HYPOCOTYL COLOR IN SOYBEANS (GLYCINE MAX (L.) MERR.)
Abstract
Soybean varieties and experimental lines which had purple, bronze, and white hypocotyl color were studied to obtain a more complete characterization of hypocotyl pigmentation, to determine the sequence of pigment development, and to gather information about the inheritance of hypocotyl color and its intensity. The athocyanins present in both the purple and bronze hypocotyl lines were considered to be delphinidin, petunidin, and malvidin. They were found in an approximate ratio of 1 : 4 : 38, respectively. The malvidin content of the purple hypocotyl lines was six times greater than that of the bronze hypocotyl lines. Pigment formation in the hypocotyl tissue showed high levels of activity for only the first 2 or 3 days after emergence. This pigment formation pattern was consistent with the high concentration of pigment near the soil surface. Reductions in the pigment formation rates after the third day after emergence resulted in low amounts of pigment toward the apical portion of the hypocotyl. Phenylalanine ammonia lyase (PAL) activity was six times greater in the cotyledons than in the hypocotyl. This observation is consistent with the interpretation that the pathway leading to the formation of anthocyanins functions at a higher rate in these structures than in the hypocotyls. Formation of anthocyanin in specific areas of the stems, flowers, and sometimes the leaves however, suggests that the final stages of anthocyanin formation occur at a higher rate in these structures. Genetic control of anthocyanin formation and its intensity was assessed using crosses among purple and white hypocotyl lines. Observations of F(,3) families from crosses between purple and white hypocotyl types indicated a single gene control system for pigmentation vs non-pigmentation. The wide range of pigment intensities and the lack of discreet pigment intensity classifications observed to be segregating from these crosses and crosses between purple hypocotyl lines suggested that genetic control of pigment intensity involves several minor genes. Use of pigment intensity as a marker trait for plant breeding and varietal identification would, therefore, be impractical.
Degree
Ph.D.
Subject Area
Agronomy
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