This chapter cover topics on: origin of garlic and the history of its cultivation (garlic in Central Asia and the Mediterranean basin; conclusions on the origin of garlic and its immediate relatives; the spread and diversity of garlic around the world; ecology); sources of genetic variation; subclassification; flowering (genetics and environment); discovery and description of fertile clones (early studies suggesting fertility; discovery and confirmation of fertility; further developments in garlic fertility; seed production and breeding of garlic).

Although nitric oxide (NO) and reactive oxygen species (ROS) are essential signalling molecules required for mediation of abscisic acid (ABA)-induced stomatal closure, it is not known whether these molecules also mediate the ABA inhibition of stomatal opening. In this study, we investigated the role of NO and ROS in the ABA inhibition of stomatal opening in Vicia faba. ABA induced both NO and ROS synthesis, and the NO scavenger reduced the ABA inhibition of stomatal opening. Exogenous NO and hydrogen peroxide (H2O2) also inhibited stomatal opening, indicating that NO and ROS are involved in the inhibition signalling process. An inhibitor of nitric oxide synthase (NOS) reversed the ABA inhibition of stomatal opening. Either the NO scavenger or the NOS inhibitor also reversed the process in the H2O2 inhibition of stomatal opening. We found that in the ABA inhibition of stomatal opening, NO is downstream of ROS in the signalling process, and NO is synthesized by a NOS-like enzyme.

F2 segregation analyses of DNA restriction fragment length polymorphisms (RFLPs) detected between a cabbage line (No. 86-16-5) resistant to race 2 of Plasmodiophora brassicae (Woronin), the fungus responsible for clubroot disease, and a rapid cycling line (CrGC No. 85) was used to construct a detailed genetic map of Brassica oleracea. RFLP markers were random and seedling-specific cDNA clones. The 201 loci so far mapped in B. oleracea covered 1112 cM. They are assembled into nine major linkage groups and four small linkage groups. Twelve loci were found unlinked to any other markers. Twenty-one loci were detected with the 18 seedling-specific cDNAs. Two dominant QTLs for resistance to race 2 of the clubroot disease causal agent were also identified. Leaf morphology and biennial flowering appeared to segregate as single Mendelian traits, but only leaf morphology could be linked to other markers. This RFLP study in B. oleracea is providing additional information on genome organization and complements current RFLP mapping effort in B. napus.Key words: genetic mapping, Brassica oleracea, Plasmodiophora brassicae, breeding, clubroot resistance, DNA markers, RFLP.

F2 segregation analyses of DNA restriction fragment length polymorphisms (RFLPs) detected between two cultivars of canola ('Westar' × Topas') was used to construct a detailed genetic map of Brassica napus. RFLP markers were from a seedling-specific cDNA library. They were either randomly selected or previously characterized as seedling-specific cDNA clones. The 120 loci so far mapped in B. napus covered 1413 recombination units. They are assembled into 19 linkage groups. Seventeen loci were found unlinked to any other markers. Few polymorphisms were detected with the seedling-specific cDNAs and only seven loci could be mapped in this cross. Duplication of RFLP loci was extensive and reflects the amphidiploid nature of this species. However, several rearrangements of the linear order of duplicated loci could be seen. This RFLP study in B. napus provides important information on genome organization of functional DNA sequences and complements our current RFLP mapping effort in Brassica oleracea. The genetic markers of this map are currently being used in several breeding applications, such as tagging important agronomic traits and fingerprinting breeding lines and cultivars of canola, a major oilseed crop.Key words: genetic mapping, Brassica napus, breeding, restriction fragment length polymorphisms.

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