Showing papers on "Plant breeding published in 2012"

Rice Blast Management Through Host-Plant Resistance: Retrospect and Prospects

Abstract: Rice (Oryza sativa) plays a significant role in achieving global food security. However, it suffers from several biotic and abiotic stresses that seriously affect its production. Rice blast caused by hemibiotropic fungal pathogen Magnaporthe oryzae is one of the most widespread and devastating diseases of rice. The crop rice is vulnerable to this pathogen from seedlings to adult plant stages affecting leaves, nodes, collar, panicles and roots. This disease can be effectively managed through host resistance. Of the 100 blast resistance genes, identified and mapped in different genotypes of rice, 19 genes have been cloned and characterized at the molecular level. Most of these genes belong to nucleotide binding sites and leucine rich repeats. Besides more than 350 quantitative trait loci (QTLs) have also been identified in the rice genome. These blast resistance genes and QTLs have been successfully mobilized in the commercial cultivars by using standard plant breeding techniques and also by marker assisted backcross breeding. With the advent of latest molecular biology techniques and our understanding of the basic mechanisms of Magnaporthe-rice pathosystem, the strategies for broad-spectrum resistance to M. oryzae can be designed in future.

Haploids and Doubled Haploids in Plant Breeding

Abstract: Haploids are plants (sporophytes) that contain a gametic chromosome number (n). They can originate spontaneously in nature or as a result of various induction techniques. Spontaneous development of haploid plants has been known since 1922, when Blakeslee first described this phenomenon in Datura stramonium (Blakeslee et al., 1922); this was subsequently followed by similar reports in tobacco (Nicotiana tabacum), wheat (Triticum aestivum) and several other species (Forster et al., 2007). However, spontaneous occurrence is a rare event and therefore of limited practical value. The potential of haploidy for plant breeding arose in 1964 with the achievement of haploid embryo formation from in vitro culture of Datura anthers (Guha and Maheshwari, 1964, 1966), which was followed by successful in vitro haploid production in tobacco (Nitsch and Nitsch, 1969). Many attempts have been made since then, resulting in published protocols for over 250 plant species belonging to almost all families of the plant kingdom (reviewed in Maluszynski et al., 2003). In fact, under optimal conditions, doubled haploids (DH) have been routinely used in breeding for several decades, although their common use is still limited to selected species. There are several reasons for this. These might be categorized as biological, based on plant status (annual, biannual, perennial, authogamous, allogamous, vegetativelly propagated) and flower morphology or technical, which are the result of the feasibility and efficiency of DH induction protocol. Induction protocols substantially vary, in fact, not only among species but also among genotypes of the same species.

Salinity tolerance in plants: Breeding and genetic engineering

Abstract: Salinity stress limits crop yield affecting plant growth and restricting the use of land. As world population is increasing at alarming rate, agricultural land is shrinking due to industrialization and/or habitat use. Hence, there is a need to utilize salt affected land to meet the food requirement. Although some success has been achieved through conventional breeding but its use is limited due to reproductive barrier and scarcity of genetic variations among major crops. The genetic engineering has proven a revolutionary technique to generate salt tolerant plants as one can transfer desired gene from any genetic resource and/or alter the expression of existing gene(s). There are examples of improved salinity tolerance in various crop plants through the use of genetic engineering. However, there is a further need of improvement for successful release of salt tolerant cultivars at field level. In this review, we have given a detailed update on production of salt-tolerant plants through genetic engineering. Future prospects and concerns, along with the importance of novel techniques, as well as plant breeding are also discussed.

