M. Koutsika-Sotiriou

Cereal landraces for sustainable agriculture. A review

Modern agriculture and conventional breeding and the liberal use of high inputs has resulted in the loss of genetic diversity and the stagnation of yields in cereals in less favourable areas. Increasingly landraces are being replaced by modern cultivars which are less resilient to pests, diseases and abiotic stresses and thereby losing a valuable source of germplasm for meeting the future needs of sustainable agriculture in the context of climate change. Where landraces persist there is concern that their potential is not fully realised. Much effort has gone into collecting, organising, studying and analysing landraces recently and we review the current status and potential for their improved deployment and exploitation, and incorporation of their positive qualities into new cultivars or populations for more sustainable agricultural production. In particular their potential as sources of novel disease and abiotic stress resistance genes or combination of genes if deployed appropriately, of phytonutrients accompanied with optimal micronutrient concentrations which can help alleviate aging-related and chronic diseases, and of nutrient use efficiency traits.We discuss the place of landraces in the origin of modern cereal crops and breeding of elite cereal cultivars, the importance of on-farm and ex situ diversity conservation; how modern genotyping approaches can help both conservation and exploitation; the importance of different phenotyping approaches; and whether legal issues associated with landrace marketing and utilisation need addressing. In this review of the current status and prospects for landraces of cereals in the context of sustainable agriculture, the major points are the following: (1) Landraces have very rich and complex ancestry representing variation in response to many diverse stresses and are vast resources for the development of future crops deriving many sustainable traits from their heritage. (2) There are many germplasm collections of landraces of the major cereals worldwide exhibiting much variation in valuable morphological, agronomic and biochemical traits. The germplasm has been characterised to variable degrees and in many different ways including molecular markers which can assist selection. (3) Much of this germplasm is being maintained both in long-term storage and on farm where it continues to evolve, both of which have their merits and problems. There is much concern about loss of variation, identification, description and accessibility of accessions despite international strategies for addressing these issues. (4) Developments in genotyping technologies are making the variation available in landraces ever more accessible. However, high quality, extensive and detailed, relevant and appropriate phenotyping needs to be associated with the genotyping to enable it to be exploited successfully. We also need to understand the complexity of the genetics of these desirable traits in order to develop new germplasm. (5) Nutrient use efficiency is a very important criterion for sustainability. Landrace material offers a potential source for crop improvement although these traits are highly interactive with their environment, particularly developmental stage, soil conditions and other organisms affecting roots and their environment. (6) Landraces are also a potential source of traits for improved nutrition of cereal crops, particularly antioxidants, phenolics in general, carotenoids and tocol in particular. They also have the potential to improve mineral content, particularly iron and zinc, if these traits can be successfully transferred to improved varieties. (7) Landraces have been shown to be valuable sources of resistance to pathogens and there is more to be gained from such sources. There is also potential, largely unrealised, for disease tolerance and resistance or tolerance of pest and various abiotic stresses too including to toxic environments. (8) Single gene traits are generally easily transferred from landrace germplasm to modern cultivars, but most of the desirable traits characteristic of landraces are complex and difficult to express in different genetic backgrounds. Maintaining these characteristics in heterogeneous landraces is also problematic. Breeding, selection and deployment methods appropriate to these objectives should be used rather than those used for high input intensive agriculture plant breeding. (9) Participatory plant breeding and variety selection has proven more successful than the approach used in high input breeding programmes for landrace improvement in stress-prone environments where sustainable approaches are a high priority. Despite being more complex to carry out, it not only delivers improved germplasm, but also aids uptake and communication between farmers, researchers and advisors for the benefit of all. (10) Previous seed trade legislation was designed primarily to protect trade and return royalty income to modern plant breeders with expensive programmes to fund. As the desirability of using landraces becomes more apparent to achieve greater sustainability, legislation changes are being made to facilitate this trade too. However, more changes are needed to promote the exploitation of diversity in landraces and encourage their use.

Response of squash (Cucurbita spp.) as rootstock for melon (Cucumis melo L.).

Abstract The effects of different Cucurbita spp. rootstocks on melon cultivars belonging to different horticultural groups were studied by comparing grafted plants with non-grafted ones under greenhouse and open field growing conditions. Winter melons (Cucumis melo L.) of the Inodorus group, cvs. ‘Thraki’, ‘Peplo’ and ‘Lefko Amynteou’, and a summer melon of the Cantalupensis group, cv. ‘Kokkini Banana’, were used as scions. The commercial hybrids of Cucurbita spp. ‘TZ-148’ and ‘Mamouth’ and the landrace of winter squash (C. moschata L.) ‘Kalkabaki’ were used as rootstocks. The commercial rootstocks were compatible with all scion cultivars tested, while the landrace was compatible with the three cultivars but with lower survival ratios. Generally, differences in stem diameter between Cucurbita and Cucumis reduced the survival ratio of grafts. Fruit yield was not affected by any rootstock. Descriptive and qualitative characteristics of the fruit of the grafted plants were similar to those of the intact ones, except for taste and texture, which showed a remarkable deterioration in some of the stock/scion combinations tried. The deterioration was more severe under protection. However, all Cucurbita spp. rootstocks were found acceptable for honeydew melons (cv. ‘Lefko Amynteou’), with C. moschata (cv. ‘Kalkabaki’) being the best. The landrace of C. moschata is recommended as a source of breeding material for rootstocks of honeydew melons.

