hs0dXdbPYxe9vr0-vr% 0-vqpWqaaeaabaGaaiaacaqabeaadaqaaqaaaOqaaiaabo8adaahaa% WcbeqaaiaabkdaaaGcdaWgaaqcbaCaaiaabMgaaSqabaaaaa!3B73!\[{\text{\sigma }}^{\text{2}} _{\text{i}} \] can be changed by recombination and/or induced mutations. Mixing of near isogenic lines with different resistance genes, and selection within a landrace, also resulted in changes in responsiveness. Recently released 2r-cultivars were more unstable than older 2r-cultivars revealed by positive correlation between the year of release and _i . Cultivars originating from southern Scandinavia were higher yielding than cultivars originating from the central or the northern regions of Scandinavia.     

An alternative approach to breeding for high diastatic power in barley

Summary Several lines from the cross Akka x Feebar were observed to have -amylase activity considerably in excess of either parent. It is suggested that, from crosses between two-rowed and six-rowed varieties, two-rowed genotypes with enhanced levels of grain nitrogen and -amylase activity may be obtained. These can be successfully exploited in a breeding programme to produce barley varities with high diastic power.     

Evaluation of methods for the assessment of malting quality in barley breeding

Summary Methods for assessing malting quality in barley breeding were evaluated for their precision, including variation between different batches, analysts and barley samples. The barley characters measured were grain moisture, ground grain moisture (two methods), grain weight, steep moisture, malt moisture (two methods), malt yield, malt nitrogen, malt soluble nitrogen, Kolbach index, malt diastatic power, malt -amylase, malt -glucanase, wort refractive index, hot water extract, extract yield, wort reducing sugars, wort total carbohydrates, wort -amino nitrogen and wort total nitrogen. The value of these measurements in barley breeding is discussed.     

Molecular adaptation of barley to cold and drought conditions

Summary Molecular adaptation to cold and drought involves a series of biochemical and molecular changes leading plants to improve their winter hardiness or drought resistance.We are interested to study the molecular basis of cold acclimation and drought response of barley to survive under stress. Several genes regulated by low temperatures and sometimes by drought have been isolated from the barley genome. In this review the most significant results of our recent work will be presented and discussed.The protein encoded by cDNA clone pt59 and induced in barley by cold was over-expressed in E. coli to produce the matching antibody, which in vivo recognizes a cold-induced protein of 14 kDa (COR14). The COR14 is stored in amounts only slightly greater in the cold resistant Onice than in the susceptible Gitane, although the former has a higher induction-temperature threshold of COR14 than the latter. This fact is an evolutionary advantage enabling the resistant varieties in the field to prepare for the cold well ahead of the susceptible ones.Two other cDNA clones, paf93 and cdr29, are regulated by low temperature and drought stress but not by exogenous ABA treatment. Indeed during the early stage of dehydration, the mRNAs are expressed before the induction of known ABA regulated genes such as dehydrins and when only a small increase occurs in ABA content. The sequence analysis revealed that paf93 encodes for a protein homologous to the cold-regulated protein COR47 of Arabidopsis, whereas cdr29 represents a plant gene homologous to yeast and mammalian sequences coding for acyl-Coenzyme A oxidase.Abbreviations ABA abscisic acid - COR cold regulated     

Simultaneous selection of segregating two-row winter barley material in England and Italy

Summary Independent but simultaneous selection by two breeding teams of the same segregating two-row winter barley material at Cambridge, England and Fiorenzuola, Italy was carried out over the years 1978–1982 with the objective of comparing the individual selection of the two breeding teams and assessing the adaptation of the surviving selections. Visual selection in the generations F₃ to F₅ did not result in any clear cut compartmentalisation of the material and both teams were as likely to select from families previously selected only by the other team as from families they had themselves previously selected. Lines with specific adaptation to each site as well as lines well adapted to both sites were identified from yield trials carried out in F₅ and F₆. The former showed only a very small yield advantage over lines with general adaptation to both sites.     

Selection environment and environmental sensitivity in barley

Summary Groups of 10 barley genotypes were selected for high grain yield under either high yielding (two groups) or low yielding conditions (two groups). The genotypes had a similar average grain yield across a wide range of yielding conditions, but differed in their linear response over environments (environmental sensitivity). The genotypes selected for high grain yield under low yielding conditions were less sensitive to changing environments than genotypes selected for high grain yield under high yielding conditions. The higher stability of genotypes selected under low yielding conditions was shown by both the linear regression analysis and the comparison of coefficients of variation. The use of a safety-first index showed that the probability of a crop failure of genotypes selected for high grain yield under high yielding conditions was between 1.8 and 2.7 times higher than for genotypes selected for high grain yield under low yielding conditions. The development of new cultivars for areas where a large proportion of the crop is grown by subsistence farmers should therefore be based on selection under low yielding conditions.     

