Detection of nifH Sequences in Sugarcane (Saccharum officinarum L.) and Pineapple (Ananas comosus [L.] Merr.)

To detect N₂-fixing bacteria in a plant without using culture methods, nifH gene segments were amplified with degenerate primers from DNA extracted from stems of sugarcane ( Saccharum officinarum L.) and leaves of pineapple ( Ananas comosus [L.] Merr.). Sequences of the nifH clones were homologous to those of bacteria in the genera Bradyrhizobium, Serratia , and Klebsiella. The bacteria with nifH sequences homologous to those of the three genera may be promising candidates for predominant endophytic diazotrophs in sugarcane and pineapple, because these sequences were commonly detected in samples from different host plants, which were collected at different locations. On the other hand, no nifH sequence related to Gluconacetobacter diazotrophicus , which is an endophytic N₂-fixing bacterium and had been previously isolated from sugarcane, was detected in sugarcane. This indicates the absence or the presence of few G. diazotrophicus in the stems of the sugarcane plants used in the current study.     

Evaluation of stability and yield potential of upland rice genotypes in North and Northeast Thailand

The planting of upland rice is one cropping option in area with limited water availability and low soil fertility in North and Northeast Thailand.The varietal selection was determined by grain yield potential,wide adaptation,and good stability.This study was aimed at evaluation of indigenous upland rice germplasm for yield and yield stability in multi-locations.Thirty-six upland rice genotypes collected from six provinces of the North and Northeast Thailand and one check variety(Sewmaejan) were assessed under five locations in the rainy seasons of 2009 and 2010.The experiment was laid out in a randomized complete block design with three replications.The genotype grain yield was highly affected by location(59.90%),followed by genotypes(G)×location(L) interaction(12.80%) and genotype(6.79%).The most suitable location for the genotype evaluation was L3(Khon Kaen-KKU10) which associated with stability of grain yield for all genotypes.Furthermore,biplot and regression analysis indicated that genotype numbers 6(Jaowmong 1),10(Neawmong 1),18(Neawdum 1),19(Leamna),20(Prayaleamkang),32(Kunwang 2),and 33(Kunwang 3) showed great yield stability over five locations.The genotypes will be applicant for upland rice production area and parental base in breeding program.