Identification of Leaf Rust Resistance Genes in Wheat Cultivars Produced in Kazakhstan

Leaf rust, caused by Puccinia recondita f. sp. tritici, is one of the major diseases of wheat in Kazakhstan. To effectively use leaf rust resistance genes (Lr), it is important for breeders to know the resistance genotype in current cultivars. In this study, 30 winter wheat entries grown and/or produced in Kazakhstan were investigated using molecular markers to determine the presence and absence of eight important Lr genes. Molecular screening of these genotypes showed contrasting differences in the frequencies of these genes. Among the 30 entries, 17 carried leaf rust resistance gene Lr1, six had Lr26 and Lr34, and Lr10 and Lr37 were found in three cultivars. Two single cultivars separately carried Lr19 and Lr68, while Lr9 was not detected in any genotypes in this study. Field evaluation demonstrated that two of the most frequent two genes (Lr1 and Lr26) to be ineffective. While Lr34 provided some protection, the remaining effective Lr genes were found only in few genotypes: Lr37 occurred in Kazakh genotypes L-1090 and Krasnovodapadskaya 210 and in the US cultivar Madsen; Lr19 and Lr68 were likely present only in Russian and Kazakh cultivars, Pallada and Yegemen, respectively. The highest resistance over three years of leaf rust testing was found in Kazakh cultivars, Karasay, Krasnovodapadskaya 210, L-1090, Arap and Yegmen, foreign cultivars Madsen, Pallada and the control Parula (Lr68). Data may assist breeders to incorporate effective Lr genes into new cultivars

Evaluation of Stripe Rust Resistance in Hungarian Winter Wheat Cultivars in China

Stripe or yellow rust (Yr), caused by Puccinia striiformis Westend. (Pst), is one of the most important wheat diseases worldwide. New aggressive Pst races can spread quickly, even between countries and continents. To identify and exploit stripe rust resistance genes, breeders must characterize first the Pst resistance and genotypes of their cultivars. To find new sources of resistances it is important to study how wheat varieties respond to Pst races that predominate in other continents. In this study we evaluated stripe rust resistance in 53 Hungarian winter wheat cultivars in China. Twenty-four cultivars (45.3%) had all stage resistance (ASR) and 1 (1.9%) had adult-plant resistance (APR), based on seedling tests in growth chambers and adult-plant tests in fields. We molecularly genotyped six Yr resistance genes: Yr5, Yr10, Yr15, Yr17, Yr18, and Yr36. Yr18, an APR gene, was present alone in five cultivars, and in ‘GK Kapos’, that also had seedling resistance. The other five Yr genes were absent in all cultivars tested

Identification of Sr31 and Sr36 stem rust resistance genes in wheat cultivars registered in Hungary

In Hungary, stem rust epidemics caused by Puccinia graminis f. sp. tritici are rare, but due to the severity of infection the stem rust fungus can pose a great hazard to wheat production. As new virulent races can appear, it is important for breeders to know of the genetic background of the stem rust resistance in their cultivars. In this study, 220 winter wheat cultivars registered in Hungary in the past 35 years were investigated using molecular markers to determine the presence or absence and frequency of the two important stem rust resistance genes Sr31 and Sr36. The results indicated that both Sr31 and Sr36 genes are widespread in wheat cultivars registered in Hungary. Sr31 was detected in 24.1% of these wheats, and Sr36 in 15.9%. These genes occurred to a somewhat larger extent in the 156 local cultivars: one-third (32.1%) had the Sr31 and 18.0% the Sr36 gene. Of these, 2 cultivars (1.3%) had both genes (Sr31+ Sr36). Among the 64 foreign cultivars only 3 (4.7%) carried the Sr31 gene. In the foreign group, Sr36 was only detected in the seven Croatian cultivars. Tests also revealed possible false pedigrees for some cultivars. Inoculation tests showed that both genes were still effective. One-sixth (16.7%) of stem rust resistant cultivars did not carry the target genes indicating the possible presence of other efficient Sr genes. Data may help breeders to incorporate effective Sr genes into new cultivars

Identification and localization of molecular markers linked to the Lr52 leaf rust resistance gene of wheat

Growing resistant wheat cultivars is considered to be an efficient and environmentally safe approach in reducing damage caused by leaf rust disease. Among the numerous leaf rust resistance genes of wheat, Lr52 is a very effective one with a broad spectrum resistance. The objective of this study was to identify and map molecular markers closely linked to the Lr52 resistance gene. Out of 280 RAPD, 44 SSR and 8 STS markers tested, three showed close linkage to the Lr52 . In our study, one SSR marker (Xwmc149) showed a close linkage (11.3 cM) to the Lr52 gene. Another SSR (Xgwm234) and an STS (Xtxw200) markers, having close linkage to a recently identified leaf rust resistance gene found in PI 289824, also showed a close linkage (7.2 and 3.6 cM, respectively) to the Lr52 . Matchings in the mapping distances of these markers linked to these resistance genes still remain open the possibility that the gene found in PI 289824 is identical to the Lr52 , or simply this locate very close to it

Stimulation of shoot regeneration in Triticum aestivum and Nicotiana plumbaginifolia Viv. tissue cultures using the ethylene inhibitor AgNO3

Silver nitrate effectively promoted shoot regeneration in wheat (Triticum aestivum L.) callus cultures derived from immature embryos. This effect could be observed in both weakly and strongly regenerating cultivars, and in using material from both field and greenhouse grown plants. The role of silver ions as an inhibitor of ethylene action was supported by a reversal of the inhibitory effects of 2,4-D and ethylene on morphogenesis in wheat callus cultures.Enhancement of shoot regeneration by silver nitrate was also observed in callus cultures of non-regenerating or weakly regenerating mutants of Nicotiana plumbaginifolia Viv. derived from cell cultures