Development of a transgenic early flowering pear ( Pyrus communis L.) genotype by RNAi silencing of PcTFL1 - 1 and PcTFL1 - 2

Abstract: Trees require a long maturation period, known as juvenile phase, before they can reproduce, complicating their genetic improvement as compared to annual plants. ‘Spadona’, one of the most important European pear (Pyrus communis L.) cultivars grown in Israel, has a very long juvenile period, up to 14 years, making breeding programs extremely slow. Progress in understanding the molecular basis of the transition to flowering has revealed genes that accelerate reproductive development when ectopically expressed in transgenic plants. A transgenic line of ‘Spadona’, named Early Flowering-Spadona (EF-Spa), was produced using a MdTFL1 RNAi cassette targeting the native pear genes PcTFL1-1 and PcTFL1-2. The transgenic line had three T-DNA insertions, one assigned to chromosome 2 and two to chromosome 14 PcTFL1-1 and PcTFL1-2 were completely silenced, and EF-Spa displayed an early flowering phenotype: flowers developed already in tissue culture and on most rooted plants 1–8 months after transfer to the greenhouse. EF-Spa developed solitary flowers from apical or lateral buds, reducing vegetative growth vigor. Pollination of EF-Spa trees generated normal-shaped fruits with viable F1 seeds. The greenhouse-grown transgenic F1 seedlings formed shoots and produced flowers 1–33 months after germination. Sequence analyses, of the non-transgenic F1 seedlings, demonstrated that this approach can be used to recover seedlings that have no trace of the T-DNA. Thus, the early flowering transgenic line EF-Spa obtained by PcTFL1 silencing provides an interesting tool to accelerate pear breeding.

Nutritionally Enhanced Staple Food Crops

Abstract: Crop biofortification is a sustainable and cost-effective strategy to address malnutrition in developing countries. This review synthesizes the progress toward developing seed micronutrient-dense cereals and legumes cultivars by exploiting natural genetic variation using conventional breeding and/or transgenic technology, and discusses the associated issues to strengthen crop biofortification research and development. Some major QTL for seed iron and zinc, seed phosphorus, and seed phytate in common bean, rice,J;md wheat have been mapped. An iron reductase QTL associated with seed-iron ~QTL is found in common bean where the genes coding for candidate enzymes involved in phytic acid synthesis have also been mapped. Candidate genes for Ipa co segregate with mutant phenotypes identified in rice and soybean. The Gpe-B1 locus in wild emmer wheat accelerates senescence and increases nutrient remobilization from leaves to developing seeds, and another gene named TtNAM-B1 affecting these traits has been cloned. Seed iron-dense common bean and rice in Latin America; seed iron-dense common bean in eastern and southern Africa;.....

Phenotyping of traits imparting drought tolerance in lentil

Abstract: Lentil is one of most important pulse crops in South Asia, and invariably encounters terminal moisture stress, leading to forced maturity and lower yield. A long and prolific root system is known to enhance capacity of the plant to extract water from the lower soil strata and thus help avoid the water stress. We assessed genetic variation for 12 traits among 43 lentil genotypes comprising improved varieties and promising breeding lines. The average root length at the 65-day plant stage ranged from 42 to 83 cm. Two genotypes (EC 208362 and VKS 16/11) with shorter root length and poor dry root weight (DRW) and three genotypes (DPL 53, JL 1, and IPL 98/193) with longer root length and high DRW were identified with stable performance over the years. Relationship of root traits with seed yield under rainfed conditions was non-significant in our study. The SPAD value (chlorophyll content) showed significantly positive correlation with DRW (r = 0.45**) and root length (r = 0.44**) and thus can be used as selection criterion for phenotyping root traits which are otherwise difficult to measure in the field. In drought-prone environments, early flowering and maturity, seedling vigour, and high SPAD value, biological yield, and harvest index were identified as key traits for higher seed yield in lentil. Our results revealed significant genetic variability for these traits in lentil germplasm. Indian genotypes adapted to rainfed conditions were shown to have longer roots and higher DRW. The three genotypes (DPL 53, JL 1, and IPL 98/193) identified with superior root traits either originated from or have in their ancestries at least one parent adapted to rainfed conditions. These genotypes can be utilised for the development of mapping populations to identify QTLs associated with these traits for marker-assisted breeding of drought-tolerant, high-yielding varieties of lentil.

