Development of Two Isogenic Sweet Corn Hybrids Differing for Glycinebetaine Content

Abstract

A hybrid of sweet corn, Zea mays L. ('1720'; Rogers Brothers Seed Co.), was found to be comprised of glycinebetaine-positive and glycinebetaine-deficient individuals in a 1:1 mixture. This phenomenon was traced to segregation for a single, nuclear, dominant gene determining leaf glycinebetaine content within the female inbred parent of this hybrid. Selection for homozygous recessive (glycinebetaine-deficient) and homozygous dominant (glycinebetaine-positive) genotypes of the female inbred parent enabled production of two isogenic versions of hybrid '1720' differing with respect to a single copy of the dominant allele, by mating these female parent selections with the common homozygous recessive (glycinebetaine-deficient) male parent. These two isogenic hybrids are shown to differ by a factor of 300-to 400-fold in glycinebetaine titer of young expanding leaves of salinized plants, but exhibit no striking differences in the levels of free amino acids or the level of N-methyinicotinic acid (nicotinic acid betaine; trigonelline). The only significant difference between the two hybrids in terms of amino acid composition was found to be in the level of alanine under nonsalinized conditions. The betaine-deficient hybrid exhibited a 14% lower alanine level than the betaine-positive hybrid. Betaine deficiency was not associated with altered stress-induced accumulation of amino acids such as proline, serine, and asparagine plus aspartate, attesting to the high specificity of the genetic difference between these isogenic hybrids with respect to betaine accumulation. This germplasm offers unique opportunities to test whether a single dominant allele determining stress-induced betaine accumulation capacity influences stress resistance in maize.Osmotic adjustment is widely considered to be an adaptive response to water deficits and salinity stress (6,7,14,20,21). Bet2 (betaine) accumulation in response to salinity stress is proposed to play an important role in osmotic adjustment in halophytic members of the Chenopodiaceae and Gramineae (7,(18)(19)(20)22), and may function as a compatible osmotic solute of the cytoplasm and/or chloroplast (17,22).

Effect of salinity on growth and accumulation of organic and inorganic solutes in the leguminous plantsAlhagi pseudoalhagiandVigna radiata

“…Plant shoots were sealed in aluminum foil, and immediately frozen in liquid nitrogen, prior to storage at -20"e. Samples were thawed and centrifuged at 1,200 X g for 25 min at 4"C to extract the cell sap (Gorham et al 1984). Aliquots of the cell sap were used for the total sugar determination using the anthrone method (Morris 1948), and the total amino acid determination as described by Rhodes et al (1989). After a-amino-n-butyrate was added as an internal standard, the cell sap was purified by Dowex-l-OH-and the fractions were eluted with 2.5 N HCl, prior to air-drying.…”

Resistance to salinity stress and available water levels at the seedling stage of the common vetch (Vicia sativa L.)

“…and maize (Zea mays L.), reduced length and dry mass of the stem (Izzo et al 1991) and affected leaf elongation and water transport in xylem vessels in the plants, as well as the length and conductivity of the root in clovers and maize (Evlagon et al 1992, Maiti et al 1994, Maiti et al 1996. A high specificity of the genetic differences between isogenic maize hybrids was found with respect to betaine accumulation (Rhodes et al 1989) and the genetic relationship of tolerance to saline-sodic soils was found in maize (Nordquist et al 1992).…”

Betaine Deficiency in Maize

“…Betaine (glycinebetaine) accumulation in response to drought or salinity stress is proposed to play an important role in osmotic adjustment in members of the Chenopodiaceae and Gramineae (6,22) by functioning as a compatible or protective osmolyte in the cytoplasm and/or chloroplast (10,13,20). Considered as a species, maize (Zea mays L.) has a moderate capacity for betaine accumulation, with maximum reported levels in the range 5 to 10 ,umol/g fresh weight (3,8,(17)(18)(19).…”

“…However, certain maize genotypes lack betaine almost completely; these include sweetcorn (18) several heterotic groups (3), and so represent considerable genetic diversity (5). Genetic analyses of betaine deficiency in a sweetcorn cross (18) and a Corn Belt dent cross (17) have indicated in both cases that a recessive allele ofa single nuclear gene is responsible.…”

“…Genetic analyses of betaine deficiency in a sweetcorn cross (18) and a Corn Belt dent cross (17) have indicated in both cases that a recessive allele ofa single nuclear gene is responsible. As it has not been established whether betaine deficiency in these and other genotypes is conditioned by the same gene or by distinct genes, one aim of the present research was to resolve this issue.…”