Procedure for artificial cross pollination in clove (Syzygium aromaticum)

Summary A technique for artificial cross pollination in clove is described. This involves emasculating flowers two days before anthesis, and pollinating four days later. Following this procedure a seed set of approximately 25% can be expected.     

General combining ability of six genotypes of spring wheat (Triticum aestivum) for biscuit-making quality characteristics

The first South African soft wheat breeding programme was initiated in 19 90 , consequently almost no information is available on soft wheat quality characteristics. The aim of this study was to determine general combining ability (GCA) of several spring wheats for biscuit-making quality characteristics. A full dialled cross was made with five spring wheats with good biscuit-making quality and a sixth hard wheat with poor biscuit-making quality. Seventeen quality characteristics were measured. When the GCA to specific combining ability (SCA) ratios were calculated, strong additive gene action was shown for all characteristics, excluding flour colour and biscuit diameter, which suggested high heritabilities for most characteristics. None of the characteristics showed more non-additive than additive gene action. Three of the soft wheat cultivars combined well for the characteristics important for biscuit-making quality.     

Genetic control of acquired high temperature tolerance in winter wheat

Summary The development of high temperature-tolerant wheat (Triticum aestivum L.) germplasm is necessary to improve plant productivity under high-temperature stress environments. The quantification of high temperature tolerance and the characterization of its genetic control are necessary for germplasm enhancement efforts. This study was conducted to determine the genetic control of acquired high temperature tolerance in common bread wheat cultivars. Reduction of 2,3,5-triphenyltetrazolium chloride (TTC) by heat-stressed seedling leaves was used as a quantitative measure to characterize acquired high temperature tolerance. Eleven-day-old seedlings of 20 F₁ progeny produced through a complete 5×5 (Payne, Siouxland, Sturdy, TAM W-101, and TAM 108) diallel mating design were acclimated at 37° C for 24 hours, followed by a 2-hour incubation at 50° C. Under these test conditions, acquired high temperature tolerance ranged from a high of 75.7% for the genotype TAM W-101 × TAM 108, to a low of 37.3% for the genotype Payne × Siouxland. Partitioning of genotypic variance revealed that only the general combining ability component effect was statistically highly significant, accounting for 67% of the total genotypic variation. These results suggest that enhancing the level of high temperature tolerance in wheat germplasm is feasible utilizing existing levels of genetic variability and exploiting additive genetic effects associated with high temperature tolerance.Contribution of the Texas Tech College of Agric. Sci. Journal no T-4-386. This work was supported by USDA specific agreement No. 58-7MNI-6-114 from the Plant Stress and Water Conservation Laboratory, USDA-ARS, Lubbock, Texas, USA     

玉米改良单交种选育方法的研究：Ⅱ.姊妹系和姊妹种的配合力研究

以ＧｒｉｆｉｎｇＩＩ双列杂交试验和ＮＣＩＩ遗传交配试验，测定玉米８个姊妹系及其２８个姊妹种的一般配合惫，结果两者基本一致。玉米妹系的一般配合力是一种遗传特性，它既可遗传给其组成的姊妹种，又能通过姊妹和种遗传给其组成的改良单交种；姊妹种的一般配合力与其双亲姊妹系一般配合力均值之间没有显著差异，并呈密切相关，这阐明了改良单交种与其对应的普通单交种相似的原因，并为改进和简化改良单交种选育程序提供理论依据     

Genetic Variability for Grain Yield and Protein Content in Barley and Its Modification by Net Blotch

Protein content, yield and 1000-grain weight of healthy and net blotch-diseased plants were studied in a diallel cross programme concerning nine different varieties of barley (Hordeum vulgare L.). F₁ hybrids and their parents were grown in the field in two randomized block design experiments each with three replications (three inoculated and three non-inoculated plots). General and specific combining abilities were determined for yield, protein percentage, 1000 grain weight, protein yield, and non-protein yield. A high genetic variability for the traits studied was observed. Non-protein yield and 1000-grain weight decreased significantly in inoculated plants where protein yield was not affected. Significant general and specific combining abilities were observed for all traits. Values for general and specific combining abilities were, in some cases, significantly modified by net blotch of barley. This indicates that attention must be paid to the danger of drawing conclusions in quantitative genetics studies dealing with both diseased and healthy plants.     

Genetics of nitrate content of lettuce, 1: Analysis of generation means

Summary The genetics of nitrate content in butterhead lettuce (Lactuca sativa L.) was studied using the mean values of five parental genotypes and several generations obtained from crosses between them. One high nitrate parental genotype was chosen and four low nitrate ones. A diallel analysis showed additive genetic effects to be the major source of variation in generation means. Estimates of additive genetic effects differed significantly between experiments, indicating genotype x experiment interactions. Effects of dominance were relatively small. The size and direction of dominance varied between experiments. Reciprocal differences were of very limited size and also varied between experiments. The inheritance of nitrate content in lettuce fitted the additive-dominance genetic model.     

