Effect of hardening on frost tolerance and fatty acid composition of leaves and stems of a set of faba bean (<Emphasis Type="Italic">Vicia faba</Emphasis> L.) genotypes

Frost tolerance is a main component of winter-hardiness and improving it would promote faba bean (Vicia faba L.) cropping in cool-temperate regions. In many species, leaf fatty acid composition was found to be related to frost tolerance. The objective of this study was to determine, in a representative sample of genotypes, the effect of hardening on leaf and stem (1) frost tolerance and (2) fatty acid composition, and to seek correlations between them. First leaf, second leaf and stem of 31 faba bean genotypes were analyzed after hardening and without hardening. High frost tolerance of known winter genotypes and several experimental lines was shown. Hardening had a significant, positive effect on frost tolerance of all three organs. Stems were on average more frost tolerant than leaves. Hardening induced significant changes in the fatty acid composition: oleic acid decreased significantly in leaves by 3.24% and in stems by 1.77%, whereas linolenic acid increased in leaves by 6.28% and in stems by 9.06%. In stems, correlations between frost tolerance and fatty acid composition were not significant. Correlation coefficients strongly indicated that non-hardened oleic acid content, changes in oleic acid and in linoleic plus linolenic acid content in leaves partly explained their frost tolerance; 0.347 (P < 0.1) < |r| < 0.543 (P < 0.01). The results corroborate the importance of using genetic differences in the fatty acid metabolism in breeding grain legumes for frost tolerance.     

Morphological and cytogenetic studies on the hybrid between bread wheat and <Emphasis Type="Italic">Psathyrostachys huashanica</Emphasis> Keng ex Kuo

Psathyrostachys huashanica Keng ex Kuo (2n = 2x = 14, NsNs), a source of wheat stripe rust, take-all fungus, and powdery mildew resistance with tolerance to salinity and drought, has been successfully hybridized as the pollen parent to bread wheat without using immature embryo rescuing culture for the first time. All of the CSph2b × P. huashanica hybrid seeds germinate well. Backcross derivatives were successfully obtained. F₁ hybrids were verified as intergeneric hybrids on the basis of morphological observation, cytological and molecular analyses. The results obviously showed the phenotypes of the hybrid plants were intermediate between bread wheat and P. huashanica. Chromosome pairing at MI of PMCs in the F₁ hybrid plants was low, and the meiotic configuration was 26.80 I + 0.60 II (rod). Cytological analysis of the hybrid plants revealed the ineffectiveness of the ph2b gene on chromosome association between the parents. Eight RAPD-specific markers for Ns genome were selected for RAPD analysis, and the results indicated that F₁ hybrids contained the Ns genome of P. huashanica. Furthermore, the significance of the finding for bread wheat improvement was discussed.     

Genetic variability and heterotic groups of Brazilian popcorn populations

The development of successful advanced lines and cultivars in maize is dependent on parental selection and assignment to defined heterotic groups. So, the objectives of this study were to evaluate genetic variability and identify heterotic groups among Brazilian popcorn varieties. Thus, diallel crosses of advanced generations of the popcorn hybrids, IAC 112 and Zélia, and of three open-pollinated popcorn varieties, RS 20, Branco, and SAM were performed. Ten hybrid combinations, the five parents, and five check treatments were arranged in a block design with four replicates in two tropical-zone locations (CWb climate). Both additive and non-additive effects were important for grain yield, plant height, ear height, and husk cover. For popping expansion, only the additive effects were important. Hybrid combinations between the local variety (Branco) and F₂ populations (IAC 112 and Zelia) resulted in the third and fourth highest values for popping expansion. The best grain yields were obtained with hybrid combinations involving SAM. Cultivars Zélia, IAC 112, and RS 20 increased popping expansion, whereas cultivar Branco increased grain yield of hybrid combinations. The following conclusions may be drawn: Brazilian popcorn populations have reduced heterosis and genetic variability to popping expansion in relation commercial cultivars; there is genetic variability among Brazilian popcorn populations that allows the exploitation of additive and non-additive effects for grain yield; it is possible to increase grain yield by using local varieties; but it would be difficult to obtain commercial hybrids from local varieties because they have poor performance for popping expansion.     

