Add 4 independent seed brands: Latham + Stine + 1st Choice + Burrus (+623 varieties) (#17)

Co-authored-by: claude <claude@jpaul.io>
Co-committed-by: claude <claude@jpaul.io>

corpus/latham/latham-lh-6149-ss-rib.md

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+# LH 6149 SS RIB-NON RETURN
+
+- **Vendor:** Latham Hi-Tech Seeds (independent family-owned, Alexander, IA)
+- **Brand:** Latham Hi-Tech Seeds
+- **Crop:** Corn
+- **Relative maturity:** 111 days
+- **Trait(s):** Smart Stax
+- **Source:** https://www.lathamseeds.com/products/lh-6149-ss-rib/
+- **Rating scale:** numeric ratings ~1-9 where LOWER = BETTER (1 = best / most tolerant / most resistant); confirmed by cross-referencing Product Overview prose vs values (top-rated stalks/roots cluster 1.0-1.5, weak traits 3.0-3.5, none approach 9). Categorical values pass through verbatim (SCN source 'PI 88788', Phytophthora 'Rps 1k', Anthracnose 'ASR', 'Medium Tall', 'Flex'). NA/blank = not rated.
+- **Service area:** Latham dealer network — Upper Midwest (IA/MN/WI/IL/ND/SD/NE)
+
+---
+
+_LH 6149 SS is widely adaptable across environments and soil types. It performs best when population is at the high end for soil type and management. This hybrid will provide excellent yields from a plant with great fall intactness and staygreen._
+
+---
+
+## Agronomic Characteristics
+
+- **Emergence:** 2.0
+- **Flowering for Maturity:** Moderately Late
+- **Early Vigor:** 2.0
+- **Stalk Strength:** 2.5
+- **Root Strength:** 2.0
+- **Stay Green:** 2.0
+- **Drydown:** 2.0
+- **Test Weight:** 2.5
+- **Drought Tolerance:** 2.5
+- **Herbicide Sensitivity:** None Known
+- **Suggested Population:** 32-38
+- **Corn-on-Corn:** 2.5
+- **Ear Height:** Medium HIgh
+- **Ear Type:** Semi-Flex
+- **Number of Kernel Rows:** 14-16
+- **Cob Color:** Red
+- **Husk Cover:** Medium
+- **Shank Length:** Medium Short
+- **Leaf Angle:** Semi-Upright
+
+## Disease Ratings
+
+- **Goss’s Wilt:** 2.5
+- **Northern Leaf Blight:** 2.5
+- **Gray Leaf Spot:** 2.0