In this study, we reported the isolation and analysis of new polymorphic microsatellites in mungbean (Vigna radiata (L.) Wilczek). Twelve out of 210 primer pairs screened in 30 mungbean accessions gave polymorphism. The polymorphic markers detected two to three alleles per locus with an average of 2.08. Observed heterozygosity varied from 0 to 0.133, while expected heterozygosity ranged from 0.095 to 0.498. Tests for Hardy-Weinberg equilibrium (HWE) and pairwise linkage disequilibrium of the polymorphic loci revealed that all loci except MB-SSR14 significantly departed from HWE and four pairwise combinations, viz. MB-SSR14 vs. MB-SSR42, MB-SSR42 vs. MB-SSR87, MB-SSR114 vs. MB-SSR121, and MB-SSR175 vs. MB-SSR231 significantly deviated from linkage disequilibrium. The markers are being used to study genetic diversity and genome mapping of mungbean.

nificant barriers to development of high-protein commercial cultivars. The physiological and biochemical basis for increased seed proteinSoybean SPC is inherited as a quantitative trait (Burconcentrations (SPC) observed in restriction-index, recurrent-selec- ton, 1987) and influenced by environmental effects tion breeding programs with soybean [Glycine max (L.) Merr.] are poorly understood. The hypothesis that soybean SPC is regulated by (Burton, 1988). Generally the trait is much less influthe supply of nitrogenous substrates available to the seed was evaluenced by the genotype of the embryo than by the genoated. Effects of supra-optimal external N on seed storage protein type on which the seeds develop (Singh and Hadley, accumulation, amino acid concentration and composition in leaves 1968). This suggests that whole plant processes such as and seeds at R5, and levels of specific storage protein subunits were N acquisition, translocation, and mobilization of C and measured. Genotypes with different SPC (NC 107, normal; N87-984-N are important in the determination of seed protein 16, intermediate; and NC 111, high) were grown in controlled-environconcentration. ment chambers and supplied with 30 mM N as NH 4 NO 3 from V5 to Brim and Burton (1979) used recurrent selection to maturity or from R5 to maturity. Control plants received 10 mM N increase SPCs in two populations (IA and IIA). Carter throughout the growth cycle. Relative to control, supra-optimal N et al. (1982) examined relationships between N accumuincreased SPC of NC 107 and N87-984-16 by an average of 28%. Greater enhancement of protein accumulation than of dry matter lation and distribution and SPC in high and low seed accumulation in the seed resulted in SPCs of 460 to 470 g kg Ϫ1 , germplasm from both populations. They observed that which are appreciably greater than concentrations observed for these high protein germplasm from population IA accumucultivars grown in the field. Supra-optimal N also increased SPC of lated more total N before reproductive development the high protein line (NC 111) by 15%, but this increase resulted than high seed protein germplasm in population IIA. entirely from a decrease in yield. Supra-optimal N supplied to NC Selected high and low seed protein lines derived from 107 and N87-984-16 from V5 until R5 increased total free amino acid Cycle 0 and advanced cycles of selection for both popuconcentrations in seeds and leaves at R5 by an average of 21 and lations were evaluated for vegetative N accumulation 46%, respectively. Enhanced accumulation of the ␤ subunit of ␤ prior to reproductive growth and vegetative N mobilizaconglycinin which does not contain methionine and cysteine accounted tion to seed during reproductive growth (Burton et al., for the increase in SPC. While enhanced N availability increased the SPC of a normal protein line into the high range, availability of sulfur 1995). The authors concluded that the high protein conamino acids in the developing seed determined which storage protein centration trait re...

Cassava {Manihot esculenta Crantz) staroh is traded in international markets more than starch from any other source. The starch industry requires cassava cultivars with novel starch characteristics for commercial exploitation. A natural source of waxy (amylose-free) cassava starch, clone AM 206-5, was identified at the International Center for Tropical Agriculture (CIAT). The granule-bound starch synthase I {GBSSl) gene is related to the waxy starch trait. The objectives of this study were to introgress the waxy starch mutation into Thailand's cassava breeding populations, to analyze the inheritance of waxy starch in cassava, and to develop molecular markers for this trait. AM 206-5 {wxwx) was crossed with several elite oultivars {WxWx) to transfer the wx alíele. Unrelated "F/' {Wxwx) genotypes were crossed among themselves to produce a "Fg" segregating population with negligible levels of inbreeding depression. The waxy starch phenotype was recovered in 25.7% ofthe 11,192 genotypes tested. This result provides further evidence that cassava is a functional diploid and that only one copy of GBSSl is present in cassava. A full-length genomic DNA sequence of GBSSl was isolated and characterized from C8, a waxy starch "f^" clone derived from AM 206-5. We exploited these sequence differences to develop two diagnostic single-nucleotideamplified polymorphism (SNAP) markers to differentiate homozygous waxy {wxwx) from the heterozygous {Wxwx) and homozygous {WxWx) nonwaxy genotypes.

Phytic acid (PA) is the main storage organic form of phosphorus (P) in seeds of cereals and legumes. It is a strong inhibitor against the absorption of nutrients in monogastric animals. The objective of this study was to determine the variation of total P (TP) in seeds of mungbean germplasm and investigate the inheritance of seed P compound and phytate contents. TP content in seeds of 250 accessions were found to range from 2.34 to 5.75 mg/g. The inheritance was studied in the F 2 population derived from a cross between 2 accessions with the lowest and highest PA contents, viz. V1658BBR and V1141BG. Broad-sense heritability estimates of TP, inorganic P (IP), and phytate P (PhyP) contents were 80.8, 78.6 and 80.7%, respectively. The 9:7 segregation ratio of F 2 population in this study indicated that high TP and PhyP were controlled by dominant alleles at 2 independent loci of major genes showing duplicated recessive epistasis.

No abstract