Authors:E. Hemaprabha, R. Balasaraswathi and R. Samiyappan
The tomato spotted wilt disease caused by tospoviruses in tomato is an important viral disease. Artificial screening of tomato wild species and cultivars for resistance to tospoviruses revealed the wild species
to be resistant to tospovirus infection. The protein profile in
showed additional proteins of molecular sizes of 45kDa, 34kDa and 26kDa and an additional 55kDa protein was detected in
. The peroxidase isozyme pattern was also found to be distinct in
. cDNAs of R genes coding for tospovirus resistance were isolated from the wild species,
(TNAU T). The partial cDNAs were cloned in the vector pTZ57R/T, sequenced and characterized. The tomato varieties, hybrid and wild species
selected in this study were susceptible to tospovirus infection and did not show presence of R genes. Sequence analysis of the partial cDNAs corresponding to the R genes isolated from the wild species
showed considerable homology on the protein level with already available resistance proteins like late blight resistance protein, root knot nematode resistance protein, potato disease resistance protein, Hero protein confirming resistance against potato cyst nematode, and
protein confirming resistance against
. In the present study, R genes effective against tospoviruses were isolated and characterized from a wild species of tomato. These results have important impact in terms of transformation strategies to develop tospovirus resistant transgenic plants.
Authors:M. Ali, Salem Alghamdi, M. Begum, A. Anwar Uddin, M. Alam and Dingcheng Huang
In order to breed rice cultivars for resistance to the brown planthopper, Nilaparvata lugens Stål (BPH) in Bangladesh, were evaluated for resistance in greenhouse screening tests. Over a period of six years (2005–2010), 1,767 entries/cultivars were screened using the plant hopper screening (PHS) system. The results showed 87 donors possessing different levels of resistance to the BPH. One exotic cultivar was highly resistant to the BPH and 86 materials showed medium resistance (tolerance) to the BPH. The rest of the materials including germplasm, F2, exotic, IRBPHN (International Rice Brown Planthopper Nursery) and advanced lines were susceptible. Most of entries coming from the International Rice Research Institute (IRRI) via the IRBPHN were moderately resistant.
Brown planthopper (BPH) is one of the destructive insect pests causing significant yield losses in rice. BPH causes direct damage to the rice plants by sucking the sap from phloem, causing hopper burn and transmitting viral diseases like grassy and ragged stunt viruses. Several resistant donors have been identified from time to time, but the new biotypes of the pest arise to defeat the extended use of resistance genes in a single variety. This necessitates the regular identification of new resistant donors along with their nature of inheritance and gene action controlling the resistance. Knowing the inheritance pattern, gene action and number of genes controlling a trait helps the plant breeders to plan the effective breeding approaches for crop improvement. The present investigation was hence carried out to know the inheritance pattern, gene action and number of genes controlling BPH resistance in newly identified sources. The results indicated that the BPH resistance in PHS 29 genotype is under the control of single recessive gene. Whereas, it is controlled by two recessive genes in MRST 3 genotype. This reveals that relatively higher population size will be required to recover desirable segregants in the segregating populations involving MRST 3 genotype as one of the parents as compared to that involving PHS 29 genotype as parent. Since, the resistance in both the cases being recessive in nature, the trait will hence show significant additive effect, indicating that pure line development will be desirable for improvement of such a trait.
The role of antibiosis components and antioxidant defense of rice genotypes, namely CR3006-8-2, RP4918-221, KAUM182-1, T12, IHRT-ME-25, W1263, Ptb33 (resistant check) and TN1 (susceptible check) was studied by phenotyping them against brown planthopper (BPH). Three genotypes, namely KAUM182-1, RP4918-221 and CR3006-8-2 were resistant to BPH and significantly low damage score (1.97–3.00); honeydew excretion area (46.76–49.64 mm2); nymphal survival (60.60–66.40%) and growth index (2.98–3.86) was recorded on them. Higher constitutive and induced level of soluble phenolics, peroxidase and polyphenol oxidase was observed in resistant genotypes without and with BPH infestation. A negative relationship between honeydew excretion, nymphal emergence, growth index and nymphal survival was observed with these biochemical constituents. Likewise, a reverse trend was observed between nymphal development period and biochemical constituents. These genotypes have emerged as a new source of resistance to BPH which can be used in hybridization programme to breed durable BPH resistant rice varieties.
Akad, F., Teverovski, E., Gidoni, D., Elad, Y., Kirshner, B., Rav-David, D., Czosnek, H. and Loebenstein, G. (2005): Resistance to Tobacco mosaic virus and Botrytis cinerea in tobacco transformed with cDNA encoding an inhibitor of viral replication
Authors:A. Tekauz, J. Mitchell Fetch, B. Rossnagel and M. Savard
Fusarium head blight (FHB) of oat in western Canada was determined to be caused by a complex of Fusarium species, the composition and proportions of which varied considerably among years, and between Manitoba and Saskatchewan, the two main oat production regions (provinces) in western Canada. The levels of deoxynivalenol (DON), associated with Fusarium graminearum infection, were considerably higher in oat than in wheat and especially in barley, when levels of DON were compared to those of F. graminearum on seed, suggesting that oat may stimulate production of the mycotoxin by this causal species during the infection process, compared to that in other cereals. Testing of oat cultivars and lines for reaction to FHB indicated that while differences existed, these were relatively small. ‘Naked’ oats, in general, were more resistant. Several of the exotic oat accessions tested appeared to have superior levels of resistance and these are being used as parents in crosses to improve resistance in adapted, high quality oats.
Authors:Annamária Molnár, Gabriella Spengler and Yvette Mándi
Shaw, K. J., Rather, P. N., Hare, R. S., Miller, G. H.: Molecular genetics of aminoglycoside resistance genes and familial relationships of the aminoglycoside-modifying enzymes. Microbiol Rev 57 , 138-163 (1993