Screening Germplasms Resistant To Soybean Rust And The Suitability Range Assessment Of Soybean Rust Using CLIMEX

This study aims at two objectives: to screen soybean germplasm resistant to soybean rust and to assess the global suitability range of soybean rust using CLIMEX system.To screen soybean germplasm resistant to soybean rust (Phakospora pachyrhzi) to provide germplasm resources for soybean breeders, germplasms resistance evaluation was made. One hundred and forty-nine, one hundred and twenty-eight varieties of soybean provided by United Stated Department of Agriculture were planted in the field in Jingdong County Jingdong, Yunnan Province in 2002 and 2003 season respectively. The test site was in a subtropical area considered the geographic origin of P. pachyrhzi, the causal agent of soybean rust. Investigating and recording the data of soybean rust, including severity of the leaf on top, medium and low plant part and reaction type. The lesion reaction type was recorded as Tan when there is not extensive necrosis around uredia, or RB when there is extensive necrosis around uredia. The plant health was quantified as good or poor based on robertness of growth and seed production. The cluster analysis and discrimination analysis was finished through SAS software and soybean resistances to rust were classified into moderately resistant (MR), moderately susceptible (MS) and high susceptible (HS), the two years results showed that there are 21 high susceptible varieties, 23 moderately susceptible varieties, and 70 moderately resistant varieties. The rust time of the moderately resistance plants was visually later than other groups. The infection period of uredia on the moderately resistance plant was shorter than others. Combining this result with plant health and seed, twenty varieties may be usable for rust management in Province Yunnan or some areas of Southern China in auiumn. In the process of canonical discrimination, the s groups of varieties (HS) have the highest value of the first canonical discrimination variable, the r groups of varieties (MR) have the lowest value of the first canonical discrimination variable, and the value of the m group of varieties (MS) is between them. The first canonical discrimination variable can generally define these three groups of varieties and have more effect than the second canonical discrimination variable. The first canonical discrimination variable was primarily affected by the disease intensity of the low parts of a plant, the second canonical discrimination variable was primarily affected by the disease intensity of the medium plant part, these results is consistent with observations that rust symptom on soybean was usually and firstly observed on the low plant part.To overcome the limitation of resources and property to investigate soybean rust, assessment of the expansion of soybean rust will enable policy makers and land managers to develop strategies for soybean rust risk management. We employed 'compare locations' module of CLIMEX to determine the areas of soybean rust in China and world, based on climatic suitability. The CLIMEX results showed that the assessed locations in China were consistent with actual occurrence of the disease indicate that CLIMEX is able to assess the suitability range of soybean rust. In the United States, soybean rust has potential to spread to other areas after onset in Gulf coast regions such as Louisiana. The potential suitability of serious epidemics is mostly between latitude 27-41.7° North and longitude 66.8-87.2° West. The potential suitability of constant rust epidemics is most likely between latitude 42-47° North andlongitude 59.2-88.2° West, the potential suitability of light rust epidemics is mostly between latitude 34-52° North and longitude 82-107.1° West. No the potential suitability of serious rust in Canada from the CLIMEX results, the potential suitability of constant rust epidemics is Lonton (Ontario) , the potential suitability of light rust epidemics is Ottawa, Toronto (Ontario), and Montreal (Quebec). In Mexico, the potential suitability of serious rust epidemics mingles with the potential suitability of constant rus...