PNL Volume 16 1984

RESEARCH REPORTS

PRELIMINARY ROOT STUDIES OF PISUM SATIVUM

Veitenheimer, E. E. and E. T. Gritton Department of Agronomy

University of Wisconsin, Madison, WI USA

In spite of the vital role roots play in the life cycle of a plant,

very little is known about the range of heritable variation for rooting

habit in peas. We therefore undertook a series of studies in an effort

to expand our knowledge of the pea root system.

Various shoot and root characteristics were measured on 42 diverse

genotypes grown in nutrient solution for one month. Freezing and can-

ning cultivars, breeding lines, and 28 uprooting-resistant and root-rot

tolerant lines from G. A. Marx were included. Highly significant

variability for most shoot and root parameters was found (Table 1).

Many significant, positive correlations were found among the shoot and

root parameters. The length of the primary root, length to the last

lateral, average lateral length, root volume, and root fresh and dry

weights were all highly, positively correlated. No correlation was

found between a plant's previously expressed tolerance to root rot

(Aphanomyces euteiches Drechs.) and its root morphology.

In order to identify the proper experimental procedure to use in

future studies, four pea lines were grown in four different culture

media (hydroponics, vermiculite, sand, and a soil/sand mix) and har-

vested at three different growth stages (9th node, flowering, and 28

days after flowering). The growth stage and culture medium had a sig-

nificant effect on entry rankings for various root traits. We

concluded, therefore, that pea root studies that are to have application

to the field should be undertaken using a soil-based medium.

Lines with root systems larger than any previously tested were

identified in greenhouse tests uitilizing soil-filled clay pots. Four

lines were chosen for a field study involving six replications in a

randomized complete block design. Each replication consisted of a nine-

plant grid with plants 15cm apart. At flowering the root system of the

center plants were dug using a core sampler 25cm in diameter and 30cm

deep. Two soil cores per plant were separately soaked overnight, poured

into screenlined boxes, and all the soil and debris were washed away.

Results are shown in Table 2. Relative differences obtained in the

field study were comparable to those obtained in the greenhouse test.

We have begun crossing lines with larger root systems to currently

grown varieties and breeding lines. A generation means analysis should

provide information on relative gene effects and heritability of root

volume and root dry weight. In addition to providing new basic

knowledge about the pea root system, studies such as these could prove

useful in improving water and mineral uptake and increasing tolerance to

root diseases.



	74 PNL Volume 16 1984	RESEARCH REPORTS

	Table 1. Ranges of root characteristics measured on 42 pea lines grown in hydroponics for one month.



	Table 2. Average values for shoot and root characteristics of field- grown peas sampled at flowering (Arlington, 1982).