Responses to divergent selection for cob color in maize

Previous studies showed that in materials derived from maize (Zea mays L.) single cross A632 × Mu195 there is association between agronomic traits and cob color (affected by P1 gene). Objectives of this study were to evaluate the responses to divergent selection for cob color in F₂-Syn 0 (obtained by selfing A632 × Mu195), estimate the genetic parameters of the involved putative quantitative trait loci (QTL), and evaluate the responses to divergent selection for cob color in A632 and Mu195 backgrounds. The populations selected in F₂-Syn 0 for red (R0) or white cob (W0) were tested in four trials. Differences between R0 and W0 were found for grain yield (85.0 vs. 75.0 g/plant) and other traits; most of these differences were related to leaf number/plant. Then, population F₂-Syn 1, derived after one random mating generation, was divergently selected for cob color, thus producing R1 and W1. Populations R0, W0, R1, and W1 were tested in two trials, allowing the estimate of genetic effects and recombination frequencies for putative QTL of several traits. Finally, a divergent selection for cob color was conducted in segregating materials of A632 and Mu195 backgrounds. The two pairs of selected populations were compared in two trials; the responses were similar to those detected by comparing R0 and W0. We conclude that divergent selection for cob color in F₂-Syn 0 is effective for several traits, that such responses are due to putative QTL linked to P1, and that selection is also effective in different genetic backgrounds.     

Research and field monitoring on transgenic crops by the Centro Internacional de Mejoramiento de Maíz y Trigo (CIMMYT)

The International Maize and Wheat Improvement Center (CIMMYT) aims to genetically enhance both crops and generate public sector-provided products for the resource poor, e.g., drought tolerant wheat and insect resistant maize, and through international–national partnerships facilitate the acquisition of improved germplasm for non-mandate crops in the cropping systems where maize and wheat thrives; e.g., GM-papaya through a national food security undertaking in Bangladesh. The Center also engages in public awareness campaigns in projects such as Insect Resistance Maize for Africa (IRMA), which includes food, feed and environmental safety, monitoring of resistance and establishment of refugia, non-target effects and gene flow. Monitoring of genetic resources is a wide concern among the centers of the Consultative Group on International Agricultural Research (CGIAR), with an emphasis on the quality of gene banks. Decisions, policies and procedures about monitoring should be science-based, and this requires education, an area where CIMMYT and other CGIAR centers can play an important role. There will be a need to continue to evaluate the need for, and type of monitoring, as new (and unique) products are developed and released in the emergent economies of the world.     

Genetics of resistance to <Emphasis Type="Italic">Cucumber mosaic virus</Emphasis> in <Emphasis Type="Italic">Cucumis sativus</Emphasis> var. <Emphasis Type="Italic">hardwickii</Emphasis> R. Alef

The genetics of resistance to Cucumber mosaic virus (CMV) in Cucumis sativus var. hardwickii R. Alef, the wild progenitor of cultivated cucumber was assessed by challenge inoculation and by natural infection of CMV. Among the 31 genotypes of C. sativus var. hardwickii collected from 21 locations in India the lowest mean percent disease intensity (PDI) was recorded in IC-277048 (6.33%) while the highest PDI was observed in IC-331631 (75.33%). All the four cultivated varieties (DC-1, DC-2, CHC-1 and CHC-2) showed very high PDI and susceptible disease reaction. Based on mean PDI, 8 genotypes were categorized as resistant, 13 as moderately resistant, 9 as moderately susceptible and one as susceptible. A chi-square test of frequency distribution based on mean PDI in F₂ progenies of six resistant × susceptible crosses revealed monogenic recessive Mendelian ratio 1(R):3(S) to be the best fit. This monogenic recessive model was further confirmed by 1(R):1(S) ratio as the best fit for back cross with resistant parent and no fit for either 3:1 or 1:1 in the back cross with the susceptible parent. The results revealed that CMV resistance in C. sativus var. hardwickii was controlled by a single recessive gene. Considering the cross compatibility between C. sativus var. hardwickii and cultivated cucumber, the resistance trait can be easily transferred to cultivated species through simple backcross breeding.     

