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Volume 3 Number 1 2009
CONTENTS AND ABSTRACTS
Andreas Peil (Germany), Vincent G. M. Bus (New Zealand), Klaus Geider, Klaus Richter, Henryk Flachowsky, Magda-Viola Hanke (Germany) Improvement of Fire Blight Resistance in Apple and Pear (pp 1-27)
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ABSTRACT
Invited Review: Fire blight caused by the bacterium Erwinia amylovora is known to incite substantial damage in pomefruit production. The disease originated in North America, from where it slowly spread around the world. Hosts of E. amylovora are members of the Maloidae, such as apple, pear and quince, and ornamentals, such as Cotoneaster, Crataegus and Mespilus. The disease can affect all tree parts such as blossoms, shoot tips and rootstock crowns. The name of the disease resembles the main symptom in host plants, i.e. the black necrosis of shoots and browning of leaves. Antibiotics provide effective control, but these are increasingly banned due to ecological considerations and the emergence of antibiotic resistant strains of E. amylovora. Alternative control strategies are based on copper ions and the application of antagonists. The use of fire blight resistant cultivars is another approach to prevent fire blight epidemics. Fire blight resistance is present in the cultivated apple, but high levels of resistance generally are found in wild species of apple and pear. The introduction of wild species’ traits into cultivars is a slow process in fruit tree breeding. Understanding the genetics of the disease resistance, biotechnology and genetic engineering can promote and accelerate classical breeding. This review focuses on crop improvement for fire blight resistance. We describe the origin of the disease, its spread and the infection tools of the pathogen, summarize the genetic resources available to breeders and strategies to improve apple and pear for fire blight resistance.
Jagdeep Kaur (Australia/USA), Urmil K. Bansal (Australia), Renu Khanna, Ram G. Saini (India), Harbans S. Bariana (Australia) Molecular Mapping of Stem Rust Resistance in HD2009/WL711 Recombinant Inbred Line Population (pp 28-33)
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Original Research Paper: The Indian wheat cultivar ‘HD2009’ exhibited moderate level of stem rust resistance both under Indian and Australian conditions since its release in 1976. Ninety two ‘HD2009’/‘WL711’-derived recombinant inbred lines (RILs) were tested in the field for three years against Puccinia graminis f. sp. tritici. Genetic analyses indicated the presence of three to four genes for resistance across all sites over three years, except at the Lansdowne site during 2004, where resistance was controlled by two to three genes. A linkage map using 46 SSR and 295 DArT markers was generated and used for molecular mapping of stem rust resistance carried by ‘HD2009’. Three consistent QTLs; QSr.sun-3BS, QSr.sun-5DL and QSr.sun-7A were identified. QSr.sun-3BS explained 9-15% phenotypic variation and was concluded to be Sr2. The most significant QTL, QSr.sun-5DL, corresponded to the previously reported location of Sr30 and explained 20-44% phenotypic variation in adult plant stem rust response. The contribution of QSr.sun-7A was almost equal to QSr.sun-3BS (7-13%). Additional inconsistent QTLs, QSr.sun-1D, QSr.sun-2B, QSr.sun-4B and QSr.sun-5B were also detected. All QTLs, except QSr.sun-4B, were contributed by ‘HD2009’. QSr.sun-4B was contributed by ‘WL711’. The physiological trait, pseudo-black chaff (PBC), which is reported to be linked with adult plant stem rust resistance gene Sr2, was controlled by QTLs, QPbc.sun-3BS, QPbc.sun-5DL and QPbc.sun-7DS. QPbc.sun-5DL and QPbc.sun-7DS corresponded to the locations of Sr30 and Lr34, respectively.
Akihide Okamoto (Japan) Alteration of Capsule-Picking Time for Improving the Germination Rate through the Histological Observation of Zygote Development in Interspecific Crossing Kurume Azalea x Rhododendron japonicum f. flavum (pp 34-36)
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Short Communication: To improve the germination rate in interspecific crossing of Kurume azalea x Rhododendron japonicum f. flavum, Kurume azalea ‘Yorozuyo’ (seed parent) was crossed with R. japonicum f. flavum and Kurume azalea ‘Wakakaede’ (as a control). 1) Histological observation was carried out to clarify the zygote development process from 10 to 100 days after pollination (DAP). From 20 DAP on, the zygote length of Yorozuyo x R. japonicum f. flavum (YxJ) was less than that of ‘Yorozuyo’ x ‘Wakakaede’ (YxW). The zygotes of YxJ 60 DAP were the same length as those of YxW 30 DAP. At 100 DAP, the embryos of YxJ entered the late heart-shaped stage, and those of YxW reached the torpedo stage. These results suggest that zygote development of this interspecific cross appeared to be about one month later than that of the intraspecific crossing of Kurume azalea cultivars. 2) The capsules were collected from YxJ and YxW at 170 DAP and YxJ at 200 DAP, and the germination rate was compared among them. The germination rate increased in YxJ when the capsule-picking time was put off for 30 days. Also, the germination rates of YxJ capsules collected at 200 DAP had no statistically significant differences from those of YxW capsules collected at 170 DAP. These results imply that delaying the capsule-picking time effectively improves germination rates in this interspecific crossing.
