ABSTRACT
. Nematodes belong to economically important pests. Here we reviewed the recent data on molecular mechanisms of plant resistance to cyst and gall nematodes including the most devastating Globodera rostochiensis, G. pallida, Heterodera schachtii, Meloidogyne chitwoodi, and M. incognita. The Golden Potato Cyst Nematode (G. rostochiensis, GPCN) may be taken as an example of an economically important pest: in Russia, it occurs in 61 regions with a total area of 1.8 million ha and may cause the yield loss from 19 to 90 %. The biological characteristics of sedentary nematodes makes their agrotechnical control problematic, i.e. the GPCN cysts remain dormant in soil for many years until a susceptible host appears, whereas nematicides are either toxic or inefficient. Introgression of resistance genes (R-genes) from related cultivated or wild species is likely to be the most appropriate way for their biocontrol. The life cycle of sedentary nematodes is based on juveniles' penetration into the host root where they reprogram plant cells into a syncytium or the so-called 'giant cells' and inhibit the plant defense response. Molecular mechanisms of plant-nematode interaction are unusual and this phenomenon provides a very interesting model for the investigation of plant morphogenesis control as well as for the development of new genetic instruments of biocontrol. Here we reviewed recent publications on plant parasitic nematode effectors used for hijacking of the plant immune system, data on R-genes and molecular mechanisms of their activities. In addition, host-induced gene silencing (HIGS) is discussed as a perspective mechanism for nematode biocontrol. HIGS is based on the RNA interference in the cells of the host plant addressed against the nematode genes important for their development and productivity. Several recent investigations demonstrated efficiency of HIGS against sedentary nematodes.
ABSTRACT
The review considers quarantine species and nematode pathotypes potentially dangerous for domestic potato production. Potatoes are affected by more than 30 types of parasitic nematodes, but the review focuses on the most harmful representatives of genera that cause great damage to potato production: Globodera, Ditylenchus, Nacobbus and Meloidogyne. Phytopathological and molecular methods of identification of species and pathotypes and the main achievements in studying the population variability of parasitic potato nematodes were analyzed. It was shown that due to the peculiarities of the life cycle of nematodes and lability of their genomes, the genetic variability of these organisms is very high, which creates a threat of forming new pathogenic genotypes of the parasites. The information about the intra- and interpopulation variability of nematodes is important for studying the ways of introduction and distribution of separate species, as well as for searching for the correlations of molecular markers with the pathotype. Phylogenetic studies based on modern data on genetic variability of populations have allowed to reveal species complexes in Globodera pallida (Stone) Behrens and Nacobbus aberrans (Thorne) Thorne & Allen (sensu lato), including cryptic species. The main components of successful protection preventing a wide distribution of parasitic nematodes are quarantine measures, agricultural techniques, biological methods of protection and cultivation of resistant cultivars. Special attention in the review is paid to the breeding of potato cultivars with durable resistance to various nematode pathotypes, because the cultivation of such varieties is the most ecologically safe and economically advantageous way to prevent epiphytoties. Currently, significant progress has been made in the genetic protection of potato cultivars, especially against cyst-forming nematodes. The review provides data on sources of potato resistance to parasitic nematodes identified in collections of wild and cultivated species. Data on identified R-gens and QTL of resistance that have been introduced into breeding varieties using different methods and approaches are analyzed. The literature data on the study of structural and functional organization of genes for resistance to potato cyst nematodes are given. The results of molecular research on revealing the polymorphisms of loci involved in the control of resistance to cyst and gall nematodes, the development of molecular markers of certain genes and their use in marker-assisted selection for developing of new resistant cultivars, including those with group resistance, are considered.
ABSTRACT
According to estimates of various taxonomists, the genus Rubus L. (Rosaceae Juss.) consists of 12-16 subgenera comprising ~750 species. The two largest subgenera are Idaeobatus (Focke) Focke, which includes raspberries, and the type subgenus Rubus (=Eubatus Focke), which contains blackberry species. Representatives of the genus Rubus have high nutritional and economic values, as well as medicinal properties. Breeding programs are aimed at broadening genetic diversity and creating new varieties of raspberries and blackberries that are resistant to biotic and abiotic stressors and have high fruit quality. Modern breeding and genetic programs increasingly use the achievements of molecular genetics and genomics. This paper reviews the literature data on the application of molecular markers in fundamental and applied research aimed at studying the genetic diversity of cultivated and wild species of the genus Rubus. The review describes the main types of molecular markers (RFLP, RAPD, SCoT, SSR, ISSR, AFLP, SCAR, SSCP) and their application for studying the species of the genus Rubus. The results of the work on the use of DNA markers for solving different tasks are presented, including: studying the phylogenetic relationships of species, clarifying controversial issues of taxonomy, analyzing interspecific and intraspecific diversity, genotyping and pedigree analysis of raspberry and blackberry varieties, studying somaclonal variation and others. The most important applied result is the development of molecular genetic maps for raspberry and blackberry species, on which numerous genes and QTLs conferring various valuable traits have been mapped. At the same time, the number of markers that are promising for effective molecular screening is still insufficient.
ABSTRACT
The active expansion of foreign potato cultivars on the territory of the Russian Federation has led to a change in the dominant pathogen species and to the emergence of new pathotypes of causal agents of harmful potato diseases. The aim of the study was to evaluate resistance to Phytophthora infestans and Globodera rostochiensis of modern potato cultivars and determine the distribution of fungal and oomycetic diseases on potato cultivars in various agroclimatic zones of Russia. The resistance of 41 foreign cultivars was evaluated to pathotype Ro1 G. rostochiensis and to isolate VZR17 P. infestans with virulence genes 1.2.3.4.5.6.7.8.9.10.11. Resistant to G. rostochiensis were 38 cultivars. 57R marker of the H1 gene conferring resistance to the Ro1 pathotype of G. rostochiensis was detected in 96.6 % of the nematode resistant cultivars studied; susceptible varieties did not possess this marker. Absolute resistance to the causative agent of late blight was demonstrated by the cultivars Alouette and Sarpo Mira (score 9); high levels of resistance (score 6 and 7) were determined for the cultivars Evolution, Red Fantasy and Ricarda. The cultivars Baltic Rose, Damaris, Desiree, Gala, Labella, Laperla, Mia, Sanibel, Zekura, Queen Anne, Red Lady and '7 for 7' were classified as susceptible, although the characteristics of originators indicated average resistance to late blight. A phytopathological test was conducted on 92 samples of 39 varieties of seed potatoes from four federal districts of the Russian Federation: Volga, NorthWest, Central and North Caucasus. Rhizoctonia solani, Fusarium spp. and Helminthosporium solani are most common on all varieties. 100 % defeat of tubers by H. solani was recorded in various regions on the cultivars Red Scarlett, Evolution, Labella, Colombo, Gala and Nevsky. Widespread Colletotrichum coccodes on tubers of the elite and 2nd reproductions of the potato cultivar Red Scarlett (50.0-71.4 %) was recorded in the Central District.
ABSTRACT
The genetic diversity of 98 potato cultivars of Russian and foreign breeding was studied using of PCR with organelle-specific primers. The polymorphism of both plastid (atpE, trnG/trnK) and mitochondrial (rps, atp6) loci was revealed. Eight different haplotypes were detected in the sample of cultivars studied. Comparatively low of polymorphism of organelle DNA in the potato cultivars was demonstrated: most cultivars (91 or 92.9%) possessed only two haplotypes (I and II); 62 cultivars of them had similar "cultural" cytoplasmic type (haplotype I). The breeding cultivars of the Russian and foreign origin did not differ from each other in frequency of basic haplotypes.
