The impact of planting times and cultivars on the excitation of innate-immunity response against populations and severity of plant parasitic nematodes in faba bean (Vicia faba L.) field.

BACKGROUND

The most important food legume crop in Egypt and worldwide is the faba bean (Vicia faba L.), which has the potential to greatly improve agricultural sustainability by providing benefits such as higher grain yields, product diversification, and better nutritional value. It accounts for nearly 90% of the world's faba bean production. These long-season faba bean crops are very vulnerable to damage from root-knot nematodes (RKNs), the main threat to vegetable farming. This study aimed to assess how RKN damage affects faba bean production in Egypt's climate, considering different planting dates and cultivars, as well as the effects these factors have on the plants' natural immunity against Meloidogyne incognita. Two field experiments were carried out on sandy soil in Egypt's North Delta during the 2021-2022 and 2022-2023 seasons to study how three faba bean cultivars (Nubaria 1, Giza 716, and Giza 843) respond to three planting dates under drip irrigation when infected with nematodes. A split-plot design with three replications was used. In both seasons, the three faba bean varieties (Nubaria 1, Giza 716, and Giza 843) were randomly assigned within the subplots, while the main plots included planting dates of October 1, October 15, and November 1.

RESULTS

Data on RKN population density and gall index were collected to evaluate the severity of Meloidogyne incognita and to detect other types of nematodes. The three examined cultivars exhibited mild to moderate M. incognita infections, alongside slight infections of Xiphinema sp. and P. brachyurus during the 2021-2022 seasons, with 80% of the roots galled. In contrast, during the 2022-2023 growing season, RKN damage was unaffected by the planting dates. However, delaying the planting date from October 15 to November 1 increased RKN population densities in the 2021-2022 season, as well as resulted in increases in plant height, total chlorophyll content, and shading percentage of faba bean plants. Additionally, on October 15, the plant immune system appeared to activate against plant-parasitic nematodes through the up-regulation of antioxidant enzymes and increased glucanase and chitinase (PPO, POD, and PR3).

CONCLUSIONS

According to our findings, the tested faba bean cultivars Giza 716 and Giza 843 are highly vulnerable to RKN, which raises concerns about the potential harm RKN could cause to commercial faba bean production and underscores the necessity of managing RKN. However, it can be asserted that fewer nematodes will infect faba beans once Nubaria 1 is planted in Egypt in mid-October.