Alabama: Cotton Leaf Roll Dwarf Virus – 4 Thoughts

    Symptoms of cotton leafroll dwarf virus include leaf distortion and upward curling of the leaf. The leaf may also be a blue-green color, hence the name Cotton Blue Disease. Photo: Tom Isakeit, Texas AgriLife Extension

    This morning I walked through several hundred lines of cotton, mostly upland cotton (Gossypium hirsutum), which Cotton Breeder Dr. Jenny Koebernick is screening for possible resistance to Cotton Leaf Roll Dwarf Virus (CLRDV).

    Here are a few thoughts about cotton and CLRDV.

    1. There is tremendous genetic diversity in the genus of upland cotton. I saw a wild range of plants. There were differences in leaf type and color, plant architecture and canopy size, and fruiting structure. Some were weird.

    As an aside and in contrast to the above statement, the general consensus of molecular geneticists is that our current commercial varieties represent a very narrow set; in other words, there’s not a lot of genetic differences among the varieties we plant today.

    2. I observed what I suspected was a variety of CLRDV symptoms but wasn’t sure that all was really CLRDV. Confirmation of symptoms involves laboratory testing, which requires a couple of days and about $30 per sample.

    Symptoms included dwarfed plants, bunched tops, bronzed foliage, significant fruit loss, abnormal leaves, etc. I’m not sharing pictures because I’m unsure that the observed abnormalities were due to CLRDV, genetic variation, other plant pathogens, or something else.

    3. From a layman’s perspective, there are several parallels between CLRDV and Covid-19. Individuals can be symptomatic or asymptomatic, and for those that are symptomatic, there can be a range of responses, some rather minor, some moderate, and a few severe. Despite significant scientific investigation and experience, there are still many, many unknowns about these viruses.

    4. We still have a lot to learn. At this point in the cotton world, the impact of CLRDV seems limited to a few situations. Why those particular fields are affected remains a puzzle.

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