Gabriela Breccia, Tatiana Vega, Graciela Nestares, María Laura Mayor, Roxana Zorzoli, Liliana Picardi (Argentina) Immature Embryo Culture for Early Screening Imidazolinone Resistance in Sunflower (pp 37-40)
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Original Research Paper: The development of imidazolinone-resistant sunflower cultivars represents a great advantage in controlling weeds. This type of herbicide resistance can only be achieved with homozygosis of two resistant genes; hence breeding for this trait is time-consuming. The objectives of this study were to develop plantlets from immature sunflower embryos to evaluate imazethapyr resistance. Three methods were used, an in vitro technique and two non-sterile techniques (dish and pot assays). Three genotypes differing in imidazolinone resistance were evaluated for germination and plantlet developmental variables. Immature embryos successfully germinated in the in vitro culture and the pot germination techniques having similar efficiency. Given the simplicity of the pot assay, plantlets from pot germination were used for screening herbicide resistance at four different doses: 2.5, 5, 7.5 and 10 µM. Susceptible plants showed chlorosis and arrested growth, mainly when exposed to 7.5 and 10 µM of imazethapyr. Surviving plants were transferred to pots and placed in a greenhouse and successfully completed their lifecycle. The techniques described herein would allow selecting sunflower inbreds for imidazolinone resistance when shortening breeding cycle.
Payal Bansal, Parminder Kaur, Shashi K. Banga, Surinder S. Banga (India) Augmenting Genetic Diversity in Brassica juncea through its Resynthesis using Purposely Selected Diploid Progenitors (pp 41-45)
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Original Research Paper: Resynthesis of novel B. juncea (AABB, 2n=36) following hybridization between genetically diverse germplasm of progenitor species (B. rapa and B. nigra) was explored to augment genetic diversity in cultivated B. juncea. Seventy two reciprocal crosses were attempted between B. rapa (10) and B. nigra (9), of which only fifteen were successful and these were subjected to colchiploidy. The resultant amphiploids (11) were confirmed morphologically and cytologically to be resynthesized B. juncea (AABB; 2n=36). Stable A3 resynthesized B. juncea (11) as well as the diploid parents (19) and natural B. juncea (4) genotypes were assayed for genetic diversity based on DNA polymorphism generated by SSR primers. Neighbour-joining analysis revealed a clear distinction between nigra, rapa, resynthesized B. juncea and natural B. juncea. As a group resynthesized B. juncea genotypes were closer to B. rapa and natural B. juncea as compared to B. nigra. The inherent genetic diversity in the germplasm of progenitor diploid species was apparent from SSR based diversity assays. Resynthesized genotypes also possessed a higher frequency of unique alleles. That the resynthesis route generated significant variability was evident from dissimilarity coefficients ranging from 0.13 to 0.74.
Gulshan Mahajan, Neerja Sharma, T. S. Bharaj (India) Grain Yield, Water Productivity and Quality Characteristics of Basmati Rice in Response to Cultivars and Transplanting Dates (pp 46-51)
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ABSTRACT
Original Research Paper: A field experiment was conducted to study the grain yield, water productivity and quality of basmati rice cultivars in relation to transplanting dates in an irrigated agro-eco system of Punjab during the 2006 and 2007 kharif season. Cultivars ‘Pusa Basmati 1’ and ‘Superbasmati’ were superior in terms of water productivity than highly photoperiod-sensitive cultivars ‘Basmati 386’ and ‘Punjab Basmati 2. The water productivity of ‘Pusa Basmati 1’ and Superbasmati was similar even when transplanted up to the 20th of July, but it decreased significantly in ‘Basmati 386’ and ‘Punjab Basmati 2’ with a shift in transplanting date from the 10th of July. Significantly more grains/panicle, higher test weight and grain yield were recorded when transplanting took place on the 10th July. A subsequent delay in transplanting, i.e., 20th and 30th July, resulted in reduced grain yield by 8.4 and 27.1%, respectively, compared to the 10th July transplanting values. Among the basmati cultivars, ‘Pusa Basmati 1’ registered the highest mean grain yield (4.7 t/ha) and it resulted in 73.6, 19.4 and 41.4% higher yield than ‘Basmati 386’, ‘Superbasmati’ and ‘Punjab Basmati 2’, respectively. Under late transplanting conditions (30th July), ‘Punjab Basmati 2’ and ‘Superbasmati’ performed significantly better than ‘Basmati 386’ with respect to grain yield and crop water productivity. The grain yield of ‘Pusa Basmati 1’ was drastically reduced under late transplanting conditions (30th July). The quality traits of ‘Basmati 386’ and ‘Punjab Basmati 2’ were very similar to each other and superior to those of ‘Pusa Basmati 1’. Of interest, the quality traits of ‘Basmati 386’ and ‘Punjab Basmati 2’ improved significantly with delayed transplanting from the 10th to 30th July.
