Thesis (Ph. D.)--University of Wisconsin--Madison, 1956. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 194-197).

Typescript, etc.

Two aspects of the Ethiopian cereal tef (Eragrostis tef) which relate to its improvement have been studied: lodging and floral biology with special reference to hybridisation. Lodging was examined in a large germplasm collection in Ethiopia. Several types of lodging were recognised. Temporary lodging, from which the plant makes a complete recovery, occurs before heading. Permanent lodging, which occurs after heading, takes one of three forms: bend-lodging, break-lodging and root-lodging. Only bendlodging is widespread and of economic importance: losses are estimated at seventeen per-cent. Lodging resistance is aS80ciated with several interacting morphological characteristics particularly plant height, length of panicle, peduncle and culm and the diameter of culm. The sequence of flowering in tef is a8 follows: flowering commences at the top of the inflorescence and proceeds basipetallYj flowering begins at the bottom of each spikelet and proceeds acropetally. The timing of flowering is complex, making it difficult to predict anthesis for any individual flower. Anthesis is rapid: exsertion of the stamens and shedding of the pollen takes less than five minutes and the pollen starts to germinate on the stigma immediately. In the presence of light, temperatures above 4°C do not prevent flower opening while in the ab8ence of light, temperatures above 4 °c inhibit flower opening and therefore enable the breeder to control anthesis. Warm humid air helps to delay the dehiscence of anthers of opening flowers by up to an hour without affecting pollen viability. Contrary to previous reports ethrel does not prevent fertilization in tef and can be used as a male gametocide; it is most effective when applied at the flag-leaf stage, though it is phytotoxic at high concentrations. Dark treatment and hot water treatment induced male sterility but produced other effects which make them unsuitable for em,asculation. A reliable and rapid method of screening seedlings for hybridity has been developed utilizing anthocyanin production. When pollen carrying the marker gene is used for crossing, only hybrid progeny produce anthocyanin. This technique reduces screening time from about three months (heading time) to less than four days.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.

No description available.