Mutant Progenies Research Articles

Diversity pattern in Sesamum mutants selected for a semi-arid cropping system

Due to the complex requirements of moisture stress, substantial genetic diversity with a wide array of character combinations and effective simultaneous selection for several variables is necessary for improving the productivity and adaptation of a component crop in order for it to fit into a cropping system under semi-arid tropical conditions. Sesamum indicum L. is grown in Venezuela after rice/sorghum/or maize under such conditions. A mutation breeding program was undertaken using six locally adapted varieties to develop genotypes suitable for the above system. The diversity pattern for nine variables was assessed by multivariate analysis in 301 M4 progenies. Analysis of the characteristic roots and principal components in three methods of selection, i.e., M2 bulks (A), individual plant selection throughout (B), and selection in M3 for single variable (C), revealed differences in the pattern of variation between varieties, selection methods, and varieties x methods interactions. Method B was superior to the others and gave 17 of the 21 best M5 progenies. 'Piritu' and 'CF' varieties yielded the most productive progenies in M5 and M6. Diversity was large and selection was effective for such developmental traits as earliness and synchrony, combined with multiple disease resistance, which could be related to their importance by multivariate analyses. Considerable differences in the variety of character combinations among the high yielding. M5 progenies of 'CF' and 'Piritu' suggested possible further yield improvement. The superior response of 'Piritu' and 'CF' over other varieties in yield and adaptation was due to major changes in plant type and character associations. Multilocation testing of M5 generations revealed that the mutant progenies had a 40%-100% yield superiority over the parents; this was combined with earliness, synchrony, and multiple disease resistance, and was confirmed in the M6 generation grown on a commercial scale. This study showed that multivariate analysis is an effective tool for assessing diversity patterns, choice of appropriate variety, and selection methodology in order to make rapid progress in meeting the complex requirements of semi-arid cropping systems.

Flower‐Colour Polymorphism in Lupinus pilosus in Israel

AbstractFour rare flower‐colour mutants were detected in natural populations of Lupinus pilosus in Israel. The breeding systems and genetic bases of three oif them were examined.Mutants were tagged in wild populations and seed obtained upon open pollination was collected and grown in a, net house which was insect‐proof. Mutant progenies were used in crosses with each other and with wild‐type plants.Our results indicate the possibility that all three mutants are simple Mendelian recessives to the wild‐type deep‐violet colour and that in L. pilosus this colour is not monogenic but determined by at least two loci.All these mutants show a high degree of selling when open‐pollinated in nature.

Mitochondrial mutagenesis in Saccharomyces cerevisiae: the origin of mit- mutants.

SUMMARYYeast cells contain many copies of mitochondrial (mit) genomes. The question we tried to answer was howmit−mutations occurring in one genome as a result of mutagenic treatment might yield homoplasmic mutant cells. Three processes were considered. First, that these cells originate by segregation of mutant and standard alleles during cell division. Secondly, that they originate through intracellular selection, for which cell division is not required. Thirdly, that recombination involving the mutant and standard alleles is non-reciprocal and unidirectionalmit+→mit−so that the mutant allele is spread into the entire population of mitochondrial genomes within a cell, thus making it homoplasmicmit−. The results indicate that the first process, although efficiently producing homoplasmic cells from heteroplasmic zygotes (for review see Birky, 1978), seems to play only a minor, if any, role in producing homoplasmic mutant progenies from mutagenized cells. The most important is the second process, that is, intracellular selection occurring in cells which have one or a few genomes carryingmit−mutations, while the remaining genomes are irreversibly damaged. The third process, unidirectionalmit+→mit−conversion, does not seem to play any part.

Radiation induced asynaptic mutations in durum wheat (Triticum durum DESF.)

The cytological behaviour and the inheritance of two asynaptic mutations independently obtained by neutron treatment of durum wheat seeds of var. Cappelli and Aziziah are considered. Mutant individuals of both lines have normal morphology, but are completely sterile. Analysis of chromosome behaviour at the several stages of PMC meiosis has been thoroughly accomplished in mutant progenies of both varieties during two subsequent generations. A completely random chromosome disjunction was found at anaphase I, together with multipolar spindles, laggard chromosomes etc. At meiotic second division a large amount of abnormalities were found, as a consequence of previous asynapsis and irregular polarization. Some differences in cytological behaviour were found between the asynaptic mutants of Cappelli and the asynaptics of Aziziah. - Genetic analysis demonstrated that both mutations behave as monogenic recessives.

Fertility of Interchange Heterozygotes inTriticum DurumDesf

SUMMARYAmong the several aspects investigated in the programme of studies on induced mutagenesis in Triticum durum, cytological analysis of mutant progenies has been particularly taken into consideration. Data obtained from microsporogenesis, pollen fertility and seed setting analysis of heterozygotes for reciprocal translocations, allowed a general appraising on the relation of translocation heterozygosis to gametic fertility.Complexively more than 50 different translocations were investigated in M3, M4 and F1 material from crosses of mutants to mother line.A much higher fertility than expected on theoretical basis was found in traslocation heterozygotes. From data obtained it seems that the deficiency — duplications originated in a micro- or macroscopore following an adjacent segregation of chromosomes tied in a translocation complex, do not lead in Triticum durum to the gametic sterility generally found in other species. Several factors influencing fertility in individual heterozygous for a translocati...