Grain yield and its components in spring barley under row and hill plot conditions

Twenty homozygous barley lines were grown in row and hill plots at two locations in Ontario in 1973. The hill plots were of two spacings –30×30 cm and 45×45 cm between hills. Within each spacing, three seeding rates were used i.e. 15, 25 and 35 seeds per hill. Grain yield and three of its components, namely; number of seeds per spike (NSS), number of spikes per plot (NSP) and seed weight (SW) were studied. It was concluded that both NSS and SW could be evaluated in hill plots. NSS was found to be an important component of grain yield and its relationship with grain yield was unaffected by plot types and locations. SW also remained unaffected by plot types and seeding rates but as a component of grain yield it was the least important of the three components measured. The correlation between SW and grain yield could be changed by locations. NSP was as important as NSS as a component of grain yield, and was highly correlated with grain yield. Unlike NSS, NSP could not be efficiently evaluated in hill plots since its correlation between row and hill plots was generally lower.     

Repetitive cycling and simple recurrent selection in traditional barley breeding programs

Summary A critical examination of three representative barley development programs from three barley producing areas of the world reveals that the evolution of each can be explained by the concepts of simple or phenotypic recurrent selection. Typically, each has utilized only 13 to 16 separate genetic sources in their program. Most of the sources were introduced over 50 years ago and have been progressively recombined through a simple recurrent selection process. The time period required for selection, testing, and reincorporation of improved genetic recombinants into the breeding program, or the completion of a cycle of recurrent selection, ranged from 6.5 to 10.5 years. If the major operative force in barley breeding is recurrent selection, then additional attention should be given to increasing the genetic base and reducing the time required to complete cycles of selection.     

Genotypic and environmental influence upon the nutritional composition of barley grain

Summary The grain yield and contents of the quantitatively predominant nutritional constituents of barley grain were determined in nine adapted spring barley varieties each grown at seven European locations with three or four replications.The largest variation in nutritional composition was due to different environmental conditions, but genotypic effects were also present. Interactions between genotype and environment were small. The average protein content at different locations varied from 8.1 to 14.7 per cent of the grain dry matter, and was not simply related to the amount of fertilizer-N applied.The nutritional composition of the grain was influenced by the grain yield level. The percentage of dietary fiber and protein decreased with increasing grain yield, but some varietal differences which were independent of the grain yield level could be established.The protein quality depended upon the protein level, as the protein contained more prolamin relatively to non-prolamin protein at high than at low protein levels. A difference between two varieties in the prolamin/non-prolamin ratio was consistent over a wide range of variation in protein content.     

Tracing sources of dwarfing genes in barley breeding in China

To study the origin ofdwarfing genes used in barley breeding inChina, pedigree data of more than 350 dwarfand semi-dwarf cultivars and entriesdeveloped since 1950 were collected. Theresults showed that 68.4% of them werederivatives of just six accessions:`Chibadamai' (CBDM), `Xiaoshanlixiahuang'(XSLXH), `Cangzhouluodamai' (CZLDM),`Aiganqi' (AGQ), `Zhepi 1' and `Yanfu Aizao3' (YFAZ 3). Therefore, these sixaccessions are considered the main donorsof dwarfing genes to barley cultivars bredin China. `CBDM', `XSLXH' and `CZLDM' arelandraces and were used between 1950 and1980. `AGQ', `Zhepi 1' and `YFAZ 3' arereleased cultivars used since 1980. `CBDM',`XSLXH', `CZLDM' and `AGQ' carry the samedwarfing gene uzu on chromosome arm3HL. `Zhepi 1' and `YFAZ 3' likely aremutations at the sdw 1 locus.     

The evaluation of superior Hordeum bulbosum L. genotypes for use in a doubled haploid barley breeding programme

Summary Eight Hordeum bulbosum selections were produced from a cross between Cb 2920/4 and Cb 2929/1, two genotypes widely used in doubled haploid breeding programmes. The selections were hybridized with barley to evaluate their ability to produce high proportions of well-differentiated haploid embryos compared with Cb 2929/1 as control. We report here an initial small-scale investigation followed by a larger-scale test in two different environments to assess seed setting, haploid embryo differentiation rates and VB hybrid formation. These VB embryos contain both parental sets of chromosomes and occur more frequently in the glasshouse during the winter. Two of the eight selections were identified as combining the desirable characteristics of both parents, namely high seed setting on cv. Vada which is partially incompatible with H. bulbosum, large numbers of well-differentiated haploid embryos and a low incidence of VB hybrids. The selections are available for release to interested research workers and plant breedersAbbreviations DH doubled haploid - VB a hybrid from H. vulgare x H. bulbosum which contains both parental sets of chromosomes     

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.