การปรับปรุงสายพันธุ์เกสรเพศผู้เป็นหมันและสายพันธุ์รักษาเกสรเพศผู้เป็นหมันของพริกโดยวิธีผสมกลับ

Abstract

Four male sterile lines (A-line: S rfrf); BC1-10 × 1450-3 (A1), BC1-16 × 1450-3 (A2), BC1-16 × 1450-7 (A3) and BC1-10 × 1450-6 (A4), one B line (N rfrf), 1450-7-10-17 (B) and four fertile lines (N RfRf), PJ.05 (C1), PJ.07 (C2), 1448-5-13-6 (C3) and 1449-3-9-15 (C4) were studied in this experiment. A-line and fertile lines were crossed by using a half diallel program. All combinations were evaluated for the heterosis of yield and horticultural characteristics. Sixteen hybrids of the crossing program were grown at the field trial with parental lines and commercial variety by using a randomized complete block design (RCBD) with three replications. The results show that the fruit yield of all hybrids ranges between 350.0 - 811.7 g/plant. The A2 × C4 hybrid has the highest yield weight potential at 811.4 g/plant but which is not significantly different from those of the A3 × C2, A1 × C2, A2 × C2, A2 × C1, A2 × C3 hybrids, and the commercial variety. Moreover, the A2 × C1 hybrid shows positive heterosis of all traits, plant height, yield weight, fruit per plant, fruit length, fruit width, and flesh thickness, measured 34.6, 22.9, 1.3, 34.0, 17.0, and 5.2 %, respectively. Meanwhile, the A1 × C2 hybrid shows high heterosis of plant height, yield, and fruit per plant at 27.6, 54.1, and 25.1%, respectively. The analysis of general combining ability values of individual line found that C1, C2, C3, and A2 lines show high combining ability in terms of height, yield, and a component of fruit. The genetic inheritance of male-sterile by backcross method of the hybrids that passed the heterosis evaluation is to be ascertained in fertile line by two times backcrossing (BC2F2) to transfer the male-sterile gene to fertile line. It was found that two hybrids, A1 × C1 and A1 × C3, show the traits of male fertile and male-sterile progenies at the theoretical Mendelian ratio of 3:1 by the Chi-square test. The cross-breeding between B-line and fertile line was undertaken by the backcross method to transfer the recessive gene to fertile line, accomplishing four F1 hybrids having the maintainer line gene which are B × C1, B × C2, B × C3, and B × C4. The marker-assisted selection (MAS) was used for selecting male-sterile lines and maintainer lines in chilies. The 3336-last2-SCAR marker was found to successfully identify the male-sterile trait (rfrf) and normal trait (RfRf or Rfrf) in chilies at the seedling stage, confirming that the MAS method is highly accurate and takes a shorter time for breed selection compared to the conventional procedure. Male sterile plants were confirmed by staining of pollen grains with 1% acetocarmine. The result showed that the pollen grains not stained by 1% acetocarmine belong to two hybrids A1 × C1 and A1 × C3. These hybrids having fertile pollens or non-viable male sterile pollens, however, could be used as the female parent for further improvement. New A-line and B-line chilies were evaluated. The results show that A-line has the first flowering at 56.0 - 61.0 days after transplanting, plant height ranging between 93.9 - 99.9 cm., and canopy width ranging between 65.0 - 69.7 cm. while B-line has the first flowering at 52.6 - 56.1 days after transplanting, plant height in the range of 75.4 - 93.9 cm., and canopy width in the range of 63.9 - 68.1 cm. This experiment was for preliminary assessment, and the new A-line and B-line must be evaluated for other quantitative and qualitative characters and subject to further breed improvement.