RESUMO
Potato (Solanum tuberosum L.) is one of the most important crops in maintaining global food security. Plant stand and yield are affected by production technology, climate, soil type, and biotic factors such as insects and diseases. Numerous fungal diseases including Neocosmospora rubicola, causing stem rot, are known to have negative effects on potato growth and yield quality. The pathogen is known to stunt growth and cause leaf yellowing with grayish-black stems. The infectivity of N. rubicola across a number of crops indicates the need to search for appropriate management approaches. Synthetic pesticides application is a major method to mitigate almost all potato diseases at this time. However, these pesticides significantly contribute to environmental damage and continuous use leads to pesticide resistance by pathogens. Consumers interest in organic products have influenced agronomists to shift toward the use of biologicals in controlling most pathogens, including N. rubicola. This review is an initial effort to carefully examine current and alternative approaches to control N. rubicola that are both environmentally safe and ecologically sound. Therefore, this review aims to draw attention to the N. rubicola distribution and symptomatology, and sustainable management strategies for potato stem rot disease. Applications of plant growth promoting bacteria (PGPB) as bioformulations with synthetic fertilizers have the potential to increase the tuber yield in both healthy and N. rubicola infested soils. Phosphorus and nitrogen applications along with the PGPB can improve plants uptake efficiency and reduce infestation of pathogen leading to increased yield. Therefore, to control N. rubicola infestation, with maximum tuber yield benefits, a pre-application of the biofertilizer is shown as a better option, based on the most recent studies. With the current limited information on the disease, precise screening of the available resistant potato cultivars, developing molecular markers for resistance genes against N. rubicola will assist to reduce spread and virulence of the pathogen.
RESUMO
Twenty-two sunflower germplasms were screened for resistance to Macrophomina phaseolina to select parental genetic resources useful for the development of charcoal rot-resistant sunflower cultivars. Potting soil inoculated with pathogen (10 mL pot-1, 2 × 105 sclerotia mL-1) sown with sunflower seeds was examined for disease severity index (%), disease incidence (%), mortality (%), and growth inhibition index (%) 90 d after inoculation. None of the germplasm was disease-free; four were found to be resistant, five moderately resistant, six moderately susceptible, five susceptible, and two highly susceptible. All inoculated plants exhibited disease symptoms both externally and internally. Mild to severe symptoms included brown lesions on aboveground plant, pith disintegration in stem, and shredded appearance of tap root. Histopathological features exposed different colonization mechanism of the pathogen in the resistant and susceptible cultivars. Physical blockage, tissue disintegration, blackening and rupturing of cortical, pith and vascular regions by fungal mycelia, and sclerotia and pycnidia causing large spaces in the center of stem rendered it a hollow structure in all susceptible germplasm. However, stem and root tissues of the resistant germplasm indicated local infection restricted to few cells. This suggested expression of true resistance genes in resistant germplasm. Therefore, the sunflower lines resistant to the M. phaseolina infection are potential genetic resources for the development of quality sunflower cultivars resistant to charcoal rot disease.
