Damage of wheat blast on the productivity and quality of seeds as a function of the initial inoculum in the field

Abstract

Information on damages caused by blast (Pyricularia oryzae) on wheat seed productivity is still scarce, especially studies on the effect of this on germination and vigor. This study aimed at evaluating blast damages on the productivity and quality of wheat seeds as a function of the initial inoculum in the field. Treatments were arranged in factorial 4x5: inoculations in four wheat genotypes (BRS 264, CD 116, CD 104 and VI 98053) with five doses of initial inoculum of P. oryzae (0, 5, 10, 20 and 30% of inoculated plants). The inoculation occurred in the stage of completely emerged spikes. The following determinations were made: incidence of blast in plants, dry matter mass of 100 plants, seed mass of 100 plants, productivity, germination, first count, germination speed index, dry mass of seedlings, hectolitric weight and incidence of P. oryzae in the seeds. There is a reduction in the productivity and physiological quality of the seeds of the genotypes due to the initial inoculum in the field. The transmission of P. oryzae occurs from the mother plant to the wheat seeds. In these genotypes, it is recommended not to use as seeds the ones coming from fields with blast incidence from 20% on in the plants, close to seed maturation.

Wheat blast: from its origins in South America to its emergence as a global threat

“…Seed‐borne inoculum probably facilitated the long‐distance dispersal of Pygt and allowed it to invade other agroecosystems in South America and now South‐East Asia (Gomes et al ., ; Goulart and Paiva, ; Goulart et al ., ). Despite the risk of introducing Pygt into their local agroecosystems, 65 countries imported Brazilian wheat or mixtures of wheat and rye between January 2006 and September 2017, with quantities as high as 1.14 million tons of seeds or grain (Ceresini et al ., ; Government of Brazil, ).…”

“…A high degree of gene flow across a spatial scale of more than 2000 km was found in Brazil (Castroagudín et al ., ). This high gene flow, which would maintain many alleles and reduce the impact of genetic drift, could reflect efficient wind dispersal of the pathogen’s conidia or ascospores over short distances (Urashima et al ., ), in addition to long‐distance dispersal via infected seeds of wheat and Urochloa (Gomes et al ., ; Goulart et al ., ; Goulart and Paiva, , ). Overall, these findings suggest that non‐wheat hosts may play an important role in the epidemiology of wheat blast, further complicating control efforts.…”

Wheat Blast- A New Challenge to Wheat Cultivation in South Asia

“…The seed-borne inoculum of P. oryzae pathotype Triticum infected the wheat seeds developed on the mother plant. The seeds harvested from fields with blast incidence from 20% on spikes were therefore not recommended for seed purposes (Gomes et al, 2017). The genotypes confining the low infection on the leaves with little infection on the spike are preferred.…”

Potential of transmission of Pyricularia graminis-tritici from plant to seed and from seed to seedling in wheat genotypes with different degrees of blast resistance

“…In general, this pathogen does not affect the emergence (Goulart and Paiva, 1990), considering favorable conditions for the host. This occurs due to the fact that the fungus does not generally affect germination either (Goulart and Paiva, 1990;Urashima et al, 2009;Gomes et al, 2017). Due to the association of P. graminis-tritici with the wheat seeds produced in field experiment, the incidence of the pathogen was observed in the seedlings evaluated under controlled conditions (Table 3).…”

“…It is present in different parts of the world, it is difficult to control, and the damage varies according to the genotype and the region. In Brazil, the disease has shown great impact in the tropical region, as in the north of the states of Paraná, São Paulo, Minas Gerais, Mato Grosso do Sul, Goiás and Distrito Federal, resulting in reductions in productivity and seed or grain quality (Goulart et al, 2007;Urashima et al, 2009;Cruz and Valent, 2017;Gomes et al, 2017). Researches affirm that blast can be caused by multiple species of Pyricularia, and the one that causes disease in wheat has recently obtained new nomenclature -Pyricularia graminis-tritici (Castroagudín et al, 2016;Cruz and Valent, 2017).…”