The breeding of two polyploid rice lines with the characteristic of polyploid meiosis stability.

Polyploidization is a basic feature of plant evolution. Nearly all of the main food, cotton and oil crops are polyploid. When ploidy levels increase, yields double; this phenomenon suggested a new strategy of rice breeding that utilizes wide crosses and polyploidization dual advantages to breed super rice. Because low seed set rates in polyploid rice usually makes it difficult to breed, the selection of Ph-liked gene lines was emphasized. After progenies of indica-japonica were identified and selected, two polyploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The procedure included seven steps: selecting parents, crossing or multiple crossing, back-crossing, doubling chromosomes, identifying the polyploid, and choosing plants with high seed set rates that can breed themselves into stable lines. The characteristics of PMeS were determined by observing meiotic behaviors and by cross-identification of seed sets. PMeS-1 and PMeS-2, (japonica rice), have several characteristics different from other polyploid rice lines, including a higher rate of seed set (more than 65%, increasing to more than 70% in their F1 offspring); and stable meiotic behaviors (pairing with bivalents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromosomes in metaphase and without micronuclei in anaphase and telophase). The latter was obviously different from control polyploid line Dure-4X, which displayed abnormal meiotic behaviors including a higher rate of multivalents, univalents and trivalents in prophase, lagging chromosomes in metaphase and micronuclei in anaphase and telophase. There were also three differences of the breeding method between PMeS lines and normal diploid lines: chromosomes doubling, polyploidism identifying and higher seed set testing. The selection of PMeS lines is the first step in polyploid rice breeding; their use will advance the progress of polyploid rice breeding, which will in turn offer a new way to breed super rice.

Performance assessment of malolactic fermenting bacteria Oenococcus oeni and Lactobacillus brevis in continuous culture.

The growth performance of malolactic fermenting bacteria Oenococcus oeni NCIMB 11648 and Lactobacillus brevis X(2) was assessed in continuous culture. O. oeni grew at a dilution rate range of 0.007 to 0.052 h(-1) in a mixture of 5:6 (g l(-1)) of glucose/fructose at an optimal pH of 4.5, and L. brevis X(2) grew at 0.010 to 0.089 h(-1) in 10 g l(-1) glucose at an optimal pH of 5.5 in a simple and safe medium. The cell dry weight, substrate uptake and product formation were monitored, as well as growth kinetics, yield parameters and fermentation balances were also evaluated under pH control conditions. A comparison of growth characteristics of two strains was made, and this showed significantly different performance. O. oeni has lower maximum specific growth rate (mu(max)=0.073 h(-1)), lower maximum cell productivity (Q (x) (max)=17.6 mg cell l(-1) h(-1)), lower maximum biomass yield (Y (x/s) (max)=7.93 g cell mol(-1) sugar) and higher maintenance coefficient (m (s)=0.45 mmol(-1) sugar g(-1) cell h(-1)) as compared with L. brevis X(2) (mu(max)=0.110 h(-1); Q (x) (max)=93.2 g(-1) cell mol(-1) glucose; Y (x/s) (max)=22.3 g cell mol(-1) glucose; m (s)=0.21 mmol(-1) glucose g(-1) cell h(-1)). These data suggest a possible more productive strategy for their combined use in maturation of cider and wine.