Sustainability in agroecosystems relies on the optimized use of resources to achieve consistent yields while maintaining or improving soil health. The monitoring of soil quality is crucial when changes from rainfall-fed to irrigated crop systems occur. The objective of this study was to assess the impact of different crop successions in the Mediterranean area under irrigation and different technical practices. The soil nitrogen–phosphorous–potassium (NPK) and soil organic carbon (SOC) balances were observed in four fields with irrigated annual crops in a two-year succession timeframe, namely, sunflower–maize (P1), sunflower–clover (P2), maize–sunflower (P3), and alfalfa–alfalfa (P4). The SOC and nutrient balance, integrating the total irrigation, mineral fertilizers, and exported yield, was calculated for each farm. Except for maize–sunflower succession (P3), all fields presented a negative SOC balance at the end of the two-year crop succession, indicating losses from 2.84 to 4.91 Mg SOC ha⁻¹ y⁻¹. While in N-fixing plants the soil N decreased, in the remaining crops a surplus was observed, possibly leading to future N losses. The continuous depletion of soil P revealed a potential underestimation of this nutrient. Soil K appears to be related to specific crop management practices, namely, crop residue incorporation after harvest. In annual irrigated crops under Mediterranean conditions, crop succession can induce soil fertility degradation if conservation practices are absent.

ISHS X International Pear Symposium IDENTIFICATION OF GENES CODING FOR NH4+ TRANSPORTERS IN 'ROCHA' PEAR/BA29

Petri disease is a Grapevine Trunk Disease (GTD) primarily associated with the ascomycete species Phaeomoniella chlamydospora, which leads to substantial losses in young vineyards, particularly during the first years after planting. Contamination of plant material before and during nursery procedures with this species represents a potential risk for future vineyards. Nurseries need tailor-made and effective methods for guaranteeing the supply of GTD-free material. This study evaluated Hot Water Treatment (HWT), a widely used method to reduce or eliminate GTD-associated fungi in grapevine propagation materials, in one of the most common scion-rootstock combinations in Portuguese grapevines. The assessment focused on the elimination of P. chlamydospora and plant viability in plants of cv. Touriga Nacional grafted onto 1103 P rootstock. Treatments included non-HWT and HWT plant parts at 46 °C, 50 °C and 54 °C for 45 min, applied to both non-inoculated and P. chlamydospora-inoculated scions and rootstocks. Fungal presence was assessed before and after HWT, and growth parameters of grafted plants were measured after stratification and three months in a nursery. HWT effectively eliminated P. chlamydospora; however, inoculated plants exhibited reduced quality traits compared to non-inoculated plants. The 46 °C treatment produced the highest-quality plants, enhancing the callogenesis process of the grafting union. Mathematical modelling of the pathosystem comprising the pathogen P. chlamydospora and hosts Vitis vinifera as scion and V. rupestris × V. berlandieri as rootstock suggests a better resilience of the symbiont plants to higher temperatures when compared to P. chlamydospora. Optimised HWT protocols are recommended to reduce GTD pathogens while maintaining plant viability.