Anatomical Traits Associated With Pod Rot Resistance in Peanut1

Abstract

Peanut (Arachis hypogaea L.) cultivars resistant to Pythium myriotylum Drechs. and Rhizoctonia solani Kuhn, are needed for effective management of pod rotting diseases. The low efficiency of field screening for disease reaction in breeding for resistance has emphasized the need for improved evaluation methods. Anatomical examinations of roots, stems, leaves, pegs, and shells were made of six genotypes (TxAG-3, PI 341885, Toalson, Starr, Florunner, and Goldin I) with various degrees of resistance to pod rots in search of traits that might be used effectively in screening for disease reaction. The palisade mesophyll cells of 50-day old plants were arranged more compactly in pod rot resistant than in susceptible genotypes. An index representing total width (pm) of palisade cells/mm leaf blade was more discriminative in distinguishing among genotypes than average of either cell width or cell number alone. The distribution of lignin in peanut shells was correlated with pod rot resistance. The cell walls in the epicarp and sclerenchymatous mesocarp were thicker and more lignified in the resistant than in the susceptible genotypes. Genotypic digerences in lignin distribution were readily apparent at lOOx when shell sections were stained with phloroglucinol. Associations between anatomical traits of stems, pegs, roots, or juvenile plant leaflets and field pod rot reaction were not consistent among all genotypes. However, lignindistribution in pods, and an index representing Fm of palisade cells/mm of leaf blade individually or in combination, might be used effectively to supplement field evaluations in screening breeding lines for pod disease reaction.'Contribution from the Texas Agric. Exp. Stn., Texas A&M Univ., College Station, TA No. 20169. Part of a Ph. D. dissertation submitted by the senior author. Partial support provided as a graduate scholarship by EMBRAPA -Empresa Brasileiria de Pesquisa Agropecuaria.

Reaction of Select Peanut (Arachis hypogaea L.) Lines to Southern Stem Rot and Pythium Pod Rot Under Varied Disease Pressure

“…Resistance to Pythium pod rot was reported in Spanish-type peanut by Frank and Krikun (4) and later reports of genotypic difference in Pythium pod disease reaction have been reported by several researchers (6, 8,9,15,21). The mechanism(s) of resistance have been explored with the conclusion that cell compaction is more dense and lignification is more uniform in the pericarps of resistant than in susceptible genotypes (13,14).…”

Lignin Content and Resistance to Sclerotinia minor in Peanut

“…Few studies have examined the relationship between lignin and disease resistance in peanut. Godoy et al (1985) found higher levels of lignin in pods in breeding lines that were more resistant to pod rot than in susceptible lines. Similarly, Liang and colleagues reported a negative correlation between lignin content in peanut seed and rate of infection by Aspergillus flavus (2006).…”

Breeding For Disease Resistance In Peanut (Arachis Hypogaea L.)

“…Constitutive aqatomical traits in mature peanut shells have been associated with resistance to P. myriotylum and Rhizoctonia solani pod-rotting diseases in Texas (50). Induction of periderl11 formation in tap and fibrous roots pas been associated with resistance to C. crotalariae (62,63).…”