Phytosanitary Quality of Genotypes of Wheat Seeds Used Northern Paraná State

Wheat seeds can be infested and/or infected by microorganisms that might cause deterioration of this propagation structure. The aim of this study was to evaluate the health quality of sixteen wheat genotypes grown in northern Paraná. Therefore, seeds of each genotype were submitted to the blotter test with 16 repetitions, 400 seeds per sample, for phytosanitary quality evaluation. The identification of the fungi was performed based on their morphological characteristics and quantified data. The results revealed variations in incidence, with 20 fungi genera in the analyzed samples. The fungi Rhizopus sp., Aspergillus sp., Penicillium sp. and Bipolaris sp. were found in 100% of the analyzed samples, while Mucor sp. and Alternaria sp. were in 89% and 78% of the samples, respectively. The main pathogens that cause diseases in the aerial part of wheat were not found, or were low incidence in all materials analyzed. The pathogens with the highest incidence associated with wheat seeds were groups of storage fungi and known to produce mycotoxins.


Introduction
Wheat (Triticum aestivum L.) is the cereal of the most economic importance worldwide, with over 600 million tons produced annually. In southern Brazil, it is most important chief winter crop, with annual production ranging from 5 to 6 million tons, and a consumption of around 10 million tons (Silva et al., 2011;CONAB, 2020).
During the development and maturation of plants in the field, these are attacked by fungi and other phytopathogenic organisms, resulting in diseased plants, seed quality is essential for the proper establishment of the plant population in the field, its full development and production (Dhingra, 1985;Souza et al., 2007). The vast majority of these fungi are agents of leaf stains and transmitted by seeds, from which they return to air organs through the transmission process (Reis & Casa, 1998;McMullen et al., 2012;Dweba et al., 2017).
The main difficulty encountered by wheat producers in southern Brazil is excess rainfall during the crop development cycle, covered days favorable to the occurrence and intensity of leaf diseases, directly interfering with the potential of phytosanitarial quality of seeds (Reis, 2001). As leaf diseases in the Southern Region of Brazil that deserve to be highlighted are as caused by idiode (Blumeria (Sin. Erysiphe) graminis (DC) Speerf. sp. tritici Em. Marchal), a rust of the leaf, (Puccinia triticina Eriks), the yellow stain (Drechslera tritici-repentis (Died) Drechs.), and a septoriosis (Septoria nodorum (Berk. Berk.) (Reis & Casa, 2005). Nicrospora sp. The fungi found associated with the seeds were Aspergillus sp., Rhizopus sp., Penicillium sp., Bipolaris sp. were found in all wheat cultivars, followed by Mucor sp., Fusarium verticillioides, Alternaria sp. and Curvularia sp., which were recorded in 12 and 7 cultivars, respectively. These fungi together represented 87.4% of the phytopathogens recorded. Moreover, Rhizopus sp. and Aspergillus sp. were highly frequent, occurring in 37.5% and 14.5% of all seeds evaluated. In contrast, Penicillium sp. and Bipolaris sp., were found in only 7.07% and 3.01% of the seeds, respectively.
Regarding the genotypes BRS Gaivota, BRS Graúna and the lineage LD 152109, Mucor sp. was the fungus with higher incidence. Finally, Alternaria sp. were found in 23% and 22% of seeds of the genotypes BRS Gralha azul and BRS Sanhaço, respectively.
The highest diversity of pathogens were found in the genotype BRS Gralha azul, which had 13 different pathogens, followed by BRS Sabiá with 11 fungi. Twelve different pathogens were found in the genotypes BRS Tangará, LD 142114 and LD 152109. On the other hand, the cultivars LD 141103 and TBIO Mestre presented the lowest diversity (4), with predominance of the fungus Rhizopus sp. affecting 63.7% and 62% of the seeds, respectively.
seeds. The materials that presented the highest incidence of Phoma sp. were LD 142114 (0.75%) and BRS Tangará (0.25%). Genotype LD 152109 was the only one to present the fungus Bipolaris sp. at 0.25% incidence.
The presence of the fungi Rhizopus sp., Mucor sp. and Alternaria sp., which are typically decay fungi, stands out among as causative agents of root rot and leaf spots of various crops. Storage time under conditions where there is some seed-associated pathogen leads directly to loss of seed germination percentage (Casa et al., 2012).
The fungi Aspergillus sp. and Penicillium sp. are associated with seed deterioration, which is often related to inadequate storage conditions, however, contamination can still occur in the field soon after harvesting (Machado, 1982). In contrast, the fungus Bipolaris sp., may be associated with diseases such as yellow spot [Bipolaris sorokiniana (Sacc.) Shoemaker], which causes serious damage to wheat crop, with up to 20% crop losses (Brancão et al., 2008).
It can be evidenced the presence of fungi of the genera Fusarium, Aspergillus and Penicillium associated with seeds, these when present in seeds and grains, produce secondary metabolic, called mycotoxins, substances capable of damage cause on human and animal health (Freire et al., 2007).
Leaf stain caused by B. sorokiniana is considered a disease of great importance to wheat crop, with yield losses of 20-80%. According to Barros et al. (2006) in very favorable conditions, the disease occurs throughout the crop cycle, infected seeds is the main survival mechanism of the fungus. In stored seeds, the fungus has the ability to survive as mycelium, in the endosperm of the seed and colonize the root system until it reaches the shoot (Neergaard, 1979;Kobayasti & Pires, 2011).
The highest percentages of seeds with phytopathogens were found in the genotypes WT 11167 (88%) and IPR Taquari TM (86.3%), and were not statistically different by the Scott-Knott test, while the lowest percentage of seeds with phytopathogens occurred in BRS Gralha azul, WT 13086, BRS Sabiá, FPS Virtude with an incidence ranging between 41.5% and 28%, respectively (Figure 1