Perspectives and Challenges for Sustainable Management of Fruit and Foliar Diseases

Rice is an important staple food for more than half of the world’s population. Though the genetic potential of commonly cultivated varieties of rice is diminished due to various biotic and abiotic constraints, bacterial leaf blight (BLB) of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is considered one of its most destructive diseases in India. Based on morpho-cultural characteristics, bacterial pathogens isolated from the leaves of a rice plant showing typical BLB symptoms were identified as Xanthomonas oryzae pv. oryzae. Morphological studies revealed that the pathogen is Gram-negative, a short rod, with rounded ends, single or in pairs, light yellow, circular, whitish yellow to straw-colored, convex, yellow, slightly raised, motile with a single polar flagellum, capsulate and non-spore-forming. Biochemical tests, viz., the Gram reaction, KOH test and catalyst test, showed a positive reaction for all the isolates. Twenty isolates of Xoo were collected from the basmati-growing areas of the Jammu, Samba and Kathua districts in the Jammu sub-tropics during 2019, and their pathogenicity was confirmed on five susceptible rice cultivars, viz., Basmati-370, Pusa-1121, TN-1, SJR and Jaya, by the leaf-clipping method, and subsequently, Koch’s postulate was established in each case. Seven Xoo pathotypes, viz., Pathotype 1, Pathotype 2, Pathotype 3, Pathotype 4, Pathotype 5, Pathotype 6 and Pathotype 7, were identified from the total sample of 20 isolates. Pathotype 2 was the most dominant (100%), followed by Pathotype 5 (44.44%), Pathotype 4 (40%), Pathotype 6 (40%), Pathotype 7 (33.33%), Pathotype 3 (22.22%) and Pathotype 1 (20%), in the Jammu sub-tropics. In Jammu district, Pathotype 5 was highly distributed (44.44%) followed by Pathotype 7 (33.33%) and Pathotype 3 (22.22%). Pathotype 4 and Pathotype 6 each showed a 40 percent distribution in Kathua district, followed by Pathotype 1 (20%). Only one pathotype, i.e., Pathotype 2, was recorded in Samba district with a 100 percent distribution. Five genes, viz., Xa13, Xa4, Xa13 and Xa5 + Xa13, showed complete resistance, whereas Xa4, Xa5, Xa7, Xa8, Xa21, Xa4 + Xa5 and Xa4 + Xa21 showed susceptible response against the test isolates. It was observed that most of the single BLB-resistant genes were moderately to highly susceptible to almost all the Xoo isolates, whereas combinations of BLB resistance genes possessed high resistance against all the Xoo isolates. The studies revealed that diverse pathogenic variations existed in the Xoo population in the basmati-growing region of Jammu and Kashmir. Based on the response exhibited by Xoo isolates on differential lines, seven pathotypes (Pathotype 1–7) were identified, and their virulence spectrum on rice differentials showed the occurrence of 5, 3, 10, 10, 20, 10 and 15 percent, respectively, in the Jammu sub-tropics. To develop durable and sustainable resistant cultivars, it is essential to identify predominate race(s) in a specific geographical area and continuously monitor the virulence pattern there. Full article

Grapevine, a crop of global economic importance, is annually affected by diseases that can compromise the quality and quantity of the harvest, producing large economic losses. Downy mildew caused by Plasmopara viticola (Berk. & M.A. Curtis) Berl. & de Toni is one of the most important diseases in the vineyard. To fight this pathogen, winegrowers often rely on conventional chemical fungicides or copper-based formulations, whose use is determined to be reduced by the European Commission due to their environmental consequences. Hence, alternative plant protection products (PPP) in grapevine must be considered and studied. In this context, we selected several alternative commercial products, based on basic substances (BS) or low-risk active substances (LRAS), to evaluate their suitability to deal with P. viticola. We measured the preventive activity of the products, both in vitro and in planta, as well as their toxicity against the sporangia and zoospores of the pathogen. Results showed that four commercial products were effective against the pathogen directly and preventively, being composed of approved basic substances, more concretely, chitosan, Equisetum arvense, lecithins, and Salix cortex. Among those, the products composed of lecithins and Salix cortex were the most toxic and active preventively. Therefore, these basic substances should be promoted in the vineyard as an alternative to conventional treatments in order to transition to a more sustainable viticulture. Full article

