According to the invention, there is provided an inbred corn plant designated 89AHD12. This invention thus relates to the plants, seeds and tissue cultures of the inbred corn plant 89AHD12, and to methods for producing a corn plant produced by crossing the inbred corn plant 89AHD12 with itself or with another corn plant, such as another inbred. This invention further relates to corn seeds and plants produced by crossing the inbred plant 89AHD12 with another corn plant, such as another inbred, and to crosses with related species. This invention further relates to the inbred and hybrid genetic complements of the inbred corn plant 89AHD12, and also to the SSR and genetic isozyme typing profiles of inbred corn plant 89AHD12.

Inbred corn plant 89AHD12 and seeds thereof

An inbred corn line, designated LH283BtMON810, is disclosed. The invention relates to the seeds of inbred corn line LH283BtMON810, to the plants of inbred corn line LH283BtMON810 and to methods for producing a corn plant, either inbred or hybrid, by crossing the inbred line LH283BtMON810 with itself or another corn line. The invention further relates to methods for producing a corn plant containing in its genetic material one or more transgenes and to the transgenic plants produced by that method and to methods for producing other inbred corn lines derived from the inbred LH283BtMON810.

Inbred corn line LH283BtMON810

According to the invention, there is provided an inbred corn line, designated PHHB9. This invention thus relates to the plants and seeds of inbred corn line PHHB9 and to methods for producing a corn plant produced by crossing the inbred line PHHB9 with itself or with another corn plant. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHHB9 with another corn line or plant.

Inbred corn line PHHB9

An inbred maize line, designated PH0HC, the plants and seeds of inbred maize line PH0HC, methods for producing a maize plant produced by crossing the inbred line PH0HC with itself or with another maize plant, and hybrid maize seeds and plants produced by crossing the inbred line PH0HC with another maize line or plant.

Inbred maize line PH0HC

Maize (Zea mays L.) yields have risen continually wherever hybrid maize has been adopted, starting in the U.S. corn belt in the early 1930s. Plant breeding and improved management practices have produced this gain jointly. On average, about 50% of the increase is due to management and 50% to breeding. The two tools interact so closely that neither of them could have produced such progress alone. However, genetic gains may have to bear a larger share of the load in future years. Hybrid traits have changed over the years. Trait changes that increase resistance to a wide variety of biotic and abiotic stresses (e.g., drought tolerance) are the most numerous, but morphological and physiological changes that promote efficiency in growth, development, and partitioning (e.g., smaller tassels) are also recorded. Some traits have not changed over the years because breeders have intended to hold them constant (e.g., grain maturity date in U.S. corn belt). In other instances, they have not changed, despite breeders' intention to change them (e.g., harvest index). Although breeders have always selected for high yield, the need to select simultaneously for overall dependability has been a driving force in the selection of hybrids with increasingly greater stress tolerance over the years. Newer hybrids yield more than their predecessors in unfavorable as well as favorable growing conditions. Improvement in the ability of the maize plant to overcome both large and small stress bottlenecks, rather than improvement in primary productivity, has been the primary driving force of higher yielding ability of newer hybrid.

The Contribution of Breeding to Yield Advances in maize (Zea mays L.)

Improvement in the genetic worth of maize (Zea mays L.) hybrids over the years can be a consequence of increased heterosis and/or improved inbred parents. The objectives of this study were to determine the nature of the genetic improvement of maize hybrids over a period of about 40 years using a representative series of hybrids and to determine any associated changes in morphological and yield component traits. Non parental single crosses of double crosses from the 1930's and the 1950's and single crosses of the 1970's, their inbred parents, and their F, generations were grown at 31 500 and 58 800 plants/ha. The study was conducted at Urbana and Shabbona, 111. However, the inbreds were grown at Urbana only and, because of poor germination of the inbreds of the earlier decades, were grown at 31 500 and 48 800 plants/ha. The majority of the improvement in inbred and hybrid yielding ability occurred between the 1950's and the 1970's. Recent inbreds and hybrids stand better, stay green longer, and have smaller tassels than their earlier counterparts. Grain yield inbreeding depression (and heterosis) increased from the 1950's to the 1970's and a part of it is manifest at loci that condition the responsiveness of the hybrids of the 1970's to increased plant densities. Plant and ear height inbreeding depression seem to have decreased from the 1950's to the 1970's

G. F. Sprague

Papers

Inbreeding Depression, Inbred and Hybrid Grain Yields, and Other Traits of Maize Genotypes Representing Three Eras1