Description and analysis of genetic diversity among squash accessions

In this work, the part of the squash core collection, maintained in the Greek Gene Bank, was assessed using the morphological and molecular data. Sixteen incompletely classified accessions of the squash were characterized along with an evaluation of their resistance against two isolates of Fusarium oxysporum. A molecular analysis using Random Amplified Polymorphic DNA (RAPD) markers was also performed, revealing high level of polymorphism. To study the genetic diversity among the squash accessions, a clustering procedure using Unweighed Pair Group Method and Arithmetic Average (UPGMA) algorithm was also adopted. Two independent dendrograms, one for the morphophysiological and one for molecular data were obtained, classifying the accessions into two and three main clusters, respectively. Despite the different number of the clusters there were many similarities between these two dendrograms, and a third dendrogram resulting from their combination was also produced, based on Gowers distance and UPGMA clustering algorithm. In order to determine the optimal number of clusters, the upper tail approach was applied. The more reliable clustering of the accessions was accomplished using RAPD markers as well as the combination of the two different data sets, classifying the accessions into three significantly different groups. These groups corresponded to the three different cultivated species of C. maxima Duch., C. moschata Duch., and C. pepo L. The same results were also obtained using Principal Component Analysis.

The cultivation revival of a landrace: pedigree and analytical breeding

This paper aims at improving the legume landrace Fava Santorinis (Lathyrus sp.) through the study of the existing variability, and an intra-landrace pedigree, combined with analytical selection, scheme. The experiments were conducted at the farm of Aristotle University of Thessaloniki during five growing seasons (2005–2009), and the selection was applied on a spaced plant conditions. In the first stage, single-plant frequency distributions of the source landrace for grain yield and pod number plant−1 was studied, and a percentage of 60.80% of non productive plants was found. In the second stage, improvement of grain yield relied on direct pedigree selection, accomplished by analytical selection for the number of pods plant−1, plant leaf color and vigor. This procedure was followed along the first generation progenies, and, later on, along two successive generations on the offsprings of two populations, one with purple and the other with white flower color. In the third stage, the evaluation of the fourth-generation progenies of each population for grain yield, showed superiority ranging from 42.48 to 107.89% compared to the source landrace. Furthermore, the breeding procedure succeeded in: (i) decreasing the coefficient of variability of grain yield and pods plant−1, thus increasing the stability of performance, (ii) reducing by 56.41 and 39.67% the non productive plants for white and purple flower populations, respectively, and (iii) maintaining the mean and the variability for pod traits as in the original landrace. Realized heritability for grain yield was positive during all selection cycle.

Assessment of tomato source breeding material through mating designs

Cultivated tomato has a narrow germplasm base because of several population bottlenecks in the form of founder events, as well as natural and artificial selections that occurred during domestication and evolution of modern cultivars. The F 2 of commercial single-cross hybrids, as well as locally well-adapted varieties, provide germplasm for developing recombinant lines and exploiting genetic variability, respectively. The present study aims to discriminate the breeding value of tomato source material, i.e. commercial hybrids or well-adapted varieties, by (i) estimating tolerance to inbreeding of hybrids or estimating heterosis of diallel hybrids between varieties, (ii) determining undesirable traits and (iii) determining general combining ability (GCA) and specific combining ability (SCA) effects from diallel crosses between hybrids and between varieties. Two hybrids and four varieties were assessed. One hybrid showed 0-03 inbreeding vigour, which was not combined with undesirable traits in the F 2 generation. However, negative GCA and positive SCA values did not support the hybrid as source material, provided that hybrids with low inbreeding depression, positive GCA and negative SCA correspond to an F 2 capable of developing recombinant lines. The assessment of the varieties showed positive GCA and 0-34 heterosis in one variety, indicating agreement between yield and GCA, and that high-yielding varieties may produce high-yielding hybrids. In conclusion, the proposed mating design, taking into account the tolerance to inbreeding for hybrids and the heritability of general worth for both resources, provides a mechanism for ensuring continued improvement in plant performance through plant selection programmes.

