Methods to synchronize the flowering time of the components in crossing plots for the production of hybrid seed corn

Abstract

The method generally adopted to produce hybrid seed corn is to plant the parent varieties (inbred lines or foundation single crosses) in an isolated crossing plot .The principal condition that must be fulfilled in order to bring about the desired crossing is, that the partners flower simultaneously . This condition is not always satisfied . Sometimes it is the pollen parent which comes in bloom too early and has shed its pollen before the seed parent has started silking . In the reverse case, the seed parent may be in full silk, whereas the male partner has not even shed one pollen grain . This situation has caused the failure of many seed production fields and seedsmen have long been looking for methods by which the flowering time of certain inbreds or single crosses can be synchronized . The difficulty is increased when the required cross is between two varieties differing markedly in maturity . In Holland, where dent-flint hybrids play an important part, this problem must be faced every year .There are two obvious possibilities of removing the obstacles :l . to make the late varieties flower earlier .2 . to retard flowering of the early varieties .Flowering might be advanced by (a) adjusting the day length or (b) by sowing early in a greenhouse or cold frame and transplanting later to the field .The method mentioned under (a) will be left out of consideration as it would not be applicable on a large scale .The last method (b) has been applied rather extensively by one of the private corn breeders in our country, the late MR BENNINK . Seeds of inbreds to be forced were planted in small pots moulded from a mixture of clay, sand and cow dung . The young plants were kept under glass until they had developed 2 or 3 leaves and then transplanted into the fields with pot and all . Provided that seeding and transplanting had been made at the proper time, it was possible to induce certain strains to flower a few days earlier than under normal conditions . This method is limited in its scope . It requires much labor and can only be used in small plots to be planted with valuable material . For large scale work this method is far too expensive .

Maturation and Yield of Corn as Influenced by Climate and Production Technique1

“…While growing season requirements of corn hybrids are usually expressed as number of days required from planting or emergence to maturity, there has been a growing dissatisfaction with tbis index because no provision is made for daily temperature variation, fertility level or moisture supply. Recently, there has been some interest in expressing maturity of corn in terms of accumulated thermal units (degree days) above a base temperature of 50° F. ( 8) as a measure of the growing season required ( 3) and in using these thermal units as a guide for planting ( 5).…”

A Gene Regulatory Network Model for Floral Transition of the Shoot Apex in Maize and Its Dynamic Modeling

“…Heat units or growing degree days to shedding and to silking are examples of empirical models widely used to synchronize shedding and silking events in seed production [22]–[24]. When these models were embedded within comprehensive physiological frameworks such as CERES [25] and APSIM [26] they were applied to understand the physiological basis of maize adaptation in different environment types, construct trait performance landscapes, and predict responses to trait selection in breeding programs [27].…”

“…The limited understanding of the genetic controls of flowering time in maize in the past decades led to the development of quantitative empirical models that use environmental and genotypic rather than genomic information to predict the floral transition and the timing of pollen shedding and silking in maize. Heat units or growing degree days to shedding and to silking are examples of empirical models widely used to synchronize shedding and silking events in seed production [22] – [24] . When these models were embedded within comprehensive physiological frameworks such as CERES [25] and APSIM [26] they were applied to understand the physiological basis of maize adaptation in different environment types, construct trait performance landscapes, and predict responses to trait selection in breeding programs [27] .…”