Host status and host sensitivity of cancer bush (Sutherlandia frutescens) to Meloidgyne enterolobii.

Abstract

Cancer bush (Sutherlandia frutescens) is an indigenous medicinal plant with significant bioactive chemicals that stimulate the human immune system. Its demand is rising in South Africa and globally due to its medicinal properties and the growing interest in plant-based remedies. However, pests such as nematodes are threatening its production. The pest challenges have been exacerbated by climate change, that has led to the emergence of new host-pest relationships. Meloidogyne javanica is the first root-knot nematode to be detected on S. frutescens, and there is still limited information on other potential nematode host of cancer bush with the potential to reproduce and affect its growth and yield. Therefore, the objectives of the study were to determine whether Meloidogyne enterolobii root-knot nematode will reproduce on S. frutescens roots and affect plant growth during summer and winter seasons. To achieve this objective, S. frutescens seedlings were subjected to 0, 25, 50, 125, 250, 625, 1250, and 3125 M. enterolobii eggs and second-stage juveniles (J2) under microplot and shade net conditions in two different seasons, 2023 (summer) and 2024 (winter). At 56 days post-inoculation, plant and nematode variables were measured, and the reproductive factor (RF) was calculated. The RF during summer and winter seasons under microplot experiments had similar trends, greater than 1 at lower nematode level, and decreased as it approached the equilibrium level with every increment of M. enterolobii inoculum level. While the RF under shade net was statistically the same for all nematode levels, the gall index (GI) was greater than 2, and the plant growth variables were not affected by the treatments. The nematode and plant variable responses indicated that S. frutescens was tolerant to M. enterolobii, irrespective of season and growing conditions. Microplot conditions was found to be a favorable environment for M. enterolobii infestation, and shade net has shown to be a less favorable environment for M. enterolobii in both seasons.