Genome-Wide Haplotype Changes Produced by Artificial Selection during Modern Rice Breeding in Japan

Abstract: During the last 90 years, the breeding of rice has delivered cultivars with improved agronomic and economic characteristics. Crossing of different lines and successive artificial selection of progeny based on their phenotypes have changed the chromosomal constitution of the ancestors of modern rice; however, the nature of these changes is unclear. The recent accumulation of data for genome-wide single-nucleotide polymorphisms (SNPs) in rice has allowed us to investigate the change in haplotype structure and composition. To assess the impact of these changes during modern breeding, we studied 177 Japanese rice accessions, which were categorized into three groups: landraces, improved cultivars developed from 1931 to 1974 (the early breeding phase), and improved cultivars developed from 1975 to 2005 (the late breeding phase). Phylogenetic tree and structure analysis indicated genetic differentiation between non-irrigated (upland) and irrigated (lowland) rice groups as well as genetic structuring within the irrigated rice group that corresponded to the existence of three subgroups. Pedigree analysis revealed that a limited number of landraces and cultivars was used for breeding at the beginning of the period of systematic breeding and that 11 landraces accounted for 70% of the ancestors of the modern improved cultivars. The values for linkage disequilibrium estimated from SNP alleles and the haplotype diversity determined from consecutive alleles in five-SNP windows indicated that haplotype blocks became less diverse over time as a result of the breeding process. A decrease in haplotype diversity, caused by a reduced number of polymorphisms in the haplotype blocks, was observed in several chromosomal regions. However, our results also indicate that new haplotype polymorphisms have been generated across the genome during the breeding process. These findings will facilitate our understanding of the association between particular haplotypes and desirable phenotypes in modern Japanese rice cultivars.

Comparison of phenotypic and molecular characterizations of some important wheat cultivars and advanced breeding lines

Abstract: Analysis of genetic variation is fundamental to plant breeding programs. The present study evaluated genetic diversity of thirty wheat cultivars and advanced breeding lines using phenological and agro-morphological characters and molecular markers (ISSRs) data. The field experiment was carried out in growing season of 2008-2009. The measured phenotypic traits (20 traits) illustrated significant differences among the wheat accessions. Variation for most of the traits was observed. The clustering pattern based on phenotypic data using WARD method assigned the wheat genotypes into four groups. The ten ISSR primers amplified a total of 86 bands in the set of thirty wheat accessions, of which 69 bands (80.2%) were polymorphic. The majority of the primers showed polymorphism information content (PIC) values close to the average (0.21-0.23), indicating diverse nature of the wheat accessions and/or highly informative ISSR markers used in this study. The genotyping data of the ISSR markers were used to assess genetic variation in the wheat accessions by CLINK- based dendrogram and principle coordinate analysis (PCoA). Both of the methods classified the 30 wheat accessions in five groups and presented similar grouping of the genotypes with some minor deviations. The results showed that the studied ISSR markers, provided sufficient polymorphism and reproducible fingerprinting profiles for evaluating genetic diversity of wheat genotypes. The analyzed wheat accessions showed a good level of genetic variability for both assessed quantitative and molecular characters. No correlation was found between variation measurements identified using molecular markers and quantitative traits. Molecular variation evaluated in this study in combination with agronomic and morphological characters of wheat can be useful in traditional and molecular breeding programs.

Animal feeding studies for nutritional and safety assessments of feeds from genetically modified plants: a review

Abstract: In the future there will be a very strong competition between arable land use for phytogenic biomass production for feed/food, fuel, fibre and other industrial materials, as well as for settlements and natural conservation areas because of the growing population and limited natural resources. Therefore plants with high and stable yields, and requiring low external inputs (low input varieties) should be the main aim of plant breeding. In addition to traditional breeding, plant biotechnology seems to have the potential to contribute to this objective. Nutritional and safety studies with feed/food made from such modified plants are one of the most important prerequisite for public acceptance, and to improve knowledge in the feed/food sciences. The first step for the nutritional and safety assessment of such modified plants is the compositional analysis of potential feed/food, including the newly expressed proteins and other new constituents, and its comparison with conventional counterparts. In vitro studies and experiments with laboratory animals comprise the next steps of the assessment. About 70-90 % of the harvested biomass from genetically modified plants (GMPs) is consumed by food producing animals. Therefore, feeding studies with target animals are of special concern for nutritional assessment, and these are considered in more detail in the present paper. Up to now most studies have been done with GMPs of the 1st generation (plants with input traits, but without substantial changes in composition). Other experimental designs for nutritional and safety assessments are recommended for GMPs with output traits or with substantial changes in composition (plants of the 2nd generation).

