Screening of phytopathogens and phytopathoges on Chenomeles (CHAENOMELES LINDL.) cultivars

The pathogenic microflora and entomofauna were studied on the Chaenomeles Lindl. cutivars (Maloideae, Rosaceae). In central Russia, the multi-year systematic monitoring of pathogens and phytophages was carried out on plants Ch. japonica, Ch. cathayensis, Ch.×superba. Among the identified pathogens, the micromycetes belonging to genera Botrytis, Cytospora, Diplocarpon, Entomosporium, Gloeosporium, Monilia, Neonectria, Penicillium, Pestalotia, Phomopsis, Phyllosticta, Septoria and Sphaeropsis were found to be injurious. With age, the accumulation of infectious background, including viral diseases and the damaging entomofauna was noted in the plantings of fruit crop Chaenomeles. The species composition of phytophages is mainly represented by autochthonous species (polyphages and oligophages), preferring the plants of Rosaceae family. Despite the abundance of species in the phytophage complex, it has a little effect on the decorativeness of Ch. japonica, Ch. cathayensis and Ch. × superba.

Although it is believed that Chaenomeles species are disease-resistant, it is known from the literature that, in China, the representatives of genera Phoma sp. and Phyllosticta sp. [9] settle on these plant bushes. Many pathogens were found on Chaenomeles plant species surfaces in Europe [3] and those of Aphis pomi in Iran [10].
The purpose of this study was to research and identify representatives of pathogenic microflora and harmful entomofauna on the Chaenomeles cultivars in the regions of central Russia.

Material and method
The study of phytopathogens and phytophages on the Chaenomeles cultivars was carried out in the Tambov region, Moscow region and in the arboretum of N.V. Tsitsin Main Botanical Garden.
In 2007-2009, the endophytic microflora was tested on the cultivars, forms and types of Ch. japonica and Ch. Cathayensis in the Tambov region. Crops taken from annual shoots were placed in sterile tubes and Petri dishes with 2 variants of nutrient media from agar-agar (15 g): in the 1 st variantwith intoxicating (hop) wort (1 l), in the 2 ndwith potato (1 l).
The analysis and registration of fungal and bacterial microflora colonies was carried out under the microscope "Biomed-4" and expressed in (%) of the total number of tests [1].
In 2010-2017, the monitoring, including the analysis of leaves and fruits on Chaenomeles samples with the symptoms of phytopathogen lesions and phytophagous damage, was carried out in field conditions. The identification of fungi was performed by standard methods [11].

Results and discussion
The breeding of Chaenomeles has been realized on the base of Michurinsk Agrarian University in the Tambov region since 2003.

The stability of the Russian cultivars of Chaenomeles
New varieties Flagman, Voshod, Sharm, Michurinsky Vitamin, Alur and Albatros have flowers of original color, the corolla diameter of 3.5-5.8 cm, and their shoots are without spikes (Table 1). They were entered in the State register of the Russian Federation. The selected forms and varieties of Chaenomeles, tested in the Tambov region for the resistance to endophytic microflora, showed their high degree of plant viability [9]. The bacterial microbiota prevailed and varied greatly. The fungal microflora was less abundant during the testing and was represented by the species of genera Alternaria sp. (Fig. 1), Penicillium sp., Stemfillium sp., Cladosporium sp. and Fusarium sp. The long-term monitoring of 6 Chaenomeles cultivars in the Michurin breeding under field conditions revealed 4 types of phytopathogens with a minimal degree of plant susceptibility ( Table 2).
Septoria cydoniicola Thüm was most often recorded on Chaenomeles cultivars. At the beginning of summer, numerous whitish-gray round spots with dark rims are formed on the leaves. The cultivars were diseaseaffected at 1 point, but the most resistant cultivar is Voshod.
The drying and premature falling of leaves having brown spots with light middles are caused by Phyllosticta cydoniae var. cydoniicola (Allesch.) Cif Phyllostictaceae). Entomosporiosis, the causative agents of which are Entomosporium eriobotryae S.Takim. and Diplocarpon mespili (Sorauer) B.Sutton, syn. Entomosporium maculatum f. maculatum Lev., identified in the cultivar Albatros (1 point), can also be a cause of the appearance of brown spots.
More seldom, Alternaria alternata (Fr.) Keissl (Pleosporaceae) was encountered in Chaenomeles cultivars at the end of spring. Small rounded dark brown spots with dark purple-red borders are visible on the leaves; later the spots merge. Heart-shaped rot appears in the course of the disease development. Cultivars Voshod, Sharm, Albatros and Michurinsky Vitamin are the most resistant to altarnariosis.  Part of the Chaenomeles harvest may be lost (1-2 points) as a result of botrytiosis, penicillosis and fomopsis, which are noticeably manifested during the storage of fruits. Botrytiosis, which is found everywhere, caused by Botrytis cinerea (Sclerotiniaceae), affects Chaehenomeles flowers and fruits. First, brown spots with clear reddish edges appear. Then the fruits rot and prematurely fall. The rotting of fallen fruits is accelerated by the contact with soil, since Penicillium expansum Link and P. cyclopium Westling (Trichomaceae) penetrate their surface. Phomopsis is caused by pathogens Phomopsis mali Roberts, Ph. perniciosa Grove and Ph. ambigua (Nitschke) Traverso (Diaporthaceae) and is accompanied by dark brown spots on the leaves, leaf fall and rotting of Chaenomeles fruits.
The single tomato annular blotch virus (ToRSV), the symptoms of which are expressed in the form of chlorosis, wrinkling and necrotic leaf blotch with a characteristic alternation of dark and light areas, was observed on Chaenomeles fruits.