Inheritance of characters determining growth and development of tomato (Lycopersicon esculentum Mill.) under low energy conditions

Summary Diallel crosses were made between 15 tomato genotypes with varying performance under a low energy regime. It appeared that differences between genotypes for 11 vegetative and generative plant characters are determined mainly by additive genetic variation. For breeding cultivars adapted to low energy conditions, crossing genotypes with a high GCA for weight of trusses and fruits (WTF) and genotypes with a high GCA for weight of vegetative plant parts (WVP) seems most promising. Complications may arise from the negative correlation between GCA values for WTF and WVP, and the strong positive correlation between GCA values for fruit number and WTF, causing small fruits.     

An analysis of hybrid sterility in rice using a diallel cross of 21 parents involving indica, japonica and wide compatibility varieties

Summary There is much interest in the inter-varietal fertility of Asian cultivated rice. In this study, we analyzed the fertility of hybrids in a diallel set of 210 crosses involving 21 parents representing a broad range of the cultivated rice germplasm including landraces, primitive cultivars, modern elite cultivars and parents of hybrid rice. The materials were also carefully selected with respect to indica-japonica classification including typical indica/japonica, more or less intermediate and wide compatibility varieties. The level of hybrid fertility varied widely among the crosses from almost completely sterile to fully fertile. In general, hybrid fertility of intra-subspecific crosses, i.e., indica by indica (I×I) and japonica by japonica (J×J), is much higher than inter-subspecific crosses (I×J or J×I). The fertility varied widely in hybrids involving wide compatibility varieties and also in inter-subspecific crosses not involving wide compatibility varieties. An analysis of variance showed that both the main effects of indica and japonica parents and the interaction between the parents are highly significant in determining hybrid fertility. We speculate that, in addition to wide compatibility, the overall genetic difference between the indica and japonica parents, that may involve a series of minor mutations, play an important role in determining the hybrid fertility. There are also genes of sizable effect that influence fertility in hybrids resulting from specific combinations of the parents.Abbreviations I×I indica by indica cross - I×J indica by japonica cross - J×I japonica by indica cross - J×J japonica by japonica cross - WCV wide compatibility variety     

Pod shatter resistance evaluation in cultivars and breeding lines of Brassica napus, B. juncea and Sinapis alba

Pod shatter susceptibility was investigated in Brassica napus germplasm and shatter resistant species of B. juncea and Sinapis alba. The comparisons were made by measuring seed yield in field plots, detached pod rupture energy (RE) and the half‐life of pod‐opening. Pod shatter resistance was significantly greater in B. napus lines derived from interspecific hybridizations of B. napus with B. rapa, B. carinata and B. juncea, than common B. napus cultivars. While these lines exhibited no significant difference in resistance to pod shatter than B. juncea, an entry of S. alba had no yield loss caused by pod shatter. Resistance to pod shatter was characterized in the field as little or no yield loss after full maturity, delayed shattering in time, and stable yield performance under variable climatic conditions during pod maturity. Yield loss caused by pod shatter ranged from a low of 4% for the B. juncea cv. ‘AC Vulcan’ to a high of 61% for the black seeded B. napus line DH12075 in 2‐year field trials after 1 month maturity. Pod shatter resistance was not significantly associated with specific plant and pod morphological traits, except pod length (P = 0.005) in tested materials. Field visual scores of pod shatter through inspections of average pod shatter per plant within plots were highly correlated with plot yield loss. Indoor quantitative evaluations of pod strength using a pendulum machine to measure pod RE and random impact test to measure half‐life of pod‐opening resistance were highly correlated with field yield loss. Multiple evaluations of pod shatter in method and in time after pod maturity are recommended for reliable evaluation of pod shatter resistance.     

AFLP analysis indicates no introgression of maize DNA in wheat x maize crosses

Amplified fragment length polymorphisms (AFLPs) were used to follow the possible introgression of maize DNA into haploids of wheat as a side‐effect of exploiting wheat x maize hybridization for haploid production. AFLPs were generated with 64 MseI/ EcoRI and 64 MseI/ PstI primer combinations, and the AFLP profiles of haploids were tested against those of maize and of the regular wheat varieties involved in the crosses. On average, 45.1 and 110.7 fragments were produced per assay with the MseI/EcoRI and MseI/PstI combinations, respectively. Different numbers of fragments were produced for wheat and maize: an average of 81 in the haploid, 80 in the wheat parent, and only 67.1 in maize. No evidence was found for introgression of maize into the wheat genome. Three unique AFLP fragments were detected in haploids, which were not present in the parental wheat genotypes. These ‘novel’ AFLP bands in the haploids could be caused by nucleo‐cytoplasmic interaction in the hybrid zygote. Such instability in the wheat genome is defined as temporal, as it was not detected in further generations when colchicine‐doubled progeny of the haploids was tested for the presence of polymorphic fragments.