Marker assisted selection (MAS) for developing powdery mildew resistant pea cultivars

Abstract: In this contribution we review the state of the art for genetic resistance to powdery mildew, caused by Erysiphe pisi, in pea (Pisum sativum L.) and potential use of marker-assisted selection (MAS) for developing disease resistant cultivars. Powdery mildew is important in many production regions worldwide and reduces yield and crop quality when present in epidemic proportions. Although genetic resistance to powdery mildew is available (er1 and er2) and has been durable since its characterization in 1969, recently a new dominant gene (Er3) has been reported in Pisum fulvum, a wild relative of pea that is different from previously reported er1 and er2. The efficacy of these genes may be at risk from the point of view of new pathotypes and pathogens. Erysiphe trifolii has been reported that was not previously known as a pathogen of pea powdery mildew. A continued search for new and diverse resistant sources remains a priority in pea breeding and special emphasis should be paid to selection of resistance that will prolong durability of existing resistance genes. Marker assisted selection is a new emerging approach for target breeding that has been intensively employed especially in cereals and has recently got popularity among legume breeders. With the advancement of genomic research, especially related to quantitative traits loci, the MAS is potentially anticipated future technique for routine plant breeding that is scarce in legumes at present. In pea, various DNA markers have been reported linked to er1, er2 and Er3 at varying distances in different mapping populations that are currently being used in breeding programs. Currently MAS of single gene is the most powerful approach and successes have been witnessed. If single marker is not close enough to the gene of interest then two flanking markers are considerably utilized to improve the correct identification that is being successfully employed in MAS for powdery mildew resistance in pea.

Plant breeding for abiotic stress tolerance

Abstract: Abiotic Stresses: Challenges for Plant Breeding in the Coming Decades.- Breeding for Stress-Tolerance or Resource-Use Efficiency?.- The Physiology of the Abiotic Stresses.- Breeding for Nitrogen Use Efficiency.- Breeding for Phosphorous Use Efficiency.- Breeding for Water Use Efficiency.- Breeding for Salinity Tolerance.- Breeding for Aluminum Tolerance.- Breeding Heat-Stress Tolerance.- Breeding Perennial Species for Abiotic Stresses.

Genetic diversity in the foxtail millet (Setaria italica ) germplasm as determined by agronomic traits and microsatellite markers

Abstract: Setaria italica (L.) P. Beauv. is a model plant that attracts international attention, which is the second most widely cultivated species of millet, especially in East Asia. It has the longest history of cultivation among the millets, having been grown in China since sometime in the sixth millennium BC. It also has been a main crop of the indigenous people of Taiwan for a long time. However, insufficient researches had been conducted about the foxtail millet germplasm in Taiwan. To assess the genetic diversity of millet population, a total of 324 landraces of foxtail millet were collected from around Taiwan, and four years of field researches were conducted for agronomic traits observation. The genetic diversity of the millet population was measured using 33 agronomic traits and 40 microsatellite markers. Average number of alleles (2.4), highly polymorphic information content (PIC) (0.381), observed heterozygosity (0.190) and expected heterozygosity (0.354) were shown. Thirty-five SSR markers showed significant deviation from Hardy-Weinberg equilibrium in 324 landraces and all these markers had low null allele frequencies. Analysis with the Unweighted Pair Group Method with Arithmetic Mean (UPGMA) method and Principal Component Analysis (PCA) revealed that the 324 landraces could be divided into three groups that coincided with the geographical areas, including northern Taiwan, central Taiwan, and sourthern Taiwan, which account for close relationship between crop distribution and human activities. Agronomical analyses with a plant height of 80.6 to 155.2 cm, spike length of 7.5 to 28.9 cm and growth periods of between 141 and 178 days had showed that there was enough variation to create promising lines for breeding programs. This study not only provides a complete foxtail millet germplasm from Taiwan but also demonstrates that the Taiwanese foxtail millets are very diverse and can be useful for selective breeding of specific traits and in enhancing the genetic base of breeding programs in the future.