Sanjib Nandy, Qin Chen, Hi Yan Li, Faiz Ahmad, Robert Graf, Gerald Kereliuk (Canada), Shan Cheng Sun (China) Inheritance of Grain Color Controlling Genes in Diverse Wheat Crosses using Near-Infrared Spectroscopy (pp 52-57)
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Original Research Paper: Wheat seeds with black, purple and blue color are more uncommon pigmentation than the red and white pigmentation. The purpose of this work was to study the genetic of seed color in wheat lines, originally from two different genetic backgrounds (China and Canada). The genotypes of the blue and black seeded parents seem to be under the effect of two genes located in two alien chromosomes from the J and Js. The purple color was controlled totally by the genes located in wheat chromosome. The gene(s) responsible for Chinese winter wheat seed color was shown to have dominant based on reflectance spectra of the hybrid seed. Genetic models from F2 population also support the presence of different genes controlling colored winter Chinese wheat grains and Canadian spring wheat grains. Interaction between two alien chromosomes may have led to the instability in blue grain color and resulted in light blue to bluish yellow grain. Duplicate dominant epistasis was playing a key role for expression of blue coloration and duplicate gene action was observed for black color controlling gene.
B. Mathi Thumilan, S. B. Dandin (India) Genetic Analysis of Diploid and Colchi-Tetraploid Mulberry (Morus indica and Morus alba) by Molecular and Morphological Markers (pp 58-64)
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Original Research Paper: This study attempts a comparative assessment of morphogenetic changes in mulberry due to colchicine treatment and doubling of chromosome complement. Out of the 10 morphological (qualitative) traits studied, eight showed changes in the diploid in comparison to its tetraploid in one or more traits. The two traits (lobation and leaf apex) remained unchanged in all the varieties irrespective of the treatment with colchicine and doubling of chromosome number. Although the SPAD (Soil Plant Analytical Device) value increased in many tetraploids in comparison to its diploids, S-13 and S-34 showed a negative correlation for SPAD values and thereby increase in ploidy levels. However, the SPAD value was significantly correlated with increased ploidy in the case of K-2 and S-36. Stomatal frequency was negatively correlated with higher ploidy, except in the case of K-2 and S-13. Among the 45 primers utilized for DNA fingerprinting, 35 showed at least one marker variation among one or more pairs of diploid mulberry varieties with respect to their colchi-tetraploid derivatives. Sequence analysis of the diploids and its tetraploids showed variation in the noncoding region of the genome. The result of the present investigation reveals that colchicine is capable of inducing ploidy, thus interfering at the morphological and molecular levels. It also demonstrates that RAPD markers are informative in divulging genetic variations taking place in the genome.
Mohd. Arif, Najma W. Zaidi, Qazi Mohd. Rizwanul Haq, Salim Khan, Amjad M. Husaini, Uma S. Singh (India) Nuclear rDNA Sequence-based Identification and Relative Efficiency of ISSR and RAPD Markers for Genetic Diversity of Fusarium sp. Associated with Mango Malformation in India (pp 65-70)
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Original Research Paper: Inter Simple Sequence Repeat (ISSR) and Random Amplified Polymorphism DNA (RAPD) analysis were used to assess genetic variations amongst 30 isolates of Fusarium sp. isolated from malformed tissues of mango (Mangifera indica L.) collected from different locations of Pantnagar, India. Fusarium sp. causes one of the most serious diseases of mango, mango malformation. All isolates were identified using two taxon selective primers, ITS-Fu-f and ITS-Fu-r. Scoreable loci 149 and 128 were obtained with 16 ISSR and 16 RAPD primers, respectively. Out of 149 loci, 106 were polymorphic with ISSR markers. Percentage polymorphism ranged from 14.3% (P-48) to a maximum of 100% (P-46 and 54), with an average of 71.1%. The 16 RAPD primers produced 102 polymorphic bands. Percentage polymorphism ranged from 50% (P-78 and 114) to 100% (P-71, 73 and P-79), with an average percentage polymorphism of 79.7% among all isolates of Fusarium sp. Results of present investigation revealed that relatively RAPD markers were more efficient than ISSR assay. Clustering of isolates remained more or less same in RAPD and combined data of RAPD and ISSR. The similarity coefficient ranged from 0.57 to 0.92, 0.47 to 0.98 and 0.57 to 0.90 with ISSR, RAPD and combined dendrogram, respectively.
Sunita Singh, Narendra Jawali (India) Development and Characterization of Trinucleotide Microsatellite Loci from Vigna radiata (pp 71-75)
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Original Research Paper: Microsatellites are very useful as co-dominant markers having a large number of alleles. We report here the development and characterization of 12 microsatellite loci from Vigna radiata L. Wilczek. These sequenced tagged microsatellite loci (STMS) were evaluated using collection of 87 mungbean genotypes. SixSTMS were polymorphic with 3 to 10 alleles per locus with an average of 6.2. The PIC values for the six STMS ranged from 0.25 to 0.98 with an average of 0.71. These STMS will be useful in assessing genetic variation within V. radiata. |
