Thursday, October 2, 2008


Breeding plants to create new varieties and improve upon old ones is a hobby that nearly everyone
can engage in. The crossing techniques are easy to learn and you can experiment with many kinds of plants. Generally, amateur plant breeders work with traits that are fairly easy to change—for example, flower color, fruit shape, or plant size. Nevertheless, although your experiment may be
simple, it is possible for you to produce unusual or beautiful plants. In order to breed plants successfully it is important to understand the principles of plant reproduction. The purpose of this circular is to explain these principles and to describe some of the simple techniques that you can use to produce new varieties or strains of plants.

Wednesday, October 1, 2008

Characterization of Colletotrichum Species Associated with Pepper Anthracnose in China, India, Indonesia, Taiwan and Thailand

Tien-cheng Wang1, Zong-ming Sheu1, Sylvia K. Green1, Deyong Zhang2, Yong Liu2, N.
Ramachandran3, Ir. Widodo4, and Srisuk Poonpolgul5

Pepper anthracnose is one of the major constraints of pepper production in the hot, humid tropics and subtropics. Several Colletotrichum species have been reported as causal agents of the disease. Their identification was almost exclusively based on morphological and cultural characteristics. However, morphological plasticity of Colletotrichum is well known and can lead to misidentification of the species. Understanding the pathogen profile is a prerequisite for managing the disease, including breeding for resistance. The objective of this study was to evaluate several phenotypic traits and specific primers for rapid and accurate differentiation of Colletotrichum species associated with pepper anthracnose in China, India, Indonesia, Taiwan and Thailand. AVRDC mycologist contributed the technique of application of phenotypic and molecular criteria for the identification of Colletotrichum spp. Isolates used were originated fromsingle conidial cultures and were maintained on silica gel at 4℃. They were then transferred from stock cultures to potato dextrose agar (PDA) to determine condial morphology, colony morphology and growth rate, casein hydrolysis medium (CHM) for protease activity determination and to potato dextrose broth (PDB) for PCR reactions with species-specific primers. Several specific PCR primers derived from the sequence of the internal transcribed spacer (ITS) region of the rDNA gene, such as CaINT2 (5'-GGGGAAGCCTCTCGCGG-3'), CgINT (5' GGCCTCCCGCCTCCGGGCGG- 3') and CcINT (5'- TCTCCCCGTCCGCGGGTGG-3')
were used for the detection of C. acutatum (Ca.), C. gloeosporioides (Cg) and C. capsici (Cc) respectively. Three species Ca, Cg and Cc were identified in China, India, Indonesia, Taiwan and Thailand based on the phenotypic and molecular criteria. This is the first report of the association of Ca species with pepper anthracnose in all countries except Taiwan. At AVRDC in Taiwan we have found diverse morphological characteristics and poor specificity in the case of C. gloeosporioides isolates from Taiwan-using the Cg specific PCR primer. This implies that previously identified Cg isolates may be a heterogeneous complex species. C. boninense was recently separated from C. gloeosporioidesas a distinct species based on morphological and
molecular evidence.