Nutrition and Quality

Abstract: Publisher Summary This chapter focuses on the relationship between nutrient supply, yield, quality, and toxicity of plants. Overall quality can be defined as the sum of individual properties that enable a plant or a plant product to meet the requirements of a user, and it depends on various physical and chemical plant properties. Physical properties determine the appearance of the plant, whereas the chemical properties of a plant determine their nutritional and sensory qualities. The quality of a plant can be improved by high concentrations of essential nutrients, carbohydrates, essential amino acids, lipids, organic acids, flavors, vitamins, and bioactive compounds. Plant quality is also controlled by genetic and physiological factors, and both conventional breeding and transgenic approaches can improve nutritional quality of crops. Various appearance parameters such as length, width, weight, or volume of a product are influenced by plant nutrition, and nutritional deficiency can often result in reduced product size of fruits and vegetables. Biofortification is considered as a sustainable and cost-effective strategy to combat element malnutrition in plants, and it includes the increase of the concentration and or the bioavailability of nutrients in plants through agronomic measures or plant breeding approaches. Of the potentially toxic elements, cadmium (Cd) is of primary concern, mainly because of its relatively high soil/plant transfer and its relatively high human but low plant toxicity. Plants with leafy vegetables and root crops generally have higher concentrations of this element, and research on various agronomic practices to solve this problem is being carried out.

Multivariate analysis of genetic diversity in wheat (Triticum aestivum L.) recombinant inbred lines using agronomic traits

Abstract: Determination of genetic diversity is useful for plant breeding and hence production of more efficient plant species under different conditions. A set of 94 bread wheat recombinant inbred lines derived from cross between Roshan and Superhed#2 varieties was evaluated using a randomized complete block design (RCBD) with two replications. Days to heading, flag leaf area, peduncle length, spike length, plant height, number of spikelet per spike, number of spikes, number of grain per spike, 1000 grain weight, grain yield, shoot biomass, percent of grain protein, straw yield and harvest index were measured. Analysis of variance revealed significant differences among the lines for all the studied traits. The level of genetic variation was higher for peduncle length, flag leaf area, number of spikes, grain yield, straw yield and shoot biomass. Cluster analysis based on all the traits using Ward’s algorithm and squared Euclidean distances assigned the lines into three groups. In these grouping, group two lines showed highest mean of grain yield. In factor analysis, five first factors explained 80.26% of total variation. First factor determining 23.94% of the variation was named as grain yield factor. Cluster analysis based on the five factors grouped the lines into three groups. The first group lines were superior with respect to grain yield.

Why Double Haploid Production is the Best Method for Genetic Improvement and Genetic Studies of Wheat

Abstract: Double haploid (DH) breeding not only helps in accelerating conventional plant breeding programmes and make early release of cultivars with superior and desirable traits possible but it has greater utility in other research aspects of plant breeding, genetics and genetic engineering. DHs are important constituent of germplasm. These also helps in complementing back cross breeding by transferring genes of interest between wild relatives thus breaking genetic barriers. On the other hand unique complete homozygous nature of DHs, less time requirement to produce a large number of DHs, absence of heterozygosity, efficiency over conventional systems and absence of gametoclonal variation in DHs make them very valuable material for very important genetic and molecular studies. So, DHs are extensively used for genetic studies like studying inheritance of quantitative traits, Quantitative Trait Loci (QTL) mapping, Genomics, gene identification, whole genome mapping and production of stable transgenic plants. In this review, we briefly discuss utility of DHs in these genetic and molecular studies.

