Phytoplasma Transmission by Seeds in Alfalfa: A Risk for Agricultural Crops and Environment

Recent research has demonstrated a presence inside the seeds of several plant species of endophytic bacteria that can directly or indirectly interact with germination and seedling growth. Phytoplasmas are plant-pathogenic bacteria that severely impact the agricultural productivity of several crops, including alfalfa, a crucial forage crop in which seed transmission was reported. Therefore, understanding the transmission pathways of phytoplasmas is essential for developing effective control strategies. This study investigates the seed transmission of phytoplasmas in alfalfa using seeds collected in Oman in 2002 and kept in a dry environment in a laboratory for 20 years. The sterilized seeds were germinated and grown in agar medium under sterile conditions and transplanted in soil under greenhouse-controlled insect-proof conditions. Utilizing polymerase chain reaction (PCR) and nested PCR followed by RFLP and sequencing analyses, the alfalfa seedlings were screened for the phytoplasma presence. The detection of phytoplasmas in 16SrIII, 16SrV, 16SrX, and 16SrXII groups was achieved, confirming the preliminary results obtained in the 2002 testing of the same seed batches. This finding indicates that seed transmission could be a critical pathway for the spread of these pathogens in alfalfa, considering their survival in seeds for more than 20 years. Further investigations into the mechanisms of seed transmission and the development of resistant alfalfa varieties are essential to enhance the sustainability and productivity of alfalfa cultivation, thereby supporting the agricultural sector’s efforts to meet the growing demand for high-quality forages.