Genetic diversity in four cabbage populations based on random amplified polymorphic DNA markers

Genetic diversity in four local Greek cabbage open-pollinated populations was investigated using RAPD (Random Amplified Polymorphic DNA) DNA markers in 18 individual plants from each population. A total of 24 random primers detected 90 polymorphic bands in the four populations studied, with an average of 3·75 bands/primer. The mean between-population differentiation was close to 40%, leaving 60% for within-population diversity. The individual plants were grouped, based on the Jaccard coefficient, by clustering (Unweighted Pair Group Method and Arithmetic Average – UPGMA) and an ordination (Principal Coordinates Analysis – PCO) methods, resulting in 7 and 6 groups, respectively. In general, there was a notable similarity in the grouping of the individuals with these two methods. In addition, Neis standard genetic distance between populations, as calculated on the basis of within-population gene frequencies, was employed to group the populations by the UPGMA method. Clustering results were in good agreement with previously reported results based on morphological descriptors applied to the same populations. It was concluded that RAPD markers could be exploited as alternative or supplementary tools to already established methods for the evaluation and classification of cabbage genetic resources.

Beneficial Exploitation of Additive Genetic Effects to Improve Yield Potential per Plant in Maize

The effect of inbreeding on yield potential per plant and the load of deleterious genes in maize ( Zea mays L.) were studied. Twelve recycled hybrids obtained though inbreeding and selection on the basis line performance per se , along with their original hybrid PR 3183 and the check hybrid B73×Mo17, were tested in a R28 honeycomb trial under very low density (0.74 plants/m 2 ). Inbreeding depression was related with reduced yield potential per plant and increased CV of individual plant yield (estimated in F 1 and F 3 ), as well as with increased heterosis. The recycled hybrids were found to have improved yield potential per plant in both F 1 and F 3 , lower CV values in F 3 , and lower inbreeding depression. Results were indicative of the effective exploitation of the additive genetic effects, which reduced the load of deleterious genes, and produced less heterozygous hybrids that were characterized by improved yield potential per plant.

The Use of RAPD Markers in Monitoring Molecular Changes During a Selection Process in Snap Bean

ABSTRACT Random Amplified Polymorphic DNA (RAPD) markers were used to follow changes occurring at the molecular level during a selection process aimed at restoring purity of a traditional Greek snap bean cultivar that presented a profound deterioration in yield, earliness of maturity and certain morphological characters, after a long period of variety maintenance. These changes, as evidenced by the final agronomic evaluation, also could be followed by molecular marker polymorphism detection throughout four cycles of honeycomb mass selection. Further, it was very interesting from a practical point of view to see that highly deviant material (most probably due to seed mixture or contamination) can very easily be detected in variety maintenance seed stocks. Finally, the data obtained suggest that RAPD markers could serve to predict the efficiency of a further selection effort based on the same breeding methodology.

Phenology and Quality Studies on a Snap Bean Cultivar Deviation

Abstract During the first stages of a pedigree intraselection for refining a snap bean cultivar, a deviation in earliness and pod and seed uniformity was observed. This research presents the procedure followed to study, evaluate and extract the deviation. It was approached by: (i) studying earliness and yield stability per se of normal and deviant selected families; (ii) comparing normal and deviant selections with commercial cultivars; and (iii) evaluating advanced selected families for uniformity and purity. The normal progenies showed a concentrated flowering period and maturity, while the deviant ones were late and unstable. The deviant selection yielded less than one-fourth of the normal one. Advanced families had a high degree and stability of earliness, high yield, normal seeds and pods, and a high-quality product. The applied procedure resulted in monitoring the cultivar deviation, estimating its undesirable performance and low market value, and removing it, saving for the breeder the valuable adapted cultivar.

Inbreeding effects on a winter squash landrace.

Estimates of inbreeding effects in a landrace are necessary in order to acquire information on the presence of different types of gene action for important traits. Twelve lines with different levels of inbreeding coefficients ( F =0, 0·25, 0·50 or 0·75) were developed from three phenotypically selected families of a winter squash landrace ( Cucurbita moschata Duchesne) between 2000 and 2002 in the area of Thermi-Thessaloniki, Greece. During 2003, a field experiment was established at this location to evaluate the lines. The agronomical characters measured were: the number and weight of total commercial fruits, days to first female blossom, seed weight, size of pollen grains and water-stress tolerance. Comparisons were also made of morphological characters, the dry matter, the total soluble solids and the pH of fruits. Lines with inbreeding coefficient F =0·50 were found to have the highest values for most of the measured characteristics. Significant family×inbreeding interactions were found, revealing different trends for the linear, quadratic and cubic components of each family with inbreeding coefficients. Three F =0·50 lines selected from within each representative family were evaluated along with four winter squash landraces from the C. moschata collection of the Greek Gene Bank, during 2004 in the area of Thermi. These F =0·50 lines showed a superior performance of three components contributing to yield, indicating that one generation of selfing improved the agronomic performance maintaining concurrently the substantial characteristics of the landrace.