Damaging entomofauna complex
A complex of entomofauna representatives was revealed on Chaenomeles plants in the regions of central Russia (Таble3). It should be noted that almost all groups of Insecta are rare and in a single amount (≥1 point), with the exception of colony-forming aphids (1-2 points).
The most dangerous are migrating species Aphis fabae, which are black insects, and the non-migrating species A. pomi (Homoptera: Aphididae), which is common on Rosaceae fruit crops. Although they are not observed in Chaenomeles every year, these insects are carriers of viral diseases. The polyphage Palomena prasina (Homoptera: Pentatomidae) and Edwardsiana rosae L. (Homoptera: Cicadellidae), the phytophage of fam. Rosaceae, were pointed out in the complex of sucking species of the Moscow region.
The polyphagous bug Acanthosoma haemorrhoidalis L. (Hemiptera: Acanthosomatidae), usually feeding on deciduous cultures of the families Rosaceae, Betulaceae, Salicaceae, Tiliaceae, etc., was found in both regions. Gnawing phyllophages are diverse, although they appear sporadically. But they are capable of worsening the decorative appearance of a bush. The gray-green caterpillar Cladius pallipes Lep., Syn. Priophorus padi L. (Hymenoptera: Tenthredinidae), capable of skeletonizing Chaenomeles leaves, is especially active at the beginning of summer. Archips variegana Schiff. and A. rosana L., syn. Сcoecia rosana L., feeding on deciduous plants, including those from the Rosaceae family, are noticeable out of leafworms (Lepidoptera: Torticidae). The second type not only turns leaves into a tube, cigar-shaped or lumpy, but also damages ovaries and fruits, gnawing holes in the pulp to the seed chamber.
An especially active development of caterpillars Acleris variegana Den. et Schiff. was noticed in 2016 in the Tambov region on the Albatross cultivar, when they were eating out fruit buds and buds, skeletizing the leaves and wrapping them into a bundle of cobwebs. Green brown head caterpillar Exapate congelatella Cl. also gnaws into the buds and leaves, forming a lump. The small wormhole, the crenellate lunate Ancylis selenana Gn., common on Rosaceae fruit crops, was noted during the monitoring on Ch. japonica in the arboretum of the MBG RAS on Ch. × superba (1-2 points). Greenish-yellow caterpillars (up to 1 cm long) skeletonize leaves, fold them in half along the central vein and, then, they gnaw them. Phytophage miners (Nepticula malella and Stigmella pomella) are few in number and have almost no effect on the decorativeness of bushes. Cochlea-in stonemason Helicigona lapicida L. (Gastropoda: Helicidae), that feeds on leaves and, less often, fruits in dense plantings, is seldom observed on Ch. Japonica plants.
The analysis of phytophages composition shows that these are mainly autochthonous species, both polyphages and oligophages, preferring plants of the Rosaceae family. Probably, this set is due to the close proximity of the experimental Chaenomeles plants with the plantings of Rosaceae family fruit crops, and it facilitates the expansion of food links and favors the creation of new potentially dangerous "introduced species-pathogen" complexes.