Molecular breeding in plants: moving into the mainstream

Abstract: Molecular breeding, including both marker-assisted breeding and genetic engineering, has experienced significant innovations and advances during the past three decades. Starting with Mendelian genetics, plant breeders have progressed from using morphological markers to protein isozymes and then ultimately to DNA-based markers, which have enabled routine genome-wide analysis. As a result, thousands of genes and quantitative trait loci (QTL) have been mapped across the major crop species, laying the foundation for marker-assisted selection (MAS) techniques, such as precise marker-assisted backcrossing, to transfer desirable loci into breeding lines. With the subsequent development of advanced MAS strategies, including QTL pyramiding, marker-assisted recurrent selection and genomic selection, marker-assisted approaches have led to rapid gains in selection for plant breeding programs. Breeding by design and genetic modeling have received great attention as designing a desirable plant based on marker and associated gene information becomes increasingly possible. Following rice as the first crop species sequenced, whole genome sequences have been increasingly available for more and more crop species, enabling genotyping by sequencing and sequence-based marker technology and molecular breeding strategies to become a viable option, one widely used in large multinational seed companies. With significant reduction of genotyping cost and increased throughput, next-generation sequencing and SNP genotyping technologies are increasingly making MAS a choice of public-sector plant breeding as well. Now crop genomic diversity can be characterized at the sequence level based on haplotype maps, and molecular breeding can be further accelerated through allele mining and haplotype-based design and selection. With all the developments and significant advances in various fields of molecular biology and their integration with platforms and tools, molecular breeding is rapidly moving into the vanguard of mainstream breeding programs. To review and evaluate new theories and technologies recently developed in relation to plant breeding, the 3rd International Conference on Plant Molecular Breeding (ICPMB) was held in Beijing, China, Sept. 5–9, 2010. The conference was organized by an International Organization Committee represented by Zhi-Kang Li (Chinese Academy of Agricultural Sciences/International Rice Research Institute), Jean-Marcel Ribaut (the Generation Challenge Program), Aimin Zhang (Chinese Y. Xu (&) Institute of Crop Sciences/International Maize and Wheat Improvement Center (CIMMYT), Chinese Academy of Agricultural Sciences, 100081 Beijing, China e-mail: y.xu@CGIAR.ORG

A molecular marker linked to the mollis gene conferring soft-seediness for marker-assisted selection applicable to a wide range of crosses in lupin (Lupinus angustifolius L.) breeding

Abstract: To broaden the gene pool of domesticated commercial cultivars of narrow-leafed lupin (Lupinus angustifolius L.), wild accessions are used as parents in crossing in lupin breeding. Among the progenies from wild × domesticated (W × D) crosses, the soft-seediness gene mollis is the most difficult domestication gene to be selected by conventional breeding methods, where molecular marker-assisted selection (MAS) is highly desirable. MAS in plant breeding requires markers to be cost-effective and high-throughput, and be applicable to a wide range of crosses in a breeding program. In this study, representative plants from an F8 recombinant inbred line (RIL) population derived from a W × D cross, together with four cultivars and four wild types, were used in DNA fingerprinting by microsatellite-anchored fragment length polymorphisms (MFLP). Two co-dominant MFLP polymorphisms were identified as candidate markers linked to the mollis gene, and one of the candidate markers was selected and converted into a co-dominant, sequence-specific PCR marker. This marker, designated MoLi, showed a perfect match with phenotypes of seed coat permeability on a segregating population consisting of 115 F8 RILs, confirming the close genetic linkage to the mollis gene. Validation tests showed that the banding pattern of marker MoLi is consistent with all the 25 historical and current commercial cultivars released in Australia, and is consistent with mollis genotypes in 119 of the 125 accessions in the Australian L. angustifolius core collection. Marker MoLi provides a cost-effective way to select the mollis gene in a wide range of W × D crosses in lupin breeding.

