Wild tomatoes have the genes to partner with fungi

Scientists have found the quantitative trait loci (QTLs) in DNA that correlate with a tomato plant’s ability to attract arbuscular mycorrhizal fungi (AMF). “Intensity (M%), instead of frequency (F%)… is genetically the best morphological measure of root AMF colonization. Wild alleles from Solanum pimpinellifolium can improve AMF colonization in tomato, and the gene contents of AMF colonization QTLs might be important for explaining the establishment and functioning of the AMF–plant symbiosis,” write Katia Plouznikoff and colleagues in their paper: Genetic analysis of tomato root colonization by arbuscular mycorrhizal fungi.

Arbuscular mycorrhizal fungi are fungi that grow into the roots of plants. The fungi get carbon compounds, food, from the plant enabling them to grow into networks around the plant. In return, the fungi can transfer phosphorus and other nutrients to the plant. The fungi around the plant dramatically increase the plant’s foraging for minerals in the soils nearby. They can also help alleviate drought stress in plants.

Understanding how tomato can better partner could be a significant benefit for food supplies. “About 177 Mt of fresh tomato fruits (Solanum lycopersicum) are produced yearly on 4.78 Mha in 144 countries, making tomato the second most important vegetable crop next to potato,” write the authors.

The scientists examined plants derived from a salt-sensitive genotype of S. lycopersicum’ Cerasiforme’ (E9) and a salt-tolerant line from S. pimpinellifolium L. (L5). Over a hundred plants were grown in greenhouses in the Netherlands and Belgium. After eight weeks, the plants were harvested, and the roots examined to see how well the fungi had colonized them. The team then studied the genome looking for QTLs associated with the best-colonized plants. The key QTLs would mark differences in the genome that affect how fungi can colonize plants. “In total, eight QTLs were detected for the AMF colonization traits. Five of them in chromosomes 1, 3, 5, 9 and 10 were significant by both procedures (MQM and KW),” write the authors.

Plouznikoff and colleagues say that this is the earliest stage of understanding tomato-AMF genetics. “[A]s a first step, the genetic basis of AMF association has to be studied to test further if those QTLs, only some of them or none of them, are involved in the beneficial effects of the AMF regarding the plant’s tolerance to biotic and abiotic stresses. Genetic variation for the AMF root colonization has not been exploited yet in tomato.”