Hybridization between salt resistant and salt susceptible genotypes of mungbean(Vigna radiata L.Wilczek)and purity testing of the hybrids using SSRs markers

Six cultivated and two wild genotypes of mungbean（Vigna radiata L. Wilczek） possessing variation for phenotypic and genotypic response for salt tolerance were hybridized. Hybridization results showed successful pod set and significant variations in cross-compatibility of investigated genotypes. Genotypes PLM 380 and PLM 562 showed promising combining ability with all genotypes. Results revealed significant crossing compatibility between V. radiata and V. sublobata. The cross ability ranged from 1.99 to 5.12%（average 3.08%）. Molecular analysis confirmed the hybrids purity. All F_1 seeds were bold, green/shiny green and germinated between 3 to 5 days. Hybrid plants were normal, fertile and healthier over their respective progenitors. Uniform flowering and maturity of the hybrids showed absence of any defect or alteration in plant habit and life cycle of the hybrids. The hybrid plants showed increase in yield characteristics as no. of pods, pod length, 100 seeds weight, and yield per plant. Number of pods containing F_2 seeds ranged from 5–8 per cluster. The F_2 seeds were collected and stored for further research. Present study suggests that salt resistant wild relatives or cultivars of mungbean can be explored by breeding as a source of useful traits/genes providing salt tolerance. This may help in development of best mungbean variety for saline prone areas. Micro-satellite markers linked to the trait/genes may assist breeding by early selection of the genotypes compared to the phenotypic screening.

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 poly- ploid lines, PMeS-1 and PMeS-2 with Polyploid Meiosis Stability (PMeS) genes were bred. The proce- dure 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 be- haviors 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 bi- valents and quarivalents nearly without over-quarivalent in prophase, nearly without lagging chromo- somes 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.