Genetic Diversity of Diploid and Tetraploid Cottons Determined by Ssr and Issr Markers

Abstract: Cotton as an annual crop is mainly grown for its fiber and oil in the seed. Determining genetic diversity in the germplasm is the first step of plant breeding. This study aimed to determine genetic diversity for diploid and tetraploid cotton genotypes grown in different parts of the world. SSR (Simple Sequence Repeats) and ISSR (Inter Simple Sequence Repeats) markers were used to determine genetic relationships among Gossypium species and genotypes. Using 39 SSR and 5 ISSR markers, 173 alleles (averaging 3.93 alleles per locus) were produced from 25 cotton genotypes. Out of 173 alleles, 155 (89.60%) were polymorphic among the genotypes and polymorphic information content (PIC) values were between 0.0040 and 0.9993 averaging 0.4396. Genetic diversity ranged from 0.04 to 0.58 among all the genotypes inspected. This ratio was 0.04-0.23 within G. hirsutum L. and 0.07-0.26 within G. barbadense L. species. Out of these two species, genetic diversity ranged from 0.23 to 0.57 among other diploid and tetraploid species. Genetic diversity was low within commercial cultivars that are also frequently used in breeding programs (0.08-0.20). It is advisable to use wild type cottons to increase present genetic diversity in germplasm pools to have a better chance for the selection of the desired traits.

Correlation and path coefficient analysis for various quantitative traits in chickpea (Cicer arietinum L.).

Abstract: The present studies were conducted in the field of the department of Plant Breeding and Genetics, University of Agriculture, Faisalabad, during the crop season 2008-2009. The higher estimate of heritability was found for plant height while genetic advance for number of pods per plant. Correlation studies showed that biomass per plant, number of pods per plant, number of secondary branches per plant, number of seeds per pod and 100-seed weight were positive and significant at genotypic level but positive and highly significant at phenotypic level. Higher direct effects were found for number of days taken to flowering and maturity, biomass per plant and 100-seed weight on grain yield per plant. It was concluded that selection can be made on the basis of number of grains per plant, 100-seed weight and grain yield per plant.

Drought stress effects on two common bean cultivars with contrasting growth habits

Abstract: In most rainfed production areas in Iran, where wheat fallow is common, crop yield and resource sustainability could be improved by changing to more diverse crop rotation. It seems necessary to identify crop cultivars suitable for such diversification. This study was aimed to determine responses of two common bean (Phaseolus vulgaris L.) cultivars with different growth habits (Sayyad as an indeterminate and D81083 as a determinate cultivar) to water stress conditions. The study was conducted in controlled conditions (the greenhouse of Department of Crop Production and Plant Breeding, College of Agriculture Shiraz University, Shiraz, Iran) during 2008 growing season. There were four water stress levels (100, 75, 50 and 25% of field capacity by weight). The results showed that plant height, number of leaves, leaf area, number of pods, pod dry weight and total dry weight of both cultivars responded significantly to water stress conditions. Water stress also reduced stem height and reduced leaf area. Furthermore, it reduced pod dry weight in both cultivars and in 50 and 25% water stress levels, all plant pods of both cultivars were aborted. Common bean cultivar with determinate growth habit (D81083) appeared to have potential as a dryland rotation crop for arid areas with dryland farming. Further field research might shed more light on sensitivity of bean cultivars to water stress levels with the aim of crop diversification for dryland areas in Iran, where adequate moisture supply is limiting.

Diversity analysis of chickpea ( Cicer arietinum L.) germplasm and its implications for conservation and crop breeding

Abstract: The exploration of genetically variable accessions is the key source of germplasm conservation and potential breeding material for the future. The more diverse group of cultivars provides an ample opportunity to breeders for releasing new and superior varieties, considering their quality traits for direct commercial utilization. In this study, we assessed the genetic diversity of Cicer arietinum 70 accessions from Pakistan and USA using morphological traits, seed protein and molecular markers. Based on four morphological traits, the average coefficient of variation was calculated as 56.8% with significant correlation among yield traits. The analysis revealed that the accessions 1898, 2819, 3022, 3037, 3040, 3043, 3054, 3059 and 3063 were best in performance with a total of 12% environmental error. The cluster analysis based on protein data revealed 50% genetic diversity among accessions. The clustering pattern did not show any grouping that could be attributed to either the geographic distribution or the field performance. For molecular characterization of germplasm 5 PCR based RAPD primers, OPA4, OPA9, OPG13, UBC181 and UBC733b used were found to be polymorphic with 37% genetic diversity among local and exotic accessions. Whereas, 3 SSR primers viz., CaSTMS2, Ca- STMS15 and CaSTMS21 scored the genetic variability up to 55% by cluster analysis through UPGMA percent disagreement. The primers, TA72 and TA130 were linked with yield related traits, indicated highest dissimilarity index value (0.69) and notable variation in the identified promising lines. The Morphometric, Biochemical and Molecular markers reported here, are helpful to assess the extent of genetic diversity among Chickpea accessions and can be used to identify the unreported cultivars with desirable quantitative traits for improving Chickpea yield in Pakistan. Based on the study, the accessions 3043 and 3054 have been recommended to the breeders for their future use in multiplication and screening against various diseases.

