Post by oxbowfarm on Sept 15, 2015 18:25:19 GMT -5
jondear asked about photos of NLB expressing in different corns but I didn't want to hijack the South American thread. Northern Leaf Blight is probably the worst foliar disease of corn for me here. It is a problem because my favorite corns are mainly in the Northern Flint race which either lost NLB resistance on the long walk up from Mexico or in the decades since they've been out of favor since the total takeover of Corn Belt Dent. I've been gifted many wonderful corn strains that include lots of interesting traits and NLB resistance/tolerance is a big interest of mine. For the last several years my White Flour Grex and my flint are often badly defoliated well before grain maturity. This has to negatively effect yield, though I don't have the actual data to prove it. I am actively crossing other corns into mine to acquire resistance to this disease.
These are classic NLB lesions, canoe shaped and not bounded by leaf veins.
Here is a row of Cargill Tuxpeño I received from maicerochico, he told me it had poor NLB resistance. I'd say it is on par with my White Flour Grex. But this pic shows one plant that is completely defoliated by NLB and the lesions are running down into the leaf sheaths. The other plants next to it are affected but they still have live leaf tissue.
Here's a plant of my White Flour Grex with badly affected leaves above the ear, the lesions are beginning to run together and kill the leaf. You don't like to see NLB this bad above your ear. The disease is cutting off carbohydrate from the ear, reducing yield, and from the lower stalk and roots, which weakens them and leads to lodging and stalk rot.
Here's a plant of Schroeder-strain Hickory King from Africa (also from maicerochico) with fantastic NLB tolerance. This plant is 5 feet away from the badly affected White Grex in the above pic. The highest lesion is 4 leaves below the ear and its a singleton. There is tons of unaffected leaf above and below the ear, despite this row of Hickory King being in the middle of my White Flour Grex with lots of innocula from the affected plants.
So far, the best corns I've grown for NLB tolerance are Cargill Coroico and this Schroeder Hickory King. They both show almost total functional immunity. Cargill Carribean Composite is also highly tolerant but not at the same level as the Coroico or the Schroeder HK. Unfortunately the Coroico/White Flour Grex hybrids are showing much lower tolerance than the Coroico parent did, so I'm going to have to do a lot of hard selection for NLB resistance even when incorporating this resistant material.
These are classic NLB lesions, canoe shaped and not bounded by leaf veins.
Here is a row of Cargill Tuxpeño I received from maicerochico, he told me it had poor NLB resistance. I'd say it is on par with my White Flour Grex. But this pic shows one plant that is completely defoliated by NLB and the lesions are running down into the leaf sheaths. The other plants next to it are affected but they still have live leaf tissue.
Here's a plant of my White Flour Grex with badly affected leaves above the ear, the lesions are beginning to run together and kill the leaf. You don't like to see NLB this bad above your ear. The disease is cutting off carbohydrate from the ear, reducing yield, and from the lower stalk and roots, which weakens them and leads to lodging and stalk rot.
Here's a plant of Schroeder-strain Hickory King from Africa (also from maicerochico) with fantastic NLB tolerance. This plant is 5 feet away from the badly affected White Grex in the above pic. The highest lesion is 4 leaves below the ear and its a singleton. There is tons of unaffected leaf above and below the ear, despite this row of Hickory King being in the middle of my White Flour Grex with lots of innocula from the affected plants.
So far, the best corns I've grown for NLB tolerance are Cargill Coroico and this Schroeder Hickory King. They both show almost total functional immunity. Cargill Carribean Composite is also highly tolerant but not at the same level as the Coroico or the Schroeder HK. Unfortunately the Coroico/White Flour Grex hybrids are showing much lower tolerance than the Coroico parent did, so I'm going to have to do a lot of hard selection for NLB resistance even when incorporating this resistant material.