An-Najah Blogs :: An-Najah Blogs :: en-us Wed, 13 Nov 2019 03:30:59 IST Wed, 13 Nov 2019 03:30:59 IST Characterization of new sources of resistance in some Palestinian barley landraces against Blumeria graminis f.sp. hordei under controlled and field conditions ArticlesEleven winter barley cultivars from Palestine screened for their resistance to powdery mildew in the field and under controlled conditions while two types of resistance were identified Three accessions showed low infection type IT at seedling stage with low disease severity DS in the mature plant Six other lines showed low DS and low infection frequency IF with no macroscopically visible necrosis These resistant accessions were selected and selfed for future studiesThe resistance to leaf rust and powdery mildew of recombinant lines of barley (Hordeum vulgare L.) derived from H. vulgare x H. bulbosum crosses ArticlesA set of 23 recombinant lines RLs of barley Hordeum vulgare L derived from H vulgare x H bulbosum L crosses was inoculated with barley leaf rust Puccinia hordei and powdery mildew Blumeria graminis fsp hordei at the seedling stage to identify their levels and mechanisms of resistance Eight RLs were studied further in glasshouse and field tests All three barley parents Emir Golden Promise and Vada were highly susceptible to powdery mildew and leaf rust isolates Several RLs showed partial resistance expressed as high relative latency periods and low relative infection frequencies against leaf rust This high level of partial resistance was due to a very high level of early aborting colonies without host cell necrosis Several RLs showed hypersensitive resistance to some or all isolates For powdery mildew one RL was completely resistant to the CC1 isolate and had a hypersensitive resistance to the CO-02 isolate Three RLs derived from Emir were completely resistant to both powdery mildew isolates and three more RLs tested in the field had higher levels of partial resistance than their parents The results indicate that H bulbosum contains major and minor genes for resistance to leaf rust and powdery mildew that can be transferred to cultivated barley Identification of QTLs for powdery mildew and scald resistance in barley ArticlesA population of 103 recombinant inbred lines RILs F9-derived lines developed from the tworow spring barley cross L94Vada was evaluated under field conditions for resistance against powdery mildew Blumeria graminis fsp hordei and scald Rhynchosporium secalis Apart from the major resistance gene mlo on chromosome 4 4H three QTLs Rbgq1 Rbgq2 and Rbgq3 for resistance against powdery mildew were detected on chromosomes 2 2H 3 3H and 7 5H respectively Rbgq1 and Rbgq2 have not been reported before and did not map to a chromosome region where a major gene for powdery mildew had been reported Four QTLs Rrsq1 Rrsq2 Rrsq3 and Rrsq4 for resistance against scald were detected on chromosomes 3 3H 4 4H and 6 6H All four mapped to places where QTLs for scald resistance had been reported before in different populationsScreening for resistance to leaf rust (Puccinia hordei) in a collection of Spanish barleys ArticlesA collection of 418 Spanish barley accessions was screened for resistance to leaf rust in the field at Crdoba Spain during the 20022003 season Six accessions displaying the lowest disease severity DS with no macroscopically visible necrosis were selected for further studies on components of resistance Five of them showed a significantly higher relative latency period RLP than the susceptible line L94 and were similar to the partially resistant Vada All of them showed lower relative infection frequency RIF and smaller colony size CS than the susceptible L94 under controlled conditions Histological studies indicated that the resistance in four of these accessions was based on a higher percentage of early aborted colonies not associated with host cell necrosis In the remaining two accessions resistance was based on hypersensitivitySearch for partial resistance against Puccinia hordei in barley landraces from Fertile Crescent ArticlesA collection of 111 barley landraces from the Fertile Crescent was screened for resistance to barley leaf rust in the eld and under controlled conditions Large variation was observed for disease severity under eld conditions Accessions with high resistance because of hypersensitivity were identied Also segregation was observed in some accessions with individual plants showing hypersensitive reactions IT 6 Partial resistance due to a reduction of infection in spite of a compatible infection was commonly found 19 Resistance of 12 accessions selected for their low disease severity and high IT was shown to be due to a prolonged latency period and increased percentage of early aborted colonies not associated with host cell necrosis A high correlation was observed between the microscopic and macroscopic components of partial resistanceIdentification of a new pathotype of Puccinia hordei with virulence for the resistance gene Rph7 ArticlesBarley leaf rust resistance gene Rph7 derived from barley accession Cebada Capa is the most effective R-gene for resistance to Puccinia hordei Virulence for this gene was known in the USA Israel and Morocco but not yet in Europe We found an unexpected leaf rust infection in the field at Crdoba Spain in 2004 on Rph7 carrying lines This virulence for Rph7 was confirmed in growth chamber experiments being the first report of Rph7 virulence in European populations of P hordei A collection of 680 barley accessions was screened for resistance against this new isolate Twelve accessions showed segregation with individual plants showing resistance based on hypersensitivity low infection type These individual resistant plants were selected and grown in the greenhouse to obtain seeds