Inheritance of resistance to root-lesion nematodes (Pratylenchus thornei and P. neglectus) in five doubled-haploid populations of wheat

Abstract: Nematode species Pratylenchus thornei and P. neglectus are the two most important root-lesion nematodes affecting wheat (Triticum aestivum L.) and other grain crops in Australia. For practical plant breeding, it will be valuable to know the mode of inheritance of resistance and whether the same set of genes confer resistance to both species. We evaluated reactions to P. thornei and P. neglectus of glasshouse-inoculated plants of five doubled-haploid populations derived from five resistant synthetic hexpaloid wheat lines, each crossed to the susceptible Australian wheat cultivar Janz. For each cross we determined genetic variance, heritability and minimum number of effective resistance genes for each nematode species. Distributions of nematode numbers for both species were continuous for all doubled-haploid populations. Heritabilities were high and the resistances were controlled by 4-7 genes. There was no genetic correlation between resistance to P. thornei and to P. neglectus in four of the populations and a significant but low correlation in one. Therefore, resistances to P. thornei and to P. neglectus are probably inherited quantitatively and independently in four of these synthetic hexaploid wheat populations, with the possibility of at least one genetic factor contributing to resistance to both species in one of the populations. Parents with the greatest level of resistance will be the best to use as donor parents to adapted cultivars, and selection of resistance to both species in early generations will be optimal to carry resistance through successive cycles of inbreeding to produce resistant cultivars for release.

Contribution of interspecific hybridization to sunflower breeding

Abstract: This investigation is directed at improving sunflower using hybrid forms resulted from interspecific hybridization. The aim is to create new B/A and R lines from interspecific hybrid forms that are resistant to diseases, the parasite broomrape, herbicides, and other stress factors and are characterized with high combining ability and to obtain on this basis highly productive oilseed sunflower hybrids with varied fatty acid composition of oil. The investigation was carried out during the period 1983-2010. It involved 16 cultivars and 18 B lines with their analogues as well hybrid material originated from 38 Helianthus species - 9 annuals and 29 perennials. Intraspecific hybridization and purposeful selection were the methods used. Crossing between interspecific hybrids and crossing of interspecific hybrids with sunflower cultivars or lines were applied. Self-pollination, sib-pollination, backcross with pollen from cultivated sunflower and pollination with pollen from different interspecific hybrids were carried out. Phytopathological and biochemical evaluation of seeds and plants and morphological characterization of sunflower forms, lines and hybrids were performed. New sunflower forms and lines were created as a result of this investigation. A greater part of them possess resistance to downy mildew, phomopsis, phoma and alternaria, tolerance to sclerotinia and full resistance to the different races of the parasite broomrape. The new forms were distinguished by new plant architecture, different vegetation period and seeds with different size and coloration. New B/A and R lines having high combining ability and seed oil and fatty acid contents were obtained. Fifteen sources of cytoplasmic male sterility (cms) were obtained from interspecific hybrid forms, as were 251 sources of genes for restoration of fertility (Rf genes). Five new hybrid cultivars of the oilseed type that were obtained on the basis of these lines were created and registered. The obtained results from the investigations showed that by interspecific hybridization new genetic material was transferred to the cultivated sunflower. These results have augmented the contribution of interspecific hybridization to sunflower breeding.