The effect of in vivo and in vitro applications of ethrel and GA<Subscript>3</Subscript> on sex expression in bitter melon (<Emphasis Type="Italic">Momordica charantia</Emphasis> L.)

Bitter melon (Momordica Charantia L.) is an important vegetable crop with nutritional and medicinal qualities. As a member of cucurbitaceae it is monoecious with varying proportions of staminate and pistillate flowers. This study was undertaken to determine the effects of various applications of ethrel and gibberellic acid (GA₃) on sex modification in M. charantia. In the first set of experiments, various concentrations of hormones were added to the seed germination medium, in the second, adult plants growing in the field were sprayed with aqueous solutions of ethrel or GA₃ three times at three-day intervals. The number and sex of open flowers was recorded daily for 60 days after the first flower opened and total number of staminate and pistillate flowers was calculated at the end of the experiment. The highest frequency (29.5%) of pistillate flowers was observed in plants treated with 500 ppm ethrel at germination. Similarly, spraying of adult plants with 100 ppm GA₃ increased the proportion of pistillate flowers to 26% relative to 15% in untreated controls. Both ethrel and GA₃ induced significantly higher number of pistillate flowers than control. In vitro hormone application during seed germination was much more successful than spraying of field grown plants.     

Conferring resistance to pre-harvest sprouting in durum wheat by a QTL identified in <Emphasis Type="Italic">Triticum spelta</Emphasis>

Pre-harvest sprouting (PHS) causes significant yield loss and degrade the end-use quality of wheat, especially in regions with prolonged wet weather during the harvesting season. Unfortunately, the gene pool of Triticum durum (tetraploid durum wheat) has narrow genetic base for PHS resistance. Therefore, finding out new genetic resources from other wheat species to develop PHS resistance in durum wheat is of importance. A major PHS resistance QTL, Qphs.sicau-3B.1, was mapped on chromosome 3BL in a recombinant inbred line population derived from ‘CSCR6’ (Triticum spelta), a PHS resistant hexaploid wheat and ‘Lang’, a PHS susceptible Australian hexaploid wheat cultivar. This QTL, Qphs.sicau-3B.1, is positioned between DArT marker wPt-3107 and wPt-6785. Two SCAR markers (Ph3B.1 and Ph3B.2) were developed to track this major QTL and were used to assay a BC₂F₈ tetraploid population derived from a cross between the durum wheat ‘Bellaroi’ (PHS susceptible) and ‘CSCR6’ (PHS resistant). Phenotypic assay and marker-assisted selection revealed five stable tetraploid lines were highly PHS resistant. This study has successfully established that PHS-resistance QTL from hexaploid wheat could be efficiently introgressed into tetraploid durum wheat. This tetraploid wheat germplasm could be useful in developing PHS resistant durum cultivars with higher yield and good end-use quality.     

Polymorphisms of the <Emphasis Type="Italic">FT</Emphasis> gene as a tool to identify underground rhizome types of bamboos

The Flowering Locus T (FT)-like genes of angiosperms are highly conserved. The FT-encoded proteins include a phosphatidylethanolamine-binding domain that is involved in the control of the shoot apical meristem identity and flowering time. In the present study, FT genes were investigated in 20 bamboo species that are grouped into sympodial, mixed and scattered bamboos based on their morphology. All examined orthologous FT genes consisted of four exons and three introns. Their encoded protein sequences contained the critical amino acid residues Tyr85, Glu109, Leu128, Tyr134, Trp138, Arg139, Gln140 and Asn152, of which each possesses a biological function. The DNA sequences were rich in single nucleotide polymorphism (SNP) sites. The SNP frequency was 1 SNP/16.8 bp, and the nucleotide diversity (π) equaled 0.265. Some SNPs altered restriction enzyme sites or resulted in changes in amino acid contents. The correlation analysis showed that several SNPs were informative in relation to the underground rhizome types of bamboos. Therefore, FT polymorphisms could be used as a tool to identify the underground rhizome types of bamboos. The phylogenetic tree constructed based on the FT gene sequences showed that the obtained clustering was consistent with the underground rhizome types. The SNP markers developed in the present study will provide information on the genetic diversity of bamboos and they can aid taxonomic study as well.