Viruses pose a serious threat to the sustainable production of economically important crops around the world. In the past 20 years, potato virus Y (PVY) emerged as a relatively new and very serious problem in potatoes, even though it is the oldest known plant virus. Multiple strains of the virus cause various symptoms on the leaves and tubers of potatoes, resulting in yield reduction and poor-quality tubers. Consequently, it would be very interesting to learn what causes systemic PVY resistance in plants. Natural compounds such as chitosan (CHT) and phosphorus have been developed as alternatives to chemical pesticides to manage crop diseases in recent years. In the current study, potato leaves were foliar-sprayed with chitosan and phosphorus to assess their ability to induce PVY resistance. Compared to untreated plants, the findings demonstrated a significant decrease in disease severity and PVY accumulation in plants for which CHT and P were applied. Every treatment includes significantly increased growth parameters, chlorophyll content, photosynthetic characteristics, osmoprotectants (glycine betaine, proline, and soluble sugar), non-enzymatic antioxidants (glutathione, phenols, and ascorbic acid), enzymatic antioxidants (peroxidase, superoxide dismutase, lipoxygenase, glutathione reductase, catalase, β-1,3 glucanase, and ascorbate peroxidase), phytohormones (gibberellic acid, indole acetic acid, jasmonic acid, and salicylic acid), and mineral content (phosphorus, nitrogen, and potassium), compared to infected plants. However, compared to PVY infection values, CHT and P treatments showed a significant decrease in malondialdehyde, DPPH, H₂O₂, O₂, OH, and abscisic acid levels. In addition, increased expression levels of some regulatory defense genes, including superoxide dismutase (SOD), ascorbic acid peroxidase (APX), relative pathogenesis-related 1 basic (PR-1b), and relative phenylalanine ammonia-lyase (PAL), were found in all treated plants, compared to PVY-infected plants. Conclusion: Phosphorus is the most effective treatment for alleviating virus infections. Full article

Mango sudden death (MSD) or quick decline (QD) is the most destructive disease found in mango orchards of Pakistan and is characterized by collapse of the vascular system by Ceratocystis fimbriata and Lasiodiplodia theobromae. Cultural practices, chemicals, and biological control are the most valuable tools for the management of MSD, but the role of micronutrient deficiencies has remained an area that is heavily ignored by the farming community. To study the impact of micronutrients, four mango orchards were selected at different locations where different combinations of micronutrients, i.e., Zinc (Zn), Boran (B), and Copper (Cu) in the form of Zinc sulphate (ZnSO₄), Borax/Boric acid (H₃BO₃), and Copper Sulphate (CuSO₄), were applied both foliar and in drench along with the recommended doses of Nitrogen: Phosphorous: Potassium (NPK), and Farmyard manure (FYM), respectively. The quantities of micronutrients were determined from the soil and leaves before and after application of the treatments. The impact of micronutrients was measured in terms of reduction in disease severity and increase in fruit yield. The results revealed that the application of all three micronutrients both in soil drench and in foliar form significantly decreased the disease severity at three locations and increased the yield in all four mango orchards. Application of ZnSO₄ (0.8%), +H₃BO₃ (0.8%), +CuSO₄ (0.5%) and as soil drench ZnSO₄ (400 g) + Borax (200 g) + CuSO₄ 200 g plant⁻¹ proved to be the best treatments, with an average of 12.88 and 14.03% reduction in disease severity and with an average yield of 128 and 119 kg, respectively. The application of micronutrients would be a promising solution in an integrated disease management program used to tackle MSD. Full article

In a quickly growing world, there is increasing demand for a secure food supply, a reduction in the intensive use of natural resources, and the enhancement of sustainability for future long-term maintenance. In this regard, plant health, including fruit and foliar diseases, which can cause a vast amount of crop loss, potentially has a huge effect on food security. The integration of new, innovative technological tools and data management techniques into the traditional agricultural practices is a promising approach to combat future food shortages. The use of the same principles of precision agriculture to “do the right thing, at the right time, in the right place” will allow for providing detailed, real-time information that will help farmers to protect their crops and choose healthier, as well as more productive, farming methods. The presented narrative review reports on several items of innovation, including monitoring and surveillance, diagnostic, and decision-making tools, with a specific focus devoted to digital solutions that can be applied in agriculture in order to improve the quality and the speed of the decision-making process and specifically, to set up a digital collaboration that can be crucial under certain circumstances to reach sustainability goals, particularly in the Near East and North Africa (NENA) Region, where an effective and rapid solution